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Atlas Table of Contents
The Skeleton of the Trunk.
The Skull and the Skull Bones.
The Appendicular Skeleton.
Röntgen Pictures of the Human Skeleton.
Joints and Ligaments of the Trunk and Head.
Joints and Ligaments of the Upper Extremity.
Joints and Ligaments of the Lower Extremity.
Muscles of the Back.
Muscles of the Thorax and Abdomen, including the Diaphragm and Iliopsoas.
Pl. A1, Fig. 1
Pl. A1, Fig. 2
Muscles of the Neck.
Muscles of the Head.
Muscles and Fasciae of the Upper Extremity.
Pl. A2, Fig. 1
Pl. A2, Fig. 2
Muscles and Fasciae of the Lower Extremity.
Pl. A3, Fig. 1
Pl. A3, Fig. 2
Pl. A4, Fig. 1
Pl. A4, Fig. 2
Regions of the Body.
Peritoneum and situs viscerum.
Respiratory Organs (including pleura).
Urogenital Organs, apparatus urogenitalis.
Excretory Organs (including Suprarenal glands).
The Male Genitalia.
The Female Genitalia.
Angiology and Neurology
The Circulation of the Blood.
The Fetal Circulation.
Vessels of the Heart.
Nerves and Vessels of the Neck, Axilla, Back and Thoracic Wall.
Nerves and Vessels of the Upper Extremity.
Nerves and Vessels of the Head and the Viscera of the Head and Neck.
Vessels of the Abdominal Viscera.
Vessels and Nerves of the false and true Pelvis and of the Perineum.
Nerves and Vessels of the Lower Extremity.
The Sympathetic Nervous System.
The Spinal Cord.
Meninges and Vessels of the Brain.
Textbook Table of Contents
I have endeavored in this work to produce an Atlas that will serve the practical needs of students of medicine and practicing physicians. It is not intended to be an Atlas for the use of experts in Anatomy. Consequently in the make-up of the book a limitation to what was absolutely necessary seemed to me a prime consideration.
In its outward form this first volume of the work is treated throughout as an Atlas, is arranged primarily for use by classes in dissection and follows closely the usual methods employed in such classes. Any difficulty that might arise for the beginner by an unusual method of presentation of the figures has, therefore, been carefully avoided.
The illustrations are so arranged that there is to be found on the opposite page, in addition to the explanation of the figures, a brief descriptive text. This enables the student using the book during his dissection to review rapidly the chief points in his preparation. In the Myology the explanatory text takes the form of tables which give at a glance the origin, insertion, nerve supply and action of the muscles. As regards the methods of reproduction of the figures, polychromatic lithography is used for the first time - so far as I am aware - in anatomical illustrations. Of the 34 colored plates 30 are reproduced by this process, the remaining 4 by the method of three (four)- color printing, again used for the first time in this connection. Nearly all the figures in the Myology are reproduced in this manner. For the other illustrations the so-called autotype process is used, and its suitability for the purpose may be seen from the Atlas itself. In addition key-figures, diagrams, etc. have been reproduced by line etching.
For greater convenience special colors have been extensively used in the illustrations reproduced by the autotype process, a chamois tint for the bones in illustrations of the articulations and many of the muscle figures, different colors for the individual skull bones in representations of the entire skull and in topographic figures of the skull bones. For the names of parts the Basel Nomenclature has been used.
The publishers have spared no pains in producing a book that certainly surpasses in excellence of reproduction all previous works, while at the same time it does not materially fall behind the most of them in the number of illustrations.
Würzburg, October 1903.
The second edition of the first volume shows very important changes. In the first place the former lithographed plates of the Myology have been entirely omitted and replaced by polychromatic autotypes, as had already been done in the second and third volumes of the first edition. This was done partly for uniformity in reproduction, partly because the illustrations of the first volume were not pleasing to many readers on account of the colors being too bright and glaring on the white paper. I have especially decided to provide new illustrations of the muscles, since those of the first edition frequently did not give a sufficiently natural impression owing to the position of the cadaver. Instead of using photographs of the cadaver, those of an athletic man of small stature were taken as a foundation. These photographs were prepared by the illustrator Mr. K. Hajek and within outlines prepared from them the muscles were drawn from dissections. In this way one obtains correct and expressive figures which, furthermore, are more in keeping with the format of the book. The use of yellow, red and blue colors is naturally merely conventional, although they approximate the natural tints. At the same time the number of the illustrations for the Myology was considerably increased and, furthermore, for the trunk, and especially the thorax and abdomen three-quarter views were employed instead of complete profiles. Mr. K. Hajek has drawn the illustrations in a thoroughly satisfactory manner.
The portions of the book dealing with the Osteology and Syndesmology have also been expanded in various places.
Würzburg, July 1913.
Unlike the earlier editions the seventh and eighth have undergone some not unimportant changes. Some Röntgen figures from Grashey's Atlas have been included, new figures of the muscles of the neck and face replace the older ones and a number of the osteological figures have been renewed. In correspondence with these changes the text has been somewhat enlarged.
Bonn, November 1929 and February 1932.
This first volume of the second Englished edition of Sobotta's Atlas of Descriptive Anatomy is translated and edited from the sixth German edition. Compared with the first Englished edition there are a number of differences, the chief one being that the text-book feature has disappeared, the book being more strictly an anatomical Atlas. The descriptions of the structures shown in the illustrations are greatly condensed and, as far as possible, are on the pages facing the illustrations under consideration. The labels on the figures are the B. N. A. terms in their original Latin form; in the text, however, it has seemed advisable to translate them, for the most part, into their English equivalents or, in rare cases, to use a term more familiar to English-speaking students. Where misunderstandings might occur the B.N.A. term in also given.
The text, however, is relatively unimportant; the illustrations are the chief glory of the book and to give these English explanations and to render them available for English-speaking students of anatomy is the object of this edition.
This second volume of the Atlas of Descriptive Anatomy treats of the anatomy of the viscera including the heart. It has seemed advantageous to include the heart since in dissection it is usually considered with the other viscera of the thorax.
The choice of preparations for illustration and their manner of representation follow the plan used in the first volume, the object being to present them from the standpoint of topographic anatomy.
Würzburg, August 1904.
In this second edition a series of changes have been made in that the lithographic plates have been replaced by others, reproduced partly by so-called three-color printing partly by polychrome autotype printing. In so doing some plates were greatly altered and especially for the situs of the abdominal viscera and the peritoneum and partly for the female genitalia new figures have been added. All the figures are from the skilled hand of K. Hajek.
Würzburg, February 1914.
In contrast to the third, fourth and fifth editions, which were essentially the same as the second, this sixth edition presents a number of new illustrations, especially of the stomach, intestines, liver, lungs and pericardium.
Bonn, November 1927.
In this seventh edition all colored figures have been reproduced by the same method, i.e. by the polychromatic autotype process. Some additions have been made, of which there may be especially mentioned a series of new figures (mouth cavity, accessory cavities of the nose, thoracic viscera, conducting bundles of the heart). Further, some of the figures have been replaced by new ones.
Bonn, June 1931.
An experience with the work of the Anatomical Laboratory, extending over many years, has convinced the author of the advisability of presenting illustrations of the peripheral nervous system and of the blood vessels as they are seen by the student in his dissections, i.e. the nerves and arteries of any region in the same figure. Consequently in the majority of the figures representing these structures arteries and nerves, arteries, veins and nerves, or arteries and veins are shown in each figure, and only occasionally is there a departure from this plan, when, for the sake of clearness, accessory figures showing only the arteries or the nerves (for example, the cranial nerves) are added.
This method of arrangement has the advantage for the student, that he finds on a single page of the Atlas representations of all the structures he has seen at any one stage of his dissection, and is not obliged to waste time in turning from page to page of the Volume. Each figure is one of a series of topographic anatomical illustrations.
The simultaneous representation of blood vessels and nerves makes reproduction in colors necessary. The arteries are shown red, the veins blue and the nerves yellow. For the reproduction in color autotypes have been used, prepared in a most satisfactory matter by Messers. Angerer and Göschl of Vienna and the various plates have at the same time been adapted for the coloration of the other tissues shown (muscles, bones, fat, skin etc.). In this way colored illustrations have been obtained, which do not, it is true, show an absolutely natural coloration, but nevertheless approximate it sufficiently to give an extraordinarily accurate general impression. All the figures of the Volume are from originals by K. Hajek, whose artistic talent and skill in anatomical illustrations are again fully manifested.
As was stated in the Preface to the first Volume, the endeavor has been to make of the Atlas a work that would be of use to students and practitioners, not one intended for expert Anatomists. Whoever wishes information in special fields of anatomy, will necessarily turn to special treatises on those fields, and this Atlas, even were it twice as extensive, would not be sufficient for him. On the other hand an undue expansion of the book and overloading it with illustrations of interest only to specialists, would only render it more difficult for the student or practitioner to get the information he desires. The chief object has therefore been to limit the illustrations to the necessities of the case, but to present these in a series of comprehensive figures, showing step by step the stages usually followed in dissection.
In correspondence with the arrangement followed in the first and second volumes, this one presents alternately pages of text and figures. The latter show the principal figures of the Atlas, the former, in addition to accessory and schematic figures and the explanations of the chief figures, a brief text intended for review during the use of the Atlas in the dissecting room, this being accompanied by references to other illustrations in the volume where the structures under consideration are shown.
Würzburg, May 1906.
The Second Edition of this Atlas differs from the first by an increase in the number of illustrations. For the brain, especially, and for the sense-organs a number of new figures have been added. The representation of the principal fibre tracts has been extensively altered and in this connection some of the schematic figures have been replaced by new ones. In addition a considerable number of schemata have been added, which have in many cases been adapted from the admirable figures by Villiger.
The alphabetical index at the end of the Volume refers to the figures. In the text brief references are given to pages on which further statements as to the structures under consideration are to be found, and a special page reference was therefore unnecessary.
Würzburg, Spring, 1915.
In contrast to the third, fourth and fifth editions, which were essentially the same as the second, this sixth edition presents a number of new illustrations, especially of the nerves and vessels of the lower limb, of the brain, the eye and the auditory organ.
This seventh edition, compared with the sixth, has been improved, apart from lesser modifications, by the addition of three large, full-page, colored representations of the cranial, cervical and thoracic portions of the sympathetic nervous system, taken, by kind permission, from the admirable publications of Mr. Braeucker of Hamburg.
Bonn, November 1930.
The eighth edition differs but little from the seventh, but contains some new illustrations of the blood vessels (and nerves), especially those of the posterior abdominal wall; and of the lymphatic vessels. Further the structure of the medulla oblongata, the pons and the corpora quadrigemina is shown in some schemata taken from the diagrams of Müller-Spatz, published by the J. F. Lehmann's Verlag.
Bonn, March 1933.
Explanation of the abbreviations used in the illustrations.
Abbreviations not listed may be determined by the context.
X after a name denotes that the part indicated has been cut away or cut through.
( ) denotes that the part is seen through another structure. In the case of the facial muscles, however, ( ) denotes the proposed new nomenclature.
1, 2, 3, etc. after a term indicates that the part concerned is shown in different parts of its course.
If a part is not named, as a rule it has already been named on the preceding figure.
For the structure of bone see here.
The skeleton of the trunk consists of the vertebral column together with the ribs and sternum.
True and False Vertebrae may be distinguished. The former are represented by 7 cervical vertebrae, 12 thoracic and 5 lumbar, while the latter are two composite bones, the sacrum and coccyx.
The essential parts of a vertebra are the body (corpus), the arch (arcus), the transverse processes, the spinous process and the articular processes.
The body (Corpus) forms the principal part of the vertebra; it lies anteriorly and has a low cylindrical form. From it arises by means of the pedicles (radices) the arch (arcus), between which and the posterior surface of the body is the vertebral foramen, usually more or less transversely elliptical in form: Each pedicle (radix) presents an upper shallower and a lower deeper notch (incisura vertebralis). When the vertebrae are articulated the notches of successive vertebrae form foramina (foramina intervertebralia) through which the spinal nerves pass. Those vertebrae with which ribs articulate present toward the posterior part of both the upper and lower border of the body on each side an articular surface (fovea costalis superior and inferior) for the head of the rib.
The transverse processes are paired processes that project laterally from the anterior part of the arch or, in the case of the cervical vertebrae, from the pedicles. Their extremities, in the case of the thoracic vertebrae, present on their anterior surface an articular surface (fovea costalis transversalis) for the tubercle of the rib.
The unpaired, median spinous process arises from the posterior part of the arch and is directed backwards or backwards and downwards. The portion of the arch between the spinous and transverse process on each side is termed the lamina.
The paired articular processes serve for the articulation of the vertebrae with one another. Each vertebra bears two superior and two inferior articular processes. They arise from the arch close behind the pedicles and bear articular surfaces, which lie in different planes in different vertebrae.
The Cervical Vertebrae have small, transversely elliptical bodies, the upper concave surface of each overlapping laterally the lower convex surface of the vertebra next above. The arches are of moderate height and the vertebral foramen relatively large, especially in its transverse diameter, and of a rounded triangular form. The articulating processes have their almost flat surfaces situated obliquely in a plane intermediate between the frontal and the horizontal. The transverse processes enclose a foramen (foramen transversarium), the anterior portion of each process representing a rudimentary rib fused with the body and transverse process. The rib element of the seventh vertebra occasionally remains separate, forming a cervical rib. Each transverse process presents on its upper surface a groove for the spinal nerve (sulcus nervi spinalis), which extends from the vertebral foramen over the foramen transversarium to the tip of the process, where it separates an anterior from a posterior tubercle. This is due to the origin of the transverse processes from the pedicles, whence they lie in the regions of the vertebral incisures. The spinous processes are short and bifid at their tips; they are almost horizontal or only slightly inclined except that of the seventh vertebra (vertebra prominens), which inclines downwards like those of the thoracic vertebrae and is never bifid, resembling the spinous processes of the thoracic vertebrae rather than those of the other cervicals. On account of its long spinous process the seventh (vertebra prominens) is the first vertebra that can be felt in the living body. Furthermore its foramen transversarium is small. It is a typical cervical vertebra, presenting, however, characters transitional to those of the thoracic series.
The atlas and axis (epistropheus) are on the contrary atypical vertebrae. The atlas has no body. Instead there is both an anterior and a posterior arch. The vertebral incisures and the spinous process are also lacking. In place of the latter there is a posterior tubercle and opposite this on the anterior surface of the anterior arch there is ani anterior tubercle. In the place of the lacking articular processes there are articulating surfaces on the upper and under surfaces of what are termed the lateral masses of the bone. The large transverse processes have a foramen transversarium, but no tubercles and no groove for the spinal nerve. The posterior arch is low; on the posterior surface of the anterior arch is a roundish, slightly concave articular surface for the odontoid process (dens) of the axis (epistropheus). The vertebral foramen is very large and consists of a smaller anterior and a larger posterior portion; it is bounded laterally by the prominent lateral masses. Over the upper surface of the posterior arch there runs a shallow groove (sulcus arteriae vertebralis) for the vertebral artery; occasionally it becomes deeper or is even converted into a canal.
The axis (epistropheus) possesses a conical process, the odontoid process (dens) arising from its body. Upon this process there is an anterior and usually a posterior articular surface. The upper articular processes are replaced by articulating surfaces and the superior vertebral incisure is wanting. The transverse processes are very small; there are no tubercles and no groove for the spinal nerve. The spinous process is especially strong and bifid and it, as we)l as the under surface of the bone, resembles the corresponding part of typical cervical vertebrae.
The thoracic vertebrae have moderately large bodies which increase both in height and depth from above downwards. The surfaces of the bodies are flat and heart-shaped. The vertebral foramen is absolutely and relatively small and almost circular. On the posterior part of both the upper and lower borders of the lateral surfaces of the body are articular facets (fovea costalis superior and inferior) which, with the corresponding half facets of adjacent vertebrae, form the articular surfaces for the heads of the ribs. The articular processes have nearly flat surfaces which lie almost in the frontal plane; the lower ones hardly project beyond the surface of the arches. The transverse processes are strong, directed laterally and distinctly backward and bear upon the anterior surfaces of their thickened, free ends articular surfaces for the tubercles of the ribs (foveae costales transversales).
The spinous processes are very strong, triangular, thickened at their ends and directed distinctly downwards; those of the middle thoracic vertebrae overlap each other like the shingles on a roof.
The first thoracic vertebra has on each side a complete fovea for the first rib and a half fovea for the second rib, that is to say one and one half instead of two half foveae. The last two thoracic vertebrae have on each side a complete fovea, each articulating with only one rib. The eleventh and especially the twelfth thoracic vertebrae form a gradual transition to the lumbar vertebrae, since the spinous processes are directed straight backwards and are laterally compressed, the foveae costales transversales are lacking and, associated with a rudimentary condition of the transverse processes, accessory and mamillary processes may occur (12 Thoracic). Also the articular surfaces and the lower articulating processes of the twelfth thoracic vertebra are already sagittal in position.
The lumbar vertebrae are the largest of all the true vertebrae. They have high and broad bodies with flat, bean-shaped (that is to say, the contact surface for the adjacent vertebra is elliptical, but somewhat concave posteriorly) not quite parallel surfaces (the surfaces are not parallel because the lumbar portion of the vertebral column is strongly convex forwards, the vertebral bodies being noticeably higher in front than behind), as well as high and strong arches with very strong processes. The anterior as well as the lateral surfaces of the bodies are hollowed out (consequently the contact surfaces are larger than the transverse section through the middle of the bodies). In size these vertebrae increase continuously and quite distinctly from the first to the fifth. The vertebral foramen is narrow and rounded triangular. The surfaces of the articular processes stand almost in the sagittal plane; they are distinctly curved, the superior processes being concave and directed medially while the inferior are convex and directed laterally.
The upper articular processes bear on their upper margins a rounded tubercle, the mamillary process. The transverse processes are long, flat, rib-like and directed almost exactly laterally. At the base of each is a sharp process directed backwards, the accessory process, which corresponds to the tip of the transverse process of a thoracic vertebra, the main portion of a transverse process corresponding to a rib fused with the vertebra. The spinous processes are strongly compressed laterally, are directed almost exactly backwards and are slightly thickened at their ends.
The sacrum is a curved, shovel-shaped bone, broader above and narrower below. Its posterior surface (facies dorsalis) is convex and roughened, the anterior surface (facies pelvina) is concave and relatively smooth, the broader upper surface is termed the base and the lower more pointed end the apex.
The dorsal surface presents a rough median ridge or crest, which in many cases is frequently interrupted. It is formed by the fusion of the spinous processes of five sacral vertebrae. In addition to this unpaired median crest there are on the dorsal surface on each side two lateral, rarely continuous ridges, which are separated by four foramina, the posterior sacral foramina. Medial to these foramina lies the sacral articular crest formed by the fusion of the articular processes and lateral is a crest (crista sacral is lateralis) formed by the fusion of the transverse processes. The upper articular process of the first sacral vertebra remains distinct for articulation with the last lumbar vertebra, while the lower process of the last sacral vertebra forms a process, the sacral cornu, for articulation with the coccyx (but without an articular surface). The two sacral cornua bound the lower opening (hiatus sacralis) of the canal contained within the sacrum (canalis sacralis).
The pelvic surface presents four pairs of anterior sacral foramina corresponding to but larger than the four posterior foramina. Extending between the foramina of each pair is a low, rough ridge (linea transversa), which indicates the boundary between the bodies of two fused sacral vertebrae. The anterior foramina diminish in size from above downwards.
The apex of the sacrum appears as if cut off and possesses a small elliptical surface to which the coccyx is apposed.
The base shows a surface corresponding with the under surface of the last lumbar vertebra, with which it articulates. Between this bean-shaped surface and the superior articular process is a superior vertebral incisure, which, with the inferior incisure of the last lumbar vertebra, forms the last intervertebral foramen. Behind the surface for the last lumbar vertebra lies the upper end of the sacral canal and laterally are the lateral masses. The base of the sacrum is separated from the concave pelvic surface by a feeble line, which is the sacral part of the linea terminalis (see here).
In a lateral view of the sacrum one sees the articulating surface of the lateral mass, which serves for articulation on each side with the innominate bone and through this for the completion of the pelvic limb-girdle. It is formed anteriorly by an uneven, ear-shaped auricular surface, which is covered with cartilage, and posteriorly by a rough, depressed area, the sacral tuberosity, which is not covered by cartilage. Below this the lateral surface of the bone, which is fairly broad above, becomes exceedingly narrow; i.e. the bone which is relatively thick at the base now becomes quite thin.
The sacral canal, the continuation of the vertebral canal, traverses the entire length of the sacrum. Posteriorly it is bounded by a flattened bony mass formed by the fused arches of the sacrum, which bear the medial sacral crest. The canal opens in front and behind into the sacral foramina by means of the intervertebral foramina, which, in the sacrum, in contrast to the true vertebrae, are contained within the bone and consist of short canals. The posterior wall of the sacral canal does not extend to the apex of the bone, but terminates at about the boundary between the fourth and fifth sacral vertebrae. There is thus formed the hiatus of the sacral canal (see here).
The Coccyx is a small bone formed by the fusion of four or five rudimentary coccygeal vertebrae. The first of these vertebrae possesses two upwardly projecting cornua which are the rudiments of articular processes and serve for articulation with the sacrum. Furthermore, this same vertebra has feebly developed transverse processes. The upper end of the coccyx unites with the apex of the sacrum.
The second to the fifth (sixth) coccygeal vertebrae represent merely the bodies of these vertebrae and are usually irregular in shape, mostly flattened spherical. The individual coccygeal vertebrae are either united with one another by synchondroses or have a bony union (synostosis).
The vertebral column is a bony column with several curvatures and is composed of 26 separate bones, i.e. 24 true vertebrae, the sacrum and the coccyx. Its curvatures are as follows: One in the cervical region slightly convex anteriorly, one in the thoracic region strongly concave anteriorly, one in the lumbar region strongly convex anteriorly and one in the sacral and coccygeal regions strongly concave anteriorly. The transition from the lumbar convexity to the sacral concavity is somewhat abrupt; the region of the last intervertebral disc is termed the promontary.
The width of the column is greatest at the upper part of the sacrum; from this level the vertebrae become gradually smaller toward the coccyx and also upwards toward the middle of the thoracic region. From there upwards the vertebrae again broaden to the upper thoracic and lower cervical regions, diminishing again up to the axis (epistropheus), while the atlas, with its strongly developed transverse processes, is again notably broader. The greatest thickness of the column is in the lumbar region.
The bodies of the vertebrae are not in actual contact with one another, but are joined together by intervertebral discs. On the other hand the articular processes are in immediate contact by their articular surfaces. Each adjacent pair of vertebral incisures form an intervertebral foramen; the uppermost pair of these lies between the second and third cervical vertebrae and the lowest pair between the fifth lumbar vertebra and the sacrum, so that there are altogether 23 pairs of foramina. They are largest in the lumbar region and smallest in the thoracic. In the cervical region the foramina lie in the intervals between the transverse processes, in the thoracic and lumbar regions they are anterior to these processes.
The intervertebral foramina lead into the vertebral canal, which represents the sum of the separate vertebral foramina and is an almost cylindrical cavity that begins at the atlas and is continued below into the sacral canal (see here).
The ribs (costae) are long flat bones and may be regarded as consisting of a bony rib and a costal cartilage,. In the bony rib there may be noted a rounded enlargement at the posterior, vertebral end, the head (capitulum), with an articular surface for articulation with the vertebral bodies. This surface, at least in the ribs that articulate with the bodies of two vertebrae, is divided into two portions by the capitular crest. On the head there follows a distinct constriction of the rib, the neck (collum), whose upper border is provided with a ridge (crista colli) that gradually fades out on the body of the rib. Where the neck passes over into the body of the rib there is a rough tubercle bearing an articular surface for articulation with the transverse process of a thoracic vertebra.
The body (corpus) of the rib forms the principal part of the bony rib. It is a long, flat, vertically placed bone curved in correspondence with the curvature of the thorax. Near the tubercle it presents a rough surface, the angle of the rib, and at this point the rib, which at first was directed somewhat backwards, bends anteriorly. At the lower border, or more exactly, on the inner surface of the body, is a groove (sulcus costae), which gradually fades out toward the anterior end of the rib. This is slightly hollowed out for the reception of the costal cartilage.
The third to the tenth bony ribs have a typical form. The first and second and the eleventh and twelfth are atypical.
The first rib is short and broad. It is not placed vertically, but almost horizontally and its surfaces are directed upwards and somewhat outwards, and downwards and somewhat inwards. As a rule it has no capitular crest and no angle. On its upper surface, not far from where it joins its costal cartilage, there is a distinctly roughened area, the scalene tubercle for the insertion of the Scalenus anterior, and behind this a slight furrow, the subclavian groove for the subclavian artery. Behind this again is a rough surface for the insertion of the Scalenus medius. The neck of the first rib is long and thin.
The second rib is markedly longer and smaller than the first. Its posterior part is similar to that of the first, one surface looking upward and outward and the other downward and inward, but its anterior part is placed nearly vertical, as in the typical ribs. The angle and the tubercle coincide, but on the other hand there is a capitular crest. At about the middle of the length of the rib its lateral surface shows a roughened area, the tuberosity, for the insertion of a serration of the Serratus anterior.
The eleventh and twelfth ribs are quite rudimentary. They possess only a head, which however has no capitular crest. The tubercle is usually wanting on the eleventh rib and frequently the angle; on the twelfth rib also both are wanting. In both the costal sulcus is absent. The twelfth rib is often very short and it varies greatly in length.
The sternum is a flat, elongated bone in which three parts may be recognized, a manubrium, a body (corpus) and a xiphoid process.
The manubrium is the upper, broadest, slightly curved portion of the sternum and is separated from the body of the bone by the sternal synchondrosis. There may be distinguished on the manubrium an upper, shallow depression, the jugular notch or incisure, lateral to which on the two upper angles of the bone are two lateral, stronger depressions, the clavicular incisures, for the reception of the sternal ends of the clavicles. Immediately below these lie two broad shallow depressions, the first costal incisures, for the attachment of the cartilage of the first rib. At the lower end of the manubrium there is on either side a half incisure for the second rib.
The body (corpus) of the sternum is narrower and thinner but longer than the manubrium. For the most part it broadens from above downwards. It unites with the manubrium at a very obtuse angle, the sternal angle, which is not always very distinct. Its anterior surface is termed the sternal plane. The lateral borders show incisures for the reception of the second to the seventh costal cartilages. Frequently low transverse ridges upon the anterior surface of the bone unite the incisures of the two sides (see Fig. A39). Only the lower half of the incisure for the cartilage of the second rib is found on the body of the sternum, the incisures for the fifth to the seventh lie close to one another, while those for the second to the fifth rib are placed at quite distinct intervals. That for the seventh rib is in the angle between the body and the xiphoid process.
The xiphoid process is usually only partly bony, being usually cartilaginous in its lower part. It is often perforated or cleft below and is especially variable in form. Its upper bony portion usually fuses with the body of the sternum in advancing years.
The thorax is formed by the twelve thoracic vertebrae, the twelve pairs of ribs and the sternum.
The ribs increase in length from the first to the seventh and then diminish rapidly. The costal cartilages of the uppermost and lower-most ribs are the shortest.
The seven upper ribs which are attached by their cartilages directly to the sternum are termed the true ribs (costae verae), in contrast to the five lower ones, the false ribs (costae spuriae), which are attached to the sternum only through the intervention of the seventh costal cartilage, or, as in the case of the eleventh and twelfth ribs, have no connection with the other ribs or with each other (floating ribs). The cartilages of the sixth (in some cases even of the fifth) to the tenth rib are united with one another by upwardly and downwardly directed processes and form the costal arch. The union may be a synchondrotic one or else diarthrotic. In the region of the costal arch the cartilages are frequently greatly broadened. They always diminish in breadth from their outer ends towards the sternum. Not infrequently the middle ribs especially form what is termed a costal window, a rib dividing, usually in its bony portion, and then uniting again in the neighbourhood of the cartilage. The eleventh and twelfth ribs have only cartilaginous tips, which are very short and end freely.
The ribs, which form the principal part of the thoracic wall, are so placed that between each two ribs there is an interspace, the intercostal space, which is considerably wider than the rib itself. There are eleven of these spaces on each side. The last is very short and, like the next to the last, is open anteriorly.
The first and second costal cartilages slope slightly downwards toward the sternum, the third to the fifth are almost horizontal, while from the sixth downwards the cartilages are directed sharply upwards, especially in expiration, during which a distinct angle is developed at the junction of the bony rib with its cartilage, an angle which is almost completely obliterated during inspiration.
The sternum with the costal cartilages and the adjacent portions of the bony ribs forms the anterior wall of the thorax. It does not lie exactly in the frontal plane, but its upper end is directed somewhat backwards and is therefore somewhat nearer the vertebral column than is the lower part. The greater distance of the lower part from the column is mainly due to the strong concavity of the thoracic portion of the column.
