Median nerve (Nervus medianus) The median nerve is formed in the axilla by the union of the lateral root of the medial cord and the medial root of the lateral cord of the brachial plexus. It has no branches in the axilla or the arm. The median nerve innervates all of the flexors in the forearm except the flexor carpi ulnaris muscle and the ulnar head of flexor digitorum profundus. In the hand it supplies the 1st and 2nd lumbrical muscle and most of the thenar muscles.