Extensor pollicis muscle

Extensor Pollicis Muscles

The extensor pollicis muscles, shown in red. Image from Gray's Anatomy.

The extensor pollicis muscles are a group of muscles in the human hand that are responsible for the extension of the thumb. They are part of the deep posterior compartment of the forearm and are primarily involved in the fine motor control of the thumb.

Anatomy

The extensor pollicis muscles consist of two individual muscles: the extensor pollicis longus muscle and the extensor pollicis brevis muscle. Both muscles originate from the ulna and interosseous membrane, and insert into the base of the thumb.

The extensor pollicis longus and brevis muscles, shown in red. Image from Gray's Anatomy.

Extensor Pollicis Longus

The extensor pollicis longus originates from the middle third of the posterior surface of the ulna and the interosseous membrane. It extends the thumb at all joints and assists in wrist abduction.

Extensor Pollicis Brevis

The extensor pollicis brevis originates from the posterior surface of the radius and the interosseous membrane. It extends the thumb at the metacarpophalangeal joint.

Function

The primary function of the extensor pollicis muscles is to extend the thumb. This action is crucial for many hand movements, including gripping, pinching, and manipulation of objects.

Clinical Significance

Damage to the extensor pollicis muscles can result in a condition known as De Quervain's tenosynovitis, which is characterized by pain and swelling in the thumb and wrist.

See Also

• List of muscles of the human body
• Hand anatomy
• Muscular system