Extensor pollicis longus muscle

Extensor pollicis longus muscle is a skeletal muscle in the forearm that extends the thumb. It is much larger than the Extensor pollicis brevis, the muscle that assists this action. The extensor pollicis longus controls the movement of the thumb and contributes to the hand's ability to grasp objects.

Etymology

The term "extensor pollicis longus" is derived from Latin, with "extensor" meaning "to stretch out", "pollicis" referring to "of the thumb", and "longus" indicating "long". This name describes the muscle's function, location, and relative size.

Anatomy

The extensor pollicis longus originates from the middle third of the posterior surface of the ulna and the interosseous membrane. It runs through the third tendon compartment and forms a tendon that passes through the Lister's tubercle on the dorsal side of the radius' lower end. This tendon then crosses the Extensor pollicis brevis' tendon and inserts into the base of the distal phalanx of the thumb.

Function

The extensor pollicis longus extends the thumb at all joints. This includes the carpometacarpal joint, the metacarpophalangeal joint, and the interphalangeal joint. It also assists in wrist abduction, moving the wrist away from the body's midline.

Clinical significance

Injury to the extensor pollicis longus can result in a condition known as "drop thumb". This is characterized by an inability to extend the thumb, which can significantly impact hand function. Treatment typically involves surgery to repair the damaged muscle or tendon.

Related terms

• Extensor pollicis brevis: A muscle in the forearm that assists the extensor pollicis longus in extending the thumb.
• Ulna: One of the two long bones in the forearm, from which the extensor pollicis longus originates.
• Lister's tubercle: A bony prominence on the dorsal side of the radius, through which the extensor pollicis longus tendon passes.