OSTEOLOGY— THE DESCRIPTION OF BONES (Part 4)

thyroid foramen below, and forms over two-fifths of the acetabulum. It presents a body, a ramus, and a tuberosity. The Pelvis as a Whole. — The pelvis (basin) is com- posed of four bones: two ossa innominata (innominate 94 OSTEOLOGY bones) on either side and in front and the sacrum and coccyx behind. It is divided by an oblique Hne passing through the prominence of the sacrum behind, and the iliopectineal line and symphysis pubis in front, into a false and true pelvis. Fig. 45 if OIL/ POSTERIOR SUPE- RIOR SPINE POSTERIOR FERIOR SP SPINE OF. ISCHIUM SMALL SCIATIC NOTCH ANTERIOR SUPE- RIOR SPINE ANTERIOR IN- FERIOR SPINE ^«IUM The right hip bone; outer surface. (Testut.) The False Pelvis. — This is the expanded portion of the pelvic cavity above this plane. It is bounded on each side by the iliac fossae of the iliac bones; in front it is incomplete; the space of the basin between the anterior superior spines is completed by the abdominal wall; behind is a deep notch. THE BONES OF THE LOWER EXTREMITY 95 The True Pelvis. — This is the real bony basin, situated below the oblique plane which divides the prominence of the sacrum, iliopectineal line, and sym- physis pubis. It is smaller than the false pelvis. For description it presents a superior circumference or inlet, an inferior circumference or outlet, and a cavity. The superior circumference forms the brim of the pelvis, the heart-shaped space being called the inlet. Fia. 46 Oyst of ilium Sup. spine of Inf.spini Obturator fo/a/m/f, ^ Body of /sc/iiufn^ fuberosity of ischium. Ramus of ischium Body of pubic bone . Great S aero sciatic notch . Acetabulum 'Cocci/x -Spine of ischium • Bamus of pubic bone -Sym/fhysis pubes Male pelvis from in front and below. The cavity of the true pelvis is bounded in front by the symphysis pubis; behind by the concavity of the sacrum and coccyx, which, curving forward above and below, contracts the inlet and outlet of the canal; laterally it is bounded by the inner surface of the ischium and that part of the ilium which is below the iliopectineal line. It is shallow in front, measuring 1^ inches in depth at the symphysis, Z\ inches in the middle, and 4| inches posteriorly. ** The^lower circumference or outlet is irregular in shape. Bounded by three eminences the point of the coccyx behind, and the tuberosities of the ischia on either side. The eminences are separated by three notches: one in 96 OSTEOLOGY front, the pubic arch formed by the rami of the ischia and pubes, and the symphyses. The other notches, one on each side, are formed by the sacrum and coccyx Fig. 47 Grmr rroc/ianter /[met of femur -Ant intrr/r(?ckanfC2-ir /ine Zfsscr rroc^o/zrcr 3 :f^% '¥:f^\ .-^^ tfiberosltij Ext, tubefvsfti/ / w0^^^ i^Bm Right thigh bone, femur. behind, the ischium in front, and the ihum above; the latter notches are called the sacrosciatic notches; in the recent state they are converted into foramina by the lesser and greater sacrosciatic ligaments. When the THE BONES OF THE LOWER EXTREMITY 97 ligaments are present, as in life, the real boundaries of the outlet are the subpubic ligament and the rami of the OS pubis and ischium in front, the great sacro- sciatic ligaments and the tip of the coccyx behind, and the tuberosities of the ischia on each side. The Femur. — ^The femur (thigh bone) is the largest, longest, and strongest bone of the skeleton. It is convex in front and concave behind, and when the body is erect the femur is inclined inward and slightly back- ward. It is divisible into an upper and lower extremity and a shaft. The Upper Extremity.-^This presents a head, a neck, and a great and small trochanter. The head is joined to the shaft by the neck, it is round and forms more than a half sphere. It articulates with the acetabulum of the innominate bone. Just below and behind the centre of the head is a depression for the interarticular or round ligament of the hip-joint, which is attached by its upper end to the centre of the acetabulum. The neck is narrow just at the junction of the head, constricted in the centre, and widens as the base is approached; is flattened slightly anteriorly and poste- riorly, concave above and below. The direction of the neck is slightly upward, forward, and inward, being set upon the shaft at an angle of 125 degrees. The junction of the neck with the shaft shows in front and behind a slight elevation or roughened surface of bone called the anterior and posterior intertrochan- teric lines, and they afford attachment to the capsular ligament and ligament of Bigelow. The posterior intertrochanteric line in the middle receives the quadratus femoris. The small trochanter is a small projection of the bone seen at the inferior aspect of the base of the neck when it unites with the shaft. The great trochanter is a projection of bone extending upward beyond the neck. It can be felt under the skin. It is quadrilateral in shape, with its base attached to the shaft of the femur. 