The proximal end of the radius illustrates the relationship of form and function. The cup-like surface of the radial head articulates with the rounded shape of the capitulum. This forms a joint that allows for .

Explanation:

The proximal end of the radius illustrates the relationship of form and function. The cup-like surface of the radial head articulates with the rounded shape of the capitulum. This forms a joint that allows for movement of elbows and forearms.

Radius and ulna are the two bones of the forearm.  Their proximal ends articulate and fit into the cup like end of the humerus. This forms a synovial joint called the elbow joint.  The movement of this joint allows the forearms to supinate and pronate.