a. The ulna, located on the medial side of the forearm, is the longer of the two
bones. Its proximal end, which forms most of the elbow joint (figure 2-3), is thick and
strong. It has two processes and two notches. Between its olecranon and coronoid
processes lies the trochlear notch (semilunar notch), which accommodates the trochlea
of the humerus. The radial notch, on the lateral side of the coronoid process, permits
articulation with the radius. The distal end is much smaller than the proximal end,
bearing a head and a styloid process. Laterally, the head articulates with the ulnar
notch of the radius distally with the articular disk separating it from the wrist joint.
Figure 2-3. The elbow joint.