Flexor digitorum profundus

The flexor digitorum profundus (Latin: musculus flexor digitorum profundus) is a flat fusiform-shaped muscle of the upper limb that is located deep within the forearm. It stretches between the bones of the forearm and phalanges. The flexor digitorum profundus belongs to the anterior compartment of the forearm muscles, and it lies in the third layer. This muscle is located directly beneath the flexor digitorum superficialis.

Flexor digitorum profundus
OriginAnterior surface of ulna, interosseous membrane of forearm
InsertionBases of 2nd to 5th distal phalanges
Action Flexion of phalanges at 2nd to 5th metacarpophalangeal and proximal and distal interphalangeal joints, flexion of wrist
Innervation

Second and third fingers - anterior interosseous branch of median nerve (C8, T1)

Fourth and fifth fingers - ulnar nerve (C8, T1)

Blood supply Ulnar and anterior interosseous arteries

Origin

The flexor digitorum profundus muscle originates from the proximal anterior surface of the ulna and interosseous membrane of the forearm.

Insertion

The flexor digitorum profundus descends and reaches the hand via the carpal tunnel. Further, the muscle splits into four tendons that insert on the bases of the second to fifth distal phalanges.

Action

The flexor digitorum profundus muscle provides the flexion of the phalanges at the second to fifth metacarpophalangeal and proximal and distal interphalangeal joints. Also, it assists in the flexion of the wrist at the wrist joint.

Innervation

The lateral part of the flexor digitorum profundus associated with the index (2nd) and middle (3rd) fingers is innervated by the anterior interosseous branch of the median nerve (C8, T1). In contrast, the medial part of the muscle associated with the ring (4th) and little (5th) fingers is innervated by the ulnar nerve (C8, T1)

Blood supply

The flexor digitorum profundus muscle receives arterial blood supply from the ulnar and anterior interosseous arteries. The ulnar artery is a branch of the brachial artery, while the latter is a branch of the common interosseous artery.