[TA] muscle of anterior (flexor) compartment of forearm; origin, via a humeral head from the medial condyle of humerus and an ulnar head from the olecranon and upper three fifths of posterior border of ulna; insertion, pisiform bone but continues to the fifth metacarpal bone via the pisometacarpal ligament; action, flexes and adducts the hand at the wrist joint ulnarward; nerve supply, ulnar. SYN: musculus flexor carpi ulnaris [TA], ulnar flexor (muscle) of wrist.