Extensor digitorum muscle

Last updated
Extensor digitorum muscle
Extensor digitorum muscle.png
Posterior surface of the forearm. Superficial muscles. Extensor digitorum muscle is labeled in purple.
Gray422.png
Transverse section across the wrist and digits. (Ext. dig. communis labeled at bottom center.)
Details
Origin Lateral epicondyle (common extensor tendon)
Insertion Extensor expansion of middle and distal phalanges of the 2nd, 3rd, 4th, and 5th fingers [1]
Artery Posterior interosseous artery
Nerve Posterior interosseous nerve
Actions Extension of hand, wrist and fingers
Antagonist Flexor digitorum superficialis muscle, flexor digitorum profundus muscle
Identifiers
Latin musculus extensor digitorum
TA98 A04.6.02.042
TA2 2500
FMA 38500
Anatomical terms of muscle

The extensor digitorum muscle (also known as extensor digitorum communis) [2] is a muscle of the posterior forearm present in humans and other animals. It extends the medial four digits of the hand. Extensor digitorum is innervated by the posterior interosseous nerve, which is a branch of the radial nerve. [3]

Contents

Structure

The extensor digitorum muscle arises from the lateral epicondyle of the humerus, by the common tendon; from the intermuscular septa between it and the adjacent muscles, and from the antebrachial fascia. It divides below into four tendons, which pass, together with that of the extensor indicis proprius, through a separate compartment of the dorsal carpal ligament, within a mucous sheath. The tendons then diverge on the back of the hand, and are inserted into the middle and distal phalanges of the fingers in the following manner. [4]

Opposite the metacarpophalangeal articulation each tendon is bound by fasciculi to the collateral ligaments and serves as the dorsal ligament of this joint; after having crossed the joint, it spreads out into a broad aponeurosis, which covers the dorsal surface of the first phalanx and is reinforced, in this situation, by the tendons of the interossei and lumbricalis. [4]

Opposite the first interphalangeal joint this aponeurosis divides into three slips; an intermediate and two collateral: the former is inserted into the base of the second phalanx; and the two collateral, which are continued onward along the sides of the second phalanx, unite by their contiguous margins, and are inserted into the dorsal surface of the last phalanx. As the tendons cross the interphalangeal joints, they furnish them with dorsal ligaments. The tendon to the index finger is accompanied by the tendon of extensor indicis, which lies on its ulnar side. On the back of the hand, the tendons to the middle, ring, and little fingers are connected by two obliquely placed bands, one from the third tendon passing inferior and laterally to the second tendon, and the other passing from the same tendon inferior and medially to the fourth. [4]

The extensor tendons are connected to the second by a thin transverse band, known as the juncturae tendinum; they serve to maintain the central alignment of the extensor tendons over the metacarpal head, [5] thus increasing the available leverage. Injuries (such as by an external flexion force during active extension) may allow the tendon to dislocate into the intermetacarpal space; the extensor tendon then acts as a flexor and the finger may no longer be actively extended. This may be corrected surgically by using a slip of the extensor tendon to replace the damaged ligamentous band. [6]

Function

The extensor digitorum muscle extends the phalanges, [2] then the wrist, and finally the elbow. It tends to separate the fingers as it extends them.

In the fingers, the extensor digitorum acts principally on the proximal phalanges, acting to extend the metacarpophalangeal joint. Extension of the proximal and distal interphalangeal joints, however, is mediated predominantly by the dorsal and palmar interossei and lumbricals of the hand.

Additional images

See also

Related Research Articles

<span class="mw-page-title-main">Foot</span> Anatomical structure found in vertebrates

The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws and/or nails.

<span class="mw-page-title-main">Carpal bones</span> Eight small bones that make up the wrist (or carpus) that connects the hand to the forearm

The carpal bones are the eight small bones that make up the wrist (carpus) that connects the hand to the forearm. The term "carpus" and "carpal" is derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In human anatomy, the main role of the carpal bones is to articulate with the radial and ulnar heads to form a highly mobile condyloid joint, to provide attachments for thenar and hypothenar muscles, and to form part of the rigid carpal tunnel which allows the median nerve and tendons of the anterior forearm muscles to be transmitted to the hand and fingers.

<span class="mw-page-title-main">Wrist</span> Part of the arm between the lower arm and the hand

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; (2) the wrist joint or radiocarpal joint, the joint between the radius and the carpus and; (3) the anatomical region surrounding the carpus including the distal parts of the bones of the forearm and the proximal parts of the metacarpus or five metacarpal bones and the series of joints between these bones, thus referred to as wrist joints. This region also includes the carpal tunnel, the anatomical snuff box, bracelet lines, the flexor retinaculum, and the extensor retinaculum.

The flexor digitorum profundus or flexor digitorum communis profundus is a muscle in the forearm of humans that flexes the fingers. It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.

<span class="mw-page-title-main">Flexor digitorum superficialis muscle</span> Forearm muscle that flexes the fingers

Flexor digitorum superficialis or flexor digitorum communis sublimis is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints.

<span class="mw-page-title-main">Ulnar nerve</span> Nerve which runs near the ulna bone

The ulnar nerve is a nerve that runs near the ulna, one of the two long bones in the forearm. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is common. This nerve is directly connected to the little finger, and the adjacent half of the ring finger, innervating the palmar aspect of these fingers, including both front and back of the tips, perhaps as far back as the fingernail beds.