The anterior wall of the thorax is markedly shorter than the posterior, since the upper border of the manubrium sterni corresponds to the interval between the second and third thoracic vertebrae in the neutral position, being lower during expiration and higher in inspiration. The tip of the xiphoid process lies at the level of the ninth thoracic vertebra, or, in accordance with its variable length, occasionally at that of the eighth or tenth.
The posterior wall of the thorax is formed by the twelve thoracic vertebrae and the posterior portions of the twelve pair of ribs. Since the bodies of the former project strongly into the thoracic cavity there is a deep groove on each side of the vertebral column, the pulmonary groove (sulcus pulmonalis).
The lateral wall of the thorax is formed by the bony ribs. It is longer posteriorly than in front, where the eleventh and twelfth ribs are lacking, and during expiration reaches, opposite the twelfth rib, the level of the second lumbar vertebra.
The walls of the thorax enclose the thoracic cavity, which is almost conical in shape, the apex being directed upwards. This cavity has an upper and a lower aperture, the upper one being markedly smaller than the lower. It is bounded by the first thoracic vertebra, the first rib and the upper border of the manubrium sterni. The much larger lower aperture is bounded by the twelfth thoracic vertebra, the twelfth, eleventh and tenth ribs, the costal arch and the xiphoid process. The angle that the costal arch forms with the xiphoid process is known as the infrasternal angle.
In transverse section the thoracic cavity is heart-shaped or kidney-shaped on account of the manner in which the bodies of the vertebrae project into it. As a result the sagittal diameter of the thorax is small, much smaller than the transverse, especially in the upper part.
The bones of the head taken together form what is termed the skull (cranium). Two groups of skull bones are usually recognized, the bones of the cranium and the bones of the face. To the former belong the occipital, the sphenoid, the temporals, the parietals, the frontal and the ethmoid.
The bones of the face are the nasals, the lacrimals, the vomer, the inferior concha, the maxillae, the palatines, the zygomatics, the mandible and the hyoid.
In the occipital bone the following parts may be distinguished:
The basilar portion lies in front of the foramen magnum, the lateral portions form the lateral boundaries of this and the squamous portion lies behind it.
The basilar portion in the skull of the adult is continuous at its anterior end with the body of the sphenoid. It presents a horizontal, roughened, lower surface, which has in the median line a tubercle, the pharyngeal tubercle. Its upper or cerebral surface is concave. This latter surface forms the larger and posterior part of the clivus and shows a shallow groove at the margin of the petro-occipital fissure, the inferior petrosal groove.
The lateral portions bear upon their under surfaces the elongated, convex occipital condyles and pass without any sharp boundary into the basilar portion anteriorly and the squamous portion posteriorly. Behind the condyles is a shallow depression, the condyloid fossa, in which a short condyloid canal usually opens. When this canal is present its inner opening is on or near a broad groove, the sigmoid sulcus (Fig. A56). This, on the cerebral surface of the lateral portion, arches around the jugular process, beginning at the jugular notch, which, together with a similar notch on the temporal bone forms the jugular foramen. A small projection (intrajugular process) on each of these two bones divides the foramen into a small anterior (medial) and a larger posterior (lateral) portion (Fig. A55). The jugular process projects strongly laterally and serves for the articulation of the lateral portion of the occipital with the pyramid of the temporal bone. Medial to the jugular process. There is on the cerebral surface of the lateral portion a rounded elevation, the jugular tubercle (Fig. A56). Between this and the condyle there passes almost transversely through the bone the hypoglossal canal for the nerve of that name.
The squamous portion is by far the largest portion of the occipital bone. It is rather flat but is curved like a shovel, being concave on the inner surface and convex on the outer. It is typically triangular. Along the occipito-mastoid suture it articulates with the mastoid portion of the temporal bone and at the lambdoid suture with the two parietal bones. The upper angle abuts in the middle of the lambdoid suture upon the posterior end of the sagittal suture. Its cerebral surface presents a cross-like figure, whose upper and lateral arms are formed by grooves, while the lower arm is formed by a ridge, the internal occipital crest, which passes toward the posterior border of the foramen magnum. The groove forming the upper arm of the cross is the lower portion of the sagittal sulcus, while the transverse grooves are the transverse sulci; the similarly named blood sinuses of the dura mater occupy these sulci. The central point of the cross-like figure is the internal occipital protuberance. The arms of the cross-like figure separate two shallow superior occipital fossae from one another and from two deeper inferior occipital fossae.
The outer surface of the squamous portion of the occipital is divided into two parts by the superior nuchal lines, which pass laterally from the external occipital protuberance. The upper, triangular, relatively smooth part is the occipital surface, the lower rough part the nuchal surface. Above the superior nuchal lines there are usually two arched supreme nuchal lines. From the external occipital protuberance the external occipital crest extends downwards toward the posterior border of the foramen magnum, and from about its middle the inferior nuchal lines curve outwards, parallel to the superior ones.
The sphenoid bone has an unpaired body (corpus), two great wings (alae magnae), two lesser wings (alae parvae) and two pterygoid processes.
The body (corpus) unites in later life by its posterior surface with the basilar portion of the occipital. It contains a cavity filled with air, the sphenoidal sinus, which is divided into two parts by a septum and communicates by two apertures with the posterior part of the nasal cavity. The septum shows itself on the anterior surface of the body as the sphenoidal crest. The anterior wall is formed by two thin bony plates, the sphenoidal conchae, which originally belong to and are often united with the ethmoid bone. The sphenoidal crest is continued upon the under surface of the body as the rostrum and serves for articulation with the wings of the vomer. The upper surface of the body is partly formed by the sella turcica, in front of which is a flat surface, which posteriorly bounds the sulcus chiasmatis of the sella turcica and anteriorly projects towards the lamina cribrosa as the ethmoidal spine. The posterior boundary of the sella turcica is the dorsum sellae with the two posterior clinoid processes at its outer ends; in front of it is the deepest part of the sella, the hypophyseal fossa, which is bounded in front by the tuberculum sellae (Fig. A48). In front of the tuberculum sellae there is a shallow, transverse groove, the sulcus chiasmatis. From the lateral parts of the tuberculum sellae the short middle clinoid processes project. At the sides of the hypophyseal fossa and on the root of the great wing there is a shallow, but broad, longitudinal groove, the carotid groove, for the internal carotid artery. It is bounded laterally by a small bony plate, the sphenoidal lingula (Fig. A48). The anterior part of the clivus, behind the dorsum sellae, belongs to the sphenoid bone (Fig. A48).
The lesser wings (alae parvae) are small horizontal plates of bone which arise from the lateral surfaces of the body of the sphenoid, each by two roots which enclose the optic foramen. Their anterior borders articulate with the orbital portion of the frontal bone in the spheno-frontal suture; their posterior sharper borders form a boundary for the anterior and middle cranial fossae and end medially, toward the sella turcica, in sharp hook-like points, the anterior clinoid processes. The lesser and greater wings are completely separated by the superior orbital fissures.
The great wing (ala magna) arises from the lateral surface of the body of the sphenoid. In its root there are three foramina, the foramen rotundum directed obliquely forward and leading into the pterygopalatine fossa, the elliptical foramen ovale also placed obliquely and the small, round foramen spinosum. The great wing has three principal surfaces, cerebral, temporal and orbital, and the following borders, a squamous border (margo squamosus) for the squamous portion of the temporal, a frontal border (margo frontalis) for the orbital portion of the frontal, a zygomatic border (margo zygomaticus) for the zygomatic and a parietal angle for the parietal. The lateral posterior process which bears the external opening of the foramen spinosum and is directed toward the under surface of the pyramid of the temporal bone is termed the spine of the sphenoid (spina angularis). The cerebral surface is concave and, in addition to the three foramina, shows digitate impressions. The orbital surface is almost flat and forms a part of the lateral wall of the orbit. A sharp orbital crest separates it from the small spheno-maxillary surface. Similarly the temporal surface is divided by the infratemporal crest into the upper temporal and the lower infratemporal surfaces, the latter, again, passing into the spheno-maxillary surface, there being frequently between the two a sphenomaxillary crest. The infratemporal surface bears the external openings of the foramen ovale and foramen spinosum, the spheno-maxillary surface that of the foramen rotundum.
The pterygoid processes extend almost vertically downwards, almost parallel with one another, from the under surface of the body of the sphenoid; they arise on each side by two roots which enclose between them the pterygoid(Vidian) canal, which is directed almost horizontally in the sagittal plane. It unites the foramen lacerum with the pterygo-palatine fossa. Below, the pterygoid processes divide into a smaller inner and a broader outer plate (lamina) separated in their upper part by a groove, the pterygoid fossa, in their lower part by a cleft, the pterygoid fissure, which is filled by the pyramidal process of the palatine bone. The inner plate has at its base an elongated shallow depression, the scaphoid fossa, and at its lower end and separated from it by a groove, the hamulus. A small process projecting toward the body of the sphenoid, the processus vaginalis, encloses the pharyngeal canal by uniting with a process of the palatine bone. From the scaphoid fossa a shallow groove, sulcus tubae auditivae extends toward the spinous process along the spheno-petrous suture. On the anterior surface of the pterygoid process is a groove, the pterygo-palatine groove, extending downwards from the anterior opening of the pterygoid canal. It forms with the corresponding grooves on the palatine bone and maxilla the pterygo-palatine canal.
The temporal bone has four parts:
These four parts group themselves around the external auditory opening, in such a way that the squamous part lies above it, the mastoid part behind, the tympanic part below and anterior, and the petrous part medial and anterior.
The squamous portion (squama temporalis) articulates by a strongly curved, irregular border with the great wing of the sphenoid (margo sphenoidalis) and with the parietal (margo parietalis), the margins of the temporal bone overlapping those of the other hones in a squamous suture. Except for a small lower portion the squama is vertical in position and has an outer temporal and inner cerebral surface, the latter having ridges and depressions for the convolutions of the cerebral hemispheres and also grooves for the middle meningeal artery. It is more or less separated from the petrous portion by a petro-squamosal fissure, which tends to become obliterated in the adult. The temporal surface is smooth and presents a shallow groove for the middle temporal artery, beginning just above the external auditory opening. In addition there arises from the temporal surface the long zygomatic process, which articulates with the temporal process of the zygomatic bone. The process arises by a root from the vertical portion of the squama and by a second root from the small, lower, horizontal portion. Between the two roots lies the articular cavity for the head of the mandible (fossa mandibularis), in front of which is an articular tubercle, also partly covered with cartilage. The zygomatic process is at first almost horizontal, but later twists so as to lie in the sagittal plane. From its posterior extremity the hinder part of the temporal line passes upwards and backwards to be continued upon the parietal bone. Above the external auditory opening there is usually a sharp projection, the suprameatal spine.
The mastoid portion has as its chief part the large mastoid process, which forms the whole outer surface of this portion of the bone; it articulates by the parietal notch with the mastoid angle of the parietal and by its occipital margin with the squamous portion of the occipital (occipito-mastoid suture). It possesses a concave inner (cerebral) surface and a strongly convex roughened outer surface. The latter forms the broad, conical mastoid process which contains cavities filled with air, the mastoid cells, which communicate with the tympanic cavity. It gives attachment to several muscles and towards its posterior border has a deep groove (mastoid incisure) for the Digastric. Near the occipito-mastoid suture is a shallow groove for the occipital artery and the external opening of the mastoid foramen.
The principal part of the temporal bone, the petrous portion, is also termed the pyramid and is a three-sided pyramidal structure lying almost horizontally. In the adult only its three surfaces can be seen, the base being almost covered by the tympanic portion of the bone; in the new-born child and even somewhat later it is visible on the outer surface of the bone (Fig. A64, A65). The schematic sections (Fig. A66 and A67) show the arrangement of the four surfaces as well as the formation of the tympanic cavity and its continuation as the Eustachian tube (musculo-tubar canal) through the petrous and tympanic portions.
In the description that follows the parts of the bony labyrinth lying within the pyramid are not considered, nor is the tympanic cavity fully described. These parts will be described later (see here).
Two surfaces of the petrous portion, the anterior and the posterior, look toward the skull cavity; the third, inferior, is at the base of the skull, while the base (not labelled) forms the medial wall of the tympanic cavity. The three surface are separated by angles; the superior angle separates the anterior and posterior surfaces, the anterior separates the anterior and inferior and the posterior the posterior and inferior surfaces. The axis of the pyramid is oblique to the long axis of the skull passing from behind and lateral, anteriorly and medially. The apex of the pyramid lies at the foramen lacerum.
The anterior surface forms a portion of the middle fossa of the skull. It is separated by the petrosquamous fissure from the squamous portion of the bone, and bears a slight transverse elevation, the arcuate eminence, which is formed by the underlying semicircular canal.
Further towards the median line is a slit-like opening the hiatus of the facial canal, with a groove for the great superficial petrosal nerve extending toward the foramen lacerum.
Lateral and anterior to this is a second opening, the aperture of the superior tympanic canaliculus, with a similarly directed groove for the lesser superficial petrosal nerve. The part of the anterior surface of the pyramid that lies between the petro-squamous fissure and the arcuate eminence forms the roof of the tympanic cavity, the tegmen tympani. Near the apex of the pyramid is a very shallow trigeminal impression (see Fig. A48). The superior angle bears the superior petrosal groove and the anterior angle bounds the spheno-petrous fissure and the foramen lacerum. The posterior surface of the pyramid forms a part of the posterior cranial fossa. It presents a roundish opening, the internal auditory opening (porus acusticus internus), which leads into a canal, the meatus acusticus internus, running obliquely into the bone. Above this opening, immediately below the superior angle, is small depression, the subarcuate fossa, and lateral to the auditory opening there is a fissure-like opening, the external opening of the aquaeductus vestibuli, which lodges a portion of the internal ear. A shallow groove, the inferior petrosal sulcus, runs parallel to the posterior angle, being a continuation of the similarly named groove on the occipital bone. The apex of the pyramid has an opening with an irregular boundary, the internal carotid foramen (see below). Beside it, near the anterior angle of the pyramid, is the opening of a large canal, the Eustachian canal (canalis musculo-tubarius), which leads into the tympanic cavity.
The posterior angle is separated from the occipital bone by- the petro-occipital fissure and bears a shallow jugular notch, which, with the corresponding notch on the occipital forms the jugular foramen (see Fig. A48).
The inferior surface of the pyramid presents the stylomastoid foramen at the base of the mastoid process; it is the outer opening of the facial canal. In front of it lies the slender, often very long styloid process, whose base is partly ensheathed by a plate-like projection of the tympanic portion, the vaginal process. Close to the styloid process is a broad, elongated groove, the jugular fossa, which abuts medially upon the jugular notch and receives the bulb of the jugular vein. In the floor of the groove is the small sulcus of the mastoid canaliculus. On the posterior margin close to the jugular fossa is a small opening, the external aperture of the cochlear canaliculus; in front of this is the large round external carotid foramen and between this and the jugular fossa is a small depression, the petrous fossula, from which a small canal, the tympanic canaliculus, passes through the floor of the tympanic cavity.
The base of the petrous portion forms the medial wall of the tympanic cavity. In the adult it is covered in by the tympanic portion of the bone, so that only a small strip of it is visible at the surface along the petro-tympanic fissure.
The tympanic cavity is an air-containing cavity lying between the petrous and the tympanic portions. The external auditory meatus leads into it from without; its roof is formed by a thin part of the petrous portion, the tegmen tympani, while its floor is formed partly by the petrous and partly by the tympanic portion. Anteriorly and medially the cavity is continued into the canal for the Eustachian tube (canalis musculo-tubarius) and posteriorly and laterally it has opening into it the antrum and the mastoid cells. It contains the three small auditory ossicles, which together with the walls of the cavity will be described in connection with the auditory organ (see here).
The tympanic portion of the temporal bone is a small trough-shaped plate of bone which forms the sides and floor of the external auditory meatus and the lateral wall of the tympanic cavity. It is separated from the petrous and squamous portions by the petro-tympanic fissure (fissure of Glaser), from the mastoid portion by the tympano-mastoid fissure and it forms the vagina of the styloid process.
The temporal bone of the new-born child differs markedly from that of the adult in that the tympanic portion has the form of a ring that is open above, and there is practically no mastoid process. The squamoso-mastoid suture is still quite distinct, separating the squamous portion from the mastoid and petrous portions, which form a single mass. In the course of the first year the tympanic ring becomes the trough-like structure, which at first has in its floor a constant foramen.
The facial canal, mainly for the facial nerve, begins at the bottom of the internal auditory meatus and runs at first horizontally and almost transversely to the axis of the petrous portion to the hiatus of the facial canal. There it bends at a right angle and runs in the medial wall of the tympanic cavity, again almost horizontally, but in the line of the axis of the pyramid, until it reaches the pyramidal eminence of the tympanic antrum (see here). Here it bends to assume a vertical direction and opens by the stylomastoid foramen. From the lower portion of the canal the canaliculus for the chorda, tympani leads to the tympanic cavity.
The carotid canal is a short, but wide canal, situated near the apex of the pyramid. It begins at the external carotid foramen and runs at first vertically, but later bends almost at a right angle so as to run horizontally, and ends at the internal carotid foramen. Small canals, the carotico-tympanic canaliculi, lead from it into the tympanic cavity.
The canal for the Eustachian tube (canalis musculo-tubarius) runs parallel with and immediately adjacent to the horizontal portion of the carotid canal, almost in the axis of the pyramid. It begins as a notch on the anterior angle of the pyramid, between that part of the bone and the squamous portion, and ends on the anterior wall of the tympanic cavity of which it seems to be a direct prolongation. An incomplete horizontal septum divides it into an upper canal for the Tensor tympani and a lower one for the Eustachian tube (tuba auditiva).
The tympanic canaliculus leads from the petrous fossula into the tympanic cavity, where it becomes the sulcus promontorii, and then leaves the cavity by its upper wall to open by the superior aperture of the tympanic canaliculus on the anterior surface of the pyramid.
The very narrow mastoid canaliculus begins as a groove in the jugular fossa, passes through the lower portion of the facial canal and opens in the tympano-mastoid fissure.
The parietal bone is large quadrangular flat bone, convex on its outer surface and concave on its inner. The four borders are
The four angles of the bone are the frontal situated at the junction of the sagittal and coronal sutures, the occipital at the junction of the sagittal and lambdoid sutures, the mastoid at the parieto-mastoid suture, where it occupies the parietal notch of the temporal bone, and the sphenoidal which articulates in the spheno-parietal suture with the great wing of the sphenoid. This last angle is the sharpest.
The outer convex surface presents at the region of greatest curvature the tuberosity and also stronger superior and weaker inferior temporal lines, both of which have an arched course. Below the latter line the parietal forms a part of the temporal surface (see Fig. A44, A45). In this region the squamosal border is rough, being overlapped by the squamous portion of the temporal bone. Near the posterior end of the sagittal border and close to the sagittal suture is the parietal foramen.
The inner (cerebral) surface shows well marked arterial grooves, especially on the anterior part of the bone, produced by the branches of the middle meningeal artery. At the sagittal border there is the one half of the sagittal sulcus and at the mastoid angle one sees a short portion of the sigmoid sulcus. Not infrequently the cerebral surface presents digitate impressions and juga cerebralia and frequently also Pacchionian depressions (foveolae granulares) which may be of considerable depth, especially in middle and old age.
The frontal bone consists of two unpaired portions, the frontal plate and the nasal portion, while the orbital portions are paired.
The frontal plate forms the principal part of the bone. It articulates by its parietal border with both parietals in the coronal suture and by its sphenoid border with the great wing of the sphenoid in the spheno-frontal suture. The outer surface is strongly convex and presents at the middle of each half the tuber frontale. Above the margins of the orbits are two arched projections, the supraciliary arches, and between these the somewhat depressed glabella. The upper border of the orbit separates the frontal plate from the orbital portion. Its lateral part is formed by the zygomatic process which unites with the fronto-sphenoidal process of the zygomatic bone in the zygomatico-frontal suture. From the zygomatic process the temporal line takes origin and separates from the frontal surface a small almost vertical portion, the temporal surface. In the inner half of the supraorbital border are two notches, the medial frontal notch and the lateral supraorbital notch, this latter being frequently converted into a foramen, the supraorbital foramen.
The cerebral surface of the frontal plate possesses in its lower portion a median ridge, the frontal crest. This begins below at a foramen, the foramen caecum, bounded by the frontal arid ethmoid bones in common, and running upwards into the sagittal sulcus. The surface is smooth, except. for some digitate impressions and juga cerebralia, as well as Pacchionian depressions (foveolae granulares). It passes over without sharp demarcation into the cerebral surface of the orbital portion.
The orbital portions are separated from one another by a deep ethmoidal notch which receives the lamina cribrosa of the ethmoid. Each possesses an upper cerebral and a lower orbital surface. The former shows very abundant digitate impressions; the latter is concave and forms the roof of the orbital cavity. It presents on its medial portion a small depression, the fovea trochlearis (occasionally also a trochlear spine), and on its lateral part a shallow depression, the lacrimal fossa, for the lacrimal gland. The borders of the ethmoidal notch are broad and rough since they bear the ethmoidal foveolae, which complete the ethmoidal cells. Furthermore they bear an anterior and posterior groove (or short canal), which serve to form the anterior and posterior ethmoidal foramina.
The nasal portion of the frontal is the small, median part that unites the two supraorbital margins. It has an irregular, rough surface, for articulation with the nasal bones and the frontal processes of the maxilla and, in addition, the frontal spine, directed downwards and serving for the fixation of the bones that form the skeleton of the nose. Near the spine lie the openings of the frontal sinus, which is divided into two parts by a septum. Above the spine on the outer surface of the bone is a smooth flattened area, the glabella.
The ethmoid is an irregular, cubical bone in which a middle unpaired and two lateral paired portions may be distinguished. The middle portion consists of a horizontal plate, the lamina cribrosa, and a vertical plate, the lamina perpendicularis. The paired lateral portions are attached to the lateral edges of the lamina cribrosa and are known as the ethmoidal labyrinths.
The lamina cribrosa occupies the ethmoidal notch of the frontal bone and is a rectangular plate situated between the nasal and cranial cavities. It is perforated by a number of roundish foramina, through which the branches of the olfactory nerve pass to the nasal cavity. At its middle it bears a -thick ridge, high in front and diminishing posteriorly, the crista galli. In front of this are two small processes of the lamina cribrosa, the alar processes, which usually assist in the boundary of the foramen caecum.
The lamina perpendicularis is a thin pentagonal plate which forms the upper anterior part of the nasal septum. It is attached by its anterior, upper border to the frontal spine of the frontal, by its upper border it is fused with the lamina cribrosa, by its posterior border it articulates with the sphenoidal crest, by its lower border with the upper border of the vomer and by its anterior lower border with the cartilaginous nasal septum (see also Fig. A82).
The ethmoidal labyrinth hangs almost vertically downwards from the lateral border of the lamina cribrosa. It contains numerous, air-containing, imperfectly separated spaces, the ethmoidal cells, which in part are completely in the ethmoid itself, but for the most part are also bounded by other bones, the maxilla, lacrimal, frontal, sphenoid and palatine. The lateral wall of the labyrinth, by its thin lamina papyracea, forms a part of the medial orbital wall. Upon it or in the suture between it and the orbital portion of the frontal lie the anterior and posterior ethmoidal foramina.
The medial wall of the ethmoidal labyrinth forms the greater part of the lateral wall of the nasal cavity. It possesses two parallel projections, having the form of thin plates, curved upon themselves at their lower border, the nasal conchae. The superior concha is markedly smaller and shorter than the middle (see here). The latter projects beyond the labyrinth both anteriorly and posteriorly and is attached by its ends to the ethmoidal crests of the maxilla and palatine bones. It sends downwards a hook shaped processus uncinatus, which partly covers the opening of the maxillary sinus (see here and Fig. A88).
The vomer is a flat, quadrangular bone which forms the lower and posterior portion of the nasal septum. Its upper end is thickened and cleft into two alae, which enclose the rostrum of the sphenoid. The small anterior border articulates with the cartilaginous part of the nasal septum, the upper border with the lower border of the lamina perpendicularis of the ethmoid, the lower border with the nasal crest of the maxilla and palatine and the posterior border forms the septum of the choanae.
The maxilla is a paired bone which takes part in the boundaries of the orbital, nasal and oral cavities. In it may be distinguished the body (corpus) and four processes. The body is irregularly cubical and encloses a large air-containing cavity, the maxillary antrum or sinus, which communicates by a wide opening with the nasal cavity. The body has four surfaces. The anterior is the facial surface and is convex; its upper infraorbital border forms part of the lower border of the orbit, below which is the infraorbital foramen, the opening of the infraorbital canal, and below this a shallow depression, the canine fossa. The orbital surface is triangular and forms the greater part of the floor of the orbit, bounding the inferior orbital fissure medially. It possesses a groove, the infraorbital groove, which gradually becomes converted into a canal. The lacrimal notch near the root of the frontal process, receives the hamulus of the lacrimal bone. The infratemporal surface is the posterior surface and forms the boundaries of the infratemporal and pterygopalatine fossae. The swollen end of this portion of the bone is termed the tuberosity; it presents several small alveolar foramina and also a pterygo-palatine groove, which completes the canal of the same name (see here).
The nasal surface forms the lower part of the lateral wall of the nasal cavity, but in its posterior portion it is covered in by the posterior part of the perpendicular portion of the palatine bone. It presents the wide irregular opening of the maxillary sinus, in front of which is a broad groove, the lacrimal groove (see below), and at the junction of the nasal surface with the frontal process the horizontal conchal crest (see below).
The frontal process of the maxilla is directed upwards and articulates by its upper border with the nasal portion of the frontal bone in the fronto-maxillary suture, by its lacrimal border with the lacrimal bone and by its medial border with the nasal bone.
It presents an outer and inner surface; the latter forms part of the lateral wall of the nasal cavity and bears an ethmoidal crest for articulation with the anterior part of the middle concha and below this a conchal crest for the inferior concha. Behind the process is the broad lacrimal groove, which, with a similar groove on the lacrimal bone forms the fossa for the lacrimal sac. The anterior wall of the groove is termed the anterior lacrimal crest. The zygomatic process is a broad, short, triangular process, projecting laterally to articulate with the zygomatic bone in the zygomatico-maxillary suture. The alveolar process is convex externally and concave on its inner surface, passing without distinct demarcation into the body on the one side and the palatine process on the other. The processes of the two maxillae meet in the intermaxillary suture, which ends anteriorly in the anterior nasal spine. The alveolar process forms the lateral and lower boundary of the piriform aperture. Its lower border is the alveolar border (limbus alveolaris) and bears the sockets for eight teeth, separated by interalveolar septa. The anterior surface of the process usually shows juga alveolaria, corresponding to the roots of the anterior teeth. The palatine process forms the greater portion of the hard palate and projects medially from the inner surface of the body. It is rough and uneven on its oral surface, smooth and concave on its nasal surface. The two processes unite by thickened borders to form the anterior part of the median palatine suture, which, on the nasal surface, forms the nasal crest. Anteriorly in the line of the suture is the incisive canal, which begins in an incisive notch on each maxilla and terminates on the nasal surface in two incisive foramina one on either side of the nasal crest.
The lacrimal bone is a very thin, flat, quadrangular bone that lies in the medial wall of the orbit between the frontal process of the maxilla and the lamina papyracea of the ethmoid. It presents orbital and ethmoidal surfaces. The latter closes certain of the ethmoidal cells and articulates on the lateral wall of the nasal cavity with the lacrimal process of the inferior concha. The former presents anteriorly the lacrimal groove, which is bounded posteriorly by the posterior lacrimal crest. This ridge runs downwards and terminates in a hook-like process, the hamulus, which fits into the lacrimal notch of the maxilla. Behind the ridge the orbital surface of the lacrimal forms a part of the medial wall of the orbit.
The inferior concha is a small, thin, porous bone whose free medial border is curled on itself, while the lateral border is attached to the conchal crests of the maxilla and palatine bone. It has three processes; the maxillary process extends downwards and laterally to the maxilla and closes a considerable portion of the opening of the maxillary sinus; the lacrimal process ascends to the lacrimal bone and forms a part of the posterior wall of the nasolacrimal canal; the ethmoidal process articulates with the uncinate process of the ethmoid, anterior to the opening of the maxillary sinus.
The palatine bone is a flat bone formed of two plates arranged at right angles to one another; one is the horizontal portion and the other the perpendicular portion. The horizontal portions of the two bones form the posterior part of the hard palate and resemble in every particular the palatine processes of the maxilla, from which they are separated by the transverse palatine suture. At the hinder end of the median palatine suture they form the posterior nasal spine and enclose on each side the greater palatine foramen, the inferior opening of the pterygopalatine canal.
The perpendicular portion is narrower, but longer than the horizontal. Its maxillary surface overlies the posterior part of the nasal surface of the maxilla, while its nasal surface forms a part of the lateral wall of the nasal cavity. It bears two parallel, horizontal ridges, a lower stronger conchal crest for the inferior and an upper ethmoidal crest for the middle concha. Posteriorly it articulates with the pterygoid process of the sphenoid, its posterior border showing a furrow, the pterygo-palatine groove, which, with corresponding grooves on the pterygoid process and maxilla, forms the pterygo-palatine canal.
