Radius (bone) ulna (center of the circle) to the edge of the radius (the circle). The ulna acts as the center point to the circle because when the arm is rotated the ulna does not move. In four-legged animals, the radius is the main load-bearing bone of the lower forelimb. Its structure is similar in most terrestrial tetrapods, but it may be fused with the ulna in some mammals (such as horses) and reduced or modified in animals with flippers or vestigial forelimbs. Radius (bone) The radius or radial bone is one of the two large bones of the forearm, the other
Posterior compartment of the forearm muscles because they both arise within the forearm and they both move the forearm. Extensor tendons pass through the extensor retinaculum at wrist joint in 6 synovial sheaths, also referred to compartments. The supinator and the anconeus are the two muscles in the posterior compartment of the forearm that do not pass through wrist extensor compartments. The muscles of the posterior compartment of the forearm are innervated by the radial nerve and its branches. The radial nerve arises from the posterior cord of the plexus. The somatomotor fibers of the radial nerve branch from the main radial nerve at the