The extensor carpi radialis longus is one of the five main

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

s that control movements at the

wrist In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...

. This muscle is quite long, starting on the lateral side of the

humerus The humerus (; : humeri) 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 (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

, and attaching to the base of the

second metacarpal bone The second metacarpal bone (metacarpal bone of the index finger) is the longest, and its base the largest, of all the Metacarpus, metacarpal bones.''Gray's Anatomy'' (1918). See infobox. Human anatomy Its base is prolonged upward and medialwar ...

(metacarpal of the

index finger The index finger (also referred to as forefinger, first finger, second finger, pointer finger, trigger finger, digitus secundus, digitus II, and many other terms) is the second digit of a human hand. It is located between the thumb and the m ...

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 ca ...

of the

, from the lateral intermuscular septum, and by a few fibers from the

lateral epicondyle of the humerus The lateral epicondyle of the humerus is a large, tuberculated eminence, curved a little forward, and giving attachment to the radial collateral ligament of the elbow joint, and to a tendon common to the origin of the supinator and some of the e ...

. The fibers end at the upper third of the forearm in a flat tendon, which runs along the lateral border of the

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

, beneath the abductor pollicis longus and

extensor pollicis brevis In human anatomy, the extensor pollicis brevis (EPB) is a skeletal muscle on the dorsal side of the forearm. It lies on the medial side of, and is closely connected with, the abductor pollicis longus. The extensor pollicis brevis belongs to t ...

; 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 In human anatomy, extensor carpi radialis brevis 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 ext ...

, immediately behind the styloid process. One of the three muscles of the radial forearm group, it initially lies beside the

brachioradialis The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way ...

, but becomes mostly tendon early on. Passing between the brachioradialis and the

, 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

, 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 compartment of the ...

, 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 ulnaris, and

extensor digiti minimi The extensor digiti minimi (extensor digiti quinti proprius) is a slender muscle of the forearm, placed on the ulnar side of the extensor digitorum communis, with which it is generally connected. It arises from the common extensor tendon by a t ...

) 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 A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

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—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.

Example exercises

* Reverse wrist curls with

dumbbell The dumbbell, a type of free weight, is a piece of equipment used in weight training. It is usually used individually and/or in pairs, with one in each hand. History The forerunner of the dumbbell, halteres, were used in ancient Greece as li ...

Structure

Innervation

Function

Exercises

Example exercises

Additional images

Notes

References