Three processes of the palatine bone are recognized. The pyramidal process is directed backwards and is short and broad. It fits into the pterygoid notch of the pterygoid process, completing the pterygoid fossa. It usually presents the posterior openings of the lesser palatine foramina. The orbital and sphenoidal processes arise from the upper border of the perpendicular portion and are separated by the spheno-palatine notch. The larger orbital process looks laterally and anteriorly, forms a small part of the floor of the orbit and articulates with the lamina papyracea of the ethmoid in the palato-ethmoidal suture and with the maxilla in the palato-maxillary suture, closing along these sutures the adjacent ethmoidal cells. The sphenoidal process is directed medially and posteriorly and articulates with the under surface of the body of the sphenoid. In addition the perpendicular portion gives origin at its base to a variable, but constant, process, the maxillary process. It is crescentic in shape and closes in, according to its size, a greater or less portion of the opening of the maxillary sinus, coming into relation with the maxillary process of the inferior concha (Fig. A90).
The nasal bones form a part of the bony arch of the nose. They are small, flat, oblong bones, separated from each other by the internasal suture. They have a shorter medial and a longer lateral border, the latter articulating with the frontal process of the maxilla in the naso-maxillary suture. The upper and lower borders are irregular; the former articulates with the nasal portion of the frontal, the latter with the nasal cartilage. The posterior surface presents an ethmoidal groove, from which one or several nasal foramina pass to the outer surface of the bone.
The zygomatic (malar) bone is a rather thick triangular bone. Of its three surfaces the malar forms part of the face and is convex; it passes over into the zygomatic process of the maxilla and presents a zygomatico- facial foramen. The orbital surface is slightly concave and forms part of the lateral wall of the orbit; in half the cases it is a boundary of the anterior part of the inferior orbital fissure and presents one or two zygomatico-orbital foramina. The temporal surface is concave and presents the zygomatico-temporal foramen.
The bone has two processes. The temporal process projects horizontally backwards and articulates with the zygomatic process of the temporal to form the zygomatic arch (zygoma). The fronto-sphenoidal process- is directed upwards to form part of the lateral wall of the orbit and articulates with the zygomatic process of the frontal and with the zygomatic border of the great wing of the sphenoid.
In the mandible there may be recognized a body (corpus) and two rami. The body is a thick curved plate from the posterior part of which the rami extend upwards almost at right angles.
The lower part of the mandible is termed the base and the tooth-bearing part the alveolar portion. The free border of the latter is termed the limbus alveolaris and bears the dental alveoli, separated from one another by interalveolar septa; it also presents juga alveolaria corresponding to the roots of the teeth. The outer surface of the body has in the middle line a roughened flat ridge, the mandibular protuberance, and lateral to this on the base on each side is a mental tubercle and further laterally the mental foramen, the anterior opening of the mandibular canal which traverses the bone. In addition there passes downwards upon the body from the anterior border of the ramus a smooth ridge which gradually diminishes in height and is termed the oblique line.
The inner surface of the body shows close to the middle line on each side a shallow digastric fossa, and between the two fossae and somewhat higher a sharp prominence, often doubled, the mental spine. Lateral to this is a distinct depression, the sublingual fovea for the sublingual gland and more laterally a much shallower, frequently indistinct, depression, the submaxillary fovea for the submaxillary gland. A rough line, beginning on the inner surface of each ramus, runs downwards and forwards upon the body, gradually becoming less distinct; it is the mylohyoid line and below it is a groove which extends downwards and forwards from the mandibular foramen, the mylohyoid groove.
Each ramus presents a medial surface, turned towards the oral cavity, and a lateral surface. Its lower posterior angle is termed the angle of the mandible. At about the middle of the medial surface is the mandibular foramen, which has a somewhat oblique position and opens into the mandibular canal; its inner border is raised into a projecting spine, the lingula. Above, each ramus divides into two processes separated by the mandibular notch. The anterior is the coronoid process, which is transversely flattened and sharp at its extremity; from its base a ridge, the bucinator ridge, extends to the neighbourhood of the last molar tooth. The posterior process is the condyloid process.
On the lateral surface of the angle of the mandible is the masseteric tuberosity and opposite it, on the medial surface, the pterygoid tuberosity for the attachment of similarly named muscles.
The condyloid process, situated posterior to the mandibular notch, bears at its upper end a head (capitulum) with an articular surface for the mandibular fossa of the temporal bone. It has the shape of an almost transversely directed cylinder. The constriction below the head is termed the neck (collum) and a depression on the anterior surface of this is termed the pterygoid fovea.
The shape of the mandible depends largely upon the age of the individual, since it is determined to a great extent by the action of the muscles of mastication and by the presence or absence of teeth. Just as the alveolar portion developes with the eruption of the teeth and degenerates with their loss, so too the muscles of mastication modify the form of the mandible. In the new-born child the ramus joins the body at an oblique angle (see Fig. A111, which only later gradually becomes a right angle.
The mandible is the only bone of the skull that articulates with other skull bones in a moveable joint, the only bone (except the hyoid) that can be readily separated from the others, which are more or less firmly united by sutures.
The orbit is a paired cavity having the form of a four-sided pyramid placed horizontally; its apex is formed by the optic foramen and its base is surrounded by the margins of the orbit, the supraorbital and infraorbital. The four sides of the pyramid form the orbital walls, one of which is superior, one medial, one inferior and one lateral. Seven bones enter into the boundaries of the orbit, the frontal, sphenoid, ethmoid, lacrimal, maxilla, zygomatic and palatine.
The superior wall is horizontal and slightly concave. It is formed partly by the orbital portion of the frontal and to a lesser extent posteriorly by the lesser wing of the sphenoid.
The medial wall is almost sagittal an~ is mainly formed by the lamina papyracea of the ethmoid and, in front of this, by the lacrimal. The fronto-ethmoidal and fronto-lacrimal sutures form the boundary between this and the upper wall. In addition the maxilla takes part in the formation of the medial wall, firstly, by the orbital surface of its body below the lamina papyracea (see below) and, secondly, by its frontal process, which forms a narrow strip of the medial wall adjacent to the lacrimal bone.
The inferior wall passes without any boundary into the medial, but in the posterior two-thirds of the orbit and towards the lateral wall it is bounded laterally by the inferior orbital fissure. It is almost horizontal in position and is formed principally by the orbital surface of the maxilla and, to a small extent posteriorly, by the orbital process of the palatine.
The lateral wall is slightly concave and almost sagittal in position. It is more definitely bounded than the other walls in that in the whole of the hinder part of the orbit it is separated from adjacent walls by fissures. Between it and the upper wall is the superior orbital fissure and between it and the lower wall is the inferior orbital fissure. In its anterior part it is formed by the orbital surface of the zygomatic, in the posterior part by the orbital surface of the great wing of the sphenoid, the spheno-zygomatic suture separating these two surfaces.
The supraorbital margin is formed by the frontal bone, the infraorbital margin by the maxilla and zygomatic. The less sharply defined medial border is formed by the frontal process of the maxilla (anterior lacrimal crest) and the lateral border by the zygomatic.
The foramina and fissures in the orbit are:
In addition in the orbit, on the frontal bone, is the trochlear fossa (sometimes a spine) and the fossa for the lacrimal gland; in the region of the frontal process of the maxilla and the lacrimal bone, the fossa for the lacrimal sac, bounded by the anterior and posterior lacrimal crests; the infraorbital groove on the orbital surface of the maxilla; and the spine for the rectus lateralis on the great wing of the sphenoid.
The hard palate forms the roof of the mouth cavity. It is an elongated, semi-elliptical, strongly concave plate of bone, in whose formation the palatine processes of the maxillae and the horizontal portions of the palatines and partly also their pyramidal processes participate. It shows a median palatine suture, a transverse palatine suture and traces of an incisive suture. Anteriorly towards the front end of the median suture is the unpaired incisive foramen, by which the bony oral cavity communicates with both nasal cavities. Posteriorly in the horizontal portion of the palatine bone there is, on either side, the greater palatine foramen and in each pyramidal process the lesser palatine foramen. These paired foramina are the openings of the pterygo-palatine canal.
The bony nasal cavity is unpaired, but is divided into two symmetrical cavities by a median partition, the nasal septum, which is often oblique or not quite in the median line. Nine bones take part in the formation of the cavity; the nasal, frontal, ethmoid, sphenoid, maxilla, palatine, inferior concha, vomer and lacrimal. Its anterior opening is the piriform aperture, its posterior the choanae. The former is bounded by the nasal bones, the frontal processes and bodies of the maxilla; the choanae by the palatine bones, the medial plates of the pterygoid processes and the body of the sphenoid. The roof of the cavity is formed anteriorly by the two nasal bones and the nasal portions of the frontals, in the middle by the lamina cribrosa of the ethmoid and, posteriorly, by the body of the sphenoid. Its floor is the upper surface of the hard palate and is formed by the palatine processes of the maxillae and the horizontal portions of the palatine bones.
The nasal septum forms the medial wall for each nasal cavity and is itself formed by the lamina perpendicularis of the ethmoid anteriorly, and posteriorly and below by the vomer (see Fig. A82); the remaining portion is cartilaginous (see here).
The lateral wall of each cavity bears three nasal conchae. The lowest is a distinct bone, the inferior nasal concha, and is the largest and longest of the three, the uppermost being the smallest and shortest. The middle and upper conchae are projections of the ethmoid bone. By these three conchae the lateral portion of each cavity is divided into three passages (meatus); the superior meatus is between the superior and middle concha, the middle meatus between the middle and inferior and the inferior meatus between the inferior concha and the floor of the cavity. Above the superior concha, between it and the roof of the nasal cavity, there is a pocket-like depression, the spheno-ethmoidal recess. The part of the cavity medial to the conchae, between their medial edges and the septum, is termed the common meatus, the part behind the posterior ends of the concha the nasopharyngeal meatus. The following bones take part in the formation of the lateral wall; the ethmoid above and behind, the nasal surface of the frontal process of the maxilla above and in front, the body of the same bone below and in front, the perpendicular portion of the palatine behind and the medial surface of the lacrimal, which forms a small part in the anterior portion of the middle meatus. In addition to the principal nasal cavities there is a number of accessory cavities, which are air-containing, in most of the skull bones and especially those of the maxilla, the frontal, the sphenoid and the ethmoid (see here). The openings into the nasal cavities are also numerous and are:
The small pterygo-palatine fossa is situated between the anterior surface of the pterygoid process of the sphenoid, the perpendicular part of the palatine and the posterior end of the maxilla. It is funnel-shaped and passes below, without any demarcation, into the pterygoid canal, bounded by the same three bones. Above it opens into the inferior orbital fissure and laterally by the pterygo-maxillary fissure into the infratemporal fossa. Into it there are three openings; the foramen rotundum leading from the skull cavity, the opening of the horizontal pterygoid canal, which passes backward in the root of the pterygoid process to the foramen lacerum, and the spheno-palatine foramen leading into the nasal cavity.
The Hyoid Bone. The skull of the new-born child differs in many points from that of the adult. Instead of meeting in sutures the bones of the vault of the skull are connected by membrane, which in several places forms fontanelles (fonticuli). There are of these two unpaired and two paired. The frontal or great fontanelle (fonticulus frontalis) is rhomboidal in shape and lies at the meeting of the frontal, coronal and sagittal sutures, that is to say, between the two halves of the frontal bone, separated by a frontal suture, and the two parietals. The occipital or lesser fontanelle (fonticulus occipitalis) is triangular and lies at the hinder end of the sagittal suture, between the two parietal bones and the occipital. The sphenoidal fontanelles (fonticuli sphenoidales) are irregularly quadrangular and lie on each side between the sphenoidal angle of the parietal bone and the parietal angle of the great wing of the sphenoid, where later is the spheno-parietal suture. The mastoid fontanelles (fonticuli mastoidei) are, like the sphenoidal, of irregular shape and lie on either side between the mastoid angle of the parietal and the mastoid portion of the temporal, where later is the parieto-mastoid suture.
The squamous portion of the occipital shows a sutura mendosa, and the bone is represented by four distinct portions, the squamous, two lateral and basilar portions, separated by anterior and posterior intraoccipital synchondroses. In the temporal bone in place of the tympanic portion there is the anulus tympanicus (see here); the mastoid process is completely absent and the squamoso-mastoid suture separates the squamous portion from the pyramid, i.e. from the petrous portion and the mastoid. On the parietal the tuberosity is very distinct, as is also that of the frontal bone, which is still in two portions separated by the frontal suture. Between the sphenoid and the occipital there is a sphenooccipital synchondrosis and in the body of the sphenoid an intrasphenoidal synchondrosis.
The maxilla and mandible are low, the alveolar portions being quite wanting. The incisive suture is quite distinct on the hard palate. Between the two halves of the mandible the remains of a suture are visible; the rami are almost in the same line as the body, i. e. they form with it a very obtuse angle.
The hyoid bone is a small, flat bone situated at the base of the tongue. Although it has no direct connection with the skull and is situated in the neck below the mandible, it is usually described as a cranial bone. It presents a body (corpus), convex in front and concave behind, and two pairs of cornua. The greater cornua are long and thin and enlarged into a knob at their ends; they arise from the sides of the body and are directed upwards and backwards. The lesser cornua often remain cartilaginous, and are much smaller than the greater ones; they arise near the base of the greater ones and are directed posteriorly laterally and upwards.
The girdle of the upper extremity is formed of two bones, the scapula and the clavicle.
The scapula is a typical flat bone of triangular shape. Its anterior surface, turned toward the ribs, is termed the costal surface, its posterior surface, the dorsal surface. Its three angles are termed medial, inferior and lateral and its three borders, the superior, vertebral or medial and axillary or lateral.
The costal surface is smooth except for some transverse lines, lineae musculares, for the attachment of the subscapular muscle, and it is slightly concave, forming the subscapular fossa for the muscle of that name.
The dorsal surface is divided into two areas by a strong, roughened ridge the spine; the upper smaller area is the supraspinous fossa and the lower larger one the infraspinous fossa, which lodge muscles of the same names. The spine of the scapula is flat at the vertebral border, but becomes higher as it passes transversely across the dorsal surface, and at the neck of the bone it is prolonged into a flattened process, projecting over the lateral angle and termed the acromion. It presents a small surface for articulation with the clavicle (facies articularis).
The vertebral border is usually slightly and obtusely angled at the base of the spine; the axillary border is thick and rough for the attachment of muscles. The superior border presents a notch in the neighborhood of the lateral angle, the scapular notch, and between the notch and the lateral angle it gives rise to a strong hook-shaped coracoid process. This arises by a broad base and is at first directed upwards, but then bends forward and laterally.
The lateral angle bears the pear-shaped, slightly concave glenoid cavity for the reception of the head of the humerus. Both above and below it is a roughened area, the supraglenoid and infraglenoid tuberosities, which, give origin respectively to the tendons of the long heads of the biceps and triceps. The constriction of the scapula medial to the borders of the glenoid cavity is called the neck (collum) and in this region the supraspinous and infraspinous fossae become continuous. The medial angle is a right angle, the inferior one is more acute, but strongly rounded.
The clavicle is an S-shaped, long bone in which a middle portion, the body (corpus), and two extremities may be recognized; of the latter the medial is termed the sternal and the lateral the acromial extremity after the bones with which they articulate. The bone is convex anteriorly at its sternal extremity and concave anteriorly at its acromial extremity. The sternal end is thick and almost triangular-prismatic; the acromial end on the contrary is flattened.
At the sternal end there is a triangular sternal articular surface, which forms part of the sterno-clavicular articulation. Lateral from this on the anterior, lower border is a roughened area, the costal tuberosity, for the attachment of the costo-clavicular ligament. The body of the bone, like the sternal extremity, is almost triangular, but with strongly rounded angles.
The flattened acromial extremity at its boundary with the body and at its posterior and lower border bears a roughened area, the coracoid tuberosity, for the attachment of the coraco-clavicular ligament and, at its very end, an acromial articular surface for articulation with the acromion.
The humerus is a typical long bone, in which may be distinguished a long shaft or body (corpus) and two thickened extremities, superior and inferior. The superior extremity bears an articular head (caput), placed at an angle with the body and directed medially, It is almost hemispherical and is separated from the shaft of the bone by a shallow, circular groove, the anatomical neck (collum anatomicum). In addition to the head, the upper extremity bears two roughened elevations for muscular attachment; a larger one, the greater tubercle directed laterally, and a smaller one, the lesser tubercle, directed medially and anteriorly. Between the two is a distinct intertubercular groove. At the junction of the upper extremity with the body below the tubercles, there is a distinct diminution in the diameter of the bone, termed the surgical neck (collum chirurgicum).
The upper end of the shaft is almost cylindrical, but below the middle it becomes somewhat triangular and, at the same time, flattened. From each tubercle a ridge (crista) passes downwards, continuing the intertubercular groove for some distance. Below the greater tubercular crest there is a large, flat, roughened area; the deltoid tuberosity, for the attachment of the deltoid muscle; it is on the lateral, posterior part of the bone, which, at this level, is still cylindrical. At about the middle of the shaft on its medial surface there is a roughened area, not always distinct, for the attachment of the coraco-brachialis muscle and near this is a frequently large nutritive foramen.
From the middle of its length downwards the shaft of the humerus presents three surfaces, posterior, anterior medial, and anterior lateral. The two anterior surfaces are separated by a low elevation, but at the lateral angles there are sharp borders, medial and lateral. The lateral border begins below the deltoid tuberosity, being separated from it by a shallow groove, the groove for the radial nerve (musculo-spiral groove). This contains the radial (musculospiral) nerve and winds around the middle portion of the shaft in an open spiral, passing from above and medially, downwards and laterally and gradually flattening out. Its borders serve for the attachment of two heads of the triceps muscle. Towards the inferior extremity the humerus becomes markedly flattened and at the same time broader. The two borders are continued into two rough muscle projections, the medial border into the strongly projecting medial epicondyle and the sharper lateral border into the smaller lateral epicondyle. The former has on its posterior surface a shallow groove for the ulnar nerve, which is bounded laterally by the border of the trochlea.
Below the epicondyles is the lower articular head of the humerus, for the bones of the forearm. There is a separate surface for each of these, the large trochlea, hour-glass shaped, on the medial side for the ulna and the smaller, hemispherical capitulum laterally, for the radius. Above the trochlea on the medial anterior surface there is at the level of the epicondyle a rather deep depression, the coronoid fossa, and above the capitulum at the lower part of the lateral anterior surface there is a much smaller and shallower one for the head of the radius. Opposite these two fossae there is on the lower part of the posterior surface a broad and deep olecranal fossa.
The ulna is a distinctly triangular-prismatic long bone, thick above and much thinner below. It presents a superior extremity, a body or shaft (corpus) and an inferior extremity. The stout superior extremity carries the semilunar notch with the constricted, or even divided, articular surface for the trochlea of the humerus. Its anterior portion lies on the upper surface of the coronoid process, a broad, beak-like projection, while its posterior portion is on the anterior surface of a very strong, upwardly projecting process, the olecranon. On its lateral side the upper extremity has a notch lined with cartilage, the radial notch for the reception of the head of the radius. From it a rough ridge extends downwards on the upper part of the dorsal surface, the supinator crest, for the muscle Immediately below the coronoid process is a broad rough area, the ulnar tuberosity.
The shaft (corpus) of the bone is much thicker above than below, and at the same time becomes rounded below, the upper distinctly triangular portion becoming cylindrical in the lower fourth. An anterior or volar, a posterior or dorsal and a medial or ulnar surface may be recognized. The dorsal border separates the dorsal and medial surfaces and the volar border the volar and medial surfaces. The third border, turned toward the radius, is sharp; it separates the volar and dorsal surfaces and is termed the interosseous crest. The volar surface bears the nutrient foramen, otherwise the surfaces present no special markings.
The distal end of the bone, the inferior extremity, is the capitulum; it is rounded and covered by cartilage. On the radial side there is also an articular surface for the radius, the articular circumference, as well as a sharp process, projecting distally beyond the capitulum on the medial side, the styloid process.
The radius is the more lateral of the two bones of the forearm. In contrast to the ulna it is small above and broad and thick below.
The superior extremity is formed by the disk-shaped capitulum and a distinct circular constriction below this is termed the neck (collum). In its upper part the bone is almost cylindrical. The capitulum bears on its upper surface an articular depression or fovea for the capitulum of the humerus and a second articular surface, the articular circumference, that completely surrounds its margin. Below the neck on the upper part of the volar surface there is a distinctly elevated rough area, the tuberosity, which gives attachment to the biceps muscle.
The shaft (corpus) of the radius, like that of the ulna, is triangular-prismatic. The three surfaces are also placed as in that bone, so that a volar, a dorsal and a lateral (radial) surface may be distinguished and volar and dorsal borders as well as an interosseous crest. The last lies opposite the similarly named crest of the ulna and is the only sharp border of the radius, the others being rounded. The three surfaces present no markings of importance except some roughenings for muscles, such as that for the pronator teres. Usually a nutrient foramen occurs on the volar surface.
The inferior extremity is greatly broadened and flattened, so that in its region only a volar and a dorsal surface may be distinguished. The interosseous crest passes below into a slightly concave surface, the ulnar notch, which furnishes an articular surface for the capitulum of the ulna. Opposite it a styloid process projects beyond the general inferior surface of the bone; it is broader and less pointed than the similarly named process of the ulna.
The volar surface of the inferior extremity is smooth and slightly concave, the dorsal surface on the contrary presents distinct grooves with intervening ridges for the extensor muscles of the hand and fingers, one, especially deep and with an oblique course, being for the tendon of the extensor pollicis longus. On the distal terminal surface, which is turned toward the hand, there is a concave carpal articular surface, usually distinctly divided into two areas. By means of this surface the radius articulates with the navicular (scaphoid) and lunate bones of the hand.
The eight bones of the carpus are arranged in two rows, a proximal and a distal. Those of the proximal row, named from the radial side are the navicular (scaphoid), the lunate, the triquetrum or cuneiform, and the pisiform; those of the distal row named in the same order are the trapezium (greater multangular), the trapezoid (lesser multangular), the capitate or os magnum, and the hamate or unciform. The bones of the proximal row do not lie in a straight line, but form an arch, slightly convex proximally and deeply concave distally. Similarly from the row of distal bones, one, the capitate, projects strongly towards the bones of the proximal row and fills their concavity.
The carpal bones are very irregular in shape; they do not lie in a plane but form a dome, convex dorsally and concave volarly. The dome is increased by two bony projections on the radial and ulnar sides of the volar surface of the carpus, a deep groove, the carpal groove, lying between them. These projections are the ulnar and radial eminences. The latter is formed by the tubercle of the navicular (scaphoid) and the tubercle of the trapezium (greater multangular), the former by the pisiform and the hamulus of the hamate (unciform). The small, almost spherical pisiform bone lies on the volar surface of the carpus; all the other bones of the carpus have each a dorsal and a volar, more or less roughened surface. In the cases of the four bones at the sides of the carpus, the navicular (scaphoid), trapezium (greater multangular), triquetrum (cuneiform) and hamate (unciform), the dorsal and ventral surfaces are united by lateral ones, radial or ulnar. The numerous remaining surfaces are smooth, articular surfaces for articulation with the radius, the metacarpal bones or adjacent carpal bones. The pisiform has only one small, flat, articulating surface for articulation with the triquetrum (cuneiform); all the other bones have several. The more important of these surfaces are the following: The navicular (scaphoid) and lunate have each a convex surface for articulation with the distal end of the radius; the triquetrum (cuneiform) does not, however, articulate with the ulna, but with a triangular cartilage that separates it from the ulna. Between the proximal and distal rows, the joint between the convex head of the capitatum (os magnum) and the concavity formed by the lunate and navicular (scaphoid) is the most important. The first metacarpal articulates by a distinctly saddle-shaped surface with the trapezium (greater multangular), the second with the trapezoid (lesser multangulum), the third with the capitate (os magnum), while the hamatum (unciform) bears the two ulnar metacarpals.
The metacarpal bones are typical long bones, in which a proximal portion or base, a body (corpus) and a distal portion or capitulum may be distinguished. The bases articulate with the distal row of carpal bones, the capitula with the proximal row of phalanges. The metacarpal of the thumb is the shortest, that of the index the longest, and from this toward the little finger they gradually diminish in length.
The bases of the metacarpals are irregularly cubical; that of the thumb bears a saddle-shaped surface for articulation with the trapezium (greater multangular), the rest, in addition to the surfaces for the carpal bones, have also lateral surfaces for articulation with one another. The base of the third metacarpal bears a styloid process, which is directed laterally (radially).
The almost triangular prismatic bodies of the metacarpals, except that of the thumb, have each a volar and a dorsal angle; the latter broadens to a surface towards the capitulum, the former flattens towards the base. The capitula are spherical in shape; at their sides are depressions that give attachment to ligaments.
The bases are closely applied to one another, except in the case of the freely moveable metacarpal of the thumb; on the other hand, the bodies and the capitula are separated by considerable intervals, the interosseous spaces.
Each finger has three phalanges, the thumb only two. The basal phalanx is termed the first phalanx, the middle one the second phalanx and the distal or terminal one the third phalanx. The thumb lacks the second phalanx. The lengths of the phalanges diminish toward the finger tips, so that the basal phalanges are much the longest, terminal phalanges the shortest.
The longest phalanx is the basal one of the middle finger. The phalanges are long bones with a proximal extremity or base, a body (corpus) and a distal extremity or trochlea. The bases of the proximal phalanges have hollow spherical sockets for the capitula of the metacarpals, those of the middle and distal phalanges are hollow cylindrical, with a median elevation, corresponding in form to the trochleae.
The bodies of the phalanges are convex dorsally and flat or very slightly concave on the volar surfaces, with sharp lateral borders. The terminal phalanges have no trochleae, but the short bodies pass into a rough horse-shoe shaped enlargement, the unguicular tuberosity. At the distal ends of the proximal and middle phalanges there are foveae for the attachment of ligaments, similar to those on the metacarpal capitula.
In addition to the bones that have been mentioned there are in the hand a variable number of sesamoid bones. Two occur constantly at the metacarpo-phalangeal joint of the thumb and occasionally others are found at the corresponding joints of the index and little fingers and at the interphalangeal joint of the thumb. In the little finger they may be replaced by fibro-cartilage. In the thumb they are usually covered with cartilage on one side and are connected with the joint (see Fig. A224).
In the region of the metacarpus and fingers the bones of the hand do not form a flat surface, but a dome convex dorsally and concave volarly, which may be markedly deepened by the action of the muscles of the hand and also not a little flattened. The highest point of the convexity of the back of the hand is the metacarpal of the index finger. From this the curvature falls gradually toward the little finger and quite suddenly toward the thumb. The bones of the thumb, the metacarpal as well as the two phalanges, are placed with their surfaces directed laterally and medially, instead of dorsally and volarly as in the other fingers; the bones of the thumb, therefore; turn towards the dorsum of the hand a border and not a surface. In the metacarpal of' the little finger, also, the dorsal surface looks distinctly medially.
While the metacarpal bone of the index is the longest the phalanges of the middle finger are longer than those of the index, so that the middle finger is the longest of all the fingers. The phalanges of the ring finger are also usually longer than those of the index. Corresponding to the function of the hand as a grasping organ the fingers are strongly developed, forming almost half the length of the entire hand. The length of the carpus is about only 1/6 the length of the entire hand.
The innominate bone ( os coxae) consists until puberty of three bones united by synchondroses, the ilium, the pubis, and the ischium. All three bones meet in the articular cavity for the femur (acetabulum). The ilium forms the upper portion of the compound bone; it is the largest of the three bones and forms the upper third of the acetabulum. It consists of a body (corpus) and an ala. The pubis forms the lower and anterior portion of the innominate and the lower anterior third of the acetabulum. It is separated from the ischium by a large roundish foramen, the obturator foramen, but is also united with it in the inferior boundary of the foramen. It has a body (corpus) and two rami, a ramus superior, forming the upper boundary of the obturator foramen, and a ramus inferior. The ischium forms the lower posterior portion of the innominate, the lower posterior third of the acetabulum and the lower and posterior boundary of the obturator foramen. It consists of a body (corpus) and two rami, superior and inferior.
The ala of the ilium has somewhat the form of a broad flat shovel. At its central part it is often as thin as paper, but its upper border is thickened and rough and is termed the iliac crest. Upon this may be seen three parallel rough lines, most distinct at the middle of the crest, where it reaches its highest point. These lines are termed the outer lip, the inner lip and the intermediate lip. Anteriorly the crest ends in a projection, the anterior superior spine; at its posterior end is a less distinct posterior superior spine, and below this, separated from it by a slight notch, is the posterior inferior spine. Upon these there follows at the posterior end of the innominate a deep, parabolic notch, the great sciatic notch (incisura ischiadic a major); its upper boundary is the posterior border of the ala of the ilium. and its lower and anterior boundaries are the bodies of the ilium and ischium. Below the anterior superior spine, on the body of the ilium, is the anterior inferior spine.
