Flexor pollicis longus is one of the deep group of flexor muscles. Its principle origin is from the radius. It is characteristically unipennate, which aids its identification during forearm surgery. The median nerve enters the forearm between the two heads of pronator teres. The ulnar nerve enters the forearm by passing between the two heads of flexor carpi ulnaris. Flexor digitorum profundus is one of the deep group of flexor muscles and principally takes origin from the ulna.