The extensor carpi radialis longus is one of the five main

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

s that control movements at the wrist. This muscle is quite long, starting on the lateral side of the

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

, and attaching to the base of the second metacarpal bone (metacarpal of the index finger).

Structure

It originates from the

lateral supracondylar ridge The lateral supracondylar ridge is a prominent, rough margin on the lower part of the lateral border of the humerus. It presents an anterior lip for the origin of forearm extensors, including the brachioradialis muscle above, and the extensor carp ...

of the

, from the lateral intermuscular septum, and by a few fibers from the lateral epicondyle of the humerus. The fibers 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 lies beside the brachioradialis, but becomes mostly tendon early on. Passing between the brachioradialis and the extensor carpi radialis brevis, this tendon continues into the second tendon compartment together with the latter muscle. It is inserted into the dorsal surface of the base of the second metacarpal bone, on its radial side.

Innervation

The extensor carpi radialis longus is a wrist extensor that is innervated by the

radial nerve The radial nerve is a nerve in the human body that supplies the posterior portion of the upper limb. It innervates the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial comp ...

, from spinal roots C6 and C7.Bradley Bowden, Illustrated Atlas of the Skeletal Muscles, 2005 All other major extensor muscles in the superficial layer of the posterior compartment (the extensor digitorum, extensor carpi radialis brevis, extensor carpi ulnaris, and extensor digiti minimi) are innervated by the posterior interosseous branch of the radial nerve.

Function

As the name suggests, this muscle is an extensor at the wrist joint and travels along the radial side of the arm, so it 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 The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position (where the palm is facing to the front), the thumb is the outermost digit. The Medical Latin English noun for thumb ...

(i.e.

abduction Abduction may refer to: Media Film and television * "Abduction" (''The Outer Limits''), a 2001 television episode * " Abduction" (''Death Note'') a Japanese animation television series * " Abductions" (''Totally Spies!''), a 2002 episode of an ...

—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).

Exercises

The muscle, like all extensors of the forearm, can be strengthened by exercise that resist its extension.

Structure

Innervation

Function

Exercises

Example exercises

Additional images

Notes

References