In human anatomy, the extensor pollicis brevis is a skeletal muscle on the dorsal side of 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 ...

. It lies on the medial side of, and is closely connected with, the

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 ...

. The extensor pollicis brevis (EPB) belongs to the deep group of the posterior fascial compartment of the forearm. It is a part of the lateral border of the anatomical snuffbox.

Structure

The extensor pollicis brevis arises from 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 ...

distal to the

, from the interosseous membrane, and from the dorsal surface 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 ...

. Its direction is similar to that of the abductor pollicis longus, its tendon passing the same groove on the lateral side of the lower end of the radius, to be inserted into the base of the first phalanx of the thumb.

Variation

Absence; fusion of tendon with that of the extensor pollicis longus or abductor pollicis longus muscle.

Function

In a close relationship to the abductor pollicis longus, the extensor pollicis brevis both extends and abducts the thumb at the carpometacarpal and

metacarpophalangeal joint The metacarpophalangeal joints (MCP) are situated between the metacarpal bones and the proximal phalanges of the fingers. These joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow ca ...

Structure

Variation

Function

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References

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