Extensor carpi radialis brevis

Extensor carpi radialis brevis
Posterior surface of the left forearm. Superficial muscles. The partially obscured extensor carpi radialis brevis is shown in blue.
Details
Origin	humerus at the anterior of lateral epicondyle (common extensor tendon)
Insertion	Posterior base of the 3rd metacarpal
Artery	radial artery
Nerve	deep branch of the radial nerve
Actions	extensor and abductor of the hand at the wrist joint
Antagonist	Flexor carpi ulnaris muscle
Identifiers
Latin	musculus extensor carpi radialis brevis
TA	A04.6.02.041
FMA	38497
Anatomical terms of muscle []

In human anatomy, extensor carpi radialis brevis (Beaver muscle) is a muscle in the forearm that acts to extend and abduct the wrist. It is shorter and thicker than its namesake extensor carpi radialis longus which can be found above the proximal end of the extensor carpi radialis brevis.

It arises from the lateral epicondyle of the humerus, by the common extensor tendon; from the radial collateral ligament of the elbow-joint; from a strong aponeurosis which covers its surface; and from the intermuscular septa between it and the adjacent muscles.

The fibres end approximately at the middle of the forearm in the form of a flat tendon, which is closely connected with that of the extensor carpi radialis longus, and accompanies it to the wrist; it passes beneath the abductor pollicis longus and extensor pollicis brevis, beneath the extensor retinaculum, and inserts into the lateral dorsal surface of the base of the third metacarpal bone, with a few fibres inserting into the medial dorsal surface of the second metacarpal bone.

Under the extensor retinaculum the tendon lies on the back of the radius in a shallow groove, to the ulnar side of that which lodges the tendon of the extensor carpi radialis longus, and separated from it by a faint ridge.

Like all the muscles in the posterior forearm, ECR brevis is supplied by a branch of the radial nerve.

It is an extensor, and an abductor of the hand at the wrist joint. That is, it serves to manipulate the wrist so that the hand moves away from the palm and towards the thumb. The muscle, like all extensors of the forearm, can be strengthened by exercise that resist its extension. A wrist roller can be used and reverse wrist curls with dumbbells can be performed.