98 OSTEOLOGY The Shaft. — The shaft is long and rounded in front and on the sides, is narrow in the centre, and enlarges gradually above and below, being the broadest at the lower extremity. It presents an anterior surface, which is covered by a flat, yet large muscle on its upper three-fourths — the crureus — and below this two small spaces of bone give origin to the subcrureus muscle. There are an internal and an external surface; they are covered by the crureus and vastus internus and externus respectively. The lateral surfaces are separated posteriorly by a longitudinal rough ridge of bone, about the middle of the shaft — called the linea aspera. It is divided into an inner and outer lip, and a middle ridge. The outer and inner lips of the linea aspera at the junction of the middle with the lower third of the bone, posteriorly, separate and include between their diverg- ing borders a triangular-shaped, smooth surface of bone, free from muscular attachments, called the pop- liteal surface. The space is crossed by the popliteal artery, vein, and the internal popliteal nerve, the artery being next to the bone. The Lower Extremity. — This presents two condyles — internal and external and intercondylar notch, and an inner and outer tuberosity or tubercle. The con- dyles articulate with the upper articular facets of the upper extremity of the tibia, and in front the articula- ting surface is extended upon the shaft for a short space (trochlear surface), to articulate with the patella (knee-cap). The capsular ligament of the knee-joint is attached just above the condyles on the shaft of the bone. The intercondylar space is filled with fat and has the crucial ligaments passing from the internal surfaces of the condyles to the upper surface of the tibia. These ligaments as they cross each other form the letter X. The femur has an internal and external rounded border. THE BONES OF THE LOWER EXTREMITY 99 The Patella or Knee-cap. — This is a flat, triangular bone, situated at the anterior part of the knee-joint. It is usually regarded as a sesamoid bone, developed in the quadriceps extensor tendon (formed by the rectus femoris, the vastus internus and externus, and the crureus muscles). The patella can always be felt beneath the skin and fascia. The right patella, ventral surface. (Testut.) INNER I BORDER \ The right patella, dorsal surface. (Testut.) Bones of the Leg. — The bones of the leg are two, the tibia and fibula. The Tibia. — This is situated at the inner and front part of the leg.; It is the longest,; and largest bone 100 OSTEOLOGY in the body, excepting the femur. In the male its direction is vertical; in the female inclined obliquely OUTER TU-k S*^^^, STYLOID. -^ ilNNER TU- BEROSITY RNTERO-EXTER- NAL BORDER m .ANTERIOR BORDER ANTERO-INTER- NAL BORDER OUTER MALLEOLUS INNER MALLEOLUS The right tibitt dnd fibaia in ^heir normal r«l»tionff, front view, (Mod'fied from Tortut.) THE BONES OF THE LOWER EXTREMITY 101 downward and outward slightly. To its outer side is the fibula. The tibia presents an upper and lower extremity, and shaft. The Upper Extremity or Head. — This is large and expanded on either side into the internal and external tuberosities. The superior surface of each tuberosity presents a concave articular surface, which receives the condyles of the femur above. The inner facet is oval, the outer circular. Posteriorly the external tuberosity presents a facet for articulation with the head of the fibula. The anterior surfaces of the tuberosities of the tibia are continuous with one another, thus forming a surface which is triangular in shape and at the lower part is the tubercle, which receives the ligamentum patellae. The Shaft. — The shaft of the tibia is long and tri- angular, broad above, gradually decreasing in size to its most slender part — the commencement of the lower fourth; it then enlarges again at its lower ex- tremity. It presents internal, external, and posterior surfaces; internal, external, and anterior borders, the anterior border forms the shin, so-called. The Lower Extremity. — This, much smaller than the upper, presents five surfaces — anterior, posterior, internal, external, and inferior. The anterior surface is smooth and rounded above, and crossed by the ex- tensor tendons of the toes and tibialis anticus muscle. The external surface is a rough, triangular depression for the attachment of the interosseous membrane above, at its lower part is a smooth hollow surface covered by car- tilage, for articulation with the lower end of the fibula. The inferior surface is quadrilateral and articulates with the upper aspect of the astragalus, one of the tarsal bones; this surface is continuous with the articular surface of the internal malleolus. The internal surface is practically the internal malleolus, a pyramidal process of bone, flattened from without inward. The inner 102 OSTEOLOGY surface is convex and just beneath the skin. The outer surface of the malleolus is smooth and articulates with the astragalus bone. The posterior surface is flattened and crossed by the flexor tendons of the toes and the tibialis posticus muscle. The Fibula. — The fibula (clasp) or peroneal bone, nearly equal in length to the tibia, is the thinnest long bone in the body. It lies parallel with the tibia at the outer side of the leg. It articulates by its upper ex- tremity with the outer tuberosity of the tibia, by its lower extremity with the astragalus. The two articu- lating extremities are held in place by ligaments, all entering into the formation of the superior and infe- rior tibiofibular articulation. The inner border has attached to it the outer edge of the interosseous mem- brane, stretching between the til^ia and fibula. The fibula is the most irregular bone in the body as its surfaces and borders are not evenly defined. The outer aspect of the lower extremity is subcuta- neous and is grooved behind for the lodgement of the tendons of the peroneus longus and brevis muscles — the latter tendon being next to the bone. The lower extremity forms the external malleolus. The Bones of the Foot. — The bones of the foot con- sist of three divisions — the tarsus, metatarsus, and phalanges (toes). The Tarsus.