Skeleton

Skeleton. The human skeleton consists of some 200 bones, though the number of separate bones varies at different times of life, bones which are distinct in early life becoming fused in old age. The vertebral column is made up in adult life of 26 sepamte bones, and is divided into a cervical portion (see Fig. k), a dorsal portion, to which the ribs are attached, a lumbar portion (see Fig. l), the sacrum (see Fig. m), and the coccyx. The sacrum originally consists of five, and the coccyx of four, distinct vertebrae. The nine vertebral, together with the five lumbar vertebrae, the twelve dorsal vertebrae, and the seven cervical vertebrae make up a total of 33 vertebrae; or, taking account of the fusion of originally separate vertebrae already alluded to, the total of 26 separate bones in the entire verlebral column is accounted for. Poised on the summit of this column is the skull. In the figure the letter a denotes the position of the frontal bones, which form the anterior wall of the cranial vault; h indicates the situation of the laterally-placed parietal bone, and c of the temporal bone, which lies beneath each parietal bone; d indicates the superior maxillary bone, and e the inferior maxillary bone. The shoulder girdle is made up of the clavicle or collar bone (see Fig. f), and the scapula, or shoulder-blade on either side. The clavicle articulates with the scapula, and the articulation of the rounded head of the humerus with the glenoid cavity of the scapula constitutes the shoulder joint. The ribs, 12 in number on each side (see Fig. g), make up the bony framework of the thorax, and, with the exception of the lowermost floating ribs, they are united to the sternum (see Fig. h) by the several costal cartilages. The bones of each upper extremity are 64 in number; in the upper arm is the humerus (see Fig. n), in the fore-arm are the radius (see Fig. o) and the ulna (see Fig. p); and then follow the bones of the carpus and metacarpus, and the phalanges. The hip girdle is formed by the pelvis (see Fig. q), and the hip-joint on either side is constituted by the articulation of the head of the femur with the acetabulum, the cavity which exists on each of the lateral aspects of the pelvis. Each lower extremity contains in all 62 bones. The thigh-bone is called the femur (see Fig. r); the bones of the leg are the tibia (see Fig. s) and the fibula (see Fig. t); and then follow the bones of the tarsus, the metatarsus, and the phalanges.