The flexor digitorum profundus is a

muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other ...

in the

forearm The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in ...

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

s that flexes the

finger A finger is a limb of the body and a type of digit, an organ of manipulation and sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrates have five fingers (Pentadactyly). Chambers 1 ...

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, 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 palmar base of the distal phalanx. Along with the

flexor digitorum superficialis Flexor digitorum superficialis (''flexor digitorum sublimis'') is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints. It is in the anterior compartment of the forearm. It is sometimes considered to be the deepest pa ...

, 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 the 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''. The lumbricals of the hand 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, 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

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 ( 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 Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); '' Gorilla'' (the ...

the belly of the FDP has a separate tendon for the FDP. In

lesser apes Gibbons () are apes in the family Hylobatidae (). The family historically contained one genus, but now is split into four extant genera and 20 species. Gibbons live in subtropical and tropical rainforest from eastern Bangladesh to Northeast India ...

, both muscles have separate bellies in the forearm, but in

Old World monkey Old World monkey is the common English name for a family of primates known taxonomically as the Cercopithecidae (). Twenty-four genera and 138 species are recognized, making it the largest primate family. Old World monkey genera include baboons ...

s 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. Tocheri ''et al.'' 2008, pp 556-7

Structure

Nerve supply

Variation

Function

Other animals

Additional images

See also

Notes

References

External links