The flexor digitorum superficialis is a second layer muscle of the forearm. It is covered by the palmaris longus, the flexor carpi radialis, and the pronator teres muscle. It originates by two heads: the humero-ulnar head arises from the medial epicondyle of the humerus and the coronoid process of the ulna, while the radial head arises from the proximal palmar surface of radius. The two heads meet to form a common belly that extends downwards along the length of the forearm as it gets narrow, ending up in four tendons. These tendons run into the hand through the carpal tunnel as they fan out to be inserted into the middle phalanges of fingers. This forearm muscle is also called flexor digitorum sublimis.
Action/Function
It flexes the middle phalanges of all four fingers: index, middle, ring, and little, closing them.
Innervation
The flexor digitorum superficialis is innervated by branches of the median nerve, which arises from the brachial plexus (C7, C8, T1).
Blood Supply
It receives oxygenated blood from collateral branches from the radial and ulnar artery.
Below, schematic drawing of the muscles of forearm, second layer, with the flexor digitorum superficialis.