The lateral surface of the ala is rough and convex and its principal markings are three rough lines, the posterior, anterior and inferior gluteal lines. The posterior line runs almost vertically over the posterior part of the ala to the upper boundary of the great sciatic notch. The longer anterior line runs from the anterior superior spine as an arch, at first almost horizontal and then almost vertical, to the upper border of the great sciatic notch where it ends not far from the posterior line. The inferior gluteal line is markedly shorter than the anterior, and forming a weak arch beginning between the anterior superior and anterior inferior spines, it runs above the acetabulum and almost horizontally to the middle of the great sciatic notch.
The medial surface of the ala of the ilium has two portions, a larger anterior one which is slightly convex and is termed the iliac fossa and an uneven posterior one. On the latter again there may be made out two portions, corresponding to portions of the sacrum with similar names, the lower and anterior auricular surface and the posterior and upper, very much roughened iliac tuberosity. The auricular surface is bounded by a slight paraglenoid groove. The iliac fossa is separated from the rest of the innominate by a line which is continued upon the pubis and is called the arcuate line; it forms a part of the boundary line (linea terminalis) separating the false and the true pelves. The body of the ilium forms the upper part of the acetabulum; it passes on the inner surface into the ala without demarcation and in the adult, in a similar manner, into the bodies of the pubis and ischium.
The pubis of the adult is intimately connected with the ilium and ischium and forms part of the acetabulum. Where the pubis and ilium meet there is a low, rounded elevation, the iliopectineal eminence. From the body of the bone there arises the triangular superior ramus, which lies almost horizontally and bears at its anterior end the elongated symphyseal surface for union with the bone of the opposite side; it also forms the upper boundary of the obturator foramen. On its upper surface is a sharp ridge, the pecten, which is a continuation of the arcuate line of the ilium. This ends anteriorly in a small elevation, the tubercle, not far from the symphyseal surface. Where the superior ramus arises from the body there is a broad obturator groove on the medial surface of the bone; it is bounded medially by the obturator crest. At the obturator groove anteriorly there is an elevation, the anterior obturator tubercle, directed toward the obturator foramen, and on the ischium a posterior tubercle. The inferior ramus passes obliquely downwards and laterally from the symphyseal surface.
The ischium forms the lower posterior part of the acetabulum, and in the adult passes over without demarcation into the ilium and pubis. It forms the lower anterior boundary of the great sciatic notch, below which it projects as a broad, flattened, but sharp spine. Below this is the lesser sciatic notch (incisura ischiadic a minor), which lies entirely in the ischium and whose lower boundary is a strong roughened protuberance, the tuberosity. From the neighborhood of this the inferior ramus ascends at a sharp angle to the superior ramus. With the lower ramus of the pubis it forms the lower boundary of the obturator foramen. The acetabulum is formed by the bodies of the three bones, but the lines of separation between these can be seen only in youthful bones. It is almost hemispherical, with elevated borders, and looks almost laterally. Below towards the obturator foramen there is a notch in its border, the acetabular notch. The bottom of the cavity shows two portions, the lunate surface, covered with cartilage, which forms the upper and lateral portions of the cavity, and the almost square, rough and uneven acetabular fossa, almost surrounded by the lunate surface.
In the femur there may be distinguished a superior extremity, a body or shaft (corpus) and an inferior extremity. The superior extremity bears the head (caput) at the extremity of a neck (collum), which passes into the shaft at an obtuse angle. The head is somewhat more than a hemisphere and is covered with cartilage, except at a slight depression near its center, the fovea. The neck (collum) is strongly constricted near the head but enlarges laterally toward the shaft of the bone; it has a long lower border and an upper border about half as long. At the upper end of the shaft, at the union of this with the neck are two large, strong processes, the trochanters. The greater trochanter is much larger than the lesser one and looks laterally. Its upper extremity, whose tip is slightly bent posteriorly and medially, projects above the neck and bears on the medial surface below the apex a trochanteric fossa. The great trochanter forms the entire lateral part of the upper extremity of the femur. The lesser trochanter is opposite the greater on the medial surface of the upper part of the femur and is a short conical projection directed medially and slightly backward; it lies at a somewhat lower level than the great trochanter. The two trochanters are connected on the anterior surface of the bone by a rough intertrochanteric line, and on the posterior surface by a distinct ridge, the intertrochanteric crest.
The shaft (corpus) of the femur is almost cylindrical, but toward its lower end it broadens and becomes triangular-prismatic with rounded borders. In this region there is an anterior medial, an anterior lateral and a posterior surface. It is distinctly convex anteriorly.
While the anterior and lateral surfaces of the bone are exceptionally smooth, the posterior surface shows a rough line, the linea aspera. This possesses two distinct lips, a medial and a lateral. Throughout the middle portion of the bone both lips lie close together, but above they diverge toward the two trochanters and below toward the epicondyles (see below). The lateral lip passes above into an elongated roughened ridge, the gluteal tuberosity, which is occasionally greatly enlarged to form the so-called third trochanter. The medial lip becomes less pronounced in its upper part and unites with the intertrochanteric line in the region of the lesser trochanter, without actually uniting with this latter, and so ends on the greater trochanter. Parallel with and somewhat lateral to it is a second rough line, the pectineal line, which passes upward toward the lesser trochanter.
Towards the lower end of the femur the two lips of the linea aspera gradually diverge from one another to bound a triangular, almost flat area on the posterior surface of the bone; this is the popliteal plane. Upon the linea aspera, above its middle, there is usually one or several nutrient foramina, that lead into canals directed distinctly proximally.
The inferior extremity of the femur is much broadened. It bears the two convex, backwardly directed articulating condyles, the larger medial condyle and the smaller lateral condyle, separated from one another behind by the intercondyloid fossa. The intercondyloid line separates the intercondyloid fossa from the popliteal plane. Anteriorly the cartilaginous surfaces of the condyles pass into a common articular surface, the patellar surface, which is concave transversely and convex sagittally; consequently, the whole cartilaginous surface at the lower end of the femur has a horse-shoe shape. Above the condyles are two rough, but only slightly prominent, processes, the medial and lateral epicondyles.
The patella is a flat disk-shaped bone, which is really a large sesamoid bone in the tendon of the Quadriceps femoris. Its upper border is broad and is termed the base, while below the bone passes into a point, the apex. The anterior surface is rough, the posterior smooth and in 2/3 of its extent covered with cartilage, this area taking part in the formation of the knee-joint and being called the articular surface. The posterior surface of the apex is, however, not covered with cartilage but is rough like the anterior surface.
The tibia is the medial and the larger of the two bones of the lower leg. It has a superior extremity, a shaft or body (corpus) and an inferior extremity.
The superior extremity is much the thickest portion of the bone. It bears medial and lateral condyles for articulation with the condyles of the femur. Their upper surfaces are the slightly concave medial and lateral superior articular surfaces which are separated by a median elevation, the inter condyloid eminence, surmounted by two tubercles, the medial and lateral intercondyloid tubercles. Both behind and in front of the eminence is a small shallow groove, the anterior and posterior intercondyloid fossae. Below the articular surfaces there is the rough, almost perpendicular border of the upper part of the bone, the infraglenoid border, and on the lateral and posterior part of this is an articular surface for the head of the fibula. Below the infraglenoid border on the anterior surface of the bone is a large roughened area, the tuberosity.
The shaft (corpus) of the tibia is distinctly triangular-prismatic. It is thick in its upper part, becomes gradually thinner lower down and then enlarges again below. It presents three surfaces and three borders. The medial and lateral surfaces are separated by the anterior crest, while the very sharp interosseous crest, directed toward the fibula, separates the lateral and posterior surfaces. The third, rounded border, the medial, separates the medial and posterior surfaces.
On the upper part of the posterior surface there is an oblique line, the popliteal line, which runs from the articular surface for the fibula downwards and medially to the medial border. Below this line is the nutrient foramen, usually large and distinct; it leads into a canal that runs obliquely downwards. The medial surface, like the anterior border, is subcutaneous and readily felt; the lateral surface shows no special markings. Towards the lower end the borders of the bone are rounded so that this part of the shaft is almost cylindrical.
The inferior extremity, which is thicker than the lower part of the shaft, is decidedly smaller than the superior extremity. It bears on its under surface a slightly concave inferior articular surface for articulation with the tarsus (talus). On its medial side there is a strongly projecting process, the medial malleolus, whose outer surface is also an articular surface for the tarsus and passes without demarcation into the inferior articular surface. On its posterior surface the medial malleolus has a broad medial malleolar groove for a muscle tendon. On its lateral surface the lower end of the tibia has a fibular notch for articulation with the lower end of the fibula; it is not, however, covered with cartilage.
The fibula is a long bone, very thin in proportion to its length; it is scarcely shorter than the tibia, beyond which it projects below. It lies on the lateral side of the lower leg and has a superior extremity, a shaft (corpus) and an inferior extremity. The superior extremity forms the head (capitulum) and the inferior extremity the lateral malleolus. The head is distinctly enlarged as compared with the slender shaft; its uppermost part is behind and somewhat lateral and is termed the apex. It bears, for articulation with the tibia, a small, almost flat surface, the capitular articular surface.
The shaft is very distinctly triangular-prismatic. The three surfaces are medial, lateral and posterior, the sharp borders, which are not always straight are termed crests. The anterior crest separates the medial and lateral surfaces, the posterior crest the posterior and medial surfaces and the lateral crest the posterior and lateral surfaces. In addition to these there is a feebly developed interosseous crest at about the middle of the medial surface, so that the fibula has really four borders.
The inferior extremity forms the lateral malleolus. This is longer and more pointed than the medial one and has upon its medial surface an articular surface, which immediately adjoins the inferior articular surface of the tibia. On the lateral surface of the malleolus there is a shallow groove for the peroneal tendons.
Like the hand, the foot consists of three portions:
but it differs from the hand not only in the number and form of its constituent bones, but also in certain special particulars. While the axis of the hand is the direct continuation of that of the forearm and arm, that of the foot is almost at right angles to that of the leg, and while in the hand the fingers are almost the half of its entire length, in the foot the tarsus forms almost the proximal half and the metatarsals and toes the distal half, the latter being only a fifth of the entire length of the foot.
The foot is more strongly arched than the bones of the hand and the arch is less capable of being modified. Its convexity is dorsal and the concavity plantar, the deepest point of the latter being at the sharp, lower edge of the second cuneiform bone. Similarly the dorsal surface of the second cuneiform is the highest point of the middle of the arch. The lower supports for the arch are the calcaneal tuberosity behind and the heads of the metatarsals in front. It is formed exclusively by the tarsus and metatarsus and is open medially, since the medial border of the foot is much higher than the lateral, which rests on the ground through almost its entire length.
The phalanges of the second to the fifth toes do not lie in a single plane, even when the toes are extended, but are strongly convex upwards and seem to be curved in a claw-like manner upon the heads of the metatarsal bones, so that only their distal ends are in contact with the ground. The second toe is the longest and is that through which the axis of the foot passes.
There are seven tarsal bones:
The arrangement of these bones is such that on the medial side of the foot there are three bones, the talus, navicular, and cuneiform, whereas on the lateral side there are only two, the calcaneus and cuboid. In contrast to the condition in the hand only a single bone, the talus, articulates with the lower leg bones.
The talus is a short bone with an irregular cubical form, and presents for examination a body (corpus), a head (caput), and a constricted portion between these, the neck (collum). The body is the thickest and most posterior part of the bone and bears on its upper surface an articular surface, the trochlea, covered with cartilage and articulating with the tibia and fibula. The trochlea extends also upon the lateral surface of the talus and upon a strong projection of the bone, the lateral process, forming the lateral malleolar surface; it extends also upon the medial surface forming the medial malleolar surface, but this is smaller in extent than the lateral one, a part of the medial surface being rough. Behind the trochlea is a backwardly projecting part of the bone, the posterior process, which bears a broad groove for the tendon of the Flexor hallucis longus. The under surface of the body bears a distinctly concave posterior calcaneal articular surface, in front of which is a broad depression, the sulcus tali. Anterior to this, in the region of the neck, there is on the under surface an elongated second articulation for the calcaneus, the middle calcaneal articular surface, and adjoining this, on the head of the talus, is an anterior calcaneal articular surface. The constricted neck (collum) is to be seen distinctly only on the upper and lateral surfaces; on the medial and lower surfaces it is clearly separated from neither the head nor body. The head (caput) is the rounded anterior end of the bone and bears the almost hemispherical navicular articular surface, for articulation with the navicular bone and navicular fibro-cartilage.
The calcaneus is the largest bone of the tarsus. Its principal part is termed the body (corpus), the posterior thickened end of which is termed the tuberosity (tuber calcanei) and projects backwards behind the other bones of the foot. On its under surface are two projections, the medial and lateral processes. Looking from above one sees three surfaces (posterior, middle, and anterior) for articulation with the talus; the posterior is the largest and is convex, the other two are slightly concave. Between the middle and posterior articular surfaces lies the calcaneal groove, which is broadly open laterally; with the sulcus tali it forms the sinus tarsi.
From the strongly concave medial surface of the calcaneus a broad process, the sustentaculum tali, projects towards the talus and bears the middle articular surface for that bone. On its under surface is the broad groove for the tendon of the Flexor hallucis longus, continuous with the similar groove on the talus. A similar, but much shallower, groove for the peroneal muscles lies on the lateral surface, which is otherwise flat, except that a small, blunt trochlear process sometimes occurs above the groove. The anterior surface bears the articular surface for the cuboid, which is somewhat saddle-shaped.
The navicular lies between the talus behind and the three cuneiforms in front. Its long axis is transverse to that of the foot and it is convex anteriorly and concave posteriorly; its dorsal surface is also distinctly convex. On its plantar surface, near the medial border, there is a strong rounded projection, the tuberosity.
The cuboid lies on the lateral border of the foot, between the anterior end of the calcaneus and the bases of the fourth and fifth metatarsals. It has an irregular cubical form, tapering toward the lateral border of the foot. Its anterior surface bears an articulating surface divided into two parts for the fourth and fifth metatarsals; its posterior surface is saddle-shaped and its medial surface has an articular facet for the external cuneiform. The plantar surface has a flat projection, the tuberosity, which is rounded and sometimes covered with cartilage; it serves as a pulley for the tendon of the Peroneus longus, which lies in a groove, the peroneal groove, in front of the tuberosity.
The cuneiform bones are wedge shaped; the internal one is the largest and has its sharp edge dorsally, while in the others it is turned plantarwards. The middle one is the smallest. They articulate with the navicular behind and the bases of three metatarsals in front; the internal one usually articulates also with the cuboid.
The metatarsals have each a base, a head (capitulum) and a body (corpus). They lie between the bones of the tarsus behind and the phalanges in front, articulating with both. In addition the bases of the second to the fifth articulate with each other. The first metatarsal is short and thick; the second is the longest. The base of the first has a broad tuberosity directed plantarwards and laterally, and a tuberosity also occurs on the base of the fifth which projects markedly upon the lateral border of the foot.
The phalanges resemble those of the hand but are markedly shorter. The great toe has two phalanges, which are much thicker than those of the other toes. Each phalanx has a base, a body, and a trochlea, this on the terminal phalanges being replaced by an unguicular tuberosity.
According to their outer form bones may be divided into three groups, long bones (ossa longa), short bones (ossa brevia) and flat bones (ossa plana). It is not, however, only on account of their external form that these three groups may be distinguished; they differ also in their structure, that is to say, in the arrangement of the two kinds of bone substance of which they are composed. These two kinds of bone substance are termed
To the long bones belong all the bones of the free extremities, with the exception of those of the carpus and tarsus and of the patella. Thus, the long bones are the humerus, ulna, radius, metacarpals, and the phalanges of the fingers; the femur, tibia, fibula, metatarsals, and the phalanges of the toes; the clavicle also belongs to this group. All these bones possess a marrow cavity. Notwithstanding their shape the ribs are not classified with the long bones since they do not possess a marrow cavity.
The short bones are the vertebrae, the bones of the carpus and tarsus, the patella, sesamoid bones and the hyoid.
The flat bones are the sternum, the scapula, the innominate bone ( os coxae), the ribs and most of the skull bones, including the mandible.
Certain bones of the human skeleton are not readily referable to any one of these groups, especially such bones as are formed by the fusion of several short bones or of short and flat bones. Such are known as irregular bones. Typical examples of these are the sacrum and the coccyx, both formed by the fusion of several short bones, and various skull bones, such as the temporal, the occipital and the sphenoid, which may be regarded as formed by the fusion of short and flat bones to a single skeletal structure.
The short bones have the simplest structure. They consist almost entirely of spongy substance, only a thin layer of a kind of compact bone, the so-called substantia corticalis, enclosing the spongiosa and forming the external boundary for the small marrow cavities (filled with red marrow) which occur between the bone trabeculae.
In the flat bones the part played by the spongy substance is markedly less and the more or less parallel bounding plates of compact bone are appreciably thicker. Indeed, where a flat bone is very thin the compact lamellae may be in contact, the spongy substance being entirely wanting. The fine spaces between the trabeculae of the spongy substance are occupied by usually red marrow. The flat bones of the skull present certain differences of structure. In place of a central spongiosa they have a much larger meshed, but still trabecular bone substance, the so-called diploë. This is enclosed between two relatively thick plates of compact bone, the outer one being usually thicker than the inner; these are termed the outer and inner vitreous tables. The wide spaces of the diploë contain blood-vessels, especially venous plexuses but no red marrow; where the bones become thin the diploë is greatly reduced and may even be wanting.
The greatest difference is seen in the structure of the long bones. The shaft (corpus) of these consists in almost its entire thickness of compact bone, which here reaches a greater development than in other bones. It forms a cylinder of compact substance and only towards the articulating ends does it enclose any considerable amount of spongy substance. These ends, however, are almost entirely formed of spongy substance, this being enclosed, as in the case of the short bones, only by an outer quite thin layer of compact cortical substance. At the junction of the articular extremities with the shaft, the small cavities between the trabeculae of the spongiosa, which contain red marrow, communicate with the cylindrical marrow cavity of the shaft; this contains yellow (in old age gelatinous) marrow.
The trabeculae and plates of the spongy substance, which are for the most part slender and thin, are not altogether irregular in their arrangement, but are influenced to a large extent both in their structure and their arrangement by pressure on the one hand and by the pull of muscles on the other. The spongiosa trabeculae strengthened in response to stress or strain are termed trajectories.
All figures are taken from the "Atlas typischer Röntgenbilder vom normalen Menschen" by R. Grashey (J. F. Lehmann, Munich).
While it is usual to study the bones of the human body in the macerated condition there is a method by which the parts of the skeleton may be made visible even in the living body, namely, the use of Röntgen rays. These readily penetrate all the soft parts of the body (all organic substance) and also cartilage, but cannot pass through the inorganic bone substance, and so by the use of Röntgen photography the bones alone are shown on the photographic plate. If the bones are not too far from the sensitized surface of the plate they appear relatively sharply outlined and undistorted, so that not only is their form made visible, but also the structure of the spongiosa is more or less evident. On the other hand, bones that are some distance from the sensitized surface of the plate appear distorted and with poorly defined outlines.
Consequently Röntgen pictures of the skull and of the pelvis are never anatomically satisfactory. But while a Röntgen picture of a bone is less satisfactory for study than the macerated bone itself, and while especially, the clearest Röntgen picture of the spongiosa is far inferior to what may be seen anatomically of the architecture of the substance in a macerated bone (Fig. A177, A178, A179, A180, A181), nevertheless the study of the bones in the living by means of the Röntgen rays is a material aid to their study by the direct, anatomical method. This is especially true in the case of young skeletons still developing; in these the Röntgen pictures are the more satisfactory since they show the ossification centres in their natural position in the transparent cartilage.
Table of Ossification (from Grashey)
The wavy lines indicate the amount of variation in the appearance of the centres.
No portions of the skeleton are so well adapted for Röntgen photography as the bones of the hand, since the hand is flat and may be brought relatively close to the sensitized surface of the photographic plate; furthermore the bones have no great thickness and the defects (distortion and blurring) of Röntgen photography, sometimes so pronounced, are here hardly noticeable.
Consequently Fig. A187 not only shows the bones with almost perfectly sharp outlines, but the spongiosa and compacta of which they are formed are also evident. So too the marrow cavity of the long bones is shown. Since the figure is that of the hand of an individual of 28 years the development of the bones has been completed; the epiphyses of the long bones (see Figs. A184, A185, A186) have completely united with the diaphyses, whose ossification began in embryonic life.
The cavities of the joints always appear very broad in Röntgen photographs, since the articular cartilages do not show. The spaces between the bones in Röntgen photographs represent accordingly the articular cavities plus the articular cartilages of both bones concerned (compare Fig. A187 and A222).
Röntgen photographs also give exceedingly important information as to the ossification of the skeleton of the lower extremity. Of the epiphyses of long bones those that are the earliest to appear are those of the ends of the bones that enter into the formation of the knee-joint, the distal epiphysis of the femur and the proximal of the tibia, the former regularly and the latter frequently beginning to ossify before birth. That the ossification of the proximal end of the fibula begins much later is clearly shown in the accompanying figure, from which it may also be seen that the ossification processes not infrequently do not go on synchronously on the two sides of the body. Considerable variation also occurs in the time of the appearance of the ossification centres (see table here; ~~ = variation).
The ossification of the epiphyses proceeds in such a way that eventually there is a fusion with the diaphysial bone, the cartilaginous epiphysial disk that first separates them undergoing conversion into bone. On the other hand, on that surface of the epiphysis which forms the articular surface the ossification fails to invade the terminal layer of cartilage, which persists throughout life, forming the articular cartilage. According to the thickness of this cartilage, which varies to a considerable extent in the various joints, the articular cavity in Röntgen pictures will sometimes appear exceedingly wide and in other cases, narrow; Röntgen pictures can never give definite evidence as to the width of the articular cavity.
The bodies of the true vertebrae are united by fibrocartilaginous disks, the intervertebral fibrocartilages . Each of these consists of a firm ring, anulus fibrosus , of interlacing and concentric connective tissue bundles and of a central pulpy nucleus. The latter is compressed within the fibrous ring and bulges out when the disk is cut across. The fibrocartilages are in relation to the opposing surfaces of the bodies of adjacent vertebrae, these surfaces being covered by a thin layer of cartilage. The fibrocartilages are larger than the surfaces of the vertebrae between which they lie; their greatest height is at the middle, where they are in relation to the slightly concave surfaces of the vertebrae. There is no disk between the first and second vertebrae; the first lies between the second and third vertebrae and the last between the fifth lumbar vertebra and the sacrum, so that there are 23 fibrocartilages. In general they increase both in circumference and height from above downwards, just as do the vertebrae. In the cervical region they are, however, smaller but higher than those between the upper and middle thoracic vertebrae; those between the lumbar vertebrae are the largest and highest of all. The lowest fibrocartilages are wedge-shaped, being distinctly higher (about 1/3) in front than behind, especially in the case of the last one, the promontory.
In addition to the mixed synarthrotic union of the bodies, the true vertebrae are also connected by intervertebral articulations. Each pair of superior articular processes unite with the pair of inferior articular processes of the vertebra next above. Each joint has an articular capsule , loose in the cervical vertebrae but compact in the lower ones; it encloses the cartilaginous surfaces. There are no accessory ligaments.
Throughout the whole length of the vertebral column, in the region of the bodies, there is both an anterior and a posterior longitudinal ligament, covering respectively the anterior and posterior surfaces of the bodies and the intervertebral disks. The anterior one is a broad band, which begins quite small at the anterior tubercle of the atlas and broadens greatly below, where it ends on the anterior surface of the sacrum. It is very closely connected with the intervertebral fibrocartilages, but over the middle of the bodies, whose anterior surfaces are concave, it is more loosely attached. It consists of long superficial and deep fibers passing from vertebra to vertebra.
The posterior longitudinal ligament lies on the posterior surface of the bodies. It is much smaller than the anterior one and diminishes in breadth from above downwards. It begins as an independent ligament at the second vertebra, but is continued above this to the skull as the tectorial membrane (see here); below it ends in the sacral canal. It broadens distinctly over each intervertebral fibrocartilage and is closely connected with these, but has no attachments to the posterior surfaces of the bodies of the vertebrae.
The ligaments between the arches, ligamenta flava, are strong elastic bands, owing their name to their marked yellow color. They completely cover in the intervals between adjacent arches, extending anteriorly to the posterior borders of the capsules of the intervertebral articulations. Consequently they close in the vertebral canal up to the margins of the intervertebral foramina. Their inner surfaces are perfectly smooth and form a common surface with the inner surfaces of the arches. On account of their elasticity the posterior wall of the vertebral canal remains smooth during bendings of the column and they aid in the return of the vertebrae to the resting position. They begin between the second and third cervical vertebrae and extend to the last lumbar. They show a distinct groove in the middle line. Their number is 23 pairs.
The intertransverse ligaments, extending between the transverse processes of adjoining vertebrae, are unimportant. They are constant only in the thoracic region. The spinous processes of successive vertebrae are united by interspinous ligaments, which are most strongly developed in the lumbar region. They are united on one edge with the ligamenta flava and on the other. with the supraspinous ligament. This unites the tips of the various spinous processes and also runs over the tips as a continuous ligament. The interspinal and supraspinal ligaments occur through the entire extent of the true vertebrae and extend somewhat upon the sacrum also. For the sacral and coccygeal articulations see here.
The ribs unite posteriorly with the thoracic vertebrae in a joint; anteriorly they unite in a joint or a synchondrosis with the sternum or with one another. Only the last two ribs fail to unite with skeletal parts at their anterior ends. In the costo-vertebral articulations the head of a rib articulates with two adjoining vertebrae and the tubercle with a transverse process, except that this latter connection is wanting in the last two ribs, which articulate with only one vertebral body. The capitular articulations with the exception of the first and the two last, are characterized by the fact that the intervertebral fibro-cartilage between the two vertebrae which form the socket is attached to the head of the rib, forming the interarticular ligament and dividing the joint into two portions. The radiate ligaments, which radiate from the head of the rib upon the lateral surfaces of the articulating vertebrae, strengthen the weak articular capsules.
The costo-transverse articulations possess a loose capsule and are characterized by possessing a whole series of accessory ligaments. As a reinforcing band for the posterior surface of the capsule there is a quadrangular, short, tense tubercular ligament, which completely fills the space between the neck of the rib and the transverse process. The anterior and posterior costotransverse ligaments pass between the necks of the ribs and the transverse processes. The posterior are much weaker than the anterior and are attached to the articular processes of the vertebrae as well as to their transverse processes. The body of the vertebra together with the anterior ligament bounds a costo-transverse foramen, through which the anterior (intercostal) ramus of the spinal nerve makes its exit.
The cartilages of the true ribs unite with the sternum by the sternocostal articulations. The first cartilage, however, is always united to the manubrium by a synchondrosis. In the articulation of the second cartilage there is always a band passing to the end of the cartilage from the sternal synchondrosis; it is the interarticular ligament and it makes the joint two-chambered. In the sternal articulations of the third to the seventh rib the interarticular ligament is inconstant and frequently, when it is present, it divides the joint cavity unequally. Reinforcing the anterior surface of the joints are the radiate ligaments, which radiate out fan-like from the end of the cartilage upon the anterior surface of the sternum (see Fig. A212). Those of the lower ribs form by the interlacing of their fibres on the lower part of the sternum the sternal membrane. Between the cartilages of the seventh to the tenth ribs interchondral articulations may occur. Sometimes the sternal synchondrosis between the manubrium and the body of the sternum has a joint cavity.
For the movement of the head upon the vertebral column there is a combination of joints, including the atlanto-occipital articulations and the atlanto-axial (atlanto-epistrophic). Peculiar to the union of the first two cervical vertebrae with the occipital bone are the atlanto-occipital membranes, which serve to close the wide intervals between the atlas and the occipital and between the atlas and axis (epistropheus). The anterior membrane extends between the occipital and the anterior arch of the atlas, the posterior one, a continuation of the ligamenta flava, closes principally the gap between the occipital and the posterior arch of the atlas, but also extends between the posterior arch of the atlas and the arch of the axis (epistropheus).
The Atlanto-occipital articulations act as a symmetrical double joint. They are formed by the union of the occipital condyles with the superior articular surfaces of the atlas and according to the form of the articulating surfaces are ellipsoid joints. The articular capsule is rather broad and loose and lacks reinforcing ligaments.