^ — This consists of seven irregular-shaped bones held in position by ligaments and reinforced by the inserted sheaths of the tendons of muscles. The bones are, viz., the os calcis or calcaneum, astragalus, cuboid, scaphoid, internal, middle, and external cuneiform. The OS calcis forms the heel, and is the largest of the seven bones. It articulates above, with the astragalus; in front, with the cuboid. It presents six surfaces — superior, inferior, internal, external, anterior, and pos- terior. The astragalus or ankle bone (talus) receives the weight of the body from the leg. It articulates with THE BONES OF THE LOWER EXTREMITY 103 four bones — the tibia above and internally; the fibula externally; os calcis below, and scaphoid in front. It belongs to the irregular group of bones. Fig. 51 P/ta/a/ixJT. P/ialc/uxJ J//t. Cf//i/ef'o/'m . . . Nid.cujdeform ... Ext. cfinieform .... Kavicalar l/o//e. . Astragalus 7}/be7'ositfj offift/i 7// eta tars a I dc//(c Cul^oid done Os Caie/'s Bones of the right foot. 104 OSTEOLOGY ' The Metatarsal Bones. — The metatarsal bones are five in number; they articulate with the tarsal bones behind and the corresponding phalanges (1 to 5) in front. They present for examination a shaft, a proximal extremity, or a base ; a distal extremity or head. The first bone is the shortest and thickest, the second the largest, and the fifth the thinnest. Each bone has a nutrient canal on its plantar surface. The Phalanges of the Foot (Bones of the Toes). — The phalanges have the same arrangement and shape as those of the fingers, except that they are longer and larger. They are fourteen in number for each foot, allowing three (1st, 2d, and 3d) for the second, third, fourth and fifth toes; the big toe has two (1st and 2d). The first or proximal phalanges articulate with the corresponding metatarsal bone above and the second phalanges below. The second phalanges articulate with the corresponding first phalanges above and third below. The last or distal phalanges articulate with the corresponding second phalanges above. QUESTIONS 1. How many bones enter into the formation of the body skeleton? 2. Name in a general way the bones which are included under the axial skeleton. Appendicular skeleton. 3. How many auditory ossicles are there? 4. Give the classification of bones? 5. Name the long bones. Short bones. Flat bones. Irregular bones. 6. Give an example of an articular eminence. Articular depres- sion. 7 Name two varieties of non-articular eminences. Non-articular depressions. 8. Give the constituents of dried bone. 9. Do the mineral salts predominate in the bones of children or adults? 10. Why are the bones of children more elastic than those of adults? 11. What is the periosteum of a bone? 12. Give the two classes of bone based on their composition? 13. Wha do you understand by the medulla of a bone? Give contents. QUESTIONS 105 14. Name the two varieties of marrow and what makes the difference in color? 15. Give the function of bone-marrow. 16. How are bones nourished during life? 17. Name the number of bones forming the cranium. The face. 18. Name the unpaired bones of the cranium. The paired bones. 19. Name the unpaired bones of the face. The paired. 20. Give the bones bounding the orbital cavity. 21. What bones and cartilage form the septum of the nasal cavity? 22. How many fontanelles are there in the skull of an infant? 23. Until what age do they remain membranous before ossifica- tion generally occurs? 24. How many separate vertebra are there? 25. Give the subdivisions of vertebra, as regards their location? 26. Name the movable vertebra. Immovable. 27. Mention the general characteristics of a typical vertebra. 28. Give the contents of the spinal canal. 29. Name the structures that pass through the upper opening of the thorax. The lower opening. 30. What structure separates the thoracic cavity from the abdomi- nal cavity? 31. What openings are found in the diaphragm and what passes through each one? 32. Differentiate the female from the male thorax. 33. How many pairs of ribs are there? 34. Give the classification of ribs as to arrangement. 35. What do you understand by the true or vertebrosternal ribs? The false or asternal ribs? Vertebrochondral ribs? Floating or vertebral ribs? 36. W^hat are the functions of the costal cartilages? 37. What bones form the shoulder girdle? 38. Name the bones of arm. Forearm. Wrist. Palm. Fingers. 39. Name the bones which form the pelvis. 40. Differentiate the true from the false pelvis. 41. Name the thigh bone. Bones of leg. Instep. 42. How many metacarpal bones are there? Phalanges? 43. W^hat bones does the humerus articulate? The femur? The Tibia? The ulna? The radius?