part of part of Homo sapiens ulna zone of long bone head of ulna of ulna 2026-03-19T00:00:00Z A zone of bone organ forming the rounded distal end of the ulna, articulating with the ulnar notch of the radius via its convex articular circumference and with the triangular fibrocartilage complex on its inferior surface, participating in the distal radioulnar joint. David Osumi-Sutherland