The Extensor pollicis longus (Extensor secundi internodii pollicis) is much larger than the Extensor pollicis brevis muscle, the origin of which it partly covers.

It arises from the lateral part of the middle third of the dorsal surface of the body of the ulna below the origin of the Abductor pollicis longus, and from the interosseous membrane.

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, in which the radial artery is found; and is finally inserted into the base of the last phalanx of the thumb.

The radial artery is crossed by the tendons of the Abductor pollicis longus and of the Extensores pollicis longus and brevis.

External links

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Muscles of the upper limb | Musculus extensor pollicis longus | Muscle long extenseur du pouce | Extensor pollicis longus