<span class="mw-page-title-main">Metacarpal bones</span> Bones of hand

In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular bones that form the intermediate part of the hand between the phalanges (fingers) and the carpal bones, which articulate with the forearm. The metacarpal bones are homologous to the metatarsal bones in the foot.

<span class="mw-page-title-main">Upper limb</span> Consists of the arm, forearm, and hand

The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. In humans, each upper limb is divided into the shoulder, arm, elbow, forearm, wrist and hand, and is primarily used for climbing, lifting and manipulating objects. In anatomy, just as arm refers to the upper arm, leg refers to the lower leg.

In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together with this muscle.

<span class="mw-page-title-main">Palmar interossei muscles</span> Muscles between the metacarpals

In human anatomy, the palmar or volar interossei are four muscles, one on the thumb that is occasionally missing, and three small, unipennate, central muscles in the hand that lie between the metacarpal bones and are attached to the index, ring, and little fingers. They are smaller than the dorsal interossei of the hand.

<span class="mw-page-title-main">Dorsal interossei of the hand</span> Muscles between the metacarpals

In human anatomy, the dorsal interossei (DI) are four muscles in the back of the hand that act to abduct (spread) the index, middle, and ring fingers away from the hand's midline and assist in flexion at the metacarpophalangeal joints and extension at the interphalangeal joints of the index, middle and ring fingers.

<span class="mw-page-title-main">Abductor digiti minimi muscle of hand</span> Muscle in the hypothenar compartment

In human anatomy, the abductor digiti minimi is a skeletal muscle situated on the ulnar border of the palm of the hand. It forms the ulnar border of the palm and its spindle-like shape defines the hypothenar eminence of the palm together with the skin, connective tissue, and fat surrounding it. Its main function is to pull the little finger away from the other fingers.

<span class="mw-page-title-main">Interphalangeal joints of the hand</span> Hinge joints between finger phalanges

The interphalangeal joints of the hand are the hinge joints between the phalanges of the fingers that provide flexion towards the palm of the hand.

<span class="mw-page-title-main">Extensor indicis muscle</span> Forearm muscle which extends the index finger

In human anatomy, the extensor indicis (proprius) is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, and parallel with, the extensor pollicis longus. Its tendon goes to the index finger, which it extends.

<span class="mw-page-title-main">Interphalangeal joints of the foot</span> Hinge joints connecting the phalanx bones of each toe

The interphalangeal joints of the foot are the joints between the phalanx bones of the toes in the feet.

<span class="mw-page-title-main">Extensor expansion</span> Special connective attachments by which the extensor tendons insert into the phalanges

An extensor expansion is the special connective attachments by which the extensor tendons insert into the phalanges.

The posterior compartment of the forearm contains twelve muscles which primarily extend the wrist and digits. It is separated from the anterior compartment by the interosseous membrane between the radius and ulna.

<span class="mw-page-title-main">Hand</span> Extremity at the end of an arm or forelimb

A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala are often described as having "hands" instead of paws on their front limbs. The raccoon is usually described as having "hands" though opposable thumbs are lacking.

<span class="mw-page-title-main">Extrinsic extensor muscles of the hand</span>

The extrinsic extensor muscles of the hand are located in the back of the forearm and have long tendons connecting them to bones in the hand, where they exert their action. Extrinsic denotes their location outside the hand. Extensor denotes their action which is to extend, or open flat, joints in the hand. They include the extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor digitorum (ED), extensor digiti minimi (EDM), extensor carpi ulnaris (ECU), abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor pollicis longus (EPL), and extensor indicis (EI).

References

PD-icon.svgThis article incorporates text in the public domain from page 451 of the 20th edition of Gray's Anatomy (1918)

  1. Moore, Keith; Anne Agur (2007). Essential Clinical Anatomy, Third Edition. Lippincott Williams & Wilkins. pp. INSERT PAGE NUMBER. ISBN   978-0-7817-6274-8.
  2. 1 2 Green, Jennifer B.; Deveikas, Charles; Ranger, Helen E.; Draghetti, Joanne G.; Groat, Lindsay C.; Schumer, Evan D.; Leslie, Bruce M. (2016-01-01), Magee, David J.; Zachazewski, James E.; Quillen, William S.; Manske, Robert C. (eds.), "Chapter 10 - Hand, Wrist, and Digit Injuries", Pathology and Intervention in Musculoskeletal Rehabilitation (Second Edition), W.B. Saunders, pp. 344–435, ISBN   978-0-323-31072-7 , retrieved 2021-01-08
  3. exonicus.com. "Extensor digitorum longus". www.anatomynext.com. Archived from the original on 2018-11-27. Retrieved 2018-03-01.
  4. 1 2 3 Gray's anatomy (1918), see infobox
  5. Lopez-Ben, Robert; Lee, Donald H.; Nicolodi, Daniel J. (September 2003). "Boxer Knuckle (Injury of the Extensor Hood with Extensor Tendon Subluxation): Diagnosis with Dynamic US—Report of Three Cases". Radiology. 228 (3): 642–646. doi:10.1148/radiol.2283020833. PMID   12869687. Archived from the original on 2012-08-09. Retrieved 2012-04-02.
  6. "Clinical Example: Sagittal band rupture reconstruction". Eaton Hand. Retrieved 25 June 2011.