The flexor digitorum sublimis is one of the nineteen muscles of the forearm, and it belongs to the second layer of muscles. It lies under the palmaris longus and the flexor carpi radialis muscle, which leave grooves on it. It flexes the second phalanges of the four fingers of the hand.
The flexor digitorum sublimis muscle originates by two heads; the humero-ulnar head, which is long and narrow, arises from the medial epicondyle of the humerus and the coronoid process of ulna; while the radial head, which is wide and short, arises from the proximal palmar surface of radius. Then the two heads join to form a common belly which runs downwards, dividing into four long tendons. These tendons travel over to the hand, running through the carpal tunnel to be inserted into the bases of the middle phalanges of the fingers. At the level of the proximal phalanges, each tendon splits into two and, therefore, has two points of insertion at the base of the middle phalanges.
Action
The flexor digitorum sublimis flexes (bends) the middle phalanx of the index, middle, ring, and little finger.
Innervation
The flexor digitorum sublimis is innervated by the median nerve (C6-C7-T1), which arises from the brachial plexus.
Blood Supply
This long muscle is supplied by collateral branches of the radial and ulnar artery.
Below, image of muscles on palmar (anterior) aspect of forearm. You can see that the flexor digitorum sublimis is partially covered by the flexor carpi radialis and the palmaris longus muscle.
