The extensor pollicis longus is a muscle within the deep compartment of the posterior forearm.
The tendon of the extensor pollicis longus passes through the 3rd extensor compartment at the wrist, where it forms the ulnar border of the anatomical snuffbox.
- Attachments: Originates from the posterior surface of the ulna and interosseous membrane. It attaches to the base of the distal phalanx of the thumb.
- Actions: Extension at the interphalangeal, metacarpophalangeal and carpometacarpal joints of the thumb.
- Innervation: Radial nerve (posterior interosseous branch).
- Blood supply: Ulnar artery
