uv.*yoJWW''^\v '• Cornell Universiw iuii^ps^fi' QM 101.M19 Osteology; a syllabus, arranged by Charles 3 1924 003 138 025 Cornell University Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/cletails/cu31924003138025 OSTEOLOGY A SYLLABUS ARRANGED BY CHAKLES S. MANGUM Professor of Anatomy TJnivebsity of North Carolina PRINTED BY E. M. UzzELL & Company RALEIGH, N. C. 1912 PREFACE Osteology, the first subject assigned to the student of anatomy, is the most difficult for him to master. The great number of unfamiliar terms and the student's lack of ex- perience in expressing himself in descriptive language make of the skeleton a veritable stumbling block for the be- ginner. It is therefore eminently practical to supply him with a text which presents the subject in a condensed form, and at the same time develops in him the power of orderly description. If, together with it, the study of the larger texts is in- sisted upon, nothing but good can result. This syllabus has been arranged from the texts of Cun- ningham, Gray, Morris, and Piersol. The method of de- scription has been developed from demonstrations by Dr. Eichard H. Whitehead. Chapel Hnx, N. C, April, 1912. CONTENTS PAGE Preface 3 Bones 7 Classification 7 Descriptive Terms 8 Axial Skeleton 10 Vertebral Column 10 General Characters of a Typical Vertebra 10 Movable or True Vertebrse 11 Cervical Vertebrae 11 Peculiar Cervical Vertebrse 12 Dorsal (Thoracic) Vertebrse 13 Peculiar Dorsal Vertebrte 14 Lumbar Vertebrse 14 Fixed or False Vertebrse 15 Sacrum 15 Coccyx 16 Sternum 17 Ribs 18 Typical Rib 18 Peculiar Ribs 19 Skull 20 Cranium 20 Occipital Bone 20 Parietal Bones 22 CONTENTS. 5 PA&E Frontal Bone 23 Sphenoid Bone 25 Temporal Bones 31 Ethmoid Bone 36 Bones of the Face 39 Inferior Nasal Concha 39 Lachrymal Bones 40 Vomer 41 Nasal Bones 41 Maxillae 42 Palate Bones 46 Zygomatic (Malar) Bones 48 Mandible 49 Hyoid Bone (Os Lingulos) 51 Ossicles of the Ear 52 Regional Anatomy of the Skull 53 Cranial Localization 53 Fossae of the Skull 53 Orbits 54 Nasal Fosses 56 Temporal Fossae 59 Zygomatic Fossae 59 Pterygo-Palatine (Spheno-Maxillary) Fossae 60 Anterior Cranial Fossa 60 Middle Cranial Fossa 61 Posterior Cranial Fossa 62 Hard Palate 63 6 CONTENTS. Bones — Continued. page Appendicular Skeleton 65 Bones of Upper Extremity 65 Clavicle (Collar Bone) 65 Scapula (Shoulder Blade) 66 Humerus 68 Radius 70 Ulna 71 Carpus 73 Metacarpus 74 Digits 75 Bones of Lower Extremity 75 Coxal Bone (Os Innominatum) 76 Regional Anatomy of Pelvis 80 Femur 81 Patella 83 Tibia 83 Fibula 85 Tarsus 86 Talus (Astragalus) 87 Calcaneus (Os Calcis) 87 Navicular ( Scaphoid) 88 Cuboid 88 Internal Cuneiform 89 Middle and External Cuneiform 89 Metatarsus 90 Toes 90 BONES CHAPTER I CLASSIFICATION The bones of the human skeleton are classified according to position: Number of Bones. ( The Vertebral Column . 26 The Axial Skeleton ^ The Eibs and Sternum . 25 ( The Skull 23 The Appendicular f The Upper Limbs ... 64 Skeleton 1 The Lower Limbs ... 62 Total 200 This does not include the ossicles of the ear (6) and the sesamoid bones, except the patella. Bones may also be classified according to shape : 1. Long Bones, which present a shaft and two extremi- ties ; found in limbs. 2. Short Bones. Illustrated by bones of Carpus and Tarsus. 3. Flat Bones. Illustrated by Cranial bones. 4. Irregular Bones. Illustrated by Vertebrse and bones of face. osteology: a syllabus. DESCRIPTIVE TERMS Antrum^^a cavity within the interior of a bone. Capitellum=a small head. Clinoid=like a bed. Condyle=a rounded, oblong, articular eminence. Cotyloid=cup-like. Cribriform=like a sieve. Facet^a small, plane, articular surface. FiSSUre=a cleft or slit. Foramen=a hole. F0SSa=a shallovr depression. Glenoid=like a shallow socket. Head=a rounded articular eminence at the extremity of a bone. HiatUS^an opening in the sense of a gap. WleatUS^^a passage or canal. Sesamoid Bone=one developed within a tendon. SinuS=a groove; also a cavity or pocket. Styloid=like a pen. SulCUS^a furrow. TrOChlea=like a pulley. Tubercle^ a small rounded prominence. TuberOSity=an exaggerated tubercle. TrOChanter^a still larger prominence, rounded in form. Ventral ^pertaining to the belly aspect of the body. Dorsal^pertaining to the back aspect of the body. Anterior^towards the ventral aspect. DESCEIPTIVE TEEMS. PostGrior=towar(is the dorsal aspect. Internal=the side towards the middle line of the hody. External^the side away from the middle line of the hody. Sliperior=towards the head end of the body. lnferior=away from the head end of the body. Medial or mesial =internai. Lateral=external. CHAPTER II AXIAL SKELETON VERTEBRAL COLUMN Composed primarily of 33 bones called vertebrae. The first 24 are separate bones and are called the mov- able or true vertebra. The 9 lovifer vertebrae are fused together to form two bones, the Sacrum (5 vertebrae) and the Coccyx (4 verte- brae), and are known as the false or fixed vertebra. GENERAL CHARACTERS OF A TYPICAL VERTEBRA. All vertebrae have certain essential characteristics in common, although the vertebrae of the different regions of the column differ markedly in many respects. Composed of a body (Centrum) and an arch. Body: Large and solid; situated in front; anterior sur- face and sides more or less constricted (concavo-convex) ; posterior surface, slightly concave; superior and inferior surfaces rough and lipped, affording attachment for the intervertebral discs of cartilage. Arch: Formed by (1) two pedicles, one on each side, which project backward from the body and are notched above and below (the vertebral notches) ; and (2) by two laminae, one on each side, broad and flat, which are directed AXIAL SKELETON. 11 backward and inward to meet in the middle line behind. From their junction springs the Spinous Process, which is directed backward. From the junction of the pedicles and laminae arise two superior articular processes, one on each side, which look backward; and two inferior articular processes, one on each side, which look forward. From the same point, on each side, springs the trans- verse process, which projects outward. The body and arch enclose a large foramen, the verte- bral (spinal) foramen. MOVABLE OR TRUE VERTEBR.a!]. Cervical, 7. Dorsal (Thoracic), 12. Lumbar, 5. CERVICAL VEETEBEiE. Seven in number. Body: Small, broadest from side to side. Superior surface, lipped on each side. Inferior surface, prolonged downward in front. Arch: Pedicles small; run backward and outward. Laminw long, narrow and thin. Spinous process short and bifid. Superior articular processes look upward and backward ; inferior articular processes look downward and forward. Transverse processes, bifid ; run downward, out- ward and forward, arising by two roots which enclose the costo-transverse (vertebrarterial) foramen; are grooved on upper surface and terminate in anterior and posterior 12 osteology: a syllabus. tubercles. Vertebral (spinal) foramen, large and heart- shaped. PECULIAE CEEVICAL VEETEBEiE. 1st, 2d, and 7th. First Cervical Vertebra or Atlas: Plas neither body nor spinous process. Consists of anterior and posterior arches and two lateral masses, which support the articular and transverse processes, the whole forming a ring of bone. Anterior Arch: Forms one-fifth of circumference; con- vex in front with median tubercle ; concave behind with median articular facet. Posterior Arch: Forms two-fifths of circumference; presents a median tubercle behind and a transverse groove above and below on each side, immediately behind the lat- eral masses ; superior groove is most prominent and is called the vertebral groove. Lateral Masses: Diverge behind; converge in front. Superior surface presents an oval, concave articular sur- face (the superior articular process), which looks upward and inward. Inferior surface presents a round, almost flat (slightly concave) articular surface (the inferior articular process) which looks downward and inward. Internal surface pre- sents a tubercle ; external surface presents the transverse process which is large and not bifid. Vertebral (Spinal) foramen, large and irregular in out- line. AXTAT. SKELETON. 13 Second Cervical Vertebra, Axis or Epistropheus: Body: Anterior surface presents a median ridge with a depression on each side. Superior surface presents the Odontoid process or dens which has a constricted neck, a head and a pointed apex, and presents an articular facet in front and behind. Arch: Pedicles short, transverse, and thick. Laminse thick and strong. Superior articular surfaces round and convex; look upward and outward and rest on body. In- ferior articular processes like succeeding vertebrae. Pedi- cles and transverse processes have superior vertebral notch behind them. Transverse processes small and not bifid. Spinous process large and strong. Seventh Cervical Vertebra, called Vertebra Prominens: Spinous process long and ends in a single broad tubercle. Costo-transverse foramen small and often absent. DOBSAL (tHOEACIC) VEETEBRiE. Twelve in number. Body: Heart-shaped and presents latero-posteriorly a demi-facet above and below on each side; called the su- perior and inferior costal pits. Arch: Pedicles short and directed backward. Inferior vertebral notch very deep. Laminae broad and thick. Su- perior articular processes flat and look backward and out- ward. Inferior articular processes flat or slightly concave and look forward and inward. Spinous process long, thin, 2 14 osteology: a syllabus. and oblique, runs downward and backward and terminates in a tubercle. Transverse processes run outward and back- ward, clubbed at end, with an articular facet in front, which is called the costal pit of transverse process. Vertebral (spinal) foramen small and circular. PECULIAR DOESAL VEETEBEyE. 1st, 9th, 10th, 11th, and 12th. First Dorsal Vertebra: Presents upon body two whole facets above, two demi-facets below. Superior articular processes look upward and backward. Spinous process, nearly horizontal and very prominent. Ninth Dorsal Vertebra: Sometimes presents only the two upper demi-facets. Tenth Dorsal Vertebra: May present two whole facets and no demi-facets. Eleventh Dorsal Vertebra: Body large and presents one whole facet on each side. Transverse processes small and do not have articular facet (costal pit). Twelfth Dorsal Vertebra: Presents one whole facet on each side, not upon body but upon pedicle. Transverse processes not articular. Inferior articular processes con- vex and look forward and outward. LUMBAE VEETEBK.T;. Five in number. The largest of the movable vertebrae. Body: Large; kidney-shaped; broadest from side to side ; thicker in front than behind ; lateral surfaces deeply constricted. AXIAL SKELETON. 15 Arch: Pedicles short and stout; directed backward. Inferior vertebral notches deep and large. Laminse short, broad, and strong. Spinous process thick, broad, hori- zontal, and quadrilateral. Transverse processes long and thin, directed outward and backward. Superior articular processes concave, look backward and inward, and present on the posterior margin the mammillary tubercle. Inferior articular processes, convex, look forward and outward. Vertebral (spinal) foramen large and triangular in shape. FIXED OR FALSE VERTEBRA. Sacrum, 5 vertebrae. Coccyx, 4 vertebrae. SACEUM. Formed of 5 fused vertebrae (the sacral vertebrae), which are more or less rudimentary. Roughly triangular in shape, with base up and apex down. Presents for exami- nation an anterior (pelvic), a posterior, and two lateral surfaces, a base and an apex. Anterior (Pelvic) Surface: Directed downward and forward; smooth and concave; crossed by four transverse ridges, leading on each side to four anterior sacral fora- mina, from which four shallow grooves lead outward. Posterior Surface: Convex and rough. Presents in the middle line four rudimentary spinous processes, the lower two being often aj^sent. In the middle line below is a gap, the hiatus sacralis, the end of the sacral canal, on each side of which is a process of bone, the sacral comu. On 16 osteology: a syllabus. each side of the middle line is a broad, shallow groove, the sacral groove, the floor of which is formed by four rudi- mentary laminae. Just outside of groove are four rudi- mentary articular processes, then four posterior sacral foramina, while most external are four rudimentary trans- verse processes. The fifth sacral vertebra is too rudimen- tary to show the above points. Lateral Surfaces (two): Broad above, narrow below, where each terminates in the inferior lateral angle, below which is a notch. Above is seen an ear-shaped articular surface in front, behind which is a rough depression. Base: Extended in front to form sacral promontory ; presents kidney-shaped surface for articular cartilage in the middle. Upper end of sacral canal behind, bounded by two laminae; superior articular process on each side of canal, with groove in front of each. Base extended on each side to form broad mass, called Ala (wing) of the sacrum. Apex: Oval, convex, articular; directed downward and forward on account of position of Coccyx. COCCYX. Formed by four fused vertebrae, all of which are rudi- mentary. Triangular in shape with base upward. Su- perior surface has oval, concave, articular surface for ar- ticulation with the Sacrum. Apex the termination of the vertebral column. AXIAL SKELETON. lY STERNUM (BREAST BONE). A flat, oblong plate of bone, situated in the anterior wall of the Thorax. Consists of three pieces: Manubrium, Griadiolus, and Xiphoid or Ensiform Process. Manubrium: Broadest and thickest part of the bone. Triangular in shape, with base upward. Presents for ex- amination two surfaces and four borders. Anterior surface concavo-convex and smooth. Posterior surface slightly concave. Superior border presents two concavo-convex articular surfaces separated by a shallow notch, the jugular (interclavicular) notch. Inferior bor- der articulates with the Gladiolus, forming a transverse ridge, the angle of the Sternum. Lateral borders present a facet above, a demi-facet below. Gladiolus (Body): Long and narrow. Presents two surfaces and four borders. Anterior surface flat, marked by three transverse ridges. Posterior surface slightly concave and marked by three transverse ridges. Superior border articulates with Manu- brium. Inferior border articulates with Xiphoid process. Lateral borders present a demi-facet above and below, with four whole facets between. Xiphoid or Ensiform Process: Often cartilaginous. Subject to great variation in form. Articulates above with Gladiolus; free below. Presents one demi-facet on each side above. 