Bones of the Axial and Appendicular Skeleton

The rest of the skeleton follows a similar plan of an axial part (skull, vertebral column, ribs and sternum) and an appendicular part (limb bones and their girdles). Man has 12 pairs of ribs: 7 pairs of true ribs attach directly to the sternum through their own costal cartilage; 3 pairs of false ribs attach only indirectly, their cartilage joining that of the seventh rib above rather than reaching the sternum on its own; and 2 pairs of floating ribs have no attachment to the sternum at all, being anchored only to the vertebral column at the back. The fore-limb skeleton begins at the pectoral girdle (a clavicle and a scapula on each side), which supports a single long upper-arm bone, the humerus; below the elbow lie two forearm bones, the radius and the ulna; the wrist has eight small carpal bones, the palm has five metacarpals, and the fingers are made of fourteen phalanges. The leg skeleton begins at the pelvic girdle — two hip bones, each formed of a fused ilium, ischium and pubis, meeting the sacrum behind at the sacroiliac joints and each other in front at the pubic symphysis, together forming the basin-shaped pelvis and carrying the acetabulum that receives the femur. Below the pelvic girdle, the single thigh bone i …