human anatomy The human body is the structure of a human being. It is composed of many different types of cells that together create tissues and subsequently organ systems. They ensure homeostasis and the viability of the human body. It comprises a he ...

, the extensor pollicis longus muscle (EPL) is a

skeletal muscle Skeletal muscles (commonly referred to as muscles) are 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 types of muscl ...

located dorsally on 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 anat ...

. It is much larger than the

extensor pollicis brevis In human anatomy, the extensor pollicis brevis is a skeletal muscle on the dorsal side of the forearm. It lies on the medial side of, and is closely connected with, the abductor pollicis longus. The extensor pollicis brevis (EPB) belongs to the ...

, the origin of which it partly covers and acts to stretch the

thumb The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...

together with this muscle.

Structure

The extensor pollicis longus arises from the dorsal surface of the

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

and from the

interosseous membrane An interosseous membrane is a thick dense fibrous sheet of connective tissue that spans the space between two bones, forming a type of syndesmosis joint. Interosseous membranes in the human body: * Interosseous membrane of forearm * Interosseou ...

, next to the origins of

abductor pollicis longus In human anatomy, the abductor pollicis longus (APL) is one of the extrinsic muscles of the hand. Its major function is to abduct the thumb at the wrist. Its tendon forms the anterior border of the anatomical snuffbox. Structure The abductor p ...

and

. Passing through the third tendon compartment, lying in a narrow, oblique groove on the back of the lower end of the

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

,''

Gray's Anatomy ''Gray's Anatomy'' is a reference book of human anatomy written by Henry Gray, illustrated by Henry Vandyke Carter, and first published in London in 1858. It has gone through multiple revised editions and the current edition, the 42nd (Octob ...

'' 1918, see infobox it crosses the wrist close to the dorsal midline before turning towards the thumb using

Lister's tubercle Lister's tubercle or dorsal tubercle of radius is a bony prominence located at the Anatomical terms of location, distal end of the radius (bone), radius. It is Palpation, palpable on the dorsum (anatomy)#human anatomy, dorsum of the wrist. Struct ...

on the distal end of the

as a pulley. It obliquely crosses the tendons of the extensores carpi radialis longus and brevis, and is separated from the

by a triangular interval, the

anatomical snuff box The anatomical snuff box or snuffbox or foveola radialis is a triangular deepening on the radial, dorsal aspect of the hand—at the level of the carpal bones, specifically, the scaphoid and trapezium bones forming the floor. The name originates ...

in which the

radial artery In human anatomy, the radial artery is the main artery of the lateral aspect of the forearm. Structure The radial artery arises from the bifurcation of the brachial artery in the antecubital fossa. It runs distally on the anterior part of the f ...

is found. At the proximal phalanx, the tendon is joined by expansions from

abductor pollicis brevis The abductor pollicis brevis is a muscle in the hand that functions as an abductor of the thumb. Structure The abductor pollicis brevis is a flat, thin muscle located just under the skin. It is a thenar muscle, and therefore contributes to the ...

and

adductor pollicis In human anatomy, the adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb. It has two heads: transverse and oblique. It is a fleshy, flat, triangular, and fan-shaped muscle deep in the thenar compartment beneath ...

. The tendon is finally inserted on the base of the

distal phalanx The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...

of the thumb. in length, the tendon passes through a long and superficial synovial sheath which, passing obliquely from the radial border of the forearm into the thumb, extends from the proximal border of the extensor retinaculum to the first carpometacarpal joint. In the synovial sheath a proximal and a distal

mesotendon In anatomy, a vinculum (pl. vincula) is a band of connective tissue, similar to a ligament, that connects a flexor tendon to a phalanx bone. They contain tiny vessels which supply blood to the tendon. In vertebrate anatomy, they are referred to a ...

connect the tendon to the floor of the sheath.

Relations

Together with the tendons of the extensor pollicis brevis and the

, its tendon crosses the

Blood supply

The tendon of extensor pollicis longus is supplied by branches from various arteries. Before the tendon enters its synovial sheath, arteries from the

anterior interosseous artery The anterior interosseous artery (volar interosseous artery) is an artery in the forearm. It is a branch of the common interosseous artery. Course It passes down the forearm on the palmar surface of the interosseous membrane. It is accompanied ...

or its muscular branches enter the tendon. The sheath itself is supplied by the posterior ramus of the same artery. In the metacarpal region, beyond the synovial sheath, the tendon is supplied directly from the

. At the phalanges, the tendon forms a dorsal aponeurosis which is supplied by a digital branch of the first dorsal metacarpal artery.

Innervation

The extensor pollicis longus muscle receives innervation from the

posterior interosseous nerve The posterior interosseous nerve (or dorsal interosseous nerve) is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared ...

(C7 and C8) which is the continuation of the deep branch of the radial nerve.

Function

Extensor pollicis longus extends the terminal phalanx of the thumb. While abductor pollicis brevis and adductor pollicis, both attached to the extensor pollicis longus tendon, can extend the thumb's interphalangeal joint to the neutral position, only extensor pollicis longus can achieve full hyperextension at the interphalangeal joint. This complete extension at the interphalangeal joint is not possible, or considerably more difficult, with the carpal, carpometacarpal, and metacarpophalangeal joints simultaneously extended. Likewise, flexion at the interphalangeal joint by

flexor pollicis longus The flexor pollicis longus (; FPL, Latin ''flexor'', bender; ''pollicis'', of the thumb; ''longus'', long) is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus. This muscle is uniqu ...

is considerably reduced in wrist flexion. It also applies an extensor force at the metacarpophalangeal joint together with the extensor pollicis brevis and extends and adducts at the carpometacarpal joint of the thumb.

Clinical significance

Injury

Tenosynovitis Tenosynovitis is the inflammation of the fluid-filled sheath (called the synovium) that surrounds a tendon, typically leading to joint pain, swelling, and stiffness. Tenosynovitis can be either infectious or noninfectious. Common clinical manifest ...

, inflammatory irritation of the synovial sheath, is relatively common in the third compartment after repetitive activities such as drum playing.

Additional images

Notes

References

* * * * {{Authority control Muscles of the upper limb