This image shows some of the superficial muscles on the distal portion of the dorsal surface of the forearm.  Note the deep muscle at the ulnar head, which is called the flexor digitorum profundus.  This muscle has five heads, most of which lie beneath more superficial muscles.  The flexor digitorum profundus acts to flex the digits.  Just medial to the exposed ulna is the flexor carpi ulnaris. This muscle is a wrist flexor. Adjacent to the flexor carpi ulnaris, moving medially, is the wide, flat palmaris longus.  This muscle originates on the medial epicondyle of the humerus and inserts on the middle phalanx of digits two through five.  Its action is flexion of the digits.  Distal to the palmaris longus is a small, triangular patch of muscle that constitutes the flexor digitorum sublimis.  The previously described flexor carpi radialis and brachioradialis can also be seen on the above image.