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 mus ...

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 carp ...

. 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 r ...

, 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 metacarpal bones.''Gray's Anatomy'' (1918). See infobox. Human anatomy Its base is prolonged upward and medialward, forming a ...

(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 mid ...

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 car ...

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 (plural, : radii) 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 name comes from the latin ''radius'', ...

, beneath the

abductor pollicis longus In human anatomy, the abductor pollicis longus (APL) is one of the extrinsic muscles of the hand. Its major function is to abduct the thumb at the wrist. Its tendon forms the anterior border of the anatomical snuffbox. Structure The abductor ...

and

extensor pollicis brevis In human anatomy, the extensor pollicis brevis 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 (EPB) belongs to the ...

; it then passes beneath the

dorsal carpal ligament The extensor retinaculum (dorsal carpal ligament, or posterior annular ligament) is an anatomical term for the thickened part of the antebrachial fascia that holds the tendons of the extensor muscles in place. It is located on the back of the fore ...

, 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 exten ...

, 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 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 The extensor digitorum muscle (also known as extensor digitorum communis) is a muscle of the posterior forearm present in humans and other animals. It extends the medial four digits of the hand. Extensor digitorum is innervated by the posterior int ...

extensor carpi ulnaris In human anatomy, the extensor carpi ulnaris is a skeletal muscle located on the ulnar side of the forearm. The extensor carpi ulnaris acts to extend and adduct at the carpus/wrist from anatomical position. Being an extensor muscle, extensor carp ...

, 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 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 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 Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * Ext ...

—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 can be used individually or in pairs, with one in each hand. History The forerunner of the dumbbell, halteres, were used in ancient Greece as lifting ...

Structure

Innervation

Function

Exercises

Example exercises

Additional images

Notes

References