The adductor pollicis is considered a forearm muscle, but is located deep in the hand's thenar compartment; it is found below the lumbrical muscles and long flexor tendons at the palm's center. It lies on top of the interosseous muscles and the metacarpal bones. It is triangular and fan-shaped, and is fleshy and flat. It is involved in the movement of the hand and fingers; its specific function is to adduct the thumb's carpometacarpal joint. The adductor pollicis is powered by the deep branch of the ulnar nerve (T1). The adductor pollicis muscle has two heads: the oblique and transverse. The oblique fibrous head of the adductor pollicis originates by proximal attachment at the bases of the trapezoid and capitate, respectively the second and third metacarpal bones. Its transverse head originates by proximal attachment at the shaft and palmar border of the capitate. Its distal attachment occurs at the base of the thumb's proximal phalanx. The adductor pollicis inserts into the ulnar sesamoid and then into the proximal phalanx's base at its ulnar side, as well as into the tendon of the extensor pollicis longus.