The atlanto-axial (atlanto-epistrophic) articulation is formed by three separate joints;
The capsules of the atlanto-axial joint are wide and loose and are reinforced by a series of accessory ligaments. The very strong and firm transverse ligament arises from the medial borders of the lateral masses of the atlas and traverses its vertebral foramen, enclosing the dens from behind. It is cartilaginous where it passes over the dens and articulates with that process. From the middle of the ligament there is an upper and a lower prolongation. The upper one passes to the occipital bone, the lower inserts into the posterior surface of the body of the axis (epistropheus). The cruciform ligament so formed is termed the cruciate ligament. Three other ligaments belonging to the articulation are attached to the dens, a weak middle one and two strong lateral. The middle one, the apical ligament of the dens, is an unimportant thin band passing from the apex of the dens to the margin of the foramen magnum. The lateral ligaments, the alar ligaments, are much stronger and pass obliquely upward from the dens to the medial border of the occipital condyles, uniting the axis (epistropheus) directly with the skull. The ligaments of the joints are covered, towards the vertebral canal, by a broad firm sheet of fibres, the membrana tectoria, which is continuous with the dura mater at the foramen magnum and with the posterior longitudinal ligament below (see here).
The mandibular articulation is between the capitulum of the mandible and the mandibular fossa and articular tubercle of the temporal bone. The joint cavity is completely divided into two parts by an articular disk, whose circumference is united with the articular capsule. The capsule is rather loose and thin. It surrounds the mandibular fossa (except the non-cartilaginous portion), the articular tubercle and the head of the mandible, having its insertion on the neck. It is reinforced by a temporo-mandibular ligament, which passes from the zygomatic arch to the neck of the mandible.
Near the mandibular articulation, but without any direct connection with it, are the spheno-mandibular and stylo-mandibular ligaments. The former arises from the under surface of the great wing of the sphenoid near the angular spine and inserts into the lingua of the mandible. The latter arises from the styloid process and goes to the angle of the mandible. Both ligaments are weak and somewhat fascia-like, the stylomandibular spreading out directly into the fascia of the internal pterygoid muscle (bucco-pharyngeal fascia).
Besides these there are two other independent ligaments in the head. The pterygospinous ligament runs between the angular spine of the sphenoid and the upper end of the lateral plate of the pterygoid process. Sometimes it ossifies and then forms the pterygospinous process (Civinini). The stylo-hyoid ligament runs from the styloid process of the temporal to the lesser cornu of the hyoid. It frequently contains pieces of cartilage or bone, remains of the middle portion of the second branchial or hyoid arch from which the lesser cornu of the hyoid and the styloid process are formed.
Several clefts between the bones of the skull are also completely or partly closed by ligamentous masses as, for instance, the two orbital fissures, the spheno-petrous and petro-occipital fissures and the foramen lacerum, except where these give passage to nerves and vessels.
The sterno-clavicular articulation is between the clavicular notch on the manubrium of the sternum and the sternal articular surface of the clavicle. The two articular surfaces are made congruent by the interposition of an articular disk, which divides the joint cavity into two portions. The loose and thin articular capsule is strengthened over its entire surface by strong reinforcing ligaments. The sterno-clavicular ligament is fused with the anterior surface of the capsule and the interclavicular ligament unites the sternal ends of the two clavicles, extending across the jugular notch and resting on the upper border of the manubrium; it thus strengthens the upper surface of both sterno-clavicular joints. The costo-clavicular ligament is only functionally apart of the sterno-clavicular articulation. It is an independent, exceedingly strong ligament, passing between the cartilage of the first rib and the costal tubercle of the clavicle, and almost filling the interval between the sternal end of the clavicle and the first rib. Its rather short fibres are put on the stretch by a relatively slight abduction of the clavicle from the thorax.
The acromio-clavicular articulation is between the acromial articular surface of the clavicle and the articular surface of the acromion. Also in this joint there is a weak articular disk, which is frequently incomplete and may be entirely wanting. The articular capsule is strengthened over its upper, stronger portion by the acromio-clavicular ligament, which unites the ends of the adjoining bones. A very strong coraco-clavicular ligament unites the acromial end of the clavicle with the scapula, arising from the upper surface of the base of the coracoid process and passing to the coracoid tuberosity of the clavicle. It consists of two portions, an anterior flat, quadrangular trapezoid ligament and a posterior, triangular conoid ligament, small below and broad above (see Fig. A216).
On the scapula there are three independent ligaments:
The shoulder joint is between the glenoid cavity of the scapula and the head of the humerus. The glenoid cavity is relatively small arid only slightly concave, but it is materially enlarged and deepened by a strong, fibrous glenoidal lip, which surrounds the whole border of the bony socket. Nevertheless the socket of the joint is decidedly smaller than the articulating head, and free movement, accordingly, is not hindered by the socket, the joint being the most freely moveable joint in the body.
The articular capsule of the shoulder joint is wide and loose, as is necessary in a joint with free movement. Although it is on the whole thin, it receives strong reinforcements from the tendons of the muscles that pass over it (behind, the Supraspinatus, Infraspinatus, Teres minor; in front the Subscapularis) and from a strong reinforcing band, the coraco-humeral ligament. The articular capsule arises from the border of the glenoidal lip and inserts on the anatomical neck of the humerus. The coracohumeral ligament arises at the root of the coracoid process and is at first independent, but later becomes completely fused with the capsule and passes to an insertion in the neighborhood of the two tubercles on the anatomical neck of the humerus.
A peculiarity of the shoulder joint is that it is traversed throughout its entire length by a tendon, that of the long, head of the Biceps. The tendon arises at the supraglenoid tubercle, where it is fused with the upper part of the glenoidal lip, and runs through the cavity of the joint beneath the coraco-humeral ligament, and then along the intertubercular groove, being enclosed in this portion of its course by a prolongation of the capsule, the intertubercular sheath. The intertubercular groove is lined with cartilage throughout the extent of the sheath. Furthermore a thin-walled subscapular bursa, lying beneath the tendon of the subscapular muscle, also communicates with the joint cavity. This bursa is situated below the concave anterior surface of the coracoid process, between the coracohumeral ligament and a slight thickening of the medial surface of the capsule.
The elbow joint is a typical composite articulation, being composed, firstly, of the articulation of the trochlea of the humerus with the semilunar notch of the ulna, the humero-ulnar articulation; secondly, of that of the capitulum of the humerus with the capitular fovea of the radius, the humero-radial articulation; and, thirdly, of that of the radial notch of the ulna with the articular circumference of the radius, the proximal radio-ulnar articulation.
All three articulations are enclosed by a common articular capsule, which is broad and loose, especially anteriorly and posteriorly. It surrounds the olecranal, coronoid and radial fossae at the lower end of the humerus and is attached below to the ulna, close below the tip of the olecranon, to the border of the semilunar notch and to the tip of the coronoid process. The entire head of the radius and the greatest part of its neck is within the capsule. The radial collateral ligament extends from the lateral epicondyle of the humerus to the anular ligament, with which its fibres partly intermingle. The ulnar collateral ligament arises on the medial epicondyle of the humerus and passes, broadening as it goes, to the border of the semilunar notch of the ulna. The anular ligament is a dense firm band that surrounds the head of the radius like a sling. It arises from the anterior border of the semilunar notch of the ulna and is inserted into the posterior border of the radial notch of the same bone, forming with the latter notch the socket of the proximal radio-ulnar joint, 3/4 of this socket being formed by the ligament and 1/4 by the notch. On its inner surface, which is turned toward the cartilage-covered articular circumference of the head of the radius, the ligament is perfectly smooth. Below it the capsule is thin and projects slightly at the neck of the radius to form the sacciform recess.
Functionally considered the elbow joint is a combination of only two joints, since the humero-radial articulation does not act as an independent mechanism. There is, then, in the first place, the humero-ulnar articulation, which is a hinge joint, and, secondly, the proximal radio-ulnar articulation, which is a pivot joint.
The obtuse angle, open radially, formed by the upper and lower arm bones when the limb is extended, is termed the arm angle.
The radius and ulna are connected throughout almost their entire length by the interosseous membrane, which is attached to the interosseous crests of the two bones, except above, where the interosseous space persists. In addition the two bones are united by the the chorda obliqua, which passes from the coronoid process of the ulna to the lower border of the tuberosity of the radius.
The distal radio-ulnar articulation is between the articular circumference of the head of the ulna and the ulnar notch of the radius and also the articular disk which separates the head of the ulna from the cuneiform (triquetral) bone, the socket for the head of the ulna being formed partly by the ulnar notch and partly by the articular disk. Part of the socket is, therefore, nearly in the vertical plane and part almost horizontal, so that the head of the ulna rests upon the lateral as well as the lower surface of the socket. The capsule sends a sacciform recess upwards between the two bones of the forearm. The articular disk is attached on the one hand to the ulnar border of the lower part of the radius, where it is continuous with the articular cartilage, and on the other hand to the styloid process of the ulna.
The joints of the hand are those of the carpus and those of the fingers. The carpal joints are:
The finger joints are the metacarpo-phalangeal and the inter-phalangeal.
The radio-carpal articulation is between the carpal articular surface of the radius, together with the articular disk, and the proximal surfaces of the first row of carpal bones, the navicular and lunate articulating with the radius and the triquetrum (cuneiform) with the disk. The joint is completely separated from the intercarpal joint by short ligaments extending between the three bones, the navicular (scaphoid), lunate and cuneiform (triquetrum). The articular capsule is lax and thin and encloses the cartilaginous articulating surfaces.
The intercarpal articulation is between the first and second rows of carpal bones, the first row forming essentially the socket for the head of the capitate (os magnum) and the proximal part of the hamate (unciform). The line of the joint is S-shaped and its cavity usually communicates between the capitate (os magnum) and lesser multangular (trapezoid) with the carpo-metacarpal joint. The articular capsule is thin.
The articulation of the pisiform bone is between the pisiform and cuneiform (triquetral) bones. The piso-uncinate (piso-hamate) and the piso-metacarpal ligaments, passing respectively from the pisiform to the hamulus of the unciform (hamate) and to the base of the fifth metacarpal, are merely continuations of the tendon of the flexor carp ulnaris.
The common carpo-metacarpal articulation is between the bases of the second to the fifth metacarpals and the distal articular surfaces of the lesser multangular(trapezoid), capitate (os magnum) and hamate (unciform). The joint cavity usually communicates with that of the intercarpal joint and sometimes is divided transversely into two parts. The articular capsule is tense and firm. The joint cavity extends a short distance between the bases of the metacarpals.
The carpo-metacarpal articulation of the thumb is always independent, neither communicating with the other carpo-metacarpal joints nor with the intercarpal. The articulating surfaces are saddle-shaped, more markedly so than in any other joint in the body.
Only one of the carpal ligaments arises from the ulna, the ulnar collateral ligament, which arises from the styloid process of that bone and is attached to the triquetrum (cuneiform). Corresponding to it on the radial side is the radial collateral ligament, passing from the styloid process of the radius to the navicular (scaphoid). In addition, the dorsal radio-carpal ligament extends obliquely from the dorsal surface of the lower end of the radius to the dorsal surfaces of the bones of the first row of the carpus, and the corresponding volar radio-carpal ligament passes, not only to the bones of the first row, but also to the capitate (os magnum). In the depth of the carpal groove, ligaments converge to the capitate (os magnum) forming the radiate ligament. The remaining carpal ligaments, which unite the carpal bones either with each other or with the metacarpals are the volar and dorsal intercarpal, the volar and dorsal carpo-metacarpal and three volar and four dorsal interosseous ligaments, these last filling the intervals between the bases of the metacarpals.
The metacarpo-phalangeal articulations are between the heads of the metacarpals and the bases of the proximal phalanges. Collateral ligaments strengthen their sides and accessory volar ligaments their volar surfaces, while the transverse capitular ligaments unite the heads of the four ulnar metacarpals. The articular capsules of the interphalangeal articulations are strengthened laterally by collateral ligaments. Imbedded in the metacarpo-phalangeal joint of the thumb there are two sesamoid bones, and smaller and inconstant ones may be found in the corresponding joint of the index and little fingers.
The apex of the sacrum and the first coccygeal vertebra are united by the sacrococcygeal symphysis and also by a number of rather unimportant ligaments. On the anterior surface is the anterior sacro-coccygeal, at the sides the lateral sacro-coccygeal and behind the posterior sacro-coccygeal ligaments, The last have a superficial portion, which unites the sacral and coccygeal cornua, and a deep portion, which is the lower end of the posterior longitudinal ligament (see here).
The symphysis pubis is an amphiarthrosis uniting the symphyseal surfaces of the two pubic bones. The union is by an interpubic fibrocartilage, which frequently contains a slit-like cavity. Strengthening the symphysis there is a superior pubic ligament, which stretches from one pubic tubercle to the other over the upper border of the symphysis, and an arcuate ligament at the lower border.
The posterior joint of the pelvic girdle, the sacro-iliac articulation, is paired and is formed by the auricular surfaces of the sacrum and ilium. It is an almost immoveable joint, since the irregular curved and uneven surfaces do not lend themselves to any extensive movement. The contact of the two bones is further maintained by a strong ligament, the interosseous ligament, which unites the tuberosities of the bones, so that these are united anteriorly by a joint, posteriorly by a syndesmosis.
In addition to the interosseous ligament there is also a posterior sacro-iliac ligament, which consists of a superficial long and a deep short sacro-iliac ligament and is formed by a number 'of oblique fibre bundles that pass from the posterior part of the tuberosity of the sacrum to the crest of the ilium in the neighborhood of the posterior superior spine. A weaker anterior sacro-iliac ligament is merely a thickening of the anterior surface of the articular capsule.
Finally the ilio-lumbar ligament unites the ilium to the fifth lumbar vertebra. It is a strong band which passes from the transverse process of the fifth (sometimes also the fourth) lumbar vertebra to the crest of the ilium. By it the last lumber vertebra and the last intervertebral fibrocartilage become part of the boundary of the pelvis.
The obturator membrane closes the obturator foramen, except for a small area at the upper part of the foramen where the obturator groove begins.
The sacro-tuberous (great sacro-sciatic) ligament arises from the lateral portions of the posterior surfaces of both the sacrum and coccyx, from the posterior part of the crest of the ilium and its posterior superior and inferior spines. It concentrates to a broad firm band which is attached to the ischial tuberosity. A prolongation of it along the lower borders of the inferior rami of the ischium and pubis is termed the falciform process.
The much shorter sacro-spinous (lesser sacro-sciatic) ligament lies on the pelvic side of the sacro-tuberous and arises from the lateral border of the lower part of the sacrum and of the upper part of the coccyx; it is inserted into the spine of the ischium. It converts the great sacro-sciatic notch into a roundish, quadrangular foramen, the great Sacro-sciatic foramen. With the sacro-tuberous ligament it converts the lesser sacro-sciatic notch into the lesser sacro-sciatic foramen. The sacro-spinous ligament separates these two foramina and forms part of the pelvic outlet.
The pelvis is bounded by the following bones, the innominates (coxae), the sacrum, the coccyx, and the fifth lumbar vertebra. In addition certain ligaments or membranes take part in its boundaries, the interpubic fibrocartilage, the obturator membrane and the sacro-spinous, sacro-tuberous and ilio-lumbar ligaments.
There may be distinguished a great or false pelvis (pelvis major) and a small or true pelvis (pelvis minor). The former is much more capacious than the latter and it is only partly bounded by bones, the ala of the ilia and the fifth lumbar vertebra. Its separation from the true pelvis is indicated by the linea terminalis.
The true pelvis is a short canal with for the most part bony walls, the front wall being quite short, while the posterior one is markedly longer.
The inlet of the true pelvis (apertura superior) is bounded by the promontory, the three parts, sacral, iliac (linea arcuata) and pubic (pecten), of the terminal line and the upper border of the interpubic fibrocartilage or rather the superior pubic ligament.
The boundaries of the pelvic cavity are, behind, the concave pelvic surface of the sacrum and the anterior surface of the coccyx; laterally the pelvic surfaces of the bodies of the ilium, ischium and pubis, the sacro-tuberous and sacro-spinous ligaments, the rami of the pubis and ischium and the obturator membranes; anteriorly, the symphysis pubis and the anterior ends of the pubic bones. The anterior wall is by far the shortest, the posterior the longest. Posteriorly on the lateral walls are the two sacrosciatic foramina, the upper and larger one being rounded quadrangular, and the lower smaller one triangular.
The outlet (apertura inferior) is bounded by the arcuate ligament, the symphysis, the ischial tuberosities, the inferior rami of the pubes and ischia, the sacro-tuberous ligaments and the apex and lateral borders of the coccyx. In contrast to the inlet the boundary of the outlet is not in one plane. Its deepest point is formed by the coccyx and the ischial tuberosities also project strongly downwards, while in the region of the sacro-tuberous ligament and symphysis pubis the boundary slopes to a higher level. The angle that the two lower pubic rami form with the symphysis is termed the pubic angle and is somewhat rounded off to a pubic arch by the arcuate ligament.
The pelvis is not placed horizontally in the body but is inclined. Its inclination varies, being on the average about 60°(inclination of the plane of the inlet to the vertical). The pelvis, and especially the true pelvis, more than any other part of the skeleton shows sexual differences. In the female the false pelvis is lower, broader and flatter, and the ala of the ilium are usually less strongly concave. The cavity of the true pelvis is larger. Its inlet in the male is heart-shaped on account of the greater projection of the promontory; in the female it is transversely oval. The outlet in the male is more strongly narrowed than in the female, owing to the ischial tuberosities being somewhat convergent. The pubic angle in the male is acute, about 75-80°; in the female it is a right angle or obtuse, 90-100°. For the inguinal ligament see here.
The Inguinal ligament (Poupart's) arises from the anterior superior spine of the ilium and passes, tensely stretched, to the pubic tubercle, where it has a broadened insertion. An almost horizontal reflexion of the ligament extends from the insertion to the upper border of the superior ramus of the pubis, forming the lacunar ligament (Gimbernat's). The inguinal ligament is the tendinous lower edge of the aponeuroses and fasciae of the abdominal muscles, and does not properly belong to the ligaments of the pelvis.
The hip joint (articulatio coxae) is between the acetabulum of the innominate bone and the head of the femur. The socket is materially deepened by a strong, fibrocartilaginous glenoidal lip, triangular in cross section, so that it embraces more than half the spherical head. Consequently the joint is a typical ball and socket arrangement (enarthrosis). The glenoidal lip bridges the acetabular notch, converting it into a wide foramen; in this part of its extent the lip is termed the transverse ligament.
The articular capsule is greatly strengthened by reinforcing bands and is the strongest in the body. It takes origin around the base of the glenoidal lip and encloses not only the head of the femur but also the greater part of its neck. Anteriorly it is attached to the intertrochanteric line, but posteriorly it does not extend so far down, enclosing on that surface only a little more than half the neck. On account of the thickness of the capsule the extent of the joint cavity is somewhat less.
The reinforcing ligaments of the capsule are firmly united with it and may be either longitudinal or circular. The latter, forming the orbicular zone, surround the neck of the femur at its narrowest part and have a circular course in the inner layers of the capsule, firmly united to the longitudinal fibre bundles. A longitudinal ligament arises from each of the constituent parts of the innominate bone and they are thus three in number, the ilio-femoral, the pubo-capsular and the ischio-capsular.
Much the strongest of the three ligaments is the thick ilio-femoral ligament, one of the thickest ligaments of the body. It arises from the body of the ilium in the region of the anterior inferior spine and passes obliquely on the anterior surface of the capsule to the intertrochanteric line, which is produced by the ligament. The pubo-capsular ligament arises from the upper ramus of the pubis and passes on the medial surface of the capsule toward the lesser trochanter. The ischio-capsular ligament arises from the body of the ischium and passes on the posterior wall of the capsule for the most part to the orbicular zone, but in part also beyond this towards the lesser trochanter.
It is a peculiarity of the hip joint that its socket is not lined with cartilage over the area of the acetabular fossa, this being occupied by a pad of fat. From it as well as from the acetabular notch a characteristic ligament arises, the ligamentum teres, which is a flat, but sometimes strong, band, containing blood vessels, that is inserted into the fovea on the head of the femur. In the complete joint it lies upon the fat pad of the acetabular fossa and on account of its length and weakness does not limit materially the movements in the joint.
The thinnest parts of the capsule are situated on its lower wall, between the pubocapsular and ischio-capsular ligaments and above the orbicular zone, between the ischiocapsular and ilio-femoral ligaments. The anterior wall is also thin between the ilio-femoral and pubo-capsular ligaments, where occasionally a communication occurs between the joint cavity and the ilio-pectineal bursa, situated beneath the ilio-psoas muscle.
The knee joint (articulatio genus) is between the condyles and patellar surface of the femur on the one hand and the condyles of the tibia on the other. In addition, the articular surface on the posterior surface of the patella takes a passive part in the formation of the joint.
On account of its form and the multiplicity of its parts the knee joint is one of the most complicated joints of the body. The line of attachment of the articular capsule follows in general the margins of the cartilage-covered surfaces; on the posterior surface of the femur the intercondyloid line indicates the line of attachment, so that the whole intercondyloid fossa is excluded from the joint cavity.
The tibial collateral ligament is connected with the capsule. It arises from the medial epicondyle of the femur and passes, always intimately connected with the capsule, by its superficial fibers to the medial border of the tuberosity of the tibia and by short deep fibres, directed obliquely backwards, to the medial meniscus and the infraglenoid margin of the medial condyle of the tibia. The fibular collateral ligament, on the contrary, is for the most part separated from the capsule by fat tissue and consequently appears as an independent firm, rather flat and relatively small ligament, extending between the lateral epicondyle of the femur and the head of the fibula.
On the posterior wall of the capsule there are two reinforcing ligaments. The oblique popliteal ligament is a prolongation of the tendon of the semi-membranous muscle and runs obliquely from below and medial, upwards and laterally over the posterior surface of the capsule, in which it loses itself. The arcuate popliteal ligament is an arched band which curves over the tendon of origin of the popliteus muscle and also radiates out in the capsule. Some of its fibres pass to the head of the fibula and form what is termed the retinaculum of the arcuate ligament.
The anterior wall of the knee joint is formed almost entirely by the tendon of the quadriceps muscle and the patella. The quadriceps tendon is actually attached to the base of the patella, but it is continued by the flat, very strong patellar ligament, which passes from the apex of the patella to the tuberosity of the tibia. It is independent of the knee joint and unconnected with its capsule. A constant deep infrapatellar bursa, separates the ligament from the anterior surface of the upper part of the tibia. Tendinous prolongations from the quadriceps tendon, the medial and lateral patellar retinacula, strengthen the anterior part of the articular capsule.
The synovial folds of the knee joint are the alar and patellar folds. The former are formed largely of fatty tissue and lie behind the patellar ligament, where masses of fat covered by the synovial membrane of the joint bulge into the joint cavity forming medial and lateral alar folds. The patellar fold (ligamentum mucosum) is a fibrous and usually fat-containing band of variable thickness, that arises, between the alar folds and connected with them, from the front wall of the capsule and is attached behind in the intercondyloid fossa.
Of the outpouchings of the joint cavity the largest is the suprapatellar bursa, which extends for almost a hand's breadth beneath the tendon of the quadriceps. It is in wide communication with the joint cavity and into its upper wall the fibers of the quadriceps that form the articularis genus muscle are inserted. The posterior wall of the bursa does not rest directly on the femur, but on an interposed fat pad. Two or three much smaller outpouchings of the capsule occur on its posterior wall, the popliteal bursa under the tendon of the popliteus, the semimembranosus bursa under the tendon of the semimembranosus, and the medial gastrocnemial bursa under the tendon of the medial head of the gastrocnemius. The last two may unite. (See Figs. A323 and A324.)
Two discoidal or semilunar fibrocartilages rest on the condyles of the tibia, the medial and lateral menisci. They are not attached to the condyles, but to the capsule by their outer margins and to the intercondyloid eminence and the cruciate ligaments. In section they are wedge shaped. The medial meniscus is smaller than the lateral and almost semicircular; it forms, however, an arc of a greater circle than does the lateral, which is almost circular and open only at its attachment to the intercondyloid eminence. It is broader than the medial and, since its radius is smaller, it covers the condyle of the tibia except over a relatively small central area. The lateral meniscus is attached to the anterior intercondyloid fossa and to the lateral intercondyloid tubercle, the medial one extends from the anterior border of the medial condyle of the tibia to the posterior inter-condyloid fossa. The two menisci are connected anteriorly by a very variable transverse ligament.
In addition to the menisci there are associated with the knee joint two remarkably strong ligaments, the cruciate ligaments. They arise from the intercondyloid fossa of the femur and pass to the intercondyloid tubercles or fossae of the tibia. The anterior cruciate ligament passes between the medial surface of the lateral condyle of the femur and the anterior intercondyloid tubercle and fossa of the tibia, and the posterior cruciate ligament arises from the lateral surface of the medial condyle of the femur and passes to the posterior intercondyloid tubercle and fossa of the tibia. The two ligaments, of which the posterior is usually the stronger, cross one another in passing from one bone to the other. The posterior one is usually connected with the lateral meniscus.
The tibio-fibular articulation is between the fibular articular surface of the femur and the articular surface on the head of the fibula. It is a pronounced amphiarthrosis, with almost flat articular surfaces and with strong connecting bands on its anterior and posterior surfaces, the fibular capitular ligaments. Rarely the joint communicates with the knee joint through the popliteal bursa.
The interosseous membrane is very similar to that of the forearm and like this, extends between the interosseous crests of the two bones. In its upper part it has a large perforation for the passage of vessels.
The tibio-fibular syndesmosis is formed by two ligaments, rich in elastic fibres, extending on the anterior and posterior surfaces between the lower ends of the tibia and fibula. They are the lateral malleolar ligaments and are put on the stretch when the broader anterior part of the talus is brought between the two bones, the stretching being possible on account of the elastic fibres of which the ligament is largely composed.
The ankle joint (talo-crural articulation) is between the talus and the two bones of the lower leg. The articular surfaces are the trochlea of the talus on the one hand and on the other hand the inferior surface of the tibia, the articular surface of the medial malleolus and that of the lateral malleolus. The thin articular capsule surrounds the articular surfaces.
The group of ligaments that radiate from the medial malleolus to the talus, calcaneus and navicular constitutes what is termed the deltoid ligament. It consists of four not very distinctly separate ligaments, the anterior and posterior talo-tibial, the calcaneo-tibial and the tibio-navicular. The first of these passes to the anterior part of the neck of the talus and is completely covered in by the calcaneo-tibial. This is attached to the border of the sustentaculum tali, while the posterior talo-tibial goes to the posterior process of the talus and the tibio-navicular to the dorsal surface of the navicular.
Three distinctly separate ligaments pass from the lateral malleolus to the talus and calcaneus, the anterior and posterior talo-tibular and the calcaneo-tibular. The first of these runs almost horizontally from the anterior surface of the malleolus to the anterior border of the trochlea of the talus; the second, also horizontal, passes to the lateral tubercle of the posterior process of the talus; and the calcaneo-fibular passes obliquely downward and backward to the lateral surface of the calcaneus.
The talo-calcaneal articulation is between the posterior articular surface of the calcaneus and the posterior calcaneal facet of the talus. The latter is concave, the former convex. Occasionally the joint cavity communicates with that of the ankle joint.
The talo-calcaneo-navicular articulation is between the head of the talus on the one hand and the anterior and middle articular surfaces of the calcaneus, the posterior surface of the navicular and the navicular fibrocartilage in the plantar calcaneo-navicular ligament (see here). The socket for the head of the talus is thus formed by four different cartilage-covered surfaces. It is a composite joint, being a combination of the anterior and middle talo-calcaneal and the talo-navicular articulations.
The ligamentous connections of the talus and calcaneus are, firstly, the interosseous talo-calcaneal ligaments which fill the sinus tarsi and, secondly, reinforcing ligaments of the posterior talo-calcaneal joint, the medial, lateral, posterior and anterior talo-calcaneal ligaments. The lateral and anterior ligaments, which bridge over the sinus tarsi, are united with the interosseous ligament, the posterior one extends between the lateral tubercle of the posterior process of the talus and the upper surface of the calcaneus, and the medial passes from the tubercle of the talus to the sustentaculum tali.
The calcaneo-cuboid articulation is between the cuboid surface of the calcaneus and the posterior surface of the cuboid. The surfaces are almost saddle-shaped. With the talo-navicular articulation it formes the transverse tarsal articulation (Chopart's).
The cuneo-navicular articulation is between the anterior surface of the navicular and the posterior surfaces of the three cuneiform bones and extends between the cuneiform bones themselves, and between the lateral surface of the cuboid and the corresponding surfaces of the navicular and lateral cuneiform. As a rule the joint also communicates between the medial and middle cuneiforms with the second tarso-metatarsal articulation.
The tarso-metatarsal articulations (Lisfranc's articulation), together with the intermetatarsal articulations, are three joints, one between the metatarsal of the great toe and the medial cuneiform, a second, between the bases of the second and third metatarsals and the middle and lateral cuneiforms, and a third, between the fourth and fifth metatarsals and the cuboid. The line of the joints is a curve convex anteriorly with a deep backward indentation between the middle cuneiform (short) and the base of the second metatarsal (long).
The dorsal tarsal ligaments pass from the talus and calcaneus on the one hand to the navicular and cuboid on the other. They are the dorsal talo-navicular, the dorsal calcaneo-navicular and the bifurcated ligaments. The latter unites the anterior medial angle of the calcaneus with the dorsal surfaces of the navicular and cuboid, dividing into two parts corresponding to the two bones.
