The palmaris longus is a superficial, spindle-shaped muscle of forearm. It lies directly under the skin, on its anterior side, medially to the flexor carpi radialis. It originates from the medial epicondyle of humerus, the intermuscular septum, and the antebrachial fascia. Then it extends down along the forearm as it becomes a very long tendon which is inserted into the palmar aponeurosis (a hard fibrous sheet of connective tissue; like a flattened tendon).
Action
The function of the palmaris longus muscle is palmar flexion, tightening the palmar aponeurosis. It assists both the flexor carpi ulnaris and the radialis in flexing the hand inwardly towards the anterior side of forearm.
Innervation
It supplied by collateral branches of the medial nerve (C7-C8), which arises from the brachial plexus.
Blood Supply
It receives oxygenated blood from muscular branches of the radial artery.
Below, schematic picture of the superficial muscles of anterior aspect of right forearm, showing the palmaris longus muscle.
