The Probert Encyclopaedia of Medicine

ULNA

The ulna is the internal of the two long bones (the other is the radius) which form the lower arm (forearm). The ulna articulates at each end with the ends of the radius, with the humerus at the elbow, and some of the carpal bones at the wrist. When the hand is turned with the palm facing up (called supination), the ulna is on the medial (little finger) side of the forearm. When the hand is placed with the palm down (called pronation), the radius crosses over the ulna in mid-forearm.
Research Ulna