The dorsal naviculari-cuneiform ligaments unite the navicular bone with the cuneiforms; the dorsal cuboideo-navicular, the cuboid with the navicular; the dorsal intercuneiform, the three cuneiforms with one another; and the dorsal cuneo-cuboid, the lateral cuneiform and the cuboid. The dorsal tarso-metatarsal ligaments unite the bases of the metatarsals with the tarsal bones and the four dorsal basal ligaments unite to one another the bases of the metatarsals.
By far the strongest ligament of the sole of the foot is the long plantar ligament. It arises from the whole of the under surface of the calcaneus and from the medial and lateral tuberosities of the tuber calcanei, covering the entire width of the bone, and passes with very strong longitudinal fibres to the tuberosity of the cuboid. From this principal portion of the ligament superficial slips pass out, which pass over the tendon sheath of the groove on the cuboid and reach the basis of the lateral metatarsals. They form the retinaculum for the tendon sheath of the Peroneus longus.
Almost as strong is the plantar calcaneo-navicular ligament. It runs with oblique, very strong fibres between the sustentaculum tali and the navicular. On its dorsal surface it contains the navicular fibrocartilage, which forms part of the socket for the head of the talus.
The plantar naviculari-cuneiform ligaments unite the navicular and the cuneiforms; the plantar cuboideo-navicular the cuboid and the navicular; the plantar cuneo-cuboid, the cuboid and the lateral cuneiform; and the plantar intercuneiform, the three cuneiforms with one another. In addition, there are plantar tarso-metatarsal and three plantar basal ligaments which correspond with the dorsal. The plantar calcaneo-cuboid ligament, which reinforces the capsule of the calcaneo-cuboid joint, unites with the dorsal surface of the long plantar ligament.
Those ligaments that are on neither the dorsal nor the plantar surfaces, but connect adjacent surfaces of the tarsal and metatarsal bones, are termed interosseous ligaments. In addition to the interosseous talo-calcaneal ligaments there is an interosseous cuneo-cuboid, interosseous intercuneiform, interosseous cuneo-metatarsal (especially between the medial cuneiform and the base of the second metatarsal where an interosseous basal ligament is wanting), and interosseous basal ligaments.
The metatarso-phalangeal and interphalangeal articulations of the foot are, with slight differences, similar to those of the hand, and present the same ligaments. The meta-tarso-phalangeal joint of the great toe shows a special structure in that two large sesamoid bones are imbedded in its capsule on the plantar surface.
The Trapezius arises from the squamous portion of occipital above the superior nuchal line, from the lig. nuchae, and from the spines of the last cervical and all the thoracic vertebrae. It is inserted into the acromial third of the clavicle, the acromion and spine of the scapula. Nerve: The spinal accessory (and branches of the cervical plexus). Action: The upper fibres raise the scapula, the lower depress it; all acting together draw the scapula backward; those to the skull rotate the head toward the opposite side, the lower fibres draw the lower angle of the scapula medialwards.
The Latissimus dorsi arises from the spinous processes of the lower six thoracic and all the lumbar vertebrae, from the dorsal surface of the sacrum, and the lateral lip of the iliac crest. Accessory slips arise from the lower three or four ribs and frequently from the lower angle of the scapula. It inserts into the crest of the lesser tuberosity of the humerus, together with the teres major from which it is separated by a bursa. Nerve: The thoraco-dorsal from the brachial plexus. Action: It draws the arm backward, adducts it and rotates it inward.
The Rhomboideus major arises from the spinous processes of the upper four thoracic vertebrae and inserts into the vertebral border of the scapula, below the spine.
The Rhomboideus minor arises from the lig. nuchae and the spinous process of the last cervical vertebra and is inserted into the vertebral border of the scapula, above the spine. Nerve: Both rhomboids are supplied by the dorsal scapular from the brachial plexus. Action: They draw the scapula towards the vertebral column and upwards.
The Levator scapulae arises by four heads from the posterior tubercles of the transverse processes of the four upper cervical vertebrae and inserts into the medial angle of the scapula. Nerve: The cervical plexus and the dorsal scapular. Action: Draws the medial angle of the scapula upwards and medially.
The Superior serratus posterior arises from the spinous processes of the two lower cervical and the two upper thoracic vertebrae and is inserted into the second to the fifth ribs, lateral to their angles.
The Inferior serratus posterior arises, through the posterior layer of the lumbodorsal fascia, from the spinous processes of the lower thoracic and upper lumbar vertebrae. It inserts into the lower borders of the four lower ribs. Nerve: Both serrati are supplied by intercostal nerves. Action: They act on the ribs in inspiration.
The Splenius capitis arises from the lig. nuchae and the spinous processes of the last cervical and first thoracic vertebrae and inserts into the lateral half of the superior nuchal line, as far out as the mastoid process. Nerve: The posterior branches of the 1-4 (5) cervical nerves. Action: Both muscles draw the head backwards; acting singly, they rotate the head to the same side.
The Splenius cervicis arises from the spinous processes of the third or fourth to the sixth thoracic vertebra and is inserted into the posterior tubercles of the transverse processes of the upper three cervical vertebrae. Nerve: The posterior branches of cervical nerves. Action: Draws the head backwards and rotates the upper cervical vertebrae and head to the same side.
The Spino-transversalis consists of the lateral Ilio-costalis and the medial, stronger Longissimus. Medial to the latter and fused with it is the Spinalis.
The Iliocostalis has three parts which pass over into one another without any sharp lines of demarcation. The Iliocostalis lumborum arises with the Longissimus dorsi from the dorsal surface of the sacrum and from the lateral lip of the iliac crest. It inserts into the angles of the fifth to the twelfth ribs. The Iliocostalis arises by digitations from the twelfth to the seventh ribs and inserts into the angles of the upper six ribs and the transverse process of the seventh cervical vertebra. The Iliocostalis cervicis arises from the upper and middle ribs and inserts into the transverse processes of the middle cervical vertebrae. Nerves: Posterior branches of the cervical, thoracic and lumbar nerves. Action: Extends the vertebral column and bends it backward, acting with the other long muscles.
The Longissimus also consists of three parts. The Longissimus dorsi arises with the iliocostalis lumborum from the dorsal surface of the sacrum and from the spinous processes of the lumbar and lower thoracic vertebrae. It inserts into the accessory processes of the upper lumbar and the transverse processes of the thoracic vertebrae, and, more laterally, into the tip of the transverse processes of the lumbar vertebrae and into all the ribs, between their angles and tubercles. The Longissimus cervicis is not clearly separated from the upper part of the Longissimus dorsi; it arises from the transverse processes of the upper thoracic vertebrae and inserts into the transverse processes of the upper and middle cervicals.
The Longissimus capitis (Trachelomastoid) arises from the transverse processes of the upper thoracic vertebrae and from the transverse and articular processes of the middle and lower cervicals. It is inserted into the posterior border of the mastoid process. Nerves : Posterior rami of the cervical and thoracic nerves. Action: Extends the vertebral column and bends it backwards; the Longissimus capitis acts also on the neck and head.
The Spinalis again has three portions. The Spinalis dorsi arises from the spinous processes of the upper lumbar and the lower thoracic and inserts into the same processes of the middle and upper thoracic vertebrae. The Spinalis Cervicis (inconstant) passes between the spinous processes of the lower cervical vertebrae and those of the upper thoracic. The Spinalis capitis is properly a portion of the Semispinalis capitis, representing its inconstant spinal head. Nerves: Posterior rami of the cervical, thoracic and lumbar nerves. Action: Bends the vertebral column sidewise; acting on both sides, it extends.
The Semispinalis has three portions. The Semispinalis dorsi and cervicis arise from the transverse processes of the thoracic and lower cervical vertebrae and, passing steeply upward and inward, inserts into the spinous processes of the middle and upper thoracic and lower cervical vertebrae. The lateral portion of the Semispinalis capitis arises from the transverse processes of the third cervical to the fifth or sixth thoracic vertebrae, the medial portion (the spinalis capitis) from the spinous process of the upper thoracic and lower cervical vertebrae. Its insertion is into the squamous portion of the occipital, between the superior and inferior nuchal lines. Nerves: Posterior rami of the cervical and thoracic nerves. Action: Extends the vertebral column and head. Acting on one side only it rotates the head toward the opposite side.
The Multifidus is a series of small muscles that arise from the dorsal surface of the sacrum and the transverse processes of all the vertebrae up to the lower cervical and pass upwards and inwards to the second or third spinous process next above.
The Rotatores longi and breves pass between the bases of the transverse processes of the thoracic vertebrae and the spinous process of the vertebra next (breves), or next but one (longi), above. Nerves: The Multifidus and Rotatores are supplied by the posterior rami of the spinal nerves. Action: Extension of the spinal column and rotation the opposite side.
The Rectus capitis posterior major arises from the spinous process of the axis (epistropheus) and is inserted into the inferior nuchal line. The Rectus capitis posterior minor arises from the posterior tubercle of the atlas and ascends to the inferior nuchal line. The Rectus capitis lateralis (see Fig. A276) takes its origin from the transverse process of the atlas and passes to the jugular process of the occipital.
The Obliquus capitis superior arises from the transverse process of the atlas and passes upwards to the inferior nuchal line. The Obliquus capitis inferior arises from the spinous process of the axis (epistropheus) and passes outwards and upwards to the transverse process of the atlas.
Nerve : All five muscles are supplied by the suboccipital nerve, the posterior ramus of the first cervical. Action: They serve for the extension and rotation of the head. The Obliquus inferior and Rectus major and minor rotate toward the same side, the Obliquus superior to the opposite one; the Rectus lateralis bends the head forward.
The Interspinales are wanting in the thoracic region. Elsewhere they extend from spinous process to spinous process. The first are between the atlas and axis (epistropheus), and throughout the cervical region they are paired, the spinous processes being bifurcated.
The Intertransversarii are, as a rule, absent in the thoracic region. In the cervical there are Anterior intertransversarii between the anterior tubercles of successive vertebrae, and Posterior intertransversarii between successive posterior tubercles. In the lumbar region there are Medial intertransversarii, between the accessory and mamillary processes of succeeding vertebrae, and Lateral intertransversarii between the transverse processes; the latter are much the larger.
Nerves: Posterior rami of the spinal nerves. Action: The interspinales bend the spinal column backwards, the intertransversarii bend it laterally.
The Levatores costarum are really the posterior portions of intercostal muscles. They arise from the transverse processes of the thoracic vertebrae and pass to the succeeding rib (Levatores costarum breves), or to the next but one (Levatores costarum longi) inserting between the tuberosity and the angle. Action: Raise the ribs, extend the vertebral column and bend it laterally.
The strongest fascia of the back is the lumbo-dorsal fascia whose relations are shown in Fig. A255. The superficial layer of muscles is covered by the general fascia, but the different layers of the long muscles are not distinctly separated by fascia and the short muscles are destitute of it.
The Pectoralis major arises by a clavicular portion from the sternal half of the clavicle, by a sterno-costal portion from the anterior surface of the manubrium and body of the sternum and from the second to the sixth costal cartilages and by an abdominal portion from the abdominal aponeurosis (sheath of the Rectus). It is inserted by a broad tendon, resembling a two-layered pouch with the opening upward, into the crest of the great tuberosity of the humerus. Nerve: The anterior thoracic from the brachial plexus. Action: Adducts the arm, draws it medially and forward, rotates it inwards.
The Pectoralis minor arises from the second to the fifth ribs, near the cartilages, and inserts into the apex of the coracoid process of the scapula. Nerve: The anterior thoracic from the brachial plexus. Action: Draws the scapula downwards; if the scapula is fixed it raises the ribs.
The Subclavius is a small muscle arising from the first costal cartilage and inserting into the under-surface of the acromial end of the clavicle. Nerve: The subclavian from the brachial plexus. Action: Fixes the clavicle in the sterno-clavicular joint, drawing it forward and downward.
Serratus anterior arises by digitations from the first to the ninth ribs. The upper portion, from the first and second ribs, is inserted into the medial angle of the scapula; the middle portion, from the second and third ribs, into almost the entire length of the vertebral border of the scapula; the lower portion, from the fourth to the ninth rib, converges on the inferior angle of the scapula. Nerve: The long thoracic from the brachial plexus. Action: Draws the scapula forward and laterally, especially its lower angle, the scapula thus being rotated on the chest wall, as in raising the arm.
The Obliquus externus arises by seven or eight digitations from the fifth or sixth to the twelfth rib. It is inserted into the lateral lip of the iliac crest and into the inguinal ligament and the anterior wall of the sheath Rectus. Nerve: The lower intercostal nerves and branches from the lumbar plexus, the ilio-hypogastric and ilio-inguinal. Action: Compresses the abdomen, draws the trunk forward or rotates it to the same side, raises the pelvis.
The Obliquus internus arises from the intermediate line of the iliac crest, from the lumbo-dorsal fascia and from the lateral two-thirds of the inguinal ligament. It is inserted into the lower borders of the last three ribs and the linea alba, its tendon forming the anterior wall of the sheath of the Rectus and the upper part of its posterior wall. Nerves: The lower intercostals and branches of the lumbar plexus (ilio-hypogastric, ilio-inguinal and genito-femoral). Action: Similar to that of the external oblique.
The Cremaster arises from the lower bundles of the Internal oblique and from the anterior wall of the sheath of the Rectus, and is continued down over the spermatic cord to the scrotum. Nerve: External Spermatic. Action: Draws the testis upwards.
The Transversus arises from the inner surfaces of the last six ribs (fleshy), from the lumbodorsal fascia (tendinous) and from the inner lip of the iliac crest and the lateral third of the inguinal ligament (fleshy). It is inserted at the linea semilunaris into the posterior wall of the sheath of the Rectus and, below, into the anterior wall. Nerves: The lower intercostals and branches from the lumbar plexus (iliohypogastric, ilioinguinal, and genito-femoral). Action: Compresses the abdomen.
The Rectus abdominis arises from the cartilages of the fifth to the seventh rib and from the xiphoid process, and inserts by a short tendon into the upper border of the pubis between the tubercle and the upper border of the symphysis. The muscle fibres are interrupted by tendinous inscriptions, of which three are constant; an upper, in the region of the costal arch; a lower in the neighborhood of the umbilicus; and a middle between these. A fourth sometimes occurs below the umbilicus and usually only in the lateral part of the muscle. At the inscriptions the muscle unites with the anterior wall of its sheath, from which elsewhere it is separated by loose connective tissue. The posterior wall does not unite with the inscriptions; it ends below at the semicircular line (Douglas' line), not always very distinct, the lower part of the muscle having behind it only the fascia transversalis. Nerves: The middle and lower intercostals and occasionally the first lumbar. Action: It bends the trunk forward or raises the pelvis; it also aids in compressing the abdominal contents.
The Pyramidalis is an inconstant muscle that arises immediately in front of the origin of the Rectus. It is inserted into the linea alba above the symphysis. Nerves: The lower intercostals. Action: Tenses the linea alba.
In the aponeurosis of the Obliquus abdominis externus a triangular cleft occurs, no fibres inserting between the pubic tubercle and the upper border of the symphysis. The lateral angle of the cleft is rounded off by superficial, arched intercrural fibres, and the medial angle by the reflexed inguinal ligament, extending upwards from the insertion of the inguinal ligament. The irregularly quadrangular opening so formed is the subcutaneous inguinal ring, through which the spermatic cord passes in the male and the ligamentum teres of the uterus in the female (see Fig. A262). The borders of the aponeurosis that bound the ring are termed the crura (superius and inferius).
The tendon of the Obliquus internus forms both walls of the sheath (vagina) of the Rectus, which is strengthened in front by the Obliquus externus and behind by the Transversus. In the lower third of the abdomen the posterior wall is completely wanting below the semicircular line (Douglasi) (see here), all three muscles passing to the anterior wall. In the middle line the sheaths of the two Rectus muscles unite to form a broad, tendinous strip, the linea alba, that extends from the xiphoid process to the upper border of the symphysis pubis (see Fig. A266).
The Quadratus lumborum arises from the medial lip of the iliac crest, the iliolumbar ligament and the transverse processes of the lower lumbar vertebrae. Its fibres form two parallel layers which are partly interwoven. It inserts into the medial half of the twelfth rib and into the transverse processes of the upper and middle lumbar vertebrae. Nerves: Branches from the lumbar plexus and the twelfth intercostal. Action: Draws the last rib downwards and bends the lumbar vertebrae laterally.
The Diaphragm arises by its sternal portion from the xiphoid process of the sternum, by its costal portion from the inner surface of the last six ribs and their cartilages, and by its lumbar portion from the lumbar vertebrae by three pairs of crura. The medial crura are attached to the anterior surface of the third and fourth vertebrae, the intermediate crura to the lateral surfaces of the body of the second vertebra and the lateral crura to the transverse processes of the first vertebra and to the lumbo-costal arches. From these origins the fibres radiate to a trifoliate central tendon. Between the medial crura is the aortic opening (hiatus); in the muscular part of its lumbar portion, the oesophageal opening; and in the central tendon, the foramen for the vena cava. Between the medial and intermediate crura and between the latter and the lateral there are gaps, and also between the costal and sternal portions. Nerve: Phrenic from the cervical plexus. Action: A muscle of respiration, inspiratory.
The Iliopsoas consists of two or three parts, the Psoas major, Psoas minor, and Iliacus. The Psoas major arises from the upper and lower borders of the bodies of the twelfth thoracic to the fourth lumbar vertebra, and from the fibrocartilages between these; also from the transverse processes of all the lumbar vertebrae. The Psoas minor is inconstant; when present it arises from the bodies of the last thoracic and first lumbar vertebrae and is inserted by a long slender tendon into the iliac fascia and the iliopectineal eminence. The Iliacus arises from the whole of the iliac fossa. It unites with the psoas major, and the combined muscle passes over the crest of the pubis and over the capsule of the hip joint, separated from this by the iliopectineal bursa, and inserts into the lesser trochanter of the femur. Nerves: Branches from the lumbar plexus. Action: Flexes the thigh, rotates it inwards and aids in adduction. The Psoas minor tenses the iliac fascia.
The External intercostals pass between the opposed borders of successive ribs, beginning behind the tuberosity and ending in front shortly before the junction of the ribs and their cartilages. Their fibres are directed from above downwards and inwards, like those of the External oblique. In the region of the costal cartilages they are continued as tendinous bundles, the external intercostal ligaments.
The Internal intercostals are covered by the external, except in the region of the cartilages. Their fibres are directed upwards and inwards, like those of the Internal oblique, and are lacking at the hinder ends of the ribs, between the angles and the tuberosities, where they are replaced by the internal intercostal ligaments.
The Subcostales immediately succeed the Internal intercostals. They are not quite constant and differ from the Internal intercostals in that they occur at the hinder portions of the ribs and pass over one or more. They occur only on the lower ribs and are usually largely tendinous.
The Transversus thoracis (triangularis sterni) arises from the posterior surface of the body of the sternum and the xiphoid process and is inserted into the inner surfaces of the cartilages of the second (third) to the sixth rib.
Nerves: The Intercostals are supplied by the intercostal nerves which run between the external and internal. The Transversus thoracis and Levatores costarum are also supplied by these nerves. Action: The Intercostals are respirator muscles; the externals and the portions of the internals between the costal cartilages serve in inspiration, as do also probably the rest of the Intercostals and the Subcostals, though they have been held to act in expiration.
For the Levatores costarum see here.
The pectoral fascia, which covers the Pectoralis major and Serratus anterior, is merely a portion of the general fascia and as such is continued downwards over the superficial abdominal muscles and backwards over the dorsal muscles (Latissimus). Directly continuous with it is the axillar fascia, perforated by numerous blood vessels. an in part much stronger sheet, the coraco-clavicular fascia lies between the Pectoralis major and Pectoralis minor, covering the Subclavius and the axillary vessels. It is especially strong where it rests on the Subclavius, and is attached to the under surface of the clavicle and to the coracoid process. The endothoracic fascia covers the inner surfaces of the ribs and Intercostal muscles and also the upper surface of the Diaphragma; it is in contact with the parietal layer of the pleurae.
The superficial layer of the abdominal muscles is covered by the general fascia, but this, in the region of the inguinal ring in the lower region of the abdomen, acquires a very considerable strength and is continued as the cremasteric fascia (Cooper's) upon the spermatic cord. It is also continuous with the fascia penis and forms the ligamentum fundiforme penis (in the female the much weaker ligamentum fundiforme clitoridis) which arises from the linea alba, to which the fascia is closely united, and, dividing into two portions, surrounds the root of the penis; it is rich in elastic fibres. The sheath of the Rectus serves as its fascia. The inner surface of the Transversus, the anterior surface of the Quadratus lumborum and the posterior surface of the posterior wall of the sheath of the Rectus are covered by the transversalis fascia. Over these structures the fascia is especially strong and it is firmly fused with the tendinous portion of the Transversus and the posterior wall of the sheath of the Rectus. Below the linea semicircularis it alone forms the posterior wall of the sheath. Above the symphysis it fuses with a triangular, tendinous offset from the superior pubic ligament, the adminiculum lineae albae. At the inguinal ligament, with which it unites, the Transversalis passes over into the iliopectineal fascia and it also passes over into that portion of the iliac fascia that covers the anterior surface of the Psoas. Above it is lost on the under surface of the Diaphragm. It is in contact with the parietal layer of peritoneum.
The Platysma arises from the skin covering the pectoral and deltoid fasciae and is inserted into the skin over the base of the mandible, the chin and face. Nerve: Ramus colli of the facial nerve. Action: contracts the skin of the neck and upper part thorax and tenses the cervical fascia.
The Sterno-mastoid (sterno-cleido-mastoid) arises by a sternal head from the anterior surface of the manubrium sterni and by a clavicular head from the sternal end of the clavicle. It is inserted into the lateral part of the base of the mastoid process and the lateral half of the superior nuchal line. Nerve: The spinal accessory. Action: Fixes the head, turns the face upwards. If only one acts, the head is drawn to the same side and rotated towards the opposite one.
The Sterno-hyoideus arises from the upper border of the first costal cartilage, the posterior surface of the manubrium and the sterno-clavicular joint. It has frequently a tendinous inscription in its lower part and inserts into the body of the hyoid bone.
The Sterno-thyreoideus arises from the inner surface of the first costal cartilage and from the posterior surface of the manubrium. It also frequently has a tendinous inscription in its lower part, and inserts into the outer surface of the thyreoid cartilage.
The Thyreo-hyoideus arises from the outer surface of the thyreoid cartilage and is inserted into the lateral third of the body of the hyoid and into the root of the greater cornu. The Omohyoideus arises from the upper border of the scapula between the medial angle and the scapular notch. It is divided in the middle of its course into two bellies by an intervening tendon, and is inserted into the lower border of the lateral part of the body of the hyoid.
Nerves: All four muscles are supplied from the ansa hypoglossi. The Thyreo-hyoideus usually has a direct branch from the hypoglossal. Action: Draw the hyoid bone and larynx downwards and assist in swallowing. The Omohyoideus by the union of its intermediate tendon with the cervical fascia, tenses that fascia.
The Digastricus is divided into two bellies by an intermediate tendon which is attached to the hyoid bone. The posterior belly (venter) arises from the notch on the mastoid process and the anterior belly is attached to the digastric fossa of the mandible. Nerves: The anterior belly is supplied by the mylohyoid and the posterior by the facial. Action: Opens the mouth, raises and fixes the hyoid bone.
The Stylo-hyoideus arises from the styloid process of the temporal and is inserted by two slips into the anterior and posterior borders of the lateral part of the hyoid. The intermediate tendon of the digastric passes between the two slips of insertion. Nerve: The facial. Action: Fixes the hyoid, drawing it upward and laterally.
The Mylo-hyoideus arises from the mylohyoid line of the mandible. The muscle forms the floor of the mouth extending across the arch of the mandible. Its more median fibres unite in a median raphe; the lateral insert into the upper border of the body of the hyoid. Nerve: The mylohyoid from the third division of the trigeminus. Action: Raises the floor of the mouth, depresses the mandible, aids in deglutition.
Th Genio-hyoideus arises from the mental spine and inserts into the anterior border of the body of the hyoid. Nerve: Hypoglossal. Action: Aids the Mylohyoid, fixes the hyoid, and depresses the mandible.
The Scalenus anterior arises from the anterior tubercles of the transverse processes of the third (fourth) to the sixth cervical vertebrae and is inserted into the scalene tubercle of the first rib.
The Scalenus medius arises from the anterior tubercles of the transverse processes of all the cervical vertebrae. It is inserted into the first rib, lateral to the preceding. The Scalenus posterior arises from the posterior tubercles of the transverse processes of the fifth to the sixth (seventh) cervical vertebrae and inserts into the upper border of the second rib.
Nerves: From the cervical and brachial plexuses. Action: Elevate the upper two ribs. Muscles of respiration.
The Longus colli arises by a medial limb from the bodies of the upper thoracic and lower cervical vertebrae; by an upper lateral limb from the anterior tubercles of the transverse processes of the upper cervical vertebrae; and by a lower lateral limb from the lateral surfaces of the bodies of the upper thoracic vertebrae. It inserts by its medial limb into the bodies of the upper cervical vertebrae; by its upper lateral limb into the anterior tubercle of the atlas and the bodies of the succeeding vertebrae; and by its lower lateral limb into the transverse processes of the lower cervical vertebrae, especially the sixth.
The Longus capitis arises from the anterior tubercles of the transverse processes of the third to the sixth cervical vertebrae and inserts into the lower surface of the basilar portion of the occipital.
The Rectus capitis anterior has its origin from the root of the transverse process of the atlas and is inserted close to the preceding muscle. Nerves: Special branches of the cervical plexus. Action: Bend the vertebral column and head anteriorly; acting singly bend the head to the same side.
The facial muscles include the Epicranius with the associated auricular muscles, the Orbicular muscle of the eyelids, the muscles of the mouth and those of the nose.
The differ from most of the other skeletal muscles in many respects; they are in the deeper layers of the skin, they generally lack fascia, they are entirely fleshy or have very short tendons. In certain regions they form sphincters. Frequently adjacent muscles are imperfectly separated; thus the muscles of the mouth region unite together in the upper and lower lip.
The epicranial muscles are attached to a common tendinous sheet, the galea aponeurotica, which covers the whole vault of the skull.
The Frontalis arises from the upper border of the orbit and is attached above to the galea aponeurotica.
The Procerus is attached to the nasal bones and is inserted into the skin over the glabella.
The Occipitalis arises from the supreme nuchal line and passes to the galea aponeurotica.
The Epicranius auricularis is a superficial muscle that is divided by the branches of the superficial temporal artery into three parts, which are quite distinct from the deeper Auriculus anterior and posterior and do not all reach the auricular cartilage.
Nerve: The facial. Action: Move the scalp.
The Auricularis anterior (attrahens) arises from the superficial temporal fascia and from the margin of the galea aponeurotica; the Auricularis superior (attollens) arises from the galea aponeurotica in the temporal region; and the Auricularis posterior (retrahens) from the tendon of insertion of the sterno-mastoid. The three muscles insert into the root of the auricular cartilage. Nerve: The facial. Action: Move the auricle.
The Orbicularis oculi has three portions: The orbital portio arise the frontal process of the maxilla at the medial angle of the orbit and its fibres surround the opening of the orbit like a sphincter; some of the fibres insert into the eyebrow (depressor capitis supercilii). The palpebral portion has its origin in the medial palpebral ligament and inserts into the lateral palpebral raphe, while the lacrimal portion (Horner's muscle) is attached medially to the posterior lacrimal crest and fuses laterally with the palpebral portion. A portion arising from the nasal part of the frontal bone and inserting into the skin of the eyebrow is termed the Corrugator supercilii. Nerve: The facial. Action: Closes the eyelids, compresses the lacrimal sac.
The Quadratus labii superioris arises by three heads. The angular head arises from the frontal process of the maxilla and passes partly to the ala of the nose and partly to the upper lip. The infraorbital head arises from the infraorbital border and the zygomatic head from the malar surface of the zygomatic bone; these two heads pass to the upper lip.
The Zygomaticus arises from the malar surface of the zygomatic bone and passes to the angle of the mouth.
Nerve: The facial. Action: Movement of the upper lip, the ala of the nose and the angle of the mouth.
The Risorius, usually part of the Platysma or of the Triangularis, arises from the parotideo-masseteric fascia and passes to the angle of the mouth.
The Triangularis (depressor anguli oris) arises from the anterior end of the base of the mandible and passes to the angle of the mouth and the lower lip.
The Caninus (levator anguli oris) arises from the canine fossa of the maxilla and passes to the upper lip and the angle of the mouth.
The Quadratus labii inferioris arises from the anterior part of the base of the mandible and passes to the lower lip.
The Incisivus labii superioris arises from the jugum of the upper lateral incisor tooth and passes to the upper lip. The Incisivus labii inferioris arises from the jugum of the lower lateral incisor tooth and passes to the lower lip. The Incisive muscles probably should not be regarded as distinct muscles any more than the slip of the Nasalis that passes to the cartilaginous septum of the nose (Depressor septi).
