[pg 228]6. The Leg and Foot Groups.—These correspond in form and arrangement to the bones of the arm and hand. Since, however, the leg and foot are used for purposes different from those of the arm and hand, certain differences in structure are to be found. The patella, or kneepan, has no corresponding bone in the arm; and the carpus, or ankle, which corresponds to the wrist, contains seven instead of eight bones. The bones of the foot and toes are the same in number as those of the hand and fingers, but they differ greatly in size and form and have less freedom of motion. The femur, which gives form to the thigh, is the longest bone of the body. The tibia, or shin bone, and the fibula, the slender bone by its side, give form to the lower part of the leg (Fig. 102).

The legs are mechanical devices (walking machines) for moving the body from place to place. The feet serve both as supports for the body and as levers for pushing the body forward. By their attachment to the legs they may be placed in all necessary positions for supporting and moving the body.

The different bone groups are shown in Fig. 97 and named in Table IV.

Adaptation to Special Needs.—When any single bone is studied in its relation to the other members of the group to which it belongs or with particular reference to its purpose in the body, its adaptation to some special place or use is at once apparent. Each bone serves some special purpose, and to this purpose it is adapted by its form and structure. Long bones, like the humerus and femur, are suited to giving strength, form, and stiffness to certain parts, while irregular bones, like the vertebræ and the pelvic bones, are fitted for supporting and protecting organs. Others, like the wrist and ear bones, make possible a peculiar kind of motion, and still others, like the ribs, are adapted to more than one purpose. The vast differences in shape, size, structure, and surface among the various bones are but the conditions that adapt them to particular forms of service in the body.

[pg 229]TABLE IV - The Principal Bones and their Grouping in the Body

I. AXIAL SKELETON A. Skull, 28. 1. Cranium, 8. a. Frontal, forehead 1b. Parietal 2c. Temporal, temple 2d. Occipital 1e. Sphenoid 1f. Ethmoid 12. Face, 14. a. Inferior maxillary 1b. Superior maxillary 2c. Palatine, palate 2d. Nasal bones 2e. Vomer 1f. Inferior turbinated 2g. Lachrymal 2h. Malar, cheek bones 23. Bones of the Ears, 6. a. Malleus 2b. Incus 2c. Stapes 2B. Spinal Column, 26. 1. Cervical, or neck, vertebræ 72. Dorsal, or thoracic, vertebræ 123. Lumbar vertebræ 54. Sacrum 15. Coccyx 1C. Thorax, 25. 1. Ribs 242. Sternum 1D. Hyoid, 1 (at base of tongue).
A. Skull, 28. 1. Cranium, 8. a. Frontal, forehead 1b. Parietal 2c. Temporal, temple 2d. Occipital 1e. Sphenoid 1f. Ethmoid 12. Face, 14. a. Inferior maxillary 1b. Superior maxillary 2c. Palatine, palate 2d. Nasal bones 2e. Vomer 1f. Inferior turbinated 2g. Lachrymal 2h. Malar, cheek bones 23. Bones of the Ears, 6. a. Malleus 2b. Incus 2c. Stapes 2
1. Cranium, 8. a. Frontal, forehead 1b. Parietal 2c. Temporal, temple 2d. Occipital 1e. Sphenoid 1f. Ethmoid 1
a. Frontal, forehead 1
b. Parietal 2
c. Temporal, temple 2
d. Occipital 1
e. Sphenoid 1
f. Ethmoid 1
2. Face, 14. a. Inferior maxillary 1b. Superior maxillary 2c. Palatine, palate 2d. Nasal bones 2e. Vomer 1f. Inferior turbinated 2g. Lachrymal 2h. Malar, cheek bones 2
a. Inferior maxillary 1
b. Superior maxillary 2
c. Palatine, palate 2
d. Nasal bones 2
e. Vomer 1
f. Inferior turbinated 2
g. Lachrymal 2
h. Malar, cheek bones 2
3. Bones of the Ears, 6. a. Malleus 2b. Incus 2c. Stapes 2
a. Malleus 2
b. Incus 2
c. Stapes 2
B. Spinal Column, 26. 1. Cervical, or neck, vertebræ 72. Dorsal, or thoracic, vertebræ 123. Lumbar vertebræ 54. Sacrum 15. Coccyx 1
1. Cervical, or neck, vertebræ 7
2. Dorsal, or thoracic, vertebræ 12
3. Lumbar vertebræ 5
4. Sacrum 1
5. Coccyx 1
C. Thorax, 25. 1. Ribs 242. Sternum 1
1. Ribs 24
2. Sternum 1
D. Hyoid, 1 (at base of tongue).
II. APPENDICULAR SKELETON A. Shoulder girdle 4. 1. Clavicle, collarbone. 22. Scapula, shoulder blade 2B. Upper extremities, 60. 1. Humerus 22. Radius 23. Ulna 24. Carpal, wrist bones 165. Metacarpal 106. Phalanges of fingers 28C. Pelvic girdle, 2. 1. Osinnominatum 2D. Lower extremities, 60. 1. Femur, thigh bone 22. Tibia, shin bone 23. Fibula 24. Patella, kneepan 25. Tarsal, ankle bones 146. Metatarsal, instep bones 107. Phalanges of toes 28
A. Shoulder girdle 4. 1. Clavicle, collarbone. 22. Scapula, shoulder blade 2
1. Clavicle, collarbone. 2
2. Scapula, shoulder blade 2
B. Upper extremities, 60. 1. Humerus 22. Radius 23. Ulna 24. Carpal, wrist bones 165. Metacarpal 106. Phalanges of fingers 28
1. Humerus 2
2. Radius 2
3. Ulna 2
4. Carpal, wrist bones 16
5. Metacarpal 10
6. Phalanges of fingers 28
C. Pelvic girdle, 2. 1. Osinnominatum 2
1. Osinnominatum 2
D. Lower extremities, 60. 1. Femur, thigh bone 22. Tibia, shin bone 23. Fibula 24. Patella, kneepan 25. Tarsal, ankle bones 146. Metatarsal, instep bones 107. Phalanges of toes 28
1. Femur, thigh bone 2
2. Tibia, shin bone 2
3. Fibula 2
4. Patella, kneepan 2
5. Tarsal, ankle bones 14
6. Metatarsal, instep bones 10
7. Phalanges of toes 28

[pg 230]

ARTICULATIONS

Any place in the body where two or more bones meet is called an articulation, or joint. At the place of meeting the bones are firmly attached to each other, thereby securing the necessary coherence of the skeleton. The large number of bones, and consequently of articulations, are necessary for the different movements of the body and also on account of the manner in which the skeleton develops, or grows. Articulations are classed with reference to their freedom of motion, as movable, slightly movable, and immovable articulations.

Most of the immovable articulations are found in the skull. Here irregular, tooth-like projections from the different bones enable them to interlock with one another, while they are held firmly together by a thin layer of connective tissue. The wavy lines formed by articulations of this kind are called sutures (Fig. 100).