Brachialis.html



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Brachialis
Deep muscles of the chest and front of the arm, with the boundaries of the axilla. (Brachialis visible at bottom right.)
Cross-section through the middle of upper arm. (Brachialis labeled at center left.)
Latin	musculus brachialis
Gray's	subject #124 444
Origin	anterior surface of the humerus, particularly the distal half of this bone
Insertion	coronoid process and the tuberosity of the ulