Flexor digitorum profundus muscle
Ventral view of the deep muscles of the forearm. FDP is shown in blue.
Latin	musculus flexor digitorum profundus
Gray's	subject #125 448
Origin	upper 3/4 of the volar and medial surfaces of the body of the ulna, interosseous membrane and deep fascia of the forearm
Insertion	base of the distal phalanges of the fingers
Artery	anterior interosseous artery
Nerve	median (anterior interosseous), muscular branches of ulnar
Actions	flex hand, interphalangeal joints
Antagonist	Extensor digitorum muscle

In human anatomy, the flexor digitorum profundus (FDP, Latin for "deep bender of the fingers") is a muscle in the forearm that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm. Together the flexor pollicis longus, pronator quadratus, and flexor digitorum profundus form the deep layer of ventral forearm muscles.^[1]

Human anatomy[link]

Origin and insertion[link]

Flexor digitorum profundus originates upper 3/4 of anterior & medial surfaces of ulna, interosseous membrane and deep fascia of the forearm. The muscle fans out into four tendons (one to each of the second to fifth fingers) to the palmer base of distal phalanx.

Along with flexor digitorum superficialis, it has long tendons that run down the arm and through the carpal tunnel and attach to the palmar side of the phalanges of the fingers.

Flexor digitorum profundus lies deep to superficialis, but it attaches more distally. Therefore, profundus's tendons go through the tendons of superficialis, and end up attaching to the distal phalanx. For this reason profundus is also called the perforating muscle.^[1]

The lumbricals of the hand arise from the radial side of its tendons.^[1]

Action[link]

Flexor digitorum profundus is a flexor of the wrist (midcarpal), metacarpophalangeal and interphalangeal joints.^[1]

Innervation[link]

Flexor digitorum profundus is innervated by the anterior interosseous and ulnar nerves.

• The medial aspect of the muscle (which flexes the 4th and 5th digit) is supplied by the ulnar nerve (C8, T1)
• The lateral aspect (which flexes the 2nd and 3rd digit) is innervated by the median nerve specifically the anterior interosseous branch (C8, T1).

It is one of two flexor muscles that is not exclusively supplied by the median nerve (the other is flexor carpi ulnaris).

Variations[link]

The tendon of the index finger often has a separate muscle belly.^[1]

Evolutionary variation[link]

In many primates, the FDP is fused with the flexor pollicis longus (FPL). In great apes the belly of the FDP has a separate tendon for the FDP. In lesser apes, both muscles have separate bellies in the forearm, but in Old World monkeys they separate in the carpal tunnel. The lack of differentiation in the FDP musculature in baboons makes it unlikely that this monkey can control individual fingers independently. ^[2]

Additional images[link]

Bones of left forearm. Anterior aspect.   Bones of left forearm. Posterior aspect.   Bones of the left hand. Volar surface.   Front of the left forearm. Deep muscles.   Cross-section through the middle of the forearm.   Posterior surface of the forearm. Deep muscles.   Transverse section across distal ends of radius and ulna.   Transverse section across the wrist and digits.   The mucous sheaths of the tendons on the front of the wrist and digits.   Ulnar and radial arteries. Deep view.   Tendons of forefinger and vincula tendina. (Flexor digitorum profundus labeled at bottom right.)

Notes[link]

References[link]

• Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.). Thieme. ISBN 3-13-533305-1. 
• Tocheri, MW; Orr, CM; Jacofsky, MC; Marzke, MW. (April 2008). "The evolutionary history of the hominin hand since the last common ancestor of Pan and Homo". J Anat. 212 (4): 544–62. DOI:10.1111/J.1469-7580.2008.00865.X. PMC 2409097. PMID 18380869. //www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2409097.  (Abstract, PubMed) (PDF, Smithsonian)

External links[link]

• LUC fdp
• UWASH flexordigprofundus