The flexor carpi ulnaris is a first-layer muscle which occupies the medial border of forearm (on the little finger's side). It has a long belly and a rather thick tendon. It arises by two heads; its humeral head originates from the medial epicondyle of humerus and the intermuscular septum, while its ulnar head springs from olecranon of ulna and the two upper third of superficial dorsal fascia of forearm. (An intermuscular septum is an aponeurotic sheet of connective tissue diving two muscles).
After emerging from its two points of origin, the flexor carpi ulnaris muscle travels downwards, superficially along the medial border of forearm, parallel to ulna. Then it tapers to a tendon which runs under the flexor retinaculum to be inserted into the pisiform of carpus (the small bones that make up the wrist). However, some of the fibers of the flexor carpi ulnaris keep stretching forward together with the pisometacarpal and pisohamate ligaments, which are in turn inserted into the hamate and the fifth metacarpal bone.
Action
This long muscle of forearm flexes the wrist (and hand) inwardly, towards the ulna.
Innervation
It is supplied by collateral nervous fibers originating from the ulnar nerve (C7-C8-T1).
Blood Supply
This long muscle receives oxygenated blood from the superior ulnar collateral, supratrochlear brachial, and ulnar artery.
Below, schematic drawing of the superficial anterior muscles of forearm, with the flexor carpi ulnaris extending along its medial border.
