Extensor pollicis longus muscle
Origin and insertion
It ends in a tendon, which passes through a separate compartment in the dorsal carpal ligament, lying in a narrow, oblique groove on the back of the lower end of the radius.
It then crosses obliquely the tendons of the Extensores carpi radialis longus and brevis, and is separated from the Extensor brevis pollicis by a triangular interval, the anatomical snuff box in which the radial artery is found; and is finally inserted into the base of the last phalanx of the thumb.
The extends the proximal phalanx, and the
Posterior surface of the forearm. Deep muscles.