Extensor carpi radialis longus muscle
|Extensor carpi radialis longus|
|Superficial muscles of the forearm. Extensor carpi radialis longus visible in blue.|
|Transverse section across the wrist and digits. (Ext. carp. rad. long. labeled at center left.)|
|Latin||musculus extensor carpi radialis longus|
|Gray's||subject #125 452|
|Origin||lateral supracondylar ridge|
|Actions||extensor at the wrist joint, abducts the hand at the wrist|
|Antagonist||Flexor carpi ulnaris muscle|
Extensor carpi radialis longus is one of the five main muscles that control movements 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 (metacarpal of the index finger).
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 (radial abduction) 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 mid-position of the hand) and away from the palmar side (i.e., extension—increased angle between the palm and the front of the forearm).
Origin, course, and insertion
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.
One of the three muscles of the radial forearm group, it initially runs along with brachioradialis, but becomes mostly tendon early on. Passing between brachioradialis and extensor carpi radialis brevis, this tendon continues into the second tendon compartment together with the latter muscle.
The extensor carpi radialis longus is a wrist extensor that is innervated by the radial nerve. Though the radial nerve receives contributions from vertebrae levels C5, C6, C7, C8 and T1, studies have shown that the neurons that innervate the extensor carpi radialis longus arise from cervical vertebrae levels C6 and C7. All other major extensor muscles in the superficial layer of the posterior compartment (the Extensor Digitorum, Extensor Carpi Radialis Brevis, Extensor Carpi Ulnaris, and the Extensor Digiti Minimi) are innervated by the posterior interosseous branch of the radial nerve.
|This article relies largely or entirely upon a single source. (August 2009)|
- Platzer 2004, p 164
- Bradley Bowden, Illustrated Atlas of the Skeletal Muscles, 2005
- Platzer, Werner (2004). Color Atlas of Human Anatomy, Vol. 1: Locomotor System (5th ed.). Thieme. ISBN 3-13-533305-1.