The Bucinator arises from the bucinator crest of the mandible, the posterior end of the alveolar process of the maxilla and the pterygo-mandibular raphe. Its fibres at the angle of the mouth are continued into the upper and lower lips, arching around the mouth to form the Orbicularis oris.
The Mentalis (levator menti) arises from near the jugum of the lower medial incisor tooth and passes to the skin of the chin.
Nerve: The facial. Action: Move the lips, cheeks and chin.
The Nasalis consists of two portions, a transverse portion arising from the maxilla and passing transversely to the bridge of the nose, and an alar portion from the jugum of the upper canine tooth to the ala of the nose and the septal cartilage. Nerve: The facial. Action: Slight movement of the nose, especially of the ala.
The Masseter arises by its superficial fibres from the lower border of the zygoma, by its deeper fibres from the posterior part of the lower border and from the inner surface of the zygoma. It is inserted into the lateral surface of the ramus of the mandible from the mandibular notch to the angle (masseteric tuberosity). Nerve: The masseteric nerve from the third division of the trigeminus. Action: Closes the jaws.
The Temporalis arises from the temporal fossa, below the inferior temporal line, and from the deep lamina of the temporal fascia. It inserts into the apex and medial surface of the coronoid process of the mandible. Nerves: The deep temporal nerves from the third division of trigeminus. Action: Closes the jaws.
The Pterygoideus externus arises by its chief head from the lateral surface of the lateral plate of the pterygoid process and from the tuberosity of the maxilla; by its accessory head from the infratemporal crest of the greater wing of the sphenoid. It is inserted into the pterygoid fovea on the condyloid process of the mandible and into the articular disk of the mandibular articulation. Nerve: The external pterygoid from the third division of the trigeminus. Action: Draws the mandible forward. By the alternate action of the two muscles lateral movements of the mandible are produced.
The Pterygoideus internus arises from the pterygoid fossa, from the pyramidal process of the palatine and from the medial surface of the lateral plate of the pterygoid process. It inserts into the medial surface of the angle of the mandible (pterygoid tuberosity). Nerve: The internal pterygoid from the third division of the trigeminus. Action: Closes the jaws.
Over the vault of the skull there is no fascia, since the galea aponeurotica is directly connected with the deeper layers of the skin.
The parotideo-masseteric fascia is a sheet that passes over the parotid gland and the Masseter muscle. At the zygoma it is continuous with the temporal fascia, at the anterior border of the Masseter with the bucco-pharyngeal and at the angle of the mandible with the cervical (Fig. A264).
The temporal fascia is the strongest fascia of the head. It extends as a dense membrane from the superior temporal line to the zygoma and at about the middle of its course it splits into two laminae, a superficial and a deep, between which there is some fat tissue. The interval between the two laminae increases downwards, the superficial lamina inserting into the lateral and the deep into the medial border of the zygoma. At its upper edge it is connected with the galea aponeurotica.
The bucco-pharyngeal fascia rests in its anterior part on the bucinator muscle and is connected with the parotideo-masseteric fascia; its posterior part is stronger and covers the inner surface of the Internal pterygoid muscle. It is in this that the pterygo-mandibular raphe and stylo-mandibular ligament are developed. This posterior part of the fascia bounds the lateral posterior wall of the mouth cavity and the lateral wall of the pharynx (see here).
In the neck the fascia colli (cervical fascia) and the praevertebral fascia may be distinguished. The former is divided into a superficial and a deep lamina, this latter being sometimes termed the middle layer. The former covers the superficial muscles of the neck and also the larynx, trachea and submaxillary gland, but is of variable strength in its different parts, being very thin over the lateral surface of the Sternomastoid. At the anterior border of the Trapezius it passes into the fascia of the back of the neck. The deep, distinctly stronger lamina covers the Omohyoid and the posterior surfaces of the other infrahyoid muscles and, anterior to the larynx and trachea, fuses with the superficial lamina. The quite distinct praevertebral fascia covers the anterior surface of the praevertebral muscles and the bodies of the cervical vertebrae, where these are uncovered by muscles; it is strong and partly tendinous.
The Supraspinatus arises from the supraspinous fossa of the scapula and is inserted into the upper facet of the greater tuberosity of the humerus. The Infraspinatus arises from the lower border of the spine of the scapula, from the infraspinous fossa and the infraspinatus fascia. It inserts into the middle facet on the greater tuberosity of the humerus. Nerve: The subscapular from the brachial plexus. Action: The Supraspinatus abducts the arm; the Infraspinatus rotates it outwards.
The Teres minor arises from the lower part of the infraspinous fossa, from about two-thirds of the lateral border of the scapula and from the infraspinatus fascia. It inserts into the lower facet of the greater tuberosity of the humerus. Nerve: The axillary from the brachial plexus. Action: External rotation of the arm.
The Teres major arises from the middle third of the axillary border of the scapula and has a tendinous insertion into the crest of the lesser tuberosity of the humerus. Its tendon is posterior to that of the Latissimus dorsi, from which it is separated by a bursa. Nerves: The lower subscapular from the brachial plexus. Action: Assists the Latissimus (see here), rotates the arm inwards.
The Subscapularis arises from the subscapular fossa and its muscular lines and inserts by a strong tendon on the lesser tuberosity of the humerus and the upper part of its crest. A subscapular bursa, between the tendon and the capsule of the shoulder joint, communicates with the latter. Nerves: Subscapular nerves from the brachial plexus. Action: Internal rotation and adduction of the arm.
The Deltoid arises from the acromial third of the clavicle, from the acromion and the spine of the scapula. It is inserted into the deltoid tuberosity of the humerus, a subdeltoid bursa being interposed between its tendon and the bone. Nerve: The axillary. Action: Abducts the arm to the horizontal position.
Eleven muscles of the trunk are attached to the skeleton of the upper limb, especially to the shoulder girdle. These are:
The large Triceps is the only muscle of the extensor surface of the upper arm, covering its entire surface and being continued upon the forearm as the Anconaeus. It takes origin by three heads. The long head arises from the infraglenoid tuberosity of the scapula; the lateral head from the lateral and posterior portions of the upper part of the shaft of the humerus, below the greater tuberosity, and also from the upper two-thirds of the lateral intermuscular septum; the medial head from the whole length of the medial intermuscular septum down to the medial epicondyle, from the posterior surface of the humerus below the crest of the great tuberosity, following the groove for the radial nerve, and from the lateral intermuscular septum down to the lateral epicondyle. From these three heads the fibres concentrate to a broad tendon that is attached to the posterior part of the upper surface of the olecranon, fibres also passing to the antebrachial fascia.
The Anconaeus is in close relation to the lower part of the medial head of the triceps. It arises from the lateral epicondyle of the humerus and inserts into the dorsal surface of the ulna, immediately below the olecranon. Nerve: The radial supplies both muscles. Action: Extension of the forearm.
The Biceps brachii has two heads of origin. The long head arises from the supraglenoid tuberosity of the scapula and the short head from the tip of the coracoid process. The two heads unite to form a common tendon which is inserted into the tuberosity of the radius and by means of the lacertus fibrosus into the antebrachial fascia. A bicipito-radial bursa lies between the tendon and the radius. Nerve: The musculo-cutaneus. Action: Supinates and flexes the forearm, tenses the antebrachial fascia; the long head abducts, the short head adducts the arm.
The Coraco-brachialis arises together with the short head of the Biceps from the tip of the coracoid process. It is inserted into the anterior and medial surfaces of the humerus, below the crest of the lesser tuberosity, and into the medial intermuscular septum. Nerve: The musculo-cutaneus, which pierces it. Action: Aids in raising the arm and in its adduction.
The Brachialis arises from the lower parts of the anterior and medial surfaces of the humerus, from the lateral surface below the deltoid tuberosity, and from the medial and lateral intermuscular septa almost down to the epicondyles. It passes over the anterior surface of the capsule of the elbow joint and is inserted into the tuberosity of the ulna. Nerve: The musculo-cutaneus and frequently also a branch from the radial. Action: Flexor of the forearm.
Between the flexor and extensor muscles there is, in the lower portion of the upper arm, on either side an intermuscular septum. The stronger medial one ends at the medial epicondyle, the much weaker lateral at the lateral epicondyle. They serve for the origin of both groups of muscles, the lateral also for that of the radial group.
The long head of the Triceps passes between the Teres major and Teres minor and divides the interval between these two muscles into a lateral quadrangular space, through which pass the axillary nerve and the posterior circumflex artery, and a medial triangular one, which gives passage to the circumflex scapular artery.
The medial head at the intermuscular septum adjoins the Brachialis and at the medial epicondyle the Anconaeus, which continues its fibre-course. The lateral head at the lateral intermuscular septum adjoins from above downwards, the Brachialis, the Brachio-radialis and sometimes also the Extensor carpi radialis longus.
The superficial layer of the flexor muscles of the forearm arises by a common tendon from the medial epicondyle of the humerus. All the muscles of the group, except the Pronator teres, pass over the wrist joint and have more or less long tendons. They occupy the ulnar side of the volar surface of the forearm and in their upper portions are firmly attached to the antebrachial fascia. A deep furrow separates them above from the muscles of the radial group, and in this groove the biceps tendon descends to its insertion.
The Pronator teres arises by a humeral head from the medial epicondyle of the humerus and the antebrachial fascia and by an ulnar head from the coronoid process of the ulna. It inserts into the middle of the lateral surface of the radius. Nerve: Median, which passes between the two heads. Action: Pronation; assists also in flexion.
The Flexor carpi radialis arises from the medial epicondyle and the antebrachial fascia and is inserted into the volar surface of the base of the second metacarpal. Nerve: Median. Action: Volar flexion and radial abduction; also pronation.
The Palmaris longus is not always present. It arises from the medial epicondyle and the antebrachial fascia and inserts into the palmar aponeurosis and the transverse carpal ligament. Nerve: Median. Action: Tenses the palmar aponeurosis and assists in flexion. The Flexor digitorum sublimis arises from the medial epicondyle by a humeral head and from the volar surface and volar border of the radius by a radial head. It is inserted by four long tendons into the middle phalanges of the second to the fifth fingers. Nerve: Median. Action: Flexes the middle phalanges of the four ulnar fingers; assists in flexion of the forearm.
The Flexor carpi ulnaris arises by a humeral head from the medial epicondyle and by an ulnar head from the olecranon and, through the antebrachial fascia, from the upper two-thirds of the posterior border of the ulna. It inserts into the pisiform bone and, by means of the ligaments of that bone (Fig. A224), into the base of the fifth metacarpal. Nerve: Ulnar. Action: Volar flexion and ulnar abduction.
The deep layer of the flexor surface of the forearm is almost completely covered by the superficial layer and consists of two deep flexors of the fingers and the Pronator quadratus. Strictly speaking it represents two layers, since the two flexors completely cover the Pronator quadratus.
The Flexor digitorum profundus arises from the volar surface of the ulna and from the interosseous membrane. It divides into four long tendons which pass to the terminal phalanges of the second to the fifth fingers. Nerve: Ulnar for its ulnar portion and for its radial part the median. Action: Flexion of the terminal phalanges of the 2-5 fingers; assists in flexing the forearm.
The Flexor pollicis longus arises by a principal radial head from the volar surface of the radius, below the insertion of the supinator, and by an inconstant humeral head from the medial epicondyle. It is inserted into the terminal phalanx of the thumb. Nerve: The volar interosseous from the median. Action: Flexes the terminal phalanx of the thumb. The Pronator quadratus (see Fig. A300) passes across from the volar border of the ulna to the volar border and surface of the radius. Nerve: The volar interosseous from the median. Action: Pronation.
The Brachio-radialis arises from the lateral border of the humerus and from the lateral intermuscular septum of the upper arm and is inserted by a flat tendon into the upper end of the styloid process of the radius. Nerve: The radial (musculo-spiral). Action: Flexion of the forearm; if the arm is flexed, either pronation or supination.
The Extensor carpi radialis longus arises from the lower end of the lateral intermuscular septum and the lateral epicondyle of the humerus and inserts into the dorsal surface of the base of the second metacarpal. The Extensor carpi radialis brevis arises from the lateral epicondyle of the humerus and from the antebrachial fascia and is inserted into the dorsal surface of the base of the third metacarpal. Nerve: The radial (musculo-spiral). Action: The brevis especially gives dorsal flexion of the hand; the longus radial abduction; the latter supinates if the arm is extended, pronates if it is flexed.
The Extensor communis digitorum arises from the lateral epicondyle of the humerus and from the antebrachial fascia. Its four tendons, which are connected by tendinous slips, pass into the dorsal aponeurosis of the second to the fifth digits. The Extensor digiti quinti proprius also arises from the lateral epicondyle of the humerus and from the antebrachial fascia and is inserted into the dorsal aponeurosis of the fifth finger. Nerve:The deep radial. Action: Extend the fingers and indirectly the hand.
The Extensor carpi ulnaris is separated from the two preceding muscles by an intermuscular septum and arises, like them, from the lateral epicondyle of the humerus and from the antebrachial fascia. It is inserted into the dorsal surface of the base of the fifth metacarpal. Nerve: The deep radial. Action: Dorsal flexion of the hand and ulnar abduction.
The Abductor pollicis longus (abductor ossis metacarpalis) arises from the dorsal surface of the ulna, the interosseous membrane and the dorsal surface of the radius, and is inserted into the base of the metacarpal of the thumb, slips passing to the trapezium (greater multangular) and to the Abductor pollicis brevis. The Extensor pollicis brevis arises from the dorsal surface of the radius and the interosseous membrane and inserts into the basal phalanx of the thumb. Nerve: The deep radial. Action: Abduction and extension of the thumb; the Abductor may also abduct the entire hand and assist in supination.
The Extensor pollicis longus arises from the dorsal surface of the ulna and the interosseous membrane and is inserted into the terminal phalanx of the thumb. The Extensor indicis proprius arises from the same parts and inserts into the dorsal aponeurosis of the index finger. Nerve: The deep radial. Action: Extension of the thumb or index finger; the Extensor pollicis assists in abducting the thumb.
The Supinator arises from the lateral epicondyle of the humerus, the radial collateral and annular ligaments and the supinator crest of the ulna. It is pierced by the deep radial nerve and so divided into a superficial and a deep layer. It is inserted into the volar surface and border, the lateral surface and dorsal border of the radius, both above and below the tuberosity. Nerve: The deep radial. Action: Supination.
The flexor tendons in the palm of the hand are covered by a strong tendinous membrane, the palmar aponeurosis, which is usually the direct expansion of the tendon of the Palmaris longus. It is always united to the transverse carpal ligament and passes laterally and medially into the thenar and hypothenar fasciae. Small at the transverse carpal ligament, it broadens toward the fingers and sends off bands which are lost in the skin of the basal portions of the second to the fifth fingers. In addition to the longitudinal fibres there are transverse fasciculi, especially distally. These bound proximally the gaps between the bands passing to the fingers, through which gaps pass nerves and vessels for the adjacent sides of the individual fingers and also the tendons of the lumbrical muscles.
The Palmaris brevis arises from the ulnar border of the palmar aponeurosis and occasionally from the trapezium (greater multangular). It is usually formed of a number of separate bundles and is inserted into the skin of the hand on its ulnar border. Nerve: Superficial volar branch of the ulnar. Action: Tenses the skin of the hand on the ulnar side.
The Abductor digiti quinti arises from the pisiform bone and is inserted into the dorsal aponeurosis of the little finger. The Flexor digiti quinti brevis is inconstant. It arises from the transverse carpal ligament and the hamulus of the unciform (hamate) bone and is inserted into the basal phalanx of the fifth finger. The Opponens digiti quinti has the same origin as the preceding and inserts into the ulnar border of the fifth metacarpal. Nerve: The deep volar branch of the ulnar. Action: Indicated by their names.
The Abductor pollicis brevis, Opponens pollicis and the superficial head of the Flexor pollicis brevis form a superficial sheet of thenar muscles, and the deep head of the Flexor and the Adductor pollicis a deep layer.
The Abductor pollicis brevis arises from the transverse carpal ligament and receives a slip from the tendon of the Abductor pollicis longus. It inserts into the basal phalanx of the thumb. Nerve: Median. Action: Abducts the thumb and aids in opposing it.
The Opponens pollicis arises from the transverse carpal ligament and the trapezium (greater multangular) and is inserted into the whole of the radial border of the metacarpal of the thumb up to its capitulum. Nerve: Median. Action: Opposes the thumb and aids in abduction.
The Flexor brevis pollicis arises by its superficial head from the tuberosity of the trapezium (greater multangular) and from the transverse carpal ligament; by its deep head from the trapezium (greater multangular) at the bottom of the carpal canal. It is inserted into the radial sesamoid bone at the metacarpo-phalangeal joint of the thumb. Nerve: The median for the superficial head, the deep volar branch of the ulnar for the deep head. Action: Flexes the basal phalanx of the thumb.
The Adductor pollicis has two heads. The oblique head arises from the os magnum (capitate) and unciform (hamate) at the bottom of the carpal canal; the transverse head arises from the volar surface of the third metacarpal. The insertion is into the ulnar sesamoid bone of the metacarpo-phalangeal joint of the thumb. Nerve: Deep volar branch of the ulnar. Action: Adducts the thumb and helps to oppose it.
The Interossei lie in the intervals between the metacarpal bones. They insert by expanded tendons into the dorsal aponeurosis of the fingers on the basal phalanges. The dorsal Interossei arise each by two heads from the borders of adjacent metacarpal bones.
The First dorsal interosseus arises from the first and second metacarpal, the Second from the second and third, the Third from the third and fourth and the Fourth from the fourth and fifth. The first and second insert into the radial side of the dorsal aponeurosis of the second and third fingers and the third and fourth into the ulnar side of the aponeurosis of the third and fourth fingers. Nerve: Deep volar branch of the ulnar. Action: Abduction of the fingers. Extension of the two distal phalanges and flexion of the basal ones.
The Interossei volares arise each by a single head, the first from the ulnar border of the second metacarpal, the second from the radial border of the fourth and the third from the radial border of the fifth. The first inserts into the ulnar side of the dorsal aponeurosis of the second finger, the second and third into the radial sides of the fourth and fifth fingers. Nerve: Deep volar branch of the ulnar. Action: Adduction of the fingers. Extension and flexion as with the dorsal interossei.
The Lumbrical muscles arise from the tendons of the Flexor digitorum profundus, the two radial usually each by a single head and the two ulnar each by two heads from the sides of adjacent tendons. They insert into the radial side of the dorsal aponeuroses of the second to the fifth fingers. Nerve: The one or two radial by the median, the two or three ulnar by the ulnar. Action: Flex the basal phalanges and extend the terminal ones, the interossei assisting.
The extensor tendons or dorsal aponeuroses, as they may be termed on account of their forming flat expansions on the dorsal surfaces of the digits, include; first, the tendons of the Extensor digitorum communis together with those of the proprii where these occur (index and little fingers), since they fuse with the tendons of the Extensor communis; second, the tendons of the Interossei and Lumbricals which, spreading out fan-like, pass into the expanded tendons of the extensor tendons on the dorsal surfaces of the basal phalanges, but are also continued upon the middle and terminal phalanges. These latter are not reached by the tendons of the Extensor. Consequently, the Extensor extends only the basal phalanges, while the two distal ones are extended by the continued action of the Interossei and Lumbricales.
In the flexor tendons it is to be noted that the tendons of the Flexor digitorum sublimis, which are perforated by the profundus in the region of the basal phalanges, have their insertions in the middle phalanges, while the perforating profundus tendons insert on the terminal phalanges. None of these tendons insert into the basal phalanx, which may be flexed by the action of the Interossei and Lumbricales. Only the small vincula tendinea fasten the tendons of the Flexores digitorum to the volar surfaces of the basal phalanges.
The muscles of the upper extremity fall into four main groups:
The muscles of the upper extremity are enclosed in a common fascia, which receives different names in different regions. At the shoulder there is an axillary fascia, a supraspinatus, an infraspinatus, and a subscapular; on the upper arm the brachial fascia; on the forearm the antebrachial fascia and in the hand the dorsal fascia and the palmar aponeurosis.
The axillary fascia (see also here) is a thin membrane which forms the base of the axillary cavity. It is pierced by many blood vessels and possesses a few stronger deeper bundles extending from the Latissimus to the Pectoralis, these being sometimes muscular and then termed the axillary arch. Anteriorly it becomes directly continuous with the pectoral fascia, posteriorly with the dorsal fascia. The supraspinatus fascia covers the muscle of that name and is partly tendinous in character. The infraspinatus fascia is a very thick, tendinous fascia covering the Infraspinatus and Teres minor and partly also the Teres major, giving origin to some of the fibres of the two former, with which it unites to form an aponeurosis. The rather dense subscapular fascia covers the muscle of that name.
The brachial fascia is continuous above with the fasciae just mentioned and reaches its greatest thickness below the insertion of the Deltoid, but is in general thin and weak. It consists largely of transverse fibres and anteriorly is moulded over the Biceps, on either side of which is a groove, a medial and less noticeable lateral bicipital groove. In the lower part of the upper arm it gives off septa, separating the two muscle groups of that region, a strong and broad medial intermuscular septum extending to the medial epicondyle and a frequently thin lateral intermuscular septum ending at the lateral epicondyle. These septa are attached to the medial and lateral borders of the humerus, respectively, and serve partly for the origin of the muscles which they separate. The medial septum is usually perforated by the ulnar nerve.
The antibrachial fascia is continuous with the brachial in the region of the cubital fossa. Below the elbow joint, especially, it becomes aponeurotic and gives origin to fibres of the proximal portion of the superficial layer of the flexors and extensors of the forearm. The lacertus fibrosus of the Biceps tendon (see here and Fig. A289) is essentially a portion of the fascia, becoming continuous with it. The fascia is weakened in the cubital fossa and over the muscles of the radial group, especially the Brachioradialis and the Extensor carpi radialis, neither of which arise from it. Toward the wrist joint it becomes thickened both dorsally and volarly by bundles of more or less transverse fibres to form the volar carpal ligament (not to be confused with the transverse carpal ligament which is also volar in position) over the flexor tendons and the dorsal carpal ligament, a broad somewhat oblique and very strong fascial band. This latter forms the six tendon compartments for the eight tendon sheaths of the eleven extensor tendons (see Fig. A305), by uniting firmly with the dorsal surfaces of the lower portion of the forearm bones and especially with the ridges on the dorsal surface of the lower end of the radius. In contrast to the brachial fascia the antibrachial has well developed longitudinal fibres, which are especially strong and tendon-like where the fascia becomes aponeurotic and muscle fibres arise from it. This always occurs only in the proximal portion of the forearm (see above) and only rarely extends to its middle portion; in the lowest third of its length, where most of the muscles have become tendons, it does not occur.
The dorsal fascia of the hand passes distally from the dorsal carpal ligament, gradually becoming thinner. In contrast the palmar aponeurosis (see here) is very strong, by far the strongest portion of the entire fascia of the upper extremity.
The muscles of the lower extremity may be classified as those of the rump, those of the thigh, those of the lower leg and those of the foot. The rump muscles pass from the innominate bone to the upper part of the thigh. The muscles of the thigh are arranged in three groups; an anterior extensor group, a posterior flexor and a medial adductor. In the lower leg three groups may again be distinguished: an anterior extensor group, a lateral peroneal group and a posterior flexor group. This last consists of two layers, a superficial and a deep. In the foot are the dorsal extensor and the plantar flexor muscles. The latter may be grouped into the medial muscles, those of the great toe, those of the little toe, the Lumbricals and the Interossei.
The Glutaeus maximus arises from the posterior part of the ala of the ilium behind the posterior gluteal line, from the dorsal surface of the sacrum and from the sacro-tuberous ligament. It is inserted into the gluteal tuberosity of the femur, also sending a slip to the iliotibial band of the fascia lata. Nerve: The inferior gluteal. Action: Extension of the thigh; aids also in adduction and outward rotation.
The Glutaeus medius arises from the lateral surface of the ala of the ilium, above the anterior gluteal line, and is inserted into the lateral surface of the great trochanter. Nerve: The superior gluteal. Action: Abduction of the thigh, assists also by its posterior portion in outward rotation and by its anterior portion in inward rotation.
The Glutaeus minimus arises from the lateral surface of the ala of the ilium, between the anterior and inferior gluteal lines. It inserts into the tip of the great trochanter. Nerve: The superior gluteal. Action: Abduction of the thigh and external and to some extent inward rotation.
The Piriformis arises from the lateral part of the pelvic surface of the sacrum, in the region of the second to the fourth sacral foramina. It passes outward through the great sciatic foramen and is inserted into the tip of the great trochanter. Nerve: Branch from the sciatic or the sciatic plexus. Action: External rotation of the thigh, assists also in abduction.
The Obturator internus arises from the pelvic surface of the circumference of the obturator foramen and from the obturator membrane. It passes out through the lesser sciatic foramen, bends around the base of the ischial tuberosity and inserts into the trochanteric fossa of the femur. The Gemellus superior takes origin from the spine of the ischium and the Gemellus inferior from the ischial tuberosity; they join the tendon of the obturator internus. Nerve: Branches from the sacral plexus. Action: External rotators and adductors.
The Quadratus femoris arises from the lateral border of the ischial tuberosity and passes outwards to the intertrochanteric crest. Nerve: A special branch from the sciatic plexus. Action: External rotation and adduction.
The Tensor fasciae latae arises from the anterior superior spine of the ilium and is inserted into the ilio-tibial band of the fascia lata. Nerve: The superior gluteal. Action: Tenses the fascia lata and assists in flexion and inward rotation of the thigh.
The muscles of the lower limb are enclosed in a fascia, which, in places, is exceptionally strong. That part that covers the Ilio-psoas is termed the iliac fascia, that which invests the muscles of the thigh, the fascia lata, that of the lower leg, the crural, and in the foot there is a dorsal fascia and the strongly tendinous plantar aponeurosis (see here).
The iliac fascia invests the ilio-psoas muscle and, at its medial border, passes over into the pelvic fascia. Below it passes upon the muscles of the thigh and unites with the pectineal fascia to form the ilio-pectineal fascia. This divides the space below the inguinal ligament into two compartments or lacunae, a lateral lacuna musculorum for the Ilio-psoas and the femoral nerve and a medial lacuna vasorum for the femoral vessels.
The fascia lata consists of two layers, separable only in certain areas and varying much in thickness. It is stronger on the posterior and lateral surfaces of the thigh than on the anterior and medial. Its superficial layer, just below the inguinal ligaments, forms a free medial border, the falciform border, which, with the deep layer, the pectineal fascia, forms the boundary of the fossa ovalis. The lower border of the fossa is termed the inferior cornu and the upper the superior cornu. The fossa is closed by a somewhat sieve-like portion of fascia, the fascia cribrosa, a larger opening in this transmitting the great saphenous vein. The fossa represents the external or subcutaneous ring, that is to say, the lower opening of the femoral canal (see here).
On the posterior surface of the thigh the fascia lata covers the Glutaeus maximus by its superficial layer, here quite thin, the deep layer passing beneath the muscle; on the part of the Glutaeus medius that is not covered by the maximus, the fascia forms a dense aponeurotic sheet (fascia glutaea). Some strong transverse fibres run in the gluteal groove at the lower border of the maximus. Over the flexor muscles the fascia lata is of moderate strength and shows predominating transverse fibres, which become especially developed in the region of the popliteal fossa, whose roof is formed by the fascia lata.
The strongest part of the fascia lata occurs on the lateral surface of the thigh; it is the ilio-tibial band (tractus) and is formed mainly of strong tendinous longitudinal bundles of fibres, which are attached below to the lateral condyle of the tibia. Between the groups of thigh muscles the fascia in the lower part of the thigh sends in to the lips of the linea aspera a medial and a lateral intermuscular septum, the medial becoming continuous with the tendon of the Adductor magnus. On the anterior surface of the thigh the fascia is divided in its upper part into two layers; the superficial one covers the surface of the Sartorius and the femoral vessels, the deeper one passes behind the Sartorius, lines the ilio-pectineal fossa and the furrow between the Vastus medialis and the Adductors. Over the Adductors the fascia is thin. The portion covering the Pectineus is termed the pectineal fascia; it unites with the lower end of the iliac fascia to form the ilio-pectineal fascia which lines the floor of the ilio-pectineal fossa.
The crural fascia invests the muscles of the lower leg and covers the muscle-free medial surface of the tibia. It is strongest anteriorly below the knee joint, where it fuses with the extensor and peroneal muscles and with the tendons of the pes anserinus. It sends the anterior intermuscular septum to the anterior crest of the fibula between the Extensors and the Peronaei, and the posterior intermuscular septum to the lateral crest of the fibula, between the Peronaei and the Flexors. On the posterior surface of the lower leg it splits into a superficial and a deep layer, the former covering the Triceps surae, the latter the deep group of Flexors. A special thickening of the crural fascia, in addition to those forming the retinacula (see here), is the transverse crural ligament, which passes transversely between the tibia and fibula above the ankle joint.
