| Extensor pollicis longus muscle | |
|---|---|
 Posterior surface of the forearm. Deep muscles. Extensor pollicis longus muscle is labeled in purple. | |
| Details | |
| Origin | Middle third of posterior surface ofulna,interosseous membrane |
| Insertion | Thumb,distal phalanx |
| Artery | Posterior interosseous artery |
| Nerve | Posterior interosseous nerve (branching from theradial nerve) |
| Actions | Extension of thethumb (metacarpophalangeal andinterphalangeal) |
| Antagonist | Flexor pollicis longus muscle,flexor pollicis brevis muscle |
| Identifiers | |
| Latin | musculus extensor pollicis longus |
| TA98 | A04.6.02.051 |
| TA2 | 2516 |
| FMA | 38521 |
| Anatomical terms of muscle | |
Inhuman anatomy, theextensor pollicis longus muscle (EPL) is askeletal muscle located dorsally on theforearm. It is much larger than theextensor pollicis brevis, the origin of which it partly covers and acts to stretch thethumb together with this muscle.
The extensor pollicis longus arises from the dorsal surface of theulna and from theinterosseous membrane,[1] next to the origins ofabductor pollicis longus andextensor pollicis brevis.[2]
Passing through the third tendon compartment,[1] lying in a narrow, oblique groove on the back of the lower end of theradius,[3] it crosses the wrist close to the dorsal midline before turning towards the thumb usingLister's tubercle on the distal end of theradius as a pulley.[2]
It obliquely crosses the tendons of theextensores carpi radialis longus andbrevis, and is separated from theextensor pollicis brevis by a triangular interval, theanatomical snuff box in which theradial artery is found.[3]
At the proximal phalanx, the tendon is joined by expansions fromabductor pollicis brevis andadductor pollicis.[2]
The tendon is finally inserted on the base of thedistal phalanx of the thumb.[1]
6.7 to 9.7 centimetres (2.6 to 3.8 in) in length, the tendon passes through a long and superficialsynovial sheath which, passing obliquely from the radial border of the forearm into the thumb, extends from the proximal border of theextensor retinaculum to the first carpometacarpal joint. In the synovial sheath a proximal and a distalmesotendon connect the tendon to the floor of the sheath.[4]
Together with the tendons of the extensor pollicis brevis and theabductor pollicis longus, its tendon crosses theradial artery.[3]
The tendon of extensor pollicis longus is supplied by branches from various arteries. Before the tendon enters its synovial sheath, arteries from theanterior interosseous artery or its muscular branches enter the tendon. The sheath itself is supplied by the posterior ramus of the same artery. In the metacarpal region, beyond the synovial sheath, the tendon is supplied directly from theradial artery. At the phalanges, the tendon forms a dorsal aponeurosis which is supplied by a digital branch of the firstdorsal metacarpal artery.[4]
The extensor pollicis longus muscle receives innervation from theposterior interosseous nerve (C7 and C8) which is the continuation of the deep branch of the radial nerve.
Extensor pollicis longus extends the terminal phalanx of the thumb. While abductor pollicis brevis and adductor pollicis, both attached to the extensor pollicis longus tendon, can extend the thumb's interphalangeal joint to the neutral position, only extensor pollicis longus can achieve full hyperextension at the interphalangeal joint. This complete extension at the interphalangeal joint is not possible, or considerably more difficult, with the carpal, carpometacarpal, and metacarpophalangeal joints simultaneously extended. Likewise, flexion at the interphalangeal joint byflexor pollicis longus is considerably reduced in wrist flexion.[2]
It also applies an extensor force at the metacarpophalangeal joint together with the extensor pollicis brevis and extends and adducts at the carpometacarpal joint of the thumb.[2]
Tenosynovitis, inflammatory irritation of the synovial sheath, is relatively common in the third compartment after repetitive activities such as drum playing.[5]
This article incorporates text in thepublic domain frompage 455 of the 20th edition ofGray's Anatomy(1918)
