Extensor Pollicis Brevis Muscle

**Semantic type:** Body Part, Organ, or Organ Component

**Definition:** A muscle in the posterior forearm that originates from the posterior surface of distal third of radius and the adjacent interosseous membrane and attaches to the posterior surface of the base of the proximal phalanx of the thumb; it functions to extend the thumb at the carpometacarpal and metacarpophalangeal joints.

**Synonyms:** - EXTENSOR POLLICIS BREVIS MUSCLE