Brachioradialis
Encyclopedia
Brachioradialis is a muscle
of the forearm
that acts to flex 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 of the brachioradialis tendon, and to the lateral supracondylar ridge
of the humerus
.
The brachioradialis is a stronger elbow flexor when the forearm is in a midposition between supination and pronation at the radioulnar joint. When pronated, the brachioradialis is more active during elbow flexion since the biceps brachii
is in a mechanical disadvantage.
With the insertion of the muscle so far from the fulcrum of the elbow, the brachioradialis does not generate as much force as the brachialis or the biceps. It is effective mainly when those muscles have already partially flexed at the elbow. The brachioradialis flexes the forearm at the elbow, especially when quick movement is required and when a weight is lifted during slow flexion of the forearm.
The muscle is used to stabilize the elbow during rapid flexion and extension while in a midposition, such as in hammering. The brachioradialis is synergistic with the brachialis and biceps brachii; the triceps brachii and anconeus are antagonistic.
. Of the muscles that receive innervation from the radial nerve, it is one of only four that receive input directly from the radial nerve. The other three are the triceps
, anconeus
, and extensor carpi radialis longus. (All other posterior compartment muscles that receive radial innervation are supplied by the deep branch of the radial nerve
.)
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
of the forearm
Forearm
-See also:*Forearm flexors*Forearm muscles...
that acts to flex the forearm at the elbow
Elbow
The human elbow is the region surrounding the elbow-joint—the ginglymus or hinge joint in the middle of the arm. Three bones form the elbow joint: the humerus of the upper arm, and the paired radius and ulna of the forearm....
. It is also capable of both pronation
Pronation
In anatomy, pronation is a rotational movement of the forearm at the radioulnar joint, or of the foot at the subtalar and talocalcaneonavicular joints. For the forearm, when standing in the anatomical position, pronation will move the palm of the hand from an anterior-facing position to a...
and supination
Supination
Supination is a position of either the forearm or foot; in the forearm when the palm faces anteriorly, or faces up . Supination in the foot occurs when a person appears "bow-legged" with their weight supported primarily on the anterior of their feet.The hand is supine in the anatomical position...
, depending on the position of the forearm. It is attached to the distal styloid process of the radius
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
by way of the brachioradialis tendon, and to the lateral supracondylar ridge
Lateral supracondylar ridge
The lower part of the lateral border of the body of the humerus forms a prominent, rough margin, a little curved from behind forward, the lateral supracondylar ridge , which presents an anterior lip for the origin of the Brachioradialis above, and Extensor carpi radialis longus below, a posterior...
of the humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
.
Action
Brachioradialis flexes the forearm at the elbow. When the forearm is pronated, the brachioradialis tends to supinate as it flexes. In a supinated position, it tends to pronate as it flexes.The brachioradialis is a stronger elbow flexor when the forearm is in a midposition between supination and pronation at the radioulnar joint. When pronated, the brachioradialis is more active during elbow flexion since the biceps brachii
Biceps brachii muscle
In human anatomy, the biceps brachii, or simply biceps in common parlance, is, as the name implies, a two-headed muscle located on the upper arm. Both heads arise on the scapula and join to form a single muscle belly which is attached to the upper forearm...
is in a mechanical disadvantage.
With the insertion of the muscle so far from the fulcrum of the elbow, the brachioradialis does not generate as much force as the brachialis or the biceps. It is effective mainly when those muscles have already partially flexed at the elbow. The brachioradialis flexes the forearm at the elbow, especially when quick movement is required and when a weight is lifted during slow flexion of the forearm.
The muscle is used to stabilize the elbow during rapid flexion and extension while in a midposition, such as in hammering. The brachioradialis is synergistic with the brachialis and biceps brachii; the triceps brachii and anconeus are antagonistic.
Innervation
Despite the bulk of the muscle body being visible from the anterior aspect of the forearm, the brachioradialis is a posterior compartment muscle and consequently is innervated by the radial nerveRadial nerve
The radial nerve is a nerve in the human body that supplies the upper limb. It supplies the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin.It...
. Of the muscles that receive innervation from the radial nerve, it is one of only four that receive input directly from the radial nerve. The other three are the triceps
Triceps brachii muscle
The triceps brachii muscle is the large muscle on the back of the upper limb of many vertebrates. It is the muscle principally responsible for extension of the elbow joint .-Terminology:...
, anconeus
Anconeus muscle
The anconeus muscle is a small muscle on the posterior aspect of the elbow joint.Some consider anconeus to be a continuation of the triceps brachii muscle...
, and extensor carpi radialis longus. (All other posterior compartment muscles that receive radial innervation are supplied by the deep branch of the radial nerve
Deep branch of the radial nerve
The deep branch of the radial nerve winds to the back of the forearm around the lateral side of the radius between the two planes of fibers of the Supinator, and is prolonged downward between the superficial and deep layers of muscles, to the middle of the forearm.Considerably diminished in size,...
.)