Extensor Pollicis Longus Muscle

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

**Definition:** A muscle in the posterior forearm that originates from the posterior surface of the middle third of the ulna and the adjacent interosseous membrane and attaches to the posterior surface of the base of distal phalanx of the thumb; it functions to extend the thumb at the metacarpophalangeal and interphalangeal joints and extend and abduct the wrist joint.

**Synonyms:** - EXTENSOR POLLICIS LONGUS MUSCLE