The Sartorius arises from the anterior superior spine of the ilium and, crossing the thigh obliquely, inserts into the medial border of the tuberosity of the tibia. It forms with the Adductor longus the femoral trigone (Scarpa's triangle), and covers the adductor canal. At its insertion it forms with the tendons of the Gracilis and Semitendinosus the pes anserinus, beneath which are one or two bursae. Nerve: The femoral. Action: Assists in flexion and abduction of the thigh, flexes the lower leg and rotates it inwards when flexed.
The Rectus femoris arises from the anterior inferior spine of the ilium and the upper margin of the acetabulum. Associated with it and uniting with it in a common tendon are three other muscles. The Vastus medialis arises from the medial lip of the linea aspera and is stronger below than above; the Vastus lateralis arises from the lateral lip of the linea aspera and from the base of the great trochanter, being stronger above than below; and the Vastus intermedius arises from the anterior surface of the femur between the other two, with which it fuses, especially with the medialis: These four muscles constitute what is termed the Quadriceps femoris and unite to form a common tendon, that is inserted into the upper and lateral borders of the patella and, by means of the patellar ligament, into the tuberosity of the tibia. Some of the deep fibres of the intermedius insert into the capsule of the knee joint, forming what is termed the Articularis genu. Nerve: The femoral. Action: Draws the patella upwards, extends the lower leg, and flexes the thigh.
Behind the tendon of the Quadriceps is the supra-patella bursa, which communicates with the knee joint, so that the tendon forms part of the anterior wall of the capsule of that joint. Extensions from the tendon to the fascia of the lower leg form the patellar retinacula. Behind the patellar ligament is a deep infrapatellar bursa.
The Pectineus arises from the pecten of the pubis and is inserted into the pectineal line of the femur. Nerve: The femoral. Action: Adducts the thigh and aids in flexion and external rotation.
The Gracilis arises from the pubis close to the symphysis and is inserted into the medial border of the tuberosity of the tibia. Nerve: The obturator. Action: Adducts the knee when the lower leg is extended, aids in flexion at the knee and rotates the flexed knee inwards.
The Adductor longus arises from the junction of the upper and lower rami of the pubis and is inserted into the middle third of the medial lip of the linea aspera. Nerve: The obturator. Action: Adduction of thigh; assists in flexion and outward rotation: The Adductor brevis arises from the upper ramus of the pubis, nearer to the obturator foramen than the Adductor longus, and is inserted into the upper third of the medial lip of the linea aspera. Nerve: The obturator. Action: Adduction of the thigh; assists in flexion and outward rotation.
The Adductor magnus arises from the lower rami of the pubis and ischium and from the lower border of the ischial tuberosity. The portion arising from the lower ramus of the pubis is sometimes termed the Adductor minimus. The muscle inserts into the medial lip of the linea aspera, from the medial epicondyle to near the gluteal tuberosity. The lower part of the tendon is pierced by the adductor hiatus. Nerve: The obturator and sciatic (tibial). Action: Adducts the thigh, partly assists the glutaeus maximus.
The Obturator externus arises from the outer surface of the circumference of the obturator foramen and from the obturator membrane. It inserts into the trochanteric fossa of the femur. Nerve: The obturator. Action: External rotator of the femur; aids in adduction and flexion.
The Biceps femoris arises by its long head from the tuberosity of the ischium and by its short head from the lower half of the lateral lip of the linea aspera. It is inserted into the head of the fibula. Nerve: The long head by the tibial, the short head by the peroneal. Action: Flexion of the lower leg and extension of the thigh, together with external rotation.
The Semitendinosus arises from the tuberosity of the ischium, with the long head of the Biceps, and is inserted into the medial border of the tuberosity of the tibia, forming part of the pes anserinus. Nerve: The tibial. Action: Flexion of the lower leg, together with internal rotation. Extension and adduction of the thigh.
The Semimembranosus arises from the tuberosity of the ischium and is inserted into the posterior part of the medial condyle of the tibia and into the oblique popliteal ligament. Nerve: The tibial. Action: Flexion and inward rotation of the lower leg; extension and adduction of the thigh.
Where the Glutaeus maximus passes over the great trochanter a trochanteric bursa is interposed and lower down one or several glutaeo-femoral bursae. Under the insertion of the Glutaeus medius there is a bursa, and, similarly, under that of the Glutaeus minimus. Where the Obturator internus tendon passes at an acute angle over the lesser sciatic notch there is an elongated bursa. Between the Ilio-psoas and the ilio-femoral ligament there is an ilio-pectineal bursa that occasionally communicates with the hip joint.
The Gastrocnemius, which has two heads, together with the Soleus forms a muscle mass sometimes termed the Triceps surae. The Gastrocnemius arises by its medial head from the medial condyle of the femur and by its lateral head from the lateral condyle. The two heads unite together and at about the middle of the lower leg the muscle unites with the Soleus lying beneath it. The Soleus takes its origin from the head, posterior surface and lateral crest of the fibula, from a tendinous arch between the tibia and fibula over the popliteal vessels and from the posterior surface of the tibia at and below the popliteal line. The muscle unites with the Gastrocnemius to form a powerful tendon (tendo Achillis) which is inserted into the tuberosity of the calcaneus. Nerve: The tibial. Action: Plantar flexion of the foot; raises the heel.
The Plantaris is a small muscle with a long slender tendon. It arises from the lateral condyle of the femur and is inserted at the heel into the deep layer of the crural fascia and the tendo Achillis. Nerve: Tibial. Action: Tenses the tendo Achillis.
The Popliteus arises from the lateral condyle of the femur and from the arcuate popliteal ligament and is inserted into the posterior surface of the tibia above the popliteal line. Nerve: The tibial. Action: Tenses the capsule of the knee; flexes the knee and rotates it inwards.
A bursa lies beneath the origin of the medial head of the Gastrocnemius and another beneath the origin of the Semimembranosus; both may communicate with the knee joint. A popliteal bursa, beneath the origin of the Popliteus, also communicates with the knee joint.
The Tibialis posterior arises from the upper part of the posterior surface of the tibia, from the interosseous membrane and the medial surface of the fibula. It inserts into the tuberosity of the navicular bone and the plantar surface of the first or all of the cuneiforms. Nerve: The tibial. Action: Plantar flexion and elevation of the inner border of the foot (supination); fixes the head of the talus.
The Flexor digitorum longus arises from the posterior surface and interosseous crest of the tibia. It divides into four tendons which insert into the terminal phalanges of the four lateral toes. Nerve: The tibial. Action: Flexes the terminal phalanges of the four lateral toes, assists in plantar flexion and supination.
The Flexor hallucis longus arises from the posterior surface and the lower two-thirds of the lateral crest of the fibula and from the interosseous membrane. It inserts into the terminal phalanx of the great toe. Nerve: The tibial. Action: Flexes the great toe, acting also on the others (see below), and assists in flexing and supinating the foot. The tendons of the Flexor digitorum longus and Tibialis posterior cross one another above the medial malleolus, so that that of the latter muscle is the more medial at the level of the laciniate ligaments (see Fig. A335). On the sole of the foot there is a crossing of the tendons of the Flexor hallucis longus and Flexor digitorum longus, by which both tendons fuse, so that the strong Flexor hallucis acts not only upon the great toe, but also on the other four.
The Tibialis anterior arises from the lateral surface of the tibia, the interosseous membrane and the crural fascia. It inserts into the medial border of the base of the first metatarsal and into the plantar surface of the medial cuneiform. Nerve: The deep branch of peroneal. Action: Dorsal flexion and supination of the foot; elevation of its inner border.
The Extensor hallucis longus arises from the medial surface of the fibula, the interosseous membrane and the crural fascia. It is inserted into the dorsal surface of the great toe. The Extensor digitorum longus arises from the anterior crest of the fibula, the interosseous membrane and the crural fascia and inserts by four tendons into the dorsal aponeuroses of the four lateral toes. The Peronaeus tertius splits off from the lower part of the Extensor digitorum longus and is inserted into the dorsal surface of the fifth metatarsal. Nerve: The deep branch of the peroneal. Action: Extension of the toes; the Peronaeus tertius assists in dorsal flexion of the foot, the Extensors in supination also.
The Peronaeus longus arises from the head of the fibula, the crural fascia, the upper two-thirds of the lateral surface and lateral crest of the fibula. It passes across the sole of the foot in the peroneal groove and is inserted into the tuberosity of the first metatarsal. The Peronaeus brevis arises from the lower half of the lateral surface and the anterior crest of the fibula and inserts into the tuberosity of the fifth metatarsal, sending prolongations to the fifth toe. Nerve: Both Peronaei are supplied by the superficial branch of the peroneal. Action: raise the lateral border of the foot (pronation) and assist in plantar flexion.
The Extensor digitorum brevis arises from the dorsal and lateral surfaces of the calcaneus, anterior to the sinus tarsi. It passes by three slender tendons into the dorsal aponeurosis of the three middle toes. The Extensor hallucis brevis arises from the dorsal surface of the calcaneus and inserts into the dorsal aponeurosis of the great toe. Nerve: The deep branch of the peroneal. Action: Extensors of the toes.
While the dorsal fascia of the foot is an unimportant thin sheet, the plantar aponeurosis is the strongest of all the fasciae of the leg. At the middle of the sole of the foot it is a thick, tendinous sheet, whose bundles are chiefly longitudinal, but have an oblique direction towards the borders of the foot. The proximal part of the aponeurosis is firmly united to the long plantar muscles and arises with them from the medial and lateral processes of the calcaneal tuberosity; it is much thicker than the distal portion. With this, it presents three plantar eminences, medial, lateral and intermediate. A fibular portion covering the Abductor digiti quinti may be distinguished from the broader tibial portion covering chiefly the Flexor digitorum brevis. From the aponeurosis numerous fine bundles pass to the skin. Towards the toes the tibial part of the aponeurosis divides into several processes, which practically agree in number with the toes, but transverse fasciculi are hardly noticeable, a condition contrasting with that of the palmar aponeurosis where they are very noticeable (see here). In the toes the prolongations of the aponeurosis are lost in the connective tissue of the skin.
The Flexor digitorum brevis arises from the medial process of the calcaneal tuberosity and from the plantar aponeurosis. It inserts by four tendons, which are perforated by the tendons of the long flexor, into the middle phalanges of the four lateral toes. Nerve: The medial plantar. Action: Flexes the toes.
The Quadratus plantae arises by two heads from the plantar surface of the calcaneus and from the long plantar ligament. It is inserted into the tendon of the Flexor digitorum longus. Nerve: The lateral plantar; Action: Assists the flexor digitorum longus, correcting its oblique pull.
The Abductor hallucis arises from the medial process of the calcaneal tuberosity and from the plantar aponeurosis. It inserts by means of the medial sesamoid bone into the basal phalanx of the great toe. The Flexor brevis hallucis arises from the plantar surfaces of the second and third cuneiforms and from the long plantar ligament. It is inserted by two heads into two sesamoid bones and the basal phalanx of the great toe. The Adductor hallucis consists of two distinct portions. The oblique head arises from the plantar surface of the third (lateral) cuneiform and the plantar ligament. The transverse head arises from the tarso-metatarsal joints of the fifth to the third toe. It is inserted into the lateral sesamoid bone and basal phalanx of the great toe. Nerves: For the Abductor and Flexor brevis the medial plantar; for the Adductor and part of the Flexor the lateral plantar. Action: Adduction and flexion of the great toe.
The Abductor digiti quinti arises from the lateral process of the tuberosity of the calcaneus and from the plantar aponeurosis, further, by a deep head, from the medial process of the calcaneal tuberosity. It inserts into the lateral border of the basal phalanx of the little toe and into the tuberosity of the fifth metatarsal. The Flexor digiti quinti brevis and the Opponens digiti quinti arise in common from the anterior part of the long plantar ligament. The Flexor inserts into the basal phalanx of the little toe, the Opponens into the lateral border of the fifth metatarsal. Nerve: The lateral plantar. Action: Abduction, flexion and opposition of little toe.
The Lumbricals of the foot arise from the tendons of the Flexor digitorum longus, the first by a single head from the medial edge of the first (medial) tendon, the other three by two heads. In the region of the metatarso-phalangeal joint they pass to the medial side of the dorsal aponeurosis of the four lateral toes. At their points of insertion there are usually small bursae. Nerves: They are supplied in a variable manner by the medial and lateral plantars. Action: Flexion of the basal phalanges and extension of the others.
The Interossei (see Fig. A336 and A337) are seven in number, four Dorsal and three Plantar. They occupy the inter-metatarsal spaces and the plantar arise by single heads, the dorsal by two. The first dorsal inserts into the dorsal aponeurosis of the second toe on the tibial side, the other three into the fibular side of the aponeurosis of the second, third and fourth toes. The plantar insert into the tibial side of the aponeurosis of the third, fourth and fifth toes. Nerve: The lateral plantar. Action: Flexion of basal phalanges, extension of the others.
The dorsal aponeurosis of the toes are essentially like those of the fingers. They are formed by the tendons of the Extensor brevis and Extensor longus, those of the Interossei and those of the Lumbricales.
The three groups of muscles passing from the lower leg into the foot have their tendons invested by tendon sheaths, which, like those of the upper extremity, are protected by retinacula. For the two Peronaei there is a double retinaculum, which is actually a thickening of the deep layer of the lateral portion of the crural fascia. The superior peroneal retinaculum extends from the neighborhood of the lateral malleolus to the calcaneus, the inferior peroneal retinaculum from the neighborhood of the trochlear process of the calcaneus, above which it blends with the cruciate ligament, to the lateral border of the plantar surface of the bone. If the trochlear process is well developed it separates the tendons and tendon sheaths of the two Peronaei. While the sheath of the Peronaeus brevis tendon ends a little beyond the process that of the longus extends into the sole of the foot, where it receives a new retinaculum, formed by the anterior part of the long plantar ligament (see here).
At the medial malleolus the retinaculum for the flexor muscles, the Tibialis posterior, Flexor digitorum longus and Flexor hallucis longus, is formed by the broad laciniate ligament, which is indistinctly separated from the crural fascia.
On the dorsum of the foot the cruciate ligament is a forked strengthening of the dorsal fascia of the foot, which forms the retinaculum for the Extensor tendons. It consists of a usually strong transverse portion (see Fig. A328), which passes from the medial malleolus to above the trochlear process of the calcaneus, and a band, at right angles to the transverse one, extending from the dorsal surface of the navicular to the anterior part of the calcaneus. The ligament contains three compartments for the tendons of the Tibialis anticus, the Extensor hallucis longus and the Extensor digitorum longus plus the Peronaeus tertius.
The body can be divided into a number of regions that are shown on Fig. A338, A339, A340, A341 and A342.
The mouth cavity (cavum oris), the beginning of the entire digestive tract, is an irregularly shaped, longish cavity in the lower part of the face, and has partly bony, and partly muscular walls. It is divided imperfectly into two portions by the teeth, the oral vestibule and the mouth cavity proper.
The vestibule is a small, somewhat semicircular space, between the lips and cheeks on the one side and the teeth on the other. When the teeth are in contact, it communicates behind the last molar with the actual mouth cavity and in front through the mouth cleft (rima oris) with the outer world. The two lips (labia) form the greatest part of the anterior wall of the vestibule and unite at the angles of the mouth in the labial commissures. The upper lip is somewhat longer than the lower one and on its outer surface presents a flat, rather broad, median furrow, the philtrum. An oblique, slightly arched groove, the nasolabial groove, passes from the ala of the nose toward the cheek. On the outer surface of the lower lip the mento-labial groove separates the lip from the chin (mentum). The lips consist of the skin with hairs, the Orbicularis oris muscle and mucous membrane. This last contains the labial glands, which are mucous glands of small size. The posterior surfaces of the lips in the middle line are connected with the mucous membrane, gingiva, covering the alveolar process of the maxilla and mandible, by thin folds of mucous membrane, the frenula, that of the upper lip being usually the larger and more distinct.
Lateral to the lips the cheeks (buccae) form the wall of the oral cavity. Like the lips they consist of the skin, with stronger hairs in the male, of the Bucinator muscle and of mucous membrane. The last is thin in this region and contains the buccal glands, which are embedded in the Bucinator muscle or even lie on its outer surface. In the angle between the Bucinator and the Masseter there is a strong development of fat tissue, the buccal fat pad (corpus adiposum buccae) which extends in the new-born child over the whole region of the cheek.
The mouth cavity proper is bounded above by the palate, which separates it from the nasal cavity. The floor of the mouth is formed principally by the tongue, which, when the mouth is closed, fills the cavity, except for a relatively small cleft between its dorsal surface and the palate. The anterior and lateral boundaries are formed by the dental arches, the posterior partly by the soft palate and the palatine arches (pillars of the fauces) and, further, at its posterior wall, it communicates with the oral portion of the pharynx by the isthmus of the fauces.
The palate consists of two portions, the hard palate and the soft palate. The former repeats the form of the palatal plates of the skeleton; its mucous membrane is thick and firm, connected closely by submucous bundles of fibres to the periosteum of the bones. It contains numerous mucous glands. In the median line the mucous membrane is raised into a low ridge, the raphe, and at the anterior end of this, at a point corresponding to the incisive foramen, there is an elongated, wart-like elevation, the incisive papilla, and anteriorly on either side three or four transverse palatine folds, which often disappear in old age, but may be in greater number in the new-born child.
The soft palate is a soft plate separating the mouth cavity from the nasal portion of the pharynx. It is muscular, is abundantly supplied with glands and is covered by mucous membrane on both surfaces. It is attached by its base to the posterior border of the bony palate, its mucous membrane passing directly into that of the palate, and it hangs obliquely downwards and backwards and ends in a rounded conical process, the uvula. This, when the palatal muscles are at rest, lies in such a position that its tip is directed forwards. The mucous membrane of the soft palate is rather smooth, much thinner than that of the hard palate, and is usually well supplied with glands. The lateral parts of the soft palate, the palatine arches (pillars of the fauces) are folds of mucous membrane containing muscles; they bound the isthmus of the fauces i.e. the transition from the mouth cavity to that of the pharynx (see here).
The teeth (dentes) are conical structures imbedded by their roots (radices) in the alveoli of the jaws. The part surrounded by the gingiva is termed the neck (collum), the part projecting into the mouth cavity the crown (corona). Of the three principal constituents of the teeth, the enamel, dentine and cement, the enamel occurs only on the crown, the cement only on the root; at the neck the enamel and cement meet. The enamel has a shining surface and is white with a bluish or yellowish tinge, while the cement is pale yellow and dull. On each crown there is a masticatory surface turned toward the teeth of the upper jaw; the surface turned towards the lips or cheek is the labial or buccal surface; that turned towards the tongue the lingual surface; and those in contact with adjacent teeth the contact surfaces.
The root of a tooth is simple or multiple and is in general conical in shape. It bears at its apex a foramen that leads into a root canal, which traverses the whole length of the root and at the level of the neck broadens to a large cavity, the pulp cavity (cavum dentis), in the interior of the crown, filled with a soft tissue, the pulp. The pulp cavity has in general the form of the tooth, but possesses, almost regularly, fine processes corresponding to the relief of the crown. The tips of the canines are slightly worn. The root canal is also a part of the tooth cavity and accordingly also contains pulp.
The dentition of an adult consists of thirty-two teeth which are arranged in an upper and lower row, the upper and lower dental arches. The upper teeth are implanted in the alveoli of the maxillae, the lower in those of the mandible. The teeth of the two rows resemble each other in form and size, without being exactly alike. The number in each row is sixteen.
The teeth of both jaws may be divided according to their form into four groups, the incisors, canines, praemolars and molars. In each half of each row there are two incisors, one canine, two praemolars and three molars. The teeth of each group represent a well-defined type, without transitions to the others, but within each type there are individual differences, as, for instance, between the corresponding teeth of the upper and lower jaws. The incisors are the most anterior, those of the two sides being in contact in the median line; then follows the canine, then the praemolars, the molars being the most posterior. The human dental formula is as follows:
The incisors have chisel-shaped crowns, convex on the labial and concave on the lingual side; they are thicker but narrower at the base, but become broader and thinner towards their free edge. The labial surface has frequently three indistinct longitudinal ridges separated by furrows. Their crowns are in the frontal plane, so that their contact surfaces are medial and lateral. On account of their chisel-shaped crowns they have no masticatory surface, but a cutting edge, originally three-lobed. The medial angle of this edge is sharp, the lateral rounded. At the base of the crown immediately above the neck there is a thickening, the tubercle. The roots are round, of moderate length and usually almost straight, those of the lateral incisors are usually shorter and slightly flattened. The upper ones are usually larger than the lower and the upper medial is always larger than the lateral, while in the lower jaw the lateral is the larger (Length up to 24 mm).
The canines have a long conical form. Their large and thick crown is conical and stands almost in the frontal plane, so that they present labial and lingual surfaces and medial and lateral contact surfaces, Their rounded tips are not exactly in the axis of the tooth, but slightly to the medial side, the labial surface is strongly convex and the lingual is provided with a tubercle. The root is very long and also conical, yet, especially in the lower ones, distinctly flattened. The canines, especially the upper ones, are the longest teeth in the dentition (on account of their long roots - 35 mm).
The praemolars possess bitubercular (bicuspid) crowns, flattened from before backwards; their contact surfaces are anterior and posterior and their lingual and buccal surfaces convex. The two tubercles are separated by an almost sagittal furrow that follows the curve of the dental arch, so that there is a weaker lingual and a stronger buccal tubercle. The lingual tubercle of the first lower praemolar is usually feebly developed and the lingual of the second lower (also low) is often double, so that this tooth may be tritubercular. The roots of the lower praemolars are always simple, of moderate length and distinctly flattened; those of the upper sets vary greatly, that of the first being usually double or at least cleft, that of the second only strongly flattened or furrowed. One root is buccal, the other lingual. The first upper praemolar is larger than the second.
The molars all possess large, low crowns with several tubercles and have two or three roots, these, as well as the positions of the tubercles differing in the upper and lower teeth. The upper molars have three roots, the larger, lower ones only two. The first molar in both the upper and lower sets has the largest and highest crown, the third the smallest and lowest. The tubercles are four, rarely five in number, two being on the lingual and two on the buccal side. In the lower molars a rather regular crucial furrow separates the four tubercles, of which the lingual are higher than the buccal. The first lower molar has usually five tubercles, three buccal and two lingual. In the upper molars the buccal tubercles are higher than the lingual and the intervening furrow has the form of an oblique H, so that the lingual and buccal tubercles are not exactly opposite one another. Frequently, but not always, the first upper molar has a super-numerary tubercle, usually very small, at the base of the anterior lingual tubercle. It is the so-called anomalous (Carabelli) tubercle. The contact surfaces of the molars are anterior and posterior.
The lower molars have two conical roots, an anterior (somewhat the stronger) and a posterior; they are flattened in the frontal plane, are furrowed and of considerable size, and their tips are usually curved backwards. The upper molars, on the contrary, have three conical roots, two buccal and one lingual or palatal; their tips are also curved. All three roots are usually well developed in the first upper molar; in the second they show, not infrequently, more or less fusion, and this is the rule in the third upper one in which the roots are almost parallel. In the upper molars the tips of the roots are often slightly curved backwards.
The third molars, also called wisdom teeth (dentes serotini), are usually more or less rudimentary. The upper is always much smaller than the lower and its roots usually fuse to a single mass with indications, in three root canals, of their original triple division. Often they possess only three tubercles, sometimes more than four. The lower wisdom tooth has usually two short roots and a crown that departs somewhat from the type.
The permanent dentition of the adult, consisting of thirty-two teeth, is preceded in childhood by a Milk dentition of only twenty teeth (dentes decidui) including eight incisors, four canines and eight molars. The formula for the milk dentition is therefore:
The incisors and canines of the milk dentition resemble the corresponding teeth of the permanent dentition not only in general but also in particular, though they are relatively smaller and the furrows are wanting on the labial surfaces of the crowns of the incisors. These teeth also occur in the same position as their successors, while the milk molars appear in the places later occupied by the praemolars. The milk molars, while resembling the permanent ones, represent a specific type; they have more than one root and have several tubercles. The second (posterior) are larger than the first; the upper ones have usually three roots like the permanent molars, two buccal and one lingual, while the lower have two roots. The crowns have three (anterior) to five (posterior) irregularly placed tubercles, which are separated by very irregular furrows.
The first milk tooth to erupt, on the average, in the sixth or seventh month after birth, is the medial incisor of the lower jaw, the teeth of the lower jaw as a rule appearing earlier than those of the upper. Then, in the seventh or eighth month the corresponding tooth of the upper jaw appears. The lateral incisors erupt usually from the eighth to the twelfth month; the anterior molars of the lower jaw from the twelfth to the sixteenth month; those of the upper jaw some months later; after these the canines, from the sixteenth to the twentieth month; and, finally, the posterior molars from the twentieth to the thirtieth month.
The milk dentition is gradually replaced by the permanent teeth, so that for a time representatives of both dentitions are present. The first, lower, permanent molars erupt at the fifth to the eighth year and soon after the corresponding teeth of the upper jaw appear. Later the process of replacement begins and, in the sixth to the ninth year, the median milk incisors are replaced by the permanent ones, and then the lateral ones in the seventh to the tenth year. The first praemolars erupt in the ninth to the thirteenth year; the permanent canines in the ninth to the fourteenth; the second praemolars in the tenth to the fourteenth; Replacement now ends and soon after, in the tenth to the fourteenth year, the second molars appear; the third molars erupt much later, in the sixteenth to the fortieth year or not at all. The upper praemolars usually appear before the lower, but otherwise the lower teeth precede the corresponding upper ones.
The tongue (lingua) presents for examination three parts, a body (corpus), the largest, middle portion, adherent to the floor of the mouth, an apex projecting freely into the mouth cavity anteriorly and a root (radix) posteriorly, attached to the hyoid bone and the epiglottis.
The inferior surface of the body is attached; the convex upper surface, lined throughout its whole extent by the oral mucous membrane, is termed the dorsum. The entire surface of the tongue facing the palate is also termed the dorsum linguae. The lateral border is free in the anterior part of the tongue, but behind passes into the soft palate by means of the glossopalatine arch. The boundary between the body and the root is indicated on the dorsum by the foramen caecum, which leads into a quite short, blindly ending canal, the lingual (thyreoglossal) duct. The vallate papillae extend outward and forward from the foramen caecum, forming an angle open anteriorly and with its apex at the foramen (V-shaped). Frequently, immediately behind and parallel to the vallate papillae there is a groove, the terminal sulcus, which, when present, marks the boundary between the body and the root. The root is connected with the epiglottis by three folds of mucous membrane, a median glosso-epiglottic fold and two lateral glosso-epiglottic folds. Between these there is on either side a roundish depression, the epiglottic vallecula.
The tongue is composed of two principal constituents, the mucous membrane and muscles. The mucous membrane of the dorsum is intimately connected with the subjacent muscle tissue, that of the under surface is only loosely connected with it. The mucous membrane of the under surface is smooth and thin and in the median line below the apex forms a sagittal fold, the frenulum. On either side of this there is a low fold with lobed edges, the plica fimbriata, which is well developed in the new-born child, but often less distinct in the adult. It runs from the anterior end of the frenulum posteriorly and laterally. At the margins of the tongue another fold of mucous membrane, the sublingual fold, runs obliquely anteriorly and median ward, to terminate at the root of the frenulum in a sublingual caruncle; it corresponds to the submaxillary duct (see here) which lies close beneath the mucous membrane. The mucous membrane of the dorsum of the tongue is divided by the terminal sulcus or vallate papillae into that of the body and tip, the papillary portion, and that of the root, the tonsillar portion.
The papillae of the mucous membrane of the anterior part of the tongue are in general conical; they project above the surface of the mucous membrane and give it a satiny appearance. They are divided by their form into:
Quite different from the anterior, papillary portion of the lingual mucous membrane is the posterior tonsillar portion, characterized by the occurrence in it of lymphatic lingual follicles, which in their sum total form the diffuse lingual tonsil. Each follicle is a small round elevation 2-3 mm in diameter, with a central, fine depression. As a whole they form on the actual root of the tongue a closely packed, almost defined mass, while towards the epiglottis and the neighbouring palatine tonsils they are more scattered.
The muscles of the tongue consist of two groups:
The Genio-glossus arises from the internal mental spine and passes mainly to the under surface of the mucous membrane of the dorsum of the tongue and partly also to the hyoid bone and the epiglottis.
The Hyoglossus and Chondro-glossus arise from the body and greater cornu of the hyoid bone (the Chondro-glossus from the lesser horn). They pass anteriorly and upwards to the lateral portions of the tongue, interlacing with the fibres of the second group.
The Stylo-glossus arises from the styloid process of the temporal bone and passes to the border of the tongue, interlacing with the fibres of Group II.
The Longitudinalis inferior lies on the under surface of the tongue between the Genio-glossus and Hyoglossus and extends from the root to the tip