Each arm has 30 bones, which constitutes 1 humerus (upper arm), 1 ulna and 1 radius (lower arm), 8 carpals (wrist), 5 metacarpals (palm) and 14 phalanges (digits). The humerus is the longest bone in the upper extremity. The top, or head, is large, smooth, and rounded and fits into the scapula in the shoulder. On the bottom of the humerus, are two depressions where the humerus connects to the ulna and radius of the forearm. Together, the humerus and the ulna make up the elbow. The ulna is longer than the radius and connected more firmly to the humerus. The radius, however, contributes more to the movement of the wrist and hand than the ulna.