Index, Long, Ring, & Little Flexor Digitorum Profundus Anatomy

Flexor Digitorum Profundus (FDP)

Origin: Ulna (proximal 3/4 of anterior and medial shaft; medial coronoid process), interosseous membrane (ulnar).
Insertion: Four tendons to digits 2–5 (distal phalanges, at base of palmar surface). Note index finger tendon is distinct in its course
Innervation: Cervical root(s): C8–T1; C8–T1; Nerve: median nerve, digits 2–3; ulnar nerve, digits 4–5.
The FDP tendon’s blood supply in forearm is from ulnar artery primarily and in the finger from the digital arteries.
To facilitate gliding (sliding), the FDP tendons are covered by internal and external synovial sheaths.
The synovial sheaths of the index, long, and ring fingers beginning at the level of the metacarpal neck and A1 pulley. The sheath of the thumb and little fingers connect to the radial and ulnar bursa respectively.
In section 8 the. flexor tendons are covered by tenosynovium in the radial and ulnar bursa.

Diagrams & Photos

Note the FDP tendons in section 9 (yellow oval).
The FDS tendons (FDS) have been cut distally and folded proximally. Note the 4 FDP tendons and their significant interconnections. The FCU and FPL tendons are also labeled.

Key Points

The flexor digitorum profundus (FDP) is an extrinsic hand muscle that originates in the volar forearm.
FDP II & III (median nerve innervated) to FDP IV & V (ulnar nerve innervated)
The FDP tendons are the origin of the lumbrical muscles. The lumbrical origins are located in palmar Section 7 and 8.
The flexors also get nutrients from synovial fluid, local vessels, and in the finger from the vincula blood supply.
In the digit the FDP gets its blood supply from the vincula longus and brevis. The vincula vessels originate from the transverse branches of the digital arteries.
In the carpal tunnel of section 8 the FDP tendons are dorsal (underneath) to the FDS tendons.