Audio LecturePro Feature Extensor Pollicis Longus 0:00 / 0:00 1x 0.25x 0.5x 0.75x 1x 1.25x 1.5x 1.75x 2x 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 By TeachMeSeries Ltd (2026) Fig 1Muscles in the deep layer of the posterior forearm. 3D ModelPro Feature You've Discovered a Pro Feature Access our 3D Model Library Explore, cut, dissect, annotate and manipulate our 3D models to visualise anatomy in a dynamic, interactive way. Learn More Dissection AtlasPro Feature Borders and contents of the anatomical snuffbox Borders and contents of the anatomical snuffbox You've Discovered a Pro Feature Access our Dissection Image Library Enhance your understanding with high-resolution dissection images showcasing real-life anatomy. Learn More In gratitude to our body donorsLearn more In gratitude to our body donors We are deeply grateful to the individuals who chose to donate their bodies for the advancement of medical education. Their generosity makes these images possible and provides students and healthcare professionals with an invaluable opportunity to study human anatomy. We recognise the profound contribution made by each donor and their families, and we use these images with the dignity and respect their gift deserves. Acknowledge Frequent questions What is the extensor pollicis longus muscle? The extensor pollicis longus is a muscle located in the deep compartment of the posterior forearm, responsible for extending the thumb at various joints. Where does the extensor pollicis longus originate and attach? This muscle originates from the posterior surface of the ulna and the interosseous membrane, attaching to the base of the distal phalanx of the thumb. What actions does the extensor pollicis longus perform? The extensor pollicis longus facilitates extension at the interphalangeal, metacarpophalangeal, and carpometacarpal joints of the thumb. Which nerve innervates the extensor pollicis longus? The extensor pollicis longus is innervated by the radial nerve, specifically its posterior interosseous branch. What is the blood supply for the extensor pollicis longus? The blood supply to the extensor pollicis longus muscle is primarily provided by the ulnar artery. Rate This Article