Extensor carpi radialis longus:
Extensor carpi radialis longus is one of the five main muscles that control movement at the wrist. This muscle is quite long, starting on the lateral side of the humerus, and attaching to the base of the second metacarpal bone of the index finger.
It initially runs along with brachioradialis, but becomes mostly tendon early on, running between brachioradialis and extensor carpi radialis brevis.
[edit] Function
As the name suggests, this muscle is an extensor at the wrist joint, and travels along the radial side of the arm, so will also abduct the hand at the wrist. That is, it manipulates the wrist so as to move the hand towards the thumb (i.e., abduction—away from the midline of the body) and away from the palm (i.e., extension—increased angle between the palm and the front of the forearm).
[edit] Origin and insertion
It originates from the lower third of the lateral supracondylar ridge of the humerus, from the lateral intermuscular septum, and by a few fibers from the lateral epicondyle of the humerus.
The fibres end at the upper third of the forearm in a flat tendon, which runs along the lateral border of the radius, beneath the Abductor pollicis longus and Extensor pollicis brevis; it then passes beneath the dorsal carpal ligament, where it lies in a groove on the back of the radius common to it and the Extensor carpi radialis brevis, immediately behind the styloid process. It is inserted into the dorsal surface of the base of the second metacarpal bone, on its radial side.
[edit] Innervation
Being an extensor contained in the forearm, it is innervated by the radial nerve.
[edit] Exercises
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 performed.
[edit] Additional images
Bones of left forearm. Posterior aspect.
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Bones of the left hand. Dorsal surface.
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Tendons of forefinger and vincula tendina.
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Cross-section through the middle of the forearm.
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Posterior surface of the forearm. Deep muscles.
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Transverse section across distal ends of radius and ulna.
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The mucous sheaths of the tendons on the back of the wrist.
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[edit] External links
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