Forearm in supine position. Artwork of an anterior (frontal) view of a human left forearm with clenched hand and protruding thumb, showing the underlying bone structure when the limb is in a supine position. The palm is facing upwards. The opposite hand position, with the forearm rotated and palm facing down, is known as pronation (see C016/2850). The two forearm bones are the ulna (left) and radius (right). Also visible are the wrist bones, some of the phalanges of the hand, and part of the humerus (upper arm bone).