18 osteology: a syllabus. RIBS. Twelve in number on each side, forming the lateral walls of the Thorax. First seven, called the true ribs (vertebro-sternal), are attached directly to the Sternum by costal cartilages. The remaining five are called false ribs, and of these the eighth, ninth, and tenth have their anterior extremities con- nected by cartilage and are called vertebro-chondral ribs, while the two last have their anterior extremities free, and are known as the floating or vertebral ribs. TYPICAL EIB. A typical rib presents for examination a posterior (ver- tebral) extremity, an anterior (sternal) extremity, and a shaft or body. Posterior Extremity consists of: (l) A head with two articular facets separated by an antero-posterior ridge. (2) A neck, flat and smooth in front, rough behind ; supe- rior border thin, called the "crest" ; inferior border thicker. (3) The tuberosity, on the posterior aspect of junction of neck with shaft, which is rough above, articular below. Anterior (Sternal) Extremity presents a pit in the end for costal cartilage. Shaft (Body): Curved, oblique, and twisted; bent up- ward and inward. Presents two surfaces and two borders. External (outside) surface is convex. Internal (inside) surface concave and presents the subcostal groove near the inferior border. Superior border, thick and rounded. In- ferior border, thin and sharp. AXIAL SKELETON. 19 The shaft presents the angle of the rib near the posterior extremity. •' PECULIAR EIBS. 1st, 2d, 10th, 11th, and 12th. First Rib: Short, flat, and not twisted. Almost hori- zontal in position. Head small and has only one articular facet. ISTeck round and slender. Tuberosity large and prominent. Shaft: Presents superior and inferior surfaces, ante- rior (external) and posterior (internal) borders. Supe- rior surface presents two oblique, shallow grooves, sep- arated by a ridge which terminates at the internal border in the scalene tubercle. Inferior surface, flat and smooth and has no subcostal groove. Anterior (External) Border thick and convex. Pos- terior (Internal) Border thin and concave. Presents scalene tubercle. The angle and tuberosity coincide. Second Rib: Shaft not twisted and presents a rough, oval tubercle about middle of outer surface. Tenth Rib: Has usually only one articular facet on head. Eleventh Rib: One articular facet on head; no tuber- osity ; no neck. Twelfth Rib: One articular facet on head; no tuber- osity ; no neck ; no angle. 20 osteology: a syllabus. SKULL. Consists of the Cranium (8 bones) ; and the Face (14 bones). BONES OF THE CRANIUM. OCCIPITAL BONE (oCCIPUT). Situated at the posterior and inferior part of the cra- nium. Consists of four parts arranged around the foramen magnum : the Squamous above and behind ; two Condylar, one on each side ; and the Basilar in front. Squamous Portion: Presents two surfaces, three an- gles and four borders. Posterior Surface: Convex in outline; presents a smooth, triangular surface above. Near the middle is the posterior (external) occipital protuberance, from which the posterior occipital crest descends in the middle line as far as the foramen magnum. Arching outward from the pro- tuberance, on each side, is a ridge, the Superior ISTuchal (curved) line. Arching outward from the middle of the posterior occipital crest is another ridge, the Inferior ISTuchal (curved) line. The bone above and below this line is marked by rough depressions. Anterior (Cerebral) Surface: Concave; divided into four fossae by a crucial ridge, at the junction of the arms of which is the Anterior (internal) Occipital Protuber- ance, and on or near this is a shallow depression, the torcu- lar Herophili. The arms of the cross are grooved for the cerebral sinuses. The descending ridge is prominent; AXIAL SKELETON. 21 called the Anterior Occipital Crest, which bifurcates below to partially surround the foramen magnum. Angles: A superior and two lateral. Borders: Two superior and two inferior. The supe- rior borders extend from the superior to the lateral angles ; deeply serrated ; form the lambdoid suture with the Pari- etal bones. The inferior borders extend on each side from the lateral angle to the jugular process and articulate with the mastoid portion of the Temporal bone. Condylar Portions: Two in number, one on each side of foramen magnum. Each presents an inferior and a superior surface. Inferior Surface: On base of skull. Presents an ar- ticular condyle on the antero-lateral margin of foramen magnum. The two condyles converge in front, diverge behind. On the inner side of each condyle is a tubercle. At the base of the condyle the hypoglossal (anterior con- dyloid) foramen perforates the bone, and is sometimes double. Behind the condyle is the condylar fossa, the floor of which is sometimes perforated by the posterior condyloid foramen. Extending outward from the base of the condyle towards the Temporal bone is a rough quad- rilateral portion called the Jugular Process, which is notched in front and forms the posterior boundary of the jugular foramen. Superior (Cerebral) Surface: Presents the internal opening of the hypoglossal, and sometimes of the posterior condyloid, foramen; and further external the superior 22 osteology: a syllabus. surface of the jugular process, which is marked by a groove (the Sigmoid Groove) leading to the jugular notch or foramen. Basilar Portion: A quadrilateral plate of bone project- ing forward and upward in front of the foramen magnum. Presents for examination two surfaces and four borders. Superior (Cerebral) Surface: Concave; marked by broad, shallow groove, the basilar groove. Inferior Surface: Convex; marked in the middle by the pharyngeal tubercle (or spine). Borders: Lateral borders articulate with petrous por- tion of Temporal bone. Posterior border forms anterior margin of foramen magnum. Anterior border articulates with body of Sphenoid bone with which it fuses to form a complete bony union. Foramen IVIagnum: Large; oval in shape; long axis from before backward ; wider behind than in front ; com- pletely surrounded by the four portions of the Occipital bone. PARIETAL BONES. Two in number ; placed on either side of the vault of the cranium, between the Occipital behind and the Frontal in front. Quadrilateral in shape, presenting two surfaces, four borders and four angles. External Surface: Convex; parietal eminence in the middle. Just below are two curved lines, separated by smooth surface, the superior and inferior temporal ridges, AXIAL SKELETON. 23 which form an arch with concavity downward. Parietal foramen near the superior border behind. Internal Surface: Concave, with many depressions for convolutions of brain; grooved for meningeal arteries. Longitudinal groove near superior border, external to which are depressions for pacchionian bodies. Internal opening of parietal foramen near superior border behind. Borders: Superior border, serrated; forms sagittal suture with its fellow of opposite side. Inferior border, curved with concavity dovwiward; thin and beveled in front and in the middle at the expense of outer plate; thick and serrated behind. Articulates from before back- ward with (1) tip of great wing of Sphenoid, (2) the squamous and (3) mastoid portions of Temporal bone. Anterior Border, serrated; forms coronal suture with Frontal bone. Posterior Border, serrated ; forms lambdoid suture with Occipital bone. Angles: Anterior superior; posterior superior; ante- rior inferior, which is thin and prolonged downward to articulate with great wing of Sphenoid and presents on its internal surface grooves for meningeal arteries; posterior inferior, which is thick and articulates with mastoid por- tion of Temporal bone and presents upon its internal sur- face a shallow groove, the sigmoid groove. ./'^W. FEONTAL BONE. Situated in the fore part of the Cranium and consists of two portions; the vertical (frontal) portion, which forms 24 osteology: a syllabus. the forehead, and the horizontal (orbital) portion, which helps to form the roof of the orbits. Vertical (Frontal) Portion: Presents two surfaces and one border. Anterior Surface: Smooth and convex; presents in the middle line a faint vertical ridge (remains of frontal suture). On each side, from above dovsmward, are the frontal eminence, a transverse depression (the sulcus transversus), the superciliary ridge or arch, and the supra- orbital ridge which forms the upper margin of the orbit, presenting the supraorbital notch or foramen at the junc- tion of the inner % with the outer % and terminating internally at the internal angular process, externally at the external angular process. On the external angular process is seen the termination of the temporal ridges, and behind it a smooth surface which enters into the formation of the temporal fossa. The superciliary ridges converge toward the median line, and between their terminations is the nasal eminence (glabella), below which are the nasal notch and spine, with the opening into the frontal sinuses on each side. Posterior (Oereiral) Surface: Concave and marked by depressions for convolutions of brain. Presents in the middle line a vertical groove (the sagittal sulcus), which becomes a ridge (the frontal crest) below, and terminates near the lower margin at the foramen coecum. Superior Border: Semi-circular, thick and serrated; forms coronal suture with Parietal bones. Contimied in- AXIAL SKELETON. 25 feriorly into a triangular rough surface on either side, which articulates with great wing of Sphenoid. Horizontal (Orbital) Portion: Consists of two orbital plates, one on either side, separated by the ethmoid notch, which is quadrilateral in shape and in the articulated skull is filled up by the cribriform plate of the Ethmoid bone. Each orbital plate presents for examination two surfaces and two borders. Superior (Cerebral) Surface: Convex; marked by de- pressions and elevations for the convolutions of the brain. Inferior Surface: Concave and smooth; forms greater part of roof of orbit ; triangular in shape, and presents the lachrymal fossa just behind the external angular process, and a small depression or a tubercle just behind the inter- nal angular process. Borders: Posterior border thin; articulates with the lesser wing of the Sphenoid bone; terminates laterally in the rough triangular surface at lower end of superior border of vertical portion; internal border forms margin of ethmoid notch and articulates with lateral mass of Eth- moid bone. This margin is cellular in structure, helping to form ethmoidal cells, and it is marked by two transverse grooves, which, with like grooves on Ethmoid, form the anterior and posterior ethmoidal canals. SPHENOID BONE. Situated in the middle of the base of the skull, and helps to form the floor of the anterior and middle cranial fossae ; 26 osteology: a syllabus. a part of the anterior boundary of the posterior cranial fossa; the temporal, zygomatic, pterygo-palatine (spheno- maxillary) and nasal fossse; and the walls of the orbit. Consists of a Body and three pairs of expanded processes, the Lesser Wings, the Great Wings, and the Pterygoid Processes. Body: Roughly cuboidal in shape and hollowed out into two large cavities, the sphenoidal sinuses^ separated by a thin septum of bone, the sphenoidal septum, and open- ing in front into the nasal fossse. Presents for examina- tion six surfaces. Superior Surface : Erom before backward presents : ( 1 ) The ethmoidal spine ; ( 2 ) a smooth surface presenting a longitudinal groove (the olfactory groove) on each side; (3) a transverse ridge (limbus sphenoidalis) which forms the anterior margin of (4) the optic groove, leading on each side to (5) the optic foramen; (6) the tuberculum sellse (olivary ridge), which separates the optic groove from (7) the hypophyseal fossa (sella turcica or pituitary fossa). The posterior boundary of this fossa is (8) a quadrilateral plate of bone, the dorsum sellse {dorsum ephippii), surmoimted on each side by (9) the posterior clinoid process. Inferior Surface: Presents in middle line a prominent ridge, the rostrum for articulation with the Vomer, which covers it in the articulated skull. On each side is the vaginal process of the internal pterygoid plate extending inward toward the rostrum, and anteriorly on each side AXIAL SKELETON. 