The flexor digitorum profundus or flexor digitorum communis profundus is a

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

in the forearm of

human Humans (''Homo sapiens'') or modern humans are the most common and widespread species of primate, and the last surviving species of the genus ''Homo''. They are Hominidae, great apes characterized by their Prehistory of nakedness and clothing ...

s that flexes the

finger A finger is a prominent digit (anatomy), digit on the forelimbs of most tetrapod vertebrate animals, especially those with prehensile extremities (i.e. hands) such as humans and other primates. Most tetrapods have five digits (dactyly, pentadact ...

s (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.Platzer 2004, p 162 The muscle is named .

Structure

Flexor digitorum profundus originates in the upper 3/4 of the anterior and medial surfaces of the

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

, interosseous membrane and

deep fascia Deep fascia (or investing fascia) is a fascia, a layer of dense connective tissue that can surround individual muscles and groups of muscles to separate into fascial compartments. This fibrous connective tissue interpenetrates and surrounds the m ...

of the forearm. The muscle fans out into four tendons (one to each of the second to fifth fingers) to the palmar base of the distal phalanx. Along with the flexor digitorum superficialis, it has long

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

s that run down the arm and through the carpal tunnel and attach to the palmar side of the

phalanges The phalanges (: phalanx ) are digit (anatomy), digital bones in the hands and foot, feet of most vertebrates. In primates, the Thumb, thumbs and Hallux, big toes have two phalanges while the other Digit (anatomy), digits have three phalanges. ...

of the fingers. Flexor digitorum profundus lies deep to the superficialis, but it attaches more distally. Therefore, profundus's

s go through the tendons of superficialis, and end up attaching to the distal phalanx. For this reason profundus is also called the ''perforating muscle''. The

lumbricals of the hand The lumbricals are intrinsic muscles of the hand that flexion, flex the metacarpophalangeal joints, and extension (kinesiology), extend the Interphalangeal articulations of hand, interphalangeal joints. p. 97 The lumbrical muscle of the foot, lu ...

arise from the radial side of its tendons.

Nerve supply

Flexor digitorum profundus is a composite muscle innervated by the anterior interosseous nerve 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 The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, and has cont ...

, 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). In the forearm, the median nerve travels distally between the flexor digitorum superficialis and the flexor digitorum profundus.

Variation

The tendon of the index finger often has a separate muscle belly.

Function

Flexor digitorum profundus is a flexor of the

wrist In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...

( midcarpal), metacarpophalangeal and interphalangeal joints. The lumbricals, intrinsic muscles of the hand, attach to the tendon of flexor digitorum profundus. Thus, the flexor muscle is used to aid the lumbrical muscles in their role as extensors of the interphalangeal joints. As the lumbrical muscles originate on the palmar side of the hand and attach on the dorsal aponeurosis, power is transferred from the flexor digitorum profundus muscle to fully extend the fingers as well as flex the metacarpophalangeal joints. The tension generated by flexor digitorum profundus at the more distal joints is determined by wrist position. Flexion of the wrist causes muscle shortening at that point, reducing tension that can be generated more distally. Fingers cannot be fully flexed if the wrist is fully flexed.

Other animals

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

baboon Baboons are primates comprising the biology, genus ''Papio'', one of the 23 genera of Old World monkeys, in the family Cercopithecidae. There are six species of baboon: the hamadryas baboon, the Guinea baboon, the olive baboon, the yellow ba ...

s makes it unlikely that this monkey can control individual fingers independently. Tocheri ''et al.'' 2008, pp 556-7

Structure

Nerve supply

Variation

Function

Other animals

Additional images

See also

Notes

References

External links