27 is the sphenoidal process of the Palate bone. These two processes, with the Vomer, cover most of this surface of the hody. Lateral Surfaces: Each lateral surface is marked by a longitudinal groove, the carotid or cavernous groove which leads from the foramen lacerum behind to the sphenoidal fissure in front. This surface gives attachment to the great wing and in front helps to form the inner wall of the orbit. Anterior Surface: Looks forward into nasal fossae; divided into two lateral halves by the sphenoidal septum (crest), with the opening of the sphenoidal sinus on each side, which is bounded laterally and below by the sphe- noidal conchse (turbinate bones) . Posterior Surface: Anchylosed with basilar process of Occipital bone. The Lesser (Orbital) Wings: One on each side; pro- jects horizontally outward on a level with the front part of the superior surface of the body; thin and triangular in shape with apex outward. Arises by two roots which en- close the optic foramen. Presents two surfaces and two borders. Superior surface smooth; forms posterior part of anterior fossa of skull. Inferior surface forms roof of sphenoid (superior orbital) fissure, the elongated opening between the small and great wings. Anterior border articulates with the orbital plate of the Frontal. 28 osteology: a syllabus. Posterior border free and rounded; prolonged backward at internal extremity into the anterior clinoid process ; sep- arates the anterior from the middle fossa of the skull. The Great (Temporal) Wings: One on each side; pro- jects from the lateral surface of the body, outward, for- ward, and upward, and then backward to the tip. Pre- sents for examination four surfaces and four borders. The borders, considered together, form the circumference of the Great Wing. Superior (Cerebral) Surface: Concave and marked by depressions and elevations for the convolutions of the brain. Enters into the formation of the middle fossa of the skull. Presents from before backward and outward three fora- mina, the foramen rotundum, foramen ovale, and foramen epinosum. Between the foramen rotundum and foramen ovale, a fourth foramen, the foramen of Vesalius, is some- times seen. Anterior (Orbital) Surface: Looks inward and forward and helps to form the outer wall of the orbit, and below this the upper part of the posterior wall of the pterygo-palatine (spheno-maxiUary) fossa. The orbital portion is quadri- lateral and smooth ; articulates above with the Frontal ; in front with the Zygomatic (Malar) bone; behind forms outer margin of the Sphenoidal (superior orbital) fissure; and below forms the outer margin of the spheno-maxillary (inferior orbital) fissure. The spheno-maxillary (lower) portion of the anterior surface of the Great Wing may be seen below and behind the posterior extremity of the AXIAL SKELETON. 29 splieiio-maxillary fissure. Forms upper part of posterior wall of the pterygo-palatine (spheno-maxillary) fossa ; per- forated by anterior opening of foramen rotundum. External Surface: Concavo-convex and smooth; forms part of temporal fossa ; separated from the inferior surface by a prominent antero-posterior ridge (the pterygoid or infratemporal). Inferior Surface: Concave and looks downward and outward into zygomatic fossa; presents inferior orifices of foramen ovale and foramen spinosum and of the foramen of Vesalius when present. The Circumference {Borders) of the Great Wing: In the orbit the anterior surface of the Great Wing presents four borders : The posterior forms the outer margin of the sphenoidal fissure ; the inferior forms the outer mar- gin of the spheno-maxillary fissure ; the superior articulates with the orbital plate of the Frontal bone; the anterior articulates with the orbital surface of the Zygomatic bone ; the superior and anterior borders meet just behind the external angular process, and between this point internally and the temporal fossa externally is a rough triangular surface for articulation with a similar surface at the lateral extremity of the border of the vertical portion of the Frontal bone. In the temporal fossa the external surface of the Great Wing articulates in front with the Frontal bone, above by its tip with the antero-inferior angle of the Parietal bone, behind with the squamous portion of the Temporal bone. In the zygomatic fossa the inferior sur- 3 30 osteology: a syllabus. face of the Great Wing articulates externally with the squamous portion of the Temporal bone, internally with the petrous portion of the Temporal bone. The most posterior extension of the Great Wing (behind the foramen ovale) is wedged into the angle between the squamous and petrous portions of the Temporal bone. From the under surface of the tip of this wedge the sphenoidal spine or ala pro- jects downward. The Pterygoid Processes: One on each side projects downward from the junction of the Body with the Great Wing. Each consists of two plates, the external and in- ternal pterygoid plates, which enclose between them pos- teriorly a deep fossa, the pterygoid fossa, which terminates below in a notch (the pterygoid notch) filled up in the ar- ticulated skull by the pyramidal process (tuberosity) of the palate bone. External Plate: Usually the broadest and shortest of the two. Internal Plate : Longer and narrower ; prolonged below into a slender, hook-like or hamular process. At upper ex- tremity of the posterior border is the pterygoid tubercle, above and external to which the pterygoid (Vidian) canal tunnels the base of the process, while below and external is the shallow scaphoid fossa in the upper angle of divergence between the two plates. From the base of the internal plate the vaginal process extends inward towards the rostrum of the Sphenoid, and presents a groove on its under surface, which, with a like groove on the upper surface of the sphe- AXIAL SKELETON. 31 noidal process of the Palate bone, forms the pharyngeal (pterygo-palatine) canal. The Anterior Border of the internal plate articulates with the vertical plate of the Palate bone. The Anterior Surface of the pterygoid process forms the lower part of the posterior wall of the pterygo-palatine (spheno-maxillary) fossa and presents the anterior orifice of the pterygoid (Vidian) canal. TEMPORAL BONES. Two in number, one on either side. Situated at the side and base of the cranium, and contains the organ of hearing. Is divided for description into: (1) the Squamous, (2) the Mastoid, (3) the Petrous Portions, and (4) the Tym- panic Plate. The Squamous Portion: Situated above and in front of the external aperture of the ear ; thin and scale-like and presents for examination two surfaces and two borders. External Surface : Convex and smooth, forming a part of the temporal fossa. Below is the Zygomatic Process, which runs first outward and then forward to articulate with the temporal process of the Zygomatic (Malar) bone, which together form the Zygoma. The external surface of the process (Zygomatic Process) is convex and subcutaneous ; its internal surface concave ; its upper border thin and sharp ; its lower border thick and notched. It arises by three roots, the anterior, called the eminentia articularis, bounds the glenoid fossa in front; 32 osteology: a syllabus. the middle, called the post-glenoid process, bounds the fossa above and behind and is just in front of the external auditory meatus ; the posterior root is prolonged from the upper border, and, passing above the external auditory meatus, joins the temporal ridge behind. Betvs^een the anterior and middle roots is a hollow, the glenoid fossa, which is divided by the petro-tympanic (Glaserian) fissure into an anterior articular half, which belongs to the squa- mous portion, and a posterior non-articular half, which belongs to the tympanic plate. At the inner end of the fissure is a slit, the canal of Huguier. Internal (Cerebral) Surface: Concave; marked by de- pressions for the convolutions of the brain and grooves for the meningeal arteries. Borders: Superior border convex and thin, beveled internally for articulation with the Parietal bone. Ante- rior border convex; articulates with the great wing of Sphenoid. The Mastoid Portion: Situated behind the external auditory meatus ; separated from the tympanic plate by the tympano-mastoid (Auricular) fissure. It presents for ex- amination two surfaces and two borders. External Surface : Convex and rough ; prolonged down- ward into an apex, the Mastoid Process^ behind and inter- nal to which is a deep groove, the mastoid notch (digastric fossa) and still more internally the occipital groove, while above, near the posterior border, is the mastoid foramen. AXIAL SKELETON. 33 Internal (Cerebral) Surface: Concave; marked by a deep groove, the sigmoid groove, and presents the internal orifice of the mastoid foramen. Borders: Superior border, thick and serrated for ar- ticulation with the Parietal bone. Posterior border, thick and serrated; articulates with Occipital bone. The inte- rior of the mastoid portion is occupied by numerous cavi- ties, the mastoid air-cells, which open into a chamber, the mastoid antrum, which communicates with the tympanum, or cavity of the middle ear. ' Thfi Pfitrniis Pnrtinn: Situated in the base of the skull internal to the external auditory meatus. Pyramidal in shape with apex directed forward and inward. Presents for examination four surfaces, four borders, a base and apex. Superior Surface: Looks forward and upward into the middle fossa of the skull, forming the back part of its floor. It presents from within outward: (1) On the apex a de- pression for the Gasserian ganglion; (2) two small grooves running backward and outward to (3) two small foramina, the internal (larger) called the hiatus canalis facialis {hiatus Fallopii), the external (smaller) the foramen for the small superficial petrosal nerve; (4) behind and out- side of these the eminentia arcuataj and still more exter- nally (5) a depression, the tegmen tympani. Posterior Surface: Looks backward and inward into the posterior fossa of the skull. Presents near the middle : (1) The internal auditory meatus, behind and external to 34 osteology: a syllabus. which is (2) the acqueductus vestihuli; while above and between the two is (3) an irregular depression (the fossa subarcuata) which sometimes presents an opening. Inferior {Basilar) Surface: Situated on the base of the skull. Presents from within outward: (1) A rough quadrilateral surface near the apex; (2) inferior orifice of the carotid canal; (3) a sharp ridge, the carotid ridge, which separates the carotid canal from (4) the jugular fossa; on the ridge is (5) the opening of the tympanic ca- naliculus (foramen for Jacobson's nerve), while posteriorly the ridge bifurcates, and in the triangle thus formed near the posterior border is (6) the three-sided opening of the acqueductus cochlece. On the outer wall of the jxigular fossa is (7) the minute opening of the mastoid canaliculus (foramen for Arnold's S'erve) ; bounding the fossa behind is (8) the rough jugular surface for articulation with the jugular process of Occipital bone, and external to the fossa ; (9) the styloid process projects downward with (10) the stylo-mastoid foramen at the outer side of its base. Anterior (External or Tympanic) Surface: Forms the inner and posterior walls of the tympanic cavity (within the interior of the Temporal bone), and cannot be seen without removing the Tympanic Plate. Apex: Looks forward and inward. Presents the inter- nal (superior) orifice of the carotid canal, which opens into the outer side of the foramen lacerum between the Tem- poral and the Sphenoid bones. AXIAL SKELETON. 35 Base: Becomes identified during development with the mastoid portion. Borders: Superior, long; separates the posterior from the superior surface; grooved, and presents a notch near the apex. Posterior: Separates the posterior from the inferior surface ; articulates internally with the, basilar portion of the Occipital; externally bounds the jugular foramen above and behind. Anterior : Short ; articulates with the posterior portion of the Great Wing of the Sphenoid. In the angle of j no- tion of the squamous and petrous portions, at the outer end of this border, are two canals, the upper for the tensor tym- pani muscle, the lower for the Eustachian tube, separated by the processus cocMeariformis. Inferior: Articulates with the tympanic plate exter- nally, while internally it runs along the rough quadrilateral surface on the inferior aspect of the apex. The Tympanic Plate: A quadrilateral plate of bone, situated in front and below the external auditory meatus. Forms the anterior, inferior and part of the posterior walls of the external auditory meatus and canal. Separated be- hind from the mastoid portion by the tympano-mastoid (auricular) fissure; separated in front from the squamous portion by the petro-tympanic (Glaserian) fissure. Pre- sents for examination two surfaces and four borders. External (Antero-inferior) Surface: Looks dovsoiward and forward and forms the posterior (non-articular) half of the glenoid fossa. 36 osteology: a syllabus. Internal (Postero-superior) Surface : Looks upward and backward into the external auditory meatus and the Tym- panum; concave and scroll-like. Borders: External : Rough and everted to form the external au- ditory process. Superior: Helps to form the petro-tympanic (Glase- rian) fissure. Inferior: Sharp and thin; prolonged downward into the vaginal process which surrounds the. base of the styloid process of the petrous portion. Internal : Very short and vertical in direction ; is seen on the base of the skull just below and to the outer side of the opening for the Eustachian tube. External Auditory Meatus is a bony canal, leading into the interior of the Temporal bone. Its walls are formed above by the squamous portion, below and in front by the tympanic plate, and behind by the mastoid portion. ETHMOID BONE. Of very delicate texture ; situated at the anterior part of the base of the Cranium, between the two orbits, and helps to form the anterior fossse of the skull, the orbits and the nasal fossse. Consists of four parts, i. e., the Horizontal (Cribriform) Plate, the Vertical (Perpendicular) Plate, and two Lateral Masses, one on either side. Horizontal (Cribriform) Plate: Fills up the ethmoid notch between the orbital plates of the Frontal bone. Pre- sents two surfaces and four borders. AXIAL SKELETON. 37 Superior (Cerebral) Surface: Forms a part of anterior cranial fossae. Presents in the middle line a triangular spine, the Crista Galli, with the foramen C cecum at its base in front. On either side is a deep groove, the olfactory groove^ the floor of which is perforated by numerous fora- mina for the olfactory nerves and in front at the side of the spine by a small slit for the nasal nerve. Inferior (Nasal) Surface: Helps to form the roof of the nasal fossae and presents foramina for olfactory nerves and slits for the nasal nerves. Borders: Anterior and two lateral articulate with the margins of the ethmoidal notch ; posterior articulates with the ethmoidal spine of the Sphenoid. Vertical (Perpendicular) Plate: Forms the upper 1/3 of the septum nasi. Presents two surfaces and four bor- ders. Its two surfaces help to form the inner walls of the nasal fossae. Anterior border articulates above with nasal spine of Frontal ; lower down with the crest of the ITasal bones. Antero-inferior border articulates with the cartilage of the nose. Postero-inferior border articulates with the anterior bor- der of the Vomer. Posterior border articulates with the crest (septum) of the Sphenoid. Lateral Masses (Labyrinth): Two in number, one on either side. Composed of very thin bone (like paper) sur- rounding a number of cavities, the anterior and posterior 38 osteology: a syllabus. ethmoidal air cells, or sinuses, and giving to the bone a honeycombed appearance. Each lateral mass presents for examination six surfaces. External (Orbital) Surface: Presents a smooth quadri- lateral surface, the lamina papyracea (os planum), which forms a large part of the internal wall of the orbit and articulates in front with the Lachrymal; behind with the Sphenoid; below with the orbital plate of the Maxilla (upper jaw) anteriorly and the orbital process of the Pal- ate bone posteriorly; above with the orbital plate of the Frontal, and perforating this last suture are the anterior and posterior ethmoidal foramina, or canals. Internal (Nasal) Surface: Called the turbinate proc- ess ; helps to form the external wall of the nasal fossa. Pre- sents two thin, scroll-like processes, the superior and middle nasal conchas (turbinate bones), which are continuous in front, but separated behind by a space called the Superior meatus of the nose, and through which the posterior eth- moidal cells open into the nasal fossa. Anterior Surface (Extremity) : Cellular in structure and articulates with similar cells on the nasal process of the Maxilla. Posterior Surface (Extremity) : Cellular, and articu- lates with the sphenoidal conchse on the anterior surface of the body of the Sphenoid. Superior Surface (Border) : Cellular ; articulates with the cellular margin of the ethmoidal notch (internal border of orbital plate of Frontal), and across it from without AXIAL SKELETOKT. 39 inward pass two grooves which, with like grooves on the Frontal, complete the anterior and posterior ethmoidal canals. Inferior Surface (Border) : Has middle meatus of nose below it. From the anterior aspect of its outer edge, just below the lamina papyracea, the uncinate process projects downward and backward to articulate with the inferior nasal concha on the outer wall of the nasal fossa, and helps to separate this cavity from the cavity within the body of the Maxilla (the antrum of Highmore) . BONES OF THE FACE. INFEEIOE NASAL CONCHA (iNFEEIOE TUEBINATe). A scroll-like, slender shell of bone, placed along the lower part of the external wall of the nasal fossa. Presents two surfaces, two extremities and two borders. External Surface: Concave; looks toward the outer wall of the nasal fossa. Internal Surface: Convex, pitted and grooved. Anterior Extremity : Mat and broad; articulates with inferior conchal crest of Maxilla. Posterior Extremity : Narrow and pointed ; articulates with the inferior conchal crest of the Palate bone. Inferior Border: Free, thick and rounded. Superior Border: Articulates, by three processes, along the outer wall of the nasal fossa from before backward, with the Lachrymal, the Maxilla and the uncinate process of the Ethmoid. 40 osteology: a syllabus. lachrymal bones. Two in number, one on each side. A small, thin, quad- rilateral bone, placed in the fore part of the inner wall of the orbit. Presents for examination two surfaces and four borders. External (Orbital) Surface: Divided into an anterior portion which presents the lachrymal sulcus (groove) and a posterior portion, which is smooth, by a vertical ridge, the lachrymal crest, which curves forward below to complete the canal for the lachrymo-nasal duct and articulates with the lachrymal tubercle of the frontal process of the Maxilla on the infra-orbital ridge. Internal (Nasal) Surface: Articulates with the lateral mass of the Ethmoid above; looks into middle meatus of nose below. Borders : Superior : Articulates with internal angular process of Frontal. Inferior : Behind the vertical crest on the external surface, it articulates with the orbital plate of Maxilla ; in front of crest it is prolonged downward to articulate with the inferior nasal concha, and helps to form the inner wall of the canal for the lachrymo-nasal duct. Anterior: Articulates with frontal process of Maxilla. Posterior: Articulates with lamina papyracea of Eth- moid. AXIAL SKELETON. 41 VOMEK. Flat, shaped like a plowshare. Forms the median sep- tum of the nose behind and below. Presents two surfaces and four borders. Lateral Surfaces: Right and left; help to form inner walls of nasal fossae; smooth and each marked by longi- tudinal groove. Borders: Superior: Thick; separates into two alee, which re- ceive the rostrum of the Sphenoid between them and articu- late with the vaginal process of the internal pterygoid plate behind and the sphenoidal process of the Palate bone in front. Posterior: Concave and free; separates the posterior nares. Anterior: Slopes from above and behind downward and forward; articulates above with the perpendicular plate of the Ethmoid, below with the septal cartilage of the nose. Inferior: Articulates from before backward with the crest of the palate processes of the Maxillse and of the Palate bones. Anterior and inferior borders meet at the anterior extremity of the bone. NASAL BONES. Two in number. Together form the bridge of the nose. Each presents two surfaces and four borders. 42 osteology: a syllabus. Anterior {Facial) Surface: Concavo-convex; small nasal foramen in the middle. Posterior (Nasal) Surface: Concave; marked by a longitudinal groove. Borders: Superior : Thick, short, articulates with nasal notch of Frontal. Inferior : Thin, notched ; articulates with nasal carti- lage. External : Articulates with frontal process of Maxilla. Internal (Medial) : Articulates with its fellow of the opposite side to form the nasal crest, and is prolonged backward behind the nasal notch of Frontal to articulate with nasal spine of Frontal above, and the perpendicular plate of Ethmoid below. MAXILLA (SUPEEIOE MAXILLAEY BONES ). Two in number, one on each side ; fused together in the middle line of the face to form the upper jaw. Each con- sists of a body and four processes. Body: Pyramidal in shape, containing a cavity, the sinus maxillaris (antrum of Highmore), which opens into the middle meatus of the nasal fossa. Body presents for examination four surfaces, each of which has one or more distinct borders. Anterior (Facial) Surface: Looks forward and out- ward. Presents above, near the margin of the orbit, the infraorbital foramen. Below this the surface is marked AXIAL SKELETON. 43 by ridges of which the most prominent, the Canine ridge, separates the incisive fossa internally from the canine fossa externally. The internal harder of this surface is concave above and forms the nasal notch, or margin of the anterior nares, and is prolonged to the middle line into the anterior nasal spine; belovir it articulates with its fellow of the opposite side. The external border is a ridge of bone which extends upward from the first molar tooth, and separates the anterior from the posterior surface. Posterior (Infratemporal or Zygomatic) Surface: Convex; presents near middle the posterior alveola (supe- rior dental) canals. Below is the posterior inferior angle, called the tuberosity, which is rough and prominent, and articulates with the tuberosity of the palate bone. Superior Surface (Orbital Plate): Smooth and trian- gular; forms greater part of floor of orbit; separated by infraorbital ridge, or margin, from the anterior surface. Presents in the middle and behind the infraorbital groove, which in front becomes the infraorbital canal and leads to the infraorbital foramen. Internal Border articulates from before backward with Lachrymal, lamina papyracea of Ethmoid, and orbital plate of Palate bone, its anterior part helping to form the orifice of the lachrymo-nasal canal. External (Posterior) Border: Articulates in front with orbital plate of Zygomatic bone; behind forms mar- gin of inferior orbital (spheno-maxillary) fissure. 4:4 osteology: a syllabus. Internal (Nasal) Surface: Helps to form the outer wall of nasal fossa. Presents the opening of the Antrum of Highmore. In front of the antrum is the lachyrmal groove ; in front of the groove a smooth surface crossed by the inferior conchal crest. The surface above the crest belongs to the middle meatus of the nose, while below the crest is the inferior meatus of the nose. Behind the antrum the bone is rough for articulation with the vertical plate of the Palate bone, and crossing it obliquely from above downward is a groove, which with a similar groove on the Palate bone, forms the posterior palatine canal. Frontal (Nasal) Process: Directed upward, inward and backward to internal angular process of Frontal. Presents two surfaces and three borders. External Surface: Presents a rounded ridge which forms part of the inner margin of the orbit below and internally. The surface in front of the ridge is concavo- convex and smooth. Behind the ridge is the lachrymal groove. Internal Surface: Forms part of outer wall of nasal fossa. Rough above for articulation with anterior sur- face of lateral mass of Ethmoid ; below this it is crossed by the superior conchal crest (agger nasi), a rough ridge for middle nasal concha, with the middle meatus below it. Borders: Superior : Articulates with internal angular process of Frontal. Anterior : Articulates with nasal bone. AXIAL SKELETON. 45 Posterior : Articulates with lachrymal bone. Zygomatic (Malar) Process: Concave in front and behind, articulates with the zygomatic (malar) bone. Palate Process: Projects horizontally inward and is thicker in front than behind ; forms, with its fellow of the opposite side, the anterior % of the hard palate (roof of mouth) . Presents two surfaces and two borders. Superior Surface : Concave and smooth ; forms greater part of floor of nasal fossa. Inferior Surface : Concave and rough. Near its lateral margin is a longitudinal groove leading backwards toward the posterior palatine canal. Borders. Internal: Articulates with fellow of opposite side, forming elevated ridge (groove on under surface) which articulates with Vomer and helps to form nasal septum. In the articulated skull, between the anterior extremities of the two inner borders is the anterior palatine canal, which divides above like a Y and opens into anterior por- tion of floor of the nasal fossse, on either side of septum. In front is the anterior nasal spine. Posterior: Articulates with horizontal plate of palate bone. Alveolar Process: Thick, rough, semi-circular; pre- sents sockets for eight teeth; i. e., from before backward, two incisors, one canine, two premolars (bicuspids) and three molars. 4 46 osteology: a syllabus. PALATE BOITES. Two in number, one on each side. L-shaped. Form the posterior 14 "^f the hard palate, and the posterior part of outer wall of nasal fossa between Maxilla in front and pterygoid process of Sphenoid behind; the inner wall of the pterygo-palatine (spheno-maxillary) fossa; and by its orbital process above it forms a small posterior part of floor of the orbit. Consists of (1) a horizontal plate, (2) a per- pendicular plate, and (3) the pyramidal process or tuber- osity at their point of junction. Horizontal Plate: Forms the back part of the hard palate. Presents two surfaces and three borders. Superior Surface : Concave ; forms back part of floor of nasal fossa. Inferior Surface: Forms back part of roof of mouth. Presents near posterior border a transverse ridge leading outward to the pyramidal process. Near the lateral mar- gin is a longitudinal groove leading backward into posterior palatine canal. Borders: Anterior : Articulates with palate process of Maxilla. Posterior : Free, thin and concave. Internal : Articulates with fellow of opposite side ; pro- longed upward into ridge for articulation with the Vomer, and prolonged backward to form the posterior nasal spine. Perpendicular Plate: On outer wall of nasal fossa, just in front of internal pterygoid plate. Presents two sur- faces, two borders and two processes. AXIAL SKELETON. 47 External Surface : Articulates with internal surface of body of Maxilla and internal pterygoid plate of Sphenoid. Presents an oblique groove which, with a like groove on the Maxilla, completes the posterior palatine canal. Internal Surface: Presents from below upward the in- ferior meatus of the nose, the inferior conchal crest, the middle meatus, the superior conchal (ethmoidal) crest, and the superior meatus of nose. The perpendicular plate is surmounted by two processes, separated by the spheno-palatine notch (or foramen). Be- hind is (1) the sphenoidal process which extends inward and backward to articulate with the body and internal pterygoid plate of the Sphenoid and with the Ala of the Vomer. In front is (2) the orbital process, which forms posterior angle of the floor of the orbit. Borders : Anterior : Thin : overlaps the opening of Antrum of Highmore. Posterior : Articulates with internal pterygoid plate. Pyramidal Process (Tuberosity): Projects backward and outward from junction of horizontal and perpendicular plates. In articulated skull it fills up the pterygoid notch between the lower extremities of the two pterygoid plates, and sometimes presents the accessory posterior palatine canal. 48 osteology: a syllabus. ZYGOMATIC (mALAe) BONES. Two in number, one on each side. Forms the promi- nence known as the cheek-bone. Presents for examination two surfaces, four processes and four borders. External (Malar) Surface: Smooth and convex; pre- sents outer opening of malar canal ; elevated near the mid- dle to form the malar tuberosity. Internal (Temporal) Surface: Smooth and concave; looks into temporal and zygomatic fossae ; presents posterior opening of malar canal. Orbital Process: Forms anterior portion of outer wall of orbit. Its orbital (internal) surface is concave and smooth and presents the orbital opening of the Y-shaped malar canal. Its temporal, or zygomatic (external) sur- face is convex and smooth; looks into the temporal and zygomatic fossas. The process articulates above with or- bital plate of Frontal ; behind with orbital plate of the great wing of the Sphenoid ; internally with orbital plate of Maxilla. Frontal Process: Extends upward and articulates with external angular process of Frontal. Maxillary (Infraorbital) Process: Extends inward; articidates with the zygomatic and frontal processes of Maxilla on the infraorbital ridge. Temporal Process: Extends backward; articulates with zygomatic process of Temporal to form the Zygoma. AXIAL SKELETON. 49 Borders: Superior (Infraorbital) : Forms about % of circum- ference of orbit. Posterior (Temporal) : Runs from frontal process above downward to become continuous with upper border of zygoma. Inferior: Forms lower edge of zygomatic arch, and is continuous behind with lower border of zygoma. Is rough, and at its inferior angle presents the blunt, rounded malar tubercle. Internal: Extends downward from base of maxillary process ; articulates with zygomatic process of Maxilla be- low the infraorbital ridge. MANDIBLE (iNFEEIOE MASILLAEY BONe). Horse-shoe shape; forms the lower jaw. Consists of a body, from which arise two rami, one on each side. Body: Horizontal, horse-shoe shaped. Presents two surfaces and two borders. Anterior Surface: Concave from above downward; convex from side to side. Presents a vertical median line, the symphysis^ terminating below in the mental protuber- ance (tubercle). On each side, from before backward, are the incisive fossa, the mental foramen and the external oblique line, running upward and backward to become con- tinuous with the anterior border of the Ramus. Posterior Surface : Convex from above downward ; con- cave from side to side. On each side of symphysis have 50 osteology: a syllabus. superior and inferior genial tubercles ; near lower border on either side of middle line is the digastric fossa; while further back the internal oblique line (mylo-hyoid ridge) separates the sublingual fossa above and in front from the submaxillary fossa below and behind. Superior Border (Alveolar Process) : Presents, on each side of symphysis, sockets for eight teeth; the same as in upper jaw. Inferior Border (Base) : Thick, smooth and rounded. Presents near ramus a shallow groove for the external maxillary (facial) artery. R^mus: ISTearly vertical in position when normal. Thinner than the Body and quadrilateral in shape. Pre- sents two surfaces and four borders. External Surface: Flat and marked by muscular im- pressions. Internal Surface: Presents the mandibular (inferior dental) foramen near the middle, which is bordered in front by a prominent spine and has the mylo-hyoid groove leading downward from it. Borders: Anterior : Thin and sharp. Posterior : Thick and rounded. Inferior: Thick, rounded and continuous with the in- ferior border of the Body. At the junction of the posterior with the inferior border is the angle of the jaw, which is either everted or inverted. AXIAL SKELETON. 61 Superior : Presents the Coronoid process in front, sep- arated by the mandibular (sigmoid) notch from the Condy- lar process behind. Coronoid Process is flat and triangu- lar in shape. Condylar Process consists of an oblong, ar- ticular condyle, placed with its long axis inward and back- ward ; supported by a flattened neck with a fossa or depres- sion in front. HTOID BONE (oS LINGTTLiE). Placed in the fore part of the neck, behind the Mandible. It is not articulated and is distinct in development, but is considered with the bones of the skull. It is U-shaped, and consists of a body, two great cornua, and two lesser cornua. Body: Arched from side to side; presents two surfaces and two borders. Anterior Surface : Convex ; presents a horizontal ridge which crosses a vertical ridge and forms the hyoid tubercle in the middle. Posterior Surface: Concave. Superior and Inferior Borders: Rough. Greater Cornua: One on each side; project backward from sides of body, and terminate in rounded extremities (tubercle). Lesser Cornua: Small conical processes which project upward and backward from the junction of body with Greater Cornua. 52 OSTEOLOGY : A SYLLABUS. OSSICLES OF THE EAR. Three in number in each ear: From without inward they are the Malleus (hammer), Incus (anvil), and Stages (stirrup), which form a chain of bones across the Tym- panum, or cavity within the Temporal bone. CHAPTER III REGIONAL ANATOMY OF THE SKULL CRANIAL LOCALIZATION. In taking measurements of the skull certain definite points are accepted as guides. Those most frequently re- ferred to are : The Bregma: The meeting point of the coronal and sagittal sutures. Location of the anterior f ontanelle in the skull at birth. The Glabella: The point in the middle line between the superciliary ridges. The Gonion: The outer margin of the angle of the mandible. The Inlon: The posterior occipital protuberance. The Lambda: The meeting point of the lambdoid and sagittal sutures. Location of the posterior fontanelle in the skull at birth. The NasJon: The center of the nasal notch. The Pterion: Point of articulation of the tip of the great wing of the Sphenoid with the antero-inferior angle of the Parietal bone. The Stephanlon: Meeting point of the temporal ridges and the coronal suture. FOSS.a} OF THE SKULL. Upon its external aspect the skull presents : in front, the two orbits and the two nasal fossae ; on each side, the tem- 54 osteology: a syllabus. poral fossa, the zygomatic fossa and the pterygo-palatine (spheno-maxillary) fossa. Within the cranium the ante- rior, middle, and posterior cranial fossse form the upper surface of the base of the skull. OEBITS. One on each side. Pyramidal in shape, with base out- ward and forward, apex inward and backward. Each orbit is formed of parts of seven bones ; the Frontal, Sphenoid, Ethmoid, Maxilla, Zygomatic (Malar), Lachrymal, and Palate. It presents for examination a roof, floor, two walls (me- dial and lateral), a base and an apex. The Roof: Triangular, concave and smooth. Anterior four-fifths formed by inferior surface of orbital plate of Frontal; posterior one-fifth formed by inferior surface of lesser wing of Sphenoid. The roof presents the lachrymal fossa behind the external angular process and a pit or tubercle behind the internal angular process. The Floor: Triangular, concave and smooth. Formed in front and externally by the orbital surface of the Zygo- matic, internally and in the middle by the orbital plate of the Maxilla, while posteriorly the floor of the apex is formed by the orbital process of the Palate bone. The floor presents the infraorbital groove which, beginning behind and externally, runs forward and inward and be- comes the infraorbital canal. At the antero-internal angle EEGIOJSTAIi ANATOMY OF THE SKULL. 55 is the opening of the canal for the lachrymo-nasal duct, and just external to this is a muscular impression. At the antero-external angle is the orbital opening of the malar canal. Medial (Inner) Wall: Formed from before backward by the frontal process of the Maxilla, the Lachrymal bone, the OS planum of the Ethmoid and the lateral surface of the body of the Sphenoid. It presents in front the lachrymal groove, leading downward into the canal for the lachrymo- nasal duct, and in the angle between the inner wall and the roof are the anterior and posterior ethmoidal canals. Lateral (Outer) Wall: Formed in front by the orbital surface of the Zygomatic (Malar) bone, and behind by the anterior surface of the great wing of the Sphenoid. At the posterior extremity of the angle between the lateral wall and the roof is the sphenoidal fissure which separates the great wing from the lesser wing of the Sphenoid. The angle between the lateral wall and the floor presents the spheno-maxillary fissure, which opens into the pterygo- palatine (spheno-maxillary) fossa below. Base: The outer opening of the orbit. Circumference marked by the supra- and infraorbital ridges. Supraorbital ridge of frontal extends above from the in- ternal angular process to the external angular process, and presents the supraorbital notch or foramen at the junction of the internal one-third with the external two-thirds. The infraorbital ridge is formed externally and below by the superior border of the Zygomatic bone, internally 56 osteology: a syllabus. and below by the median ridge on the external surface of the frontal process of the Maxilla. It presents the lachry- mal tubercle. Apex: Presents the optic foramen at the back of the orbit with the sphenoidal fissure just external to it opening into the cavity of the cranium. Openings into tlie Orbit: Mne in number: (1) Optic foramen; (2) sphenoidal fissure ; (3) spheno-maxillary fis- sure; (4) supraorbital notch or foramen; (5) infraorbital canal; (6) anterior and (7) posterior ethmoidal canals; (8) orbital opening of the malar canal; and (9) the canal for the lachrymo-nasal duct. NASAL FOSS^. Two deep, narrow cavities, one on each side, separated in the middle line by the nasal septum. Each fossa pre- sents a roof, a floor, anterior, posterior, internal (medial), and external (lateral) walls. Tlie Roof: Highest in the middle where it is formed by the cribriform plate of the Ethmoid and presents the foramina for the olfactory nerves and the slit for the nasal nerve ; lowest behind, where it is formed by the inferior surface of the body of the Sphenoid, which is cov- ered internally by the ala of the Vomer, externally by the sphenoidal process of the Palate bone and the vaginal process of the internal pterygoid plate of the Sphenoid. Tlie Floor: Anterior three-fourths formed by the pal- ate process of the Maxilla, posterior one-fourth by the hori- REGIONAL ANATOMY OF THE SKULL. 57 zontal portion of the Palate bone. It is concave and smooth, continuous laterally with the inferior meatus of the nose, and presents in front one of the superior orifices of the Y-shaped anterior palatine canal. Anterior Wall: Formed above by the nasal bone, be- low by the cartilage of the nose ; wanting where the ante- rior naris opens upon the face. It presents a groove and foramen for the nasal nerve. Posterior Wall: Formed above by the anterior surface of the body of the Sphenoid ; wanting below, where the pos- terior naris opens into the naso-pharynx. It presents above the opening of the sphenoidal sinus. Internal (Medial) Wall: Formed by the nasal septum. It presents the Vomer behind and below, which articu- lates above with the rostrum of the Sphenoid, below with the crests of the Palate bones and the maxillae from the posterior nasal spine behind to the anterior nasal spine in front, antero-superiorly with the perpendicular plate of the Ethmoid and the triangular cartilage of the septum nasi. It presents in front and above the perpendicular plate of the Ethmoid, which articulates behind with the sphe- noidal crest, in front with the spine of the Frontal and the crests of the nasal bones, postero-iirferiorly with the Vomer and antero-inferiorly with the triangular cartilage of the septum nasi. The nasal septum is usually deflected to one side, which causes the two nasal fossae to be unequal in breadth. 58 osteology: a syllabus. External (Lateral) Wall: Formed in front by the Lachrymal bone and the nasal (frontal) process of the Maxilla ; in the middle by the lateral mass of the Ethmoid and the body of the Maxilla; behind by the vertical plate of the Palate bone and the internal pterygoid plate of the Sphenoid. Extending across its lower aspect from the nasal process of the Maxilla in front to vertical plate of the Palate bone behind is the inferior turbitvite hone. Viewed from in front, the lateral wall presents from be- low upward the inferior meatus of the nose, the inferior turbinate bone, the middle meatus of the nose, the turbi- nate process of the lateral mass of the Ethmoid which in front is not divided. Viewed from behind, it presents from below upward the inferior meatus of the nose, the inferior Turbinate bone, the middle meatus, the middle Turbinate bone, the superior meatus, the superior Turbinate bone. Opening into the anterior portion of the inferior meatus is the canal for the lachrymo-nasal duct. The middle meatus receives the opening of the Antrum of Highmore and the orifice of the infundibulum, a canal leading to the anterior ethmoidal cells and the frontal sinus. The supe- rior meatus communicates with the spheno-maxillary (pterygo-palatine) fossa through the spheno-palatine fora- men, and also receives the openings from the posterior ethmoidal cells and the sphenoidal sinus. BEQIONAL ANATOMY OF THE SKULL. 59 TEMPORAL FOSS^. Two in number, one on each side of the cranium. Bounded above and behind by the temporal ridge; below by a plane extending from the Zygoma inward to the ptery- goid ridge which separates the external from the inferior surface of the great wing of the Sphenoid; bounded in front by the Malar bone and the external angular process of the Frontal. Its floor is formed by the Malar, the Frontal, the great wing of the Sphenoid, the Parietal and the squamous por- tion of the Temporal. It is shallow above, deeper below, where it is continuous with the zygomatic fossa. To outline the temporal fossa, start at the external angu- lar process of the Frontal and follow the temporal ridge backward to the point where it joins the posterior root of the Zygoma ; thence forward along the Zygoma and the pos- terior border of the Malar bone to the external angular process, the starting point. ZYGOMATIC FOSS^. One on each side of the base of the skull. Bounded .above by the inferior surface of the great wing of the Sphenoid, which presents the foramen ovale and the for- amen spinosum. Above and in front it communicates with the orbit through the spheno-maxillary fissure ; above and externally it is continuous with the temporal fossa. It is bounded below by a plane extending backward from the alveolar process of the Maxilla; in front by the pos- 60 osteology: a syllabus. terior surface of the body of the Maxilla; behind by the eminentia articularis and by the spine of the Sphenoid; externally by the ramus of the mandible ; internally by the external pterygoid plate of the Sphenoid and the pterygo- maxillary fissure, through which it communicates with the ptery go-palatine (spheno-maxillary) fossa. PTEBYGO-PALATINE (sPHENQ-MAXILLAEy) F0SS2E. One on each side. Situated below and behind the apex of the orbit. Bounded in front by the posterior surface of the body of the Maxilla ; behind by the infraorbital portion of the ante- rior surface of the great wing and by the pterygoid process of the Sphenoid ; internally by the vertical plate of the Pal- ate bone which separates it from the nasal fossa. Its anterior and posterior walls converge below and articulate. It communicates above with the orbit through the spheno- maxillary fissure, and externally through the pterygo-max- illary fissure with the zygomatic fossa. Through its in- ternal wall the spheno-palatine foramen connects it with the superior meatus of the nose. Its posterior wall presents the anterior openings of the Vidian canal, the foramen rotundum and the pharyngeal canal ; and its anterior wall presents the upper openings of the posterior palatine and accessory posterior palatine canals. ANTEKIOE CRANIAL FOSSA. The highest of the fossae within the cranium. Bounded in front and on each side by the vertical por- EEGIONAL ANATOMY OF THE SKULL. 61 tion of the Frontal bone ; behind by the posterior borders of the lesser wings of the Sphenoid, the anterior clinoid proc- esses and the anterior margin of the optic groove (limbus sphenoidalis) . Its floor is formed on each side by the orbital plates of the Frontal bone and the lesser wings of the Sphenoid, and in the middle by the horizontal plate of the Ethmoid and the body of the Sphenoid. It is concave in the middle, convex on each side, and presents in the middle line from before backward the frontal crest, the foramen coecum, the crista galli, the ethmoidal spine, and the smooth upper surface of the body of the Sphenoid. On each side it presents from within outward the olfactory groove, perforated by the slit for the nasal nerve and the foramina for the olfactory nerves (cribriform plate), and the internal openings of the anterior and posterior eth- moidal canals. Further out are elevations and depressions for the convolutions of the brain, and the smooth upper surface of the lesser wing of the Sphenoid and the anterior clinoid process. MIDDLE CEANLiL FOSSA. Depressed on each side; narrow and elevated in the middle. Bounded in front by the posterior borders of the lesser wings of the Sphenoid and the limhv^ sphenoidalis; behind by the superior borders of the petrous portions of the Tem- poral bones and the dorsum sellce; on each side by the squa- mous portion of the Temporal bone, the antero-inferior angle of the Parietal and the tip of the great wing of the Sphenoid. 62 OSTEOLOGY : A SYLLABUS. Its floor is formed in the middle by the body of the Sphenoid, and on each side by the great wing of the Sphe- noid and the superior surface of the petrous portion of the Temporal bone. It presents in the middle line, from before backward, the optic groove, leading on each side to the optic foramen ; the olivary ridge and the sella turcica. It presents on each side, from within outward, the carotid (cavernous) groove, leading from the sphenoidal fissure in front to the foramen lacerum behind ; the foramina rotun- dum, ovale and spinosum, and sometimes the foramen Vesalii. Near the lateral wall are elevations and depres- sions for the convolutions of the brain and grooves for the meningeal arteries; while posteriorly the petrous portion of the Temporal bone presents the tegmen tympani, the eminentia arcuata, the hiatus Fallopii and foramen for the small superficial petrosal nerve, with a groove leading into each, and the fossa for the Gasserian ganglion. Opening into the outer side of the foramen lacerum is the superior orifice of the carotid canal. POSTERIOR CRANIAL FOSSA. The lowest and deepest of the cranial fossse. Formed by the posterior portion of the body of the Sphenoid, the posterior surfaces of the petrous portions and the internal surfaces of the mastoid portions of the Temporals, the postero-inferior angles of the Parietals and the basilar, condylar, and squamous portions of the Occipital bone. Bounded in front by the dorsum sellse of the Sphenoid and by the superior borders of the petrous portions of the EEGIONAL ANATOMY OF THE SKULL. 63 Temporal bones ; behind by the internal occipital protuber- ance and the grooves for the lateral sinuses (sigmoid grooves), which last form also the lateral boundaries. It presents in the middle the foramen magnum, with the basilar groove in front, and the anterior occipital crest leading to the internal occipital protuberance behind. On each side, from within outward and forward, are a tubercle on margin of foramen magnum, internal opening of anterior condylar (hypoglossal) foramen, the jugular foramen, the internal auditory meatus, external to which is the aqueductus vestibuli, while above and between the two is the fossa subarcuata. Still further lateral the sig- moid groove for the lateral sinus turns downward and in- ward to reach the jugular foramen, and in it may be seen the internal opening of the mastoid foramen. Posteriorly, on each side, the fossa is depressed to receive the lobes of the cerebellum; while behind and external to the foramen magnum is the internal opening of the posterior condylar foramen, when present. IIAED PALATE. The hard palate (roof of the mouth) is formed by the inferior surfaces of the palate processes of the Maxillse (anterior %) and horizontal plates of the Palate bones (posterior l^). It is horse-shoe shaped and is bounded in front and on the two sides by the alveola processes of the Maxillse, con- taining sixteen teeth. Behind it is bounded by the pos- terior borders of the horizontal plates of the Palate bones. 64 osteology: a syllabus. It is concave and rough, and presents in the middle line a groove terminating anteriorly at the anterior palatine canal, posteriorly at the posterior nasal spine. On either side, just internal to the alveola process, a shallov? groove leads backveard to the posterior palatine canal. Behind the posterior palatine canal the pyramidal process {tuberosity) of the Palate bone projects backward and outward to iill the pterygoid notch and is sometimes pierced by the accessory posterior palatine canal. Lead- ing inward from the pyramidal processes to the posterior nasal spine in the middle are two ridges just in front of the concave posterior borders of the horizontal plates of the Palate bones. CHAPTER IV APPENDICULAR SKELETON BONES OF THE UPPER EXTREMITY. The Shoulder Girdle is composed of the Clavicles and the ScapulcB. CLAVICLE (COLLAE BONe). Forms the front of the shoulder girdle. Presents a shaft and two extremities. Internal (Sternal) Extremity: Triangular, surmounted by a concavo-convex articular surface, surrounded by a prominent margin, except below, where there is an articu- lar facet. External (Acromial) Extremity: Flattened, surmount- ed by a smooth, oval, articular facet which looks down- ward, forward and outward. Shaft: S-shaped; internal two-thirds rounded, or pris- matic ; external one-third flat. Superior Surface : Internal two-thirds rounded, marked by many muscular impressions ; external one-third flat and rough. Inferior Surface: Presents from within outward the rhomboid (costal) tuberosity, the subclavian groove, conoid (coracoid) tubercle, and trapezoid ridge (oblique line). Anterior Border: Internal two-thirds convex and thick ; external one-third concave and thin and presents the deltoid tubercle. 66 osteology: a syllabus. Posterior Border: Internal two-thirds concave and thick ; external one-third convex and thin. SCAPULA (SHOULDEE blade). Triangular vs^ith base upvpard ; very flat and thin. Forms back part of shoulder girdle and extends from the first to the eighth rib. Presents for examination two surfaces, three borders and three angles. Anterior Surface (Venter): Internal two-thirds con- cave ; forms subscapular fossa marked with oblique ridges ; presents a deep transverse depression, the subscapular angle, which corresponds to the attachment of the spine behind. External one-third convex and smooth. Posterior Surface (Dorsum): Presents the supraspi- nous and infraspinous fossae, separated by the Spine. The two fossae communicate through the great scapular notch at the outer border of the spine. 1. Supraspinous Fossa: Small, triangular, with base inward ; smooth and concave. 2. Infraspinous Fossa: Large, triangular, with base inward ; internal two-thirds convex and smooth ; external one-third presents a deep vertical groove, and outside of groove, from above downward, a vertical ridge and an oblique line with a smooth triangular surface below it. 3. Spine: Triangular, with apex inward, at junction of upper one-third with lower two-thirds of internal (verte- bral) border of Scapula. Projects upward and backward and is prolonged outward and forward into the Acromian process. Presents two surfaces and two free borders. APPENDICtJLAE SKELETON. 67 Superior Surface : Smooth and concave ; forms part of supraspinous fossa. Inferior Surface : Smooth and concave ; forms part of infraspinous fossa. External Border: Short, thick, smooth and concave; helps to form the great scapular notch. Posterior Border: Called the Crest; long, thick, sinu- ous, lipped; upper lip continuous with internal border of acromian process; lower lip continuous with posterior border of acromian process. Acromian Process: Projects upward, outward and for- ward. Presents two surfaces and four borders : Superior surface convex and rough; inferior surface concave and smooth; external border long and rough; internal border presents a smooth, oval articular facet ; posterior border continuous with lower lip of spine ; anterior border short ; apex. Angles of Scapula. Superior: Thin and sharp. Inferior: Thin and sharp. External {Anterior Angle) : Presents for examination (1) a head, surmounted by (2) the coracoid process. 1. Head : Looks forward and outward, supported by a constricted neck, and presents the glenoid cavity, which is a shallow, concave, articular surface, oval in shape, with large end dovTnward, and presents the supra-glenoid tuber- cle above it. 68 osteology: a syllabus. 2. Coracoid Process: Ascends above head, then turns forward and outward and terminates in apex. The verti- cal portion is concave and smooth in front and behind. The horizontal portion is convex and rough on superior surface ; concave and smooth on inferior surface ; ends in apex. Borders of Scapula: Superior border, short and thin; presents suprascapular notch at base of coracoid process. Internal (Vertebral) Border: Long, thin, and vertical. External (Axillary) Border: Hough line above, pre- senting infraglenoid tubercle just below glenoid cavity; oblique groove crosses it in the middle ; sharp and thin below. HUMERUS. The bone of the arm. A long bone, consisting of two extremities connected by a shaft. Superior Extremity: Large; consists of: (l) An artic- ular head which forms two-fifths of a sphere ; looks upward, inward, and backward ; articular surface surrounded by a groove called the anatomical neck. (2) Two tuberosities, separated by the intertubercular (bicipital) groove; the edges of the groove are called the bicipital ridges (external or anterior, internal, or posterior). Greater tuberosity is external to head ; marked on top by three muscular impres- sions ; external surface rough. Lesser tuberosity ante- rior to head ; marked with one muscular impression. Be- low the tuberosities the bone is constricted to form the surgical neck. APPENDICULAE SKELETON. 69 Inferior Extremity: Flattened from before backward and curved forward. Laterally it presents two prominent knuckles of bone, the internal and external condyles (epi- condyles). The internal condyle most prominent and has a shallow groove (the Ulnar groove) behind it. Leading upward from the condyles are the internal and external supracondylar ridges, the external most prominent. Below are two articular surfaces, separated by an articular groove. Of these the external is the capitellum (radial head) ; convex; articular below and in front, with a shallow de- pression (the radial fossa) above it in front. The internal is the trochlea (pulley), a saddle-shaped, articular surface, with the coronoid fossa above it in front; the olecranon fossa above it behind. Shaft: Cylindrical above, prismatic below. Presents three borders and three surfaces. Anterior 5orcZer extends from external (anterior) bicipi- tal ridge above to outer side of coronoid fossa below. Internal Border extends from internal (posterior) bicipital ridge above to internal supracondylar ridge below. External Border, from back of great tuberosity above to external supracondylar ridge below ; crossed about the mid- dle by the musculo-spiral (radial) groove. Internal Surface, narrow and smooth. External Surface, smooth and convex above, smooth and concave below, deltoid "V" in the middle, with musculo- spiral (radial) groove below it. 70 osteology: a syllabus. Posterior Surface, rounded above, broad and flat below ; crossed by musculo-spiral (radial) groove, and presents nutrient foramen. RADIUS. The outer bone of the forearm. A long bone with two extremities and a shaft. Superior Extremity: Small; presents a head, sur- mounted by a cup-shaped articular cavity, surrounded by an articular rim ; supported by a rounded neck, below and in front of which is seen the bicipital tuberosity projecting inward; smooth in front, rough behind. Inferior Extremity: Large; presents five surfaces. Inferior (Carpal) Surface: Triangular, concave, artic- ular ; divided by antero-posterior ridge. Anterior Surface: Broad, smooth, and concave. Posterior Surface: Broad and convex; marked by ridges and grooves. External Surface: Presents the styloid process, project- ing downward, rough externally, articular internally, grooved behind. Internal Surface : Presents a concave articular surface, the ulnar notch (sigmoid cavity), with a triangular depres- sion above it. Shaft: Bowed outward; tapers from below upward; presents three borders and three surfaces. Anterior Border extends from tuberosity above to front of styloid process below; its upper one-third runs down- ward and outward and is called the oilique line of the Radius. APPENDICULAR SKELETON. 71 Internal (Interosseous) Border: Sharp and prominent. Extends from inner side of tuberosity above to bifurcate below to enclose the ulnar notch (sigmoid cavity). Posterior Border from back of neck above to back of lower extremity; rounded and indistinct. Anterior (Volar) Surface: Narrow and concave above, broad and flat below. External (Lateral) Surface: Narrow and convex; ver- tical ridge in middle third. Posterior (Dorsal) Surface: Narrow, convex above; broad, convex below. ULNA. The inner bone of the forearm. A long bone with two extremities and a shaft. Superior Extremity: Large; presents the olecranon process behind and the coronoid process in front, separated by the Semilunar notch (the greater sigmoid cavity). 1. The Olecranon Process: Projects upward, then for- ward, and presents for examination three surfaces and two borders. Posterior Surface: Smooth and triangular, with base upward. Superior Surface : Quadrilateral and rough, with trans- verse groove in front ; terminates in a beak. Anterior Surface: Porms upper half of greater sig- moid cavity (semilunar notch) ; saddle-shaped and ar- ticular. Lateral borders are rough; sometimes grooved. 72 osteology: a syllabus. 2. The Goronoid Process: Projects forward, and pre- sents four surfaces. Superior Surface : Saddle-shaped and articular ; forms lower half of greater sigmoid cavity (semilunar notch). Inferior (Anterior) Surface : Triangular ; concave above; tubercle (ulnar tuberosity) below at apex of tri- angle. External Surface: Presents radial notch (lesser sig- moid cavity), which is articular; and presents a triangular depression below. Internal Surface: Concave, with a tubercle in front and above on inner margin of semilunar notch. Inferior Extremity: Small; presents a head which is articular below and externally; separated internally and behind by a pit from the styloid process, which projects downward and is grooved behind ; articular in front and externally. Shaft : Tapers from above downward ; prismatic above, rounded below. Presents three borders and three sur- faces. Anterior {Internal) Border: Extends from inner side of coronoid process above to front of styloid process below. External {Interosseous) Border: Sharp and promi- nent. Extends from apex of triangular depression below radial notch above, to outer side of head below. Posterior Border: From back of olecranon process above to back of styloid process below. APPENDICULAE SKELETON. 73 Anterior ( Volar) Surface : Upper two-thirds concave ; lower one-third convex. Internal (Medial) Surface: Narrow, convex, smooth, and subcutaneous. Posterior (Dorsal) Surface: Broad above, narrow be- low; presents just below upper extremity an oblique line leading from posterior margin of radial notch downward and inward to posterior border ; above this is a triangular depression, while below a vertical ridge divides the surface. CARPUS. Consists of eight bones, arranged in two rows of four bones each. These bones are small and six-sided, and ar- ticidate with one another to form altogether the Carpus or Wrist. First (Proximal) Row: Prom radial to ulnar side, con- sists of (1) navicular (scaphoid), (2) lunate (semilunar), (3) triquetral (cuneiform) and (4) pisiform. Second (Distal) Row: From radial to ulnar side; (1) greater multangular (trapezium), (2) lesser multangular (trapezoid), (3) capitate (os magnum), and (4) hamate (unciform,). Superior surface of each row, convex and articular. Inferior surface of each row, irregular and articular. The Corpus, as a whole, is quadrilateral and presents two surfaces and four borders. Anterior Surface: Concave. Posterior Surface: Convex. Superior Border: Convex and articular. 74r osteology: a syllabus. Inferior Border: Irregular and articular. Lateral Borders are rough, and each present two tuber- cles; on the radial border the navicular (superior tuber- cle), and the greater multangular (inferior tubercle) ; on the ulnar border the pisiform (superior tubercle), and the hamate (inferior tubercle). METACARPUS. Consists of five bones, which together form the palm of the hand. Are miniature long bones with two extremi- ties connected by a shaft. TYPICAL METACARPAL BONE. 2d, 3d, and 4th. Superior Extremity (Base): Wedge-shaped, with sharp edge forward; articular above and on each side (facet). Inferior Extremity (Head): Presents a condyle which is articular further upward in front than behind and has a pit on each side with a tubercle behind it. Shaft: Prismatic; concave (bent) forward; lateral surfaces smooth and concave ; posterior surface presents a median ridge which bifurcates below, leading to a tubercle on each side of head. Borders: Anterior and two lateral. PECULIAE METACARPAL BONES. 1st and 5th. First (Thumb) Metacarpal: Thickest and shortest; superior extremity, saddle-shaped and articular, no lateral APPENDICULAR SKELETON. 75 articular facets ; inferior extremity, articular condyle flat- tened and less convex. May present two sesamoid bones on palmar aspect. Shaft lacks the median ridge on the dorsal surface, which is convex and smooth. Fifth Metacarpal: Smallest; has only one lateral ar- ticular facet on base (radial side). DIGITS. Five in number. Each consists of three phalanges, ex- cept the thumb, which has only two. PHALANGES. Each presents a shaft and two extremities. Shaft tapers from above downward; convex and smooth behind, concave in front. Superior Extremity (Base) of first Phalanx presents an articular receiving surface for a condyle. Superior Extremity (Base) of second and third Pha- langes presents an articular receiving surface for a trochlea (pulley). Inferior Extremity (Head) of first and second Pha- langes presents an articular trochlea. Last Phalanx is flattened and expanded at end to receive the nail. BONES OF THE LOWER EXTREMITY. The Pelvic Girdle, or Pelvis, is formed by the two hip bones, connected behind by the Sacrum and in front by the Symphysis Pubis. 76 osteology: a syllabus. COXAL BONE (oS INNOMINATUm). The bone of the hip. A large irregular bone. Consists of three parts, the Ilium, the Ischium, and the Pubis, which meet together and form the Cotyloid Cavity, or Acetabulum, a large cup-like socket, and are fused into one bone. 1. Ilium; The upper expanded portion of the bone. Presents for examination three surfaces and three borders. External Surface (Dorsum) : Concave behind, convex in front; marked by three curved lines (gluteal ridges), anterior, posterior, and inferior. Anterior Gluteal Eidge begins 1% inches behind the anterior superior spinous process and runs dovsmward and backward to great sciatic notch. Posterior Gluteal Eidge begins 2% inches in front of the posterior superior spinous process and runs downward to margin of great sciatic notch in front of posterior in- ferior spinous process. Inferior Gluteal Eidge begins just above anterior infe- rior spinous process and runs backward towards great sciatic notch. Internal Surface: Anterior two-thirds concave and smooth; forms iliac fossa, which is bounded below by the ilio-pectineal (terminal) line; posterior third presents ear- shaped articular surface below, rough above. Inferior Surface: Sometimes called a border; con- cave and articular; forms a little less than two-fifths of acetabulum and is separated from external surface by rim of acetabulum. APPENDICULAB SKELETON. 77 Superior Border: Called the Crest; thick, sinuous, lipped; terminates at the anterior and posterior superior spinous processes. Presents a prominent tubercle near the middle. Anterior Border: Presents the anterior-superior and anterior-inferior spinous processes with a notch below each. Posterior Border: Presents posterior-superior and pos- terior-inferior spinous processes separated by a notch, and with the great sciatic notch below the inferior process. 2. Ischium: The lower and posterior portion of the bone. Presents for examination a body, a tuberosity, and a ramus. Body : Triangular or wedge-shaped ; presents three sur- faces and three borders. External Surface : Concave and articular ; forms a little more than two-fifths of the acetabulum. Internal Surface: Broad, triangular, smooth, slightly concave ; forms inclined plane of ischium. Posterior Surface: Broad, quadrilateral, convex; lim- ited below by a broad, shallow groove (the obturator groove), just below the acetabulum. Internal Border : Thin and sharp ; forms outer margin of obturator (thyreoid) foramen. External Border: Forms posterior part of the rim of the acetabulum; wanting below where a deep notch (the acetabular or cotyloid notch) separates this part of the bone from the Pubis. Posterior Border: Continuous with the posterior bor- der of Ilium, and with it forms the great sciatic notch. 6 78 OSTEOLOGY : A SYLLABUS. Below this notch is the spine of the Ischium, and below the spine is the small sciatic notch. Tuberosity : Looks downward, backward, and outward; rough with many muscular impressions. Ramus: Kuns upward, inward, and forward from tuberosity and becomes fused with the descending ramus of the pubis. Anterior (External) Surface is concave and rough. Posterior (Internal) Surface is convex and smooth. Inferior (Internal) Border, thick and everted. Superior (External) Border, thin and sharp; helps to form inner and lower margin of obturator (thyreoid) foramen. 3. Pubis: The anterior portion of the bone. Presents a body and two rami, a horizontal and a descending ramus. For convenience of description, the body and horizontal ramus may he considered together. Body and Horizontal Ramus: Present together six sur- faces. Internal Surface (Body) : A rough oval surface for articulation with cartilage of symphysis jiubis. External Surface (Horizontal Ramus) : Concave and articular ; forms one-fifth of acetabulum. Superior Surface (Body and Horizontal Ramus) : Pre- sents externally the pectineal eminence, just internal to which is a smooth triangular surface, called the pectineal triangle ; bounding the triangle behind is a ridge, the con- APPENDICULAR SKELETON. Y9 tinuation of the ilio-pectineal line, which terminates inter- nally at the pubic spine ; from the spine a ridge, the pubic crest (the pecten), leads inward to the pubic angle (the junction of the superior and internal surfaces). Inferior Surface (Horizontal Eamus) : Forms upper margin of obturator (thyreoid) foramen. Deeply grooved externally (obturator groove), thin and sharp internally (like a border) . Anterior Surface (Body) : Flat or slightly concave and rough. Posterior Surface (Body) : Saddle-shaped and smooth. The Descending Ramus: Short, runs dovsraward, out- ward, and backward to join the ramus of the Ischium. At point of junction the margin of obturator foramen presents a notch. The angle of divergence between the descending rami of the two pubic bones is called the pubic arch. Acetabulum: A large cup-like cavity on the outer side of the OS innominatum; formed by the union of all three parts of the bone. It is articular above, in front and be- hind, nonarticular below and internally (at the bottom). Surrounded by a prominent rim except below where it presents the acetabular or cotyloid notch. Obturator (Thyreoid) Foramen: A large oval or tri- angular foramen in the lateral wall of the Pelvis, sur- rounded by the parts which form the Ischium and the Os Pubis. Margins are sharp and thin except above where it is grooved. 80 OSTEOLOGY : A SYLLABUS. REGIONAL ANATOMY OF THE PELVIS. The pelvis is a bony case, formed in front and on each side by the Coxal bones (Ossa Innominata), and behind by the Sacrum and Coccyx. The bones are firmly articulated, in front at the symphysis pubis, behind at the sacro-iliac joints. The cavity of the pelvis is divided by the ilio-pectineal line and the promontory of the Sacrum (brim of the pelvis) into the false pelvis above and the true pelvis below. False Pelvis: Broad and shallow. Lateral walls formed by the iliac fossae of the Coxal bones. Limited be- hind by the alse of the Sacrum and the body of the last lum- bar vertebra. True Pelvis: Narrow and deep. Bounded in front by the symphysis pubis, behind by the Sacrum and Coccyx, on each side by the Ischium and Pubis. Openings in the True Pelvis. 1. The pelvic inlet; looks forward and upward; outlined by the ilio-pectineal line and the promontory of the sacrum. Boughly heart- shaped. 2. The pelvic outlet; looks downward and backward; diamond-shaped. Anterior triangle outlined by the pubic arch to form the pubic angle. Posterior triangle bounded by lines drawn from the tip of the coccyx to the tuberosities of the ischia. 3. The obturator (thyreoid) foramina. One on each side ; situated antero-laterally ; large and oval in the male, smaller and triangular in the female. APPENDICTJLAE SKELETON. 81 4. The greater and lesser sciatic notches on each side. Situated postero-laterally and converted by the sacro- spinous and sacro-tuberous ligaments into the greater and lesser sacro-sciatic foramina. Both cavities of the pelvis are more roomy in the female than in the male. FEMUR. The bone of the thigh. The longest bone in the body. Presents for examination two extremities and a shaft. Superior Extremity: Presents an articular head which forms two-thirds of a sphere; looks upward, inward, and forward, and has a pit (fovea) a little below and behind the center. Head is supported by an oblique neck whose long diameter is vertical; anterior surface convex and rough ; posterior surface concave and smooth ; upper border short and thick ; lower border long and narrower. The Great Trochanter projects upward from junction of upper border of neck with shaft of bone; external surface convex and rough and divided by an oblique ridge ; internal surface concave and presents the digital pit (trochanteric fossa) ; anterior, posterior, and superior borders rough. The Lesser Trochanter projects inward and backward from junction of lower border of neck with shaft of bone; is small and conical. Connecting the two trochanters in front and behind are the anterior and posterior inter- trochanteric lines. About the middle of the posterior in- tertrochanteric line is an eminence, the tubercle of the 82 OSTEOLOGY : A SYLLABUS. quadratus, running downward, from which is a faint line, the "linea quadrati." Inferior Extremity: Presents two condyles, separated behind by a notch (the intercondylar fossa), fused together in front to form a trochlea. Internal Condyle: Long and narrow; internal surface presents the internal tuberosity in the middle, and above and behind this is the adductor tubercle. External sur- face, concave, forms margin of intercondylar notch. In- ferior surface, convex, long, narrow, and articular. External Condyle : Shorter and broader than internal. External Surface presents the external tuberosity in the middle, and below and behind this a groove. Internal Surface, concave, forms margin of intercondy- lar notch. Inferior Surface, broad, convex, and articular. Siiaft: Cylindrical, bowed forward, long diameter (in articulated skeleton) from above downward and inward. Presents three borders and three surfaces. Borders: Internal and external borders rounded and indistinct. Posterior, very prominent. Divided for description into thirds. Middle third called the linea aspera; rough and lipped. Upper third divides into three lines, of which the external (gluteal line) passes to the back of the tro- chanter major; the internal (spiral line) winds upward, inward, and forward to the front of the trochanter major to become continuous with the anterior intertrochanteric APPENDICULAE SKELETON. 83 line; the middle (linea pectinea), sometimes double, runs upward to the trochanter minor. The lower third bifur- cates to form the internal and external supracondylar ridges, which enclose a smooth, triangular space, the pop- liteal triangle. Outer ridge most prominent; inner ridge obliterated near its beginning by a broad, shallow groove; and terminates below at the adductor tubercle. Surfaces: Anterior, broad, convex, and smooth; inter- nal and external, concave and smooth. PATELLA. The Knee-cap or Knee-pan. The largest sesamoid bone in the body. Developed in the tendon of the quadriceps femoris muscle. Triangular in shape, with apex down- ward. Presents two surfaces, two borders, a base and an apex. Anterior Surface : Convex and rough. Posterior Surface: Articular, receiving surface for a trochlea, with a rough depression below. Lateral Borders, Base and Apex : Rough. TIBIA. The shin bone. Situated at the front and inner side of the leg. A long bone with two extremities connected by a shaft. Upper Extremity (Head): Consists of two tuberosities which are fused together into one mass. Presents five sur- faces. 84 osteology: a syllabus. Superior Surface : Presents two oval, concave articular surfaces, separated by a bifid spine, v^ith a pit in front and behind the spine. The internal articular surface is nar- row, larger, and more concave than the external. The ex- ternal articular surface is almost circular and nearly flat. Anterior Surface: Convex and triangular, with base upward; smooth above; large prominent tubercle (anterior tuberosity) below at apex of triangle. Posterior Surface: Presents a transverse groove on in- ternal tuberosity; and on the external tuberosity an ar- ticular facet which looks downward, backward, and out- ward. Between the two tuberosities is a notch. Lateral Surfaces of the two tuberosities (internal and external), convex and rough. Lower Extremity: Small ; presents five surfaces. Anterior Surface: Convex and smooth; transverse groove just above lower margin. Posterior Surface: Convex and rough. Presents a vertical groove behind internal malleolus. External Surface: Presents a rough triangular depres- sion, sometimes an articular facet. Internal Surface: Prolonged downward to form the internal malleolus, which is pyramidal in shape, with a notch on apex ; convex and subcutaneous internally ; con- cave and articular externally. Inferior Surface: Quadrilateral, concavo-convex, and articular ; receiving surface for a trochlea. APPENDICULAE SKELETON. 85 Shaft: Prismatic; tapers from above downward. Pre- sents three borders and three surfaces. Borders: Anterior : Called the crest or "shin" ; extends from anterior tubercle above to front of malleolus below ; promi- nent, sinuous, and subcutaneous. External (Interosseous): Thin and sharp; extends from outer tuberosity above to bifurcate below around tri- angular depression on outer surface of lower extremity. Internal: Extends from internal tuberosity above to back of malleolus below ; indistinct. Surfaces : External : Concave above ; convex below in the direc- tion of the axis of the bone. Internal : Convex and smooth above ; concave below in the direction of the axis of the bone. Posterior: Presents on upper aspect a smooth trian- gular surface (the popliteal triangle), with its base upward and apex downward. Limited below by an oblique line (the popliteal line), which runs from above and without downward and inward. Prom the middle of this line a vertical ridge descends through the middle third of the posterior surface. FIBULA. Sometimes called the "peroneal" bone. A long bone, situated on the outer side of the leg, and consists of two extremities and a shaft. 86 osteology: a syllabus. Upper Extremity: Consists of a rounded head, with a rough circumference, surmounted by an articular facet which looks upward, forward and inward, and a styloid process (apex) which projects upward behind. Lower Extremity: Pyramidal in shape; forms the ex- ternal malleolus. External Surface : Convex and subcutaneous. Internal Surface: Presents a triangular, convex, ar- ticular facet above and in front, and below and behind this a deep pit. Anterior Border: Rough. Posterior Border: Grooved. Shaft: Very slender; twisted so that external surface above becomes posterior below ; posterior surface above be- comes internal below ; internal surface above becomes ante- rior below. TARSUS. Consists of seven bones grouped in two irregular rows. First (proximal) row contains the Talus and Calcaneus. Second (distal) row contains, from within outward, the internal, middle, and external Cuneiform bones, and the Cuboid. Between the two rows, on the inner side of the foot, is the Navicular. These bones are all six-sided, and articulate together to form the Tarsus or Instep, which is arched, with the convexity upward and the concavity dovsTiward underneath the sole of the foot. APPENDICULAE SKELETOIf. 87 TALUS (astragalus). Superior Surface: Broad, smooth, articular trochlea with a depression (neck) in front. Articulates with Tibia. Inferior Surface: Two articular surfaces; anterior, long, narrow, and convex ; posterior, rounded and concave ; separated by an oblique groove. Articulates with Cal- caneus. Anterior Surface: Oblong head, convex and articular, supported by constricted neck. Articulates with ISTavic- ular. Posterior Surface: Transverse groove, turning from without downward and inward. In the middle line. below the groove is a tubercle. Internal Surface: Pear-shaped, articular surface above (continuous with superior surface) for articulation with Internal Malleolus ; a. rough depression below. External Surface: Large, triangular, concave articular surface for External Malleolus. CALCANEUS (oS CALCIs). Superior Surface: Concavo-convex; rough and narrow behind. In front, broad with two articular surfaces, of which the anterior is long, narrow, and concave; the pos- terior, round and convex; separated by an oblique groove. Articulates with Talus. Inferior Surface: Narrow, convex, and rough in front; two tubercles behind, inner one the larger. 00 osteology: a syllabus. Anterior Surface: Saddle-shaped and articular. Ar- ticulates with Cuboid. Posterior Surface: Presents the posterior tuberosity (forms heel) ; convex; smooth above, rough belovy. Internal Surface: Concave and smooth; presents a shelf -like projection, the sustentaculum tali above and in front, which is grooved on its inferior surface. External Surface: Convex and rough; presents a tubercle in the middle separating two oblique grooves which run from behind and above dovsmward and forward. NAVICULAE (scaphoid). Superior Surface: Broad, convex, and rough. Inferior Surface: Narrow, rough, and notched. Anterior Surface: Convex and articular; divided by two vertical ridges into three facets for articulation with the three Cuneiform bones. Posterior Surface: Oval, concave, and articular. Ar- ticulates with the head of the Talus. Internal Surface: Tapers to blunt point called tuber- osity. External Surface: Broad, convex, and rough; some- times presents an articular facet for Cuboid. CUBOID. Superior Surface: Broad, rough, and convex; looks upward and outward. Inferior Surface: Presents an oblique (peroneal) groove in front, behind which is the tuberosity. APPENDICtTLAE SKELETON. 89 Anterior Surface: Two articular facets for fourth and fifth Metatarsal bones, separated by a vertical ridge. Posterior Surface: Saddle-shaped and articular. Ar- ticulates with Calcaneus. Internal Surface: Articular facet for the external Cu- neiform above in the middle ; sometimes one for Navicular behind ; elsewhere rough. External Surface: Narrow and notched. Notch marks beginning of peroneal groove on inferior surface. INTERNAL CUNEIFOEM. Wedge-shaped with apex up. Superior Surface: Narrow and rough; directed up- ward and outward. Inferior Surface: Thick and rough (tuberosity). Anterior Surface: Kidney-shaped and articular. Ar- ticulates with the first Metatarsal bone. Posterior Surface: Triangular, concave, and articular. Articulates with Navicular. Internal Surface: Broad, convex, and rough; small ar- ticular facet (for tendon) at the antero-inferior angle. External Surface: Concave; articular above and be- hind for second Metatarsal and Middle Cuneiform; else- where rough. MIDDLE AND EXTERNAL CUNEIFOEM BONES. Articulate in front with the second and third Metatarsal bones, respectively; behind with Navicular. 90 OSTEOLOGY : A SYLLABUS. METATARSUS. Consists of fi\'e bones, which in general character resem- ble the Metacarpal bones of the hand, but are larger and stronger. TOES. Five in number. Each consists of three phalanges, ex- cept the great toe, which has only two. The phalanges are small and rudimentary. A pair of sesamoid bones are situated on the under surface of the metatarso-phalangeal articulation of the great toe ; sometimes in connection with the other toes. \ '-rO' ''/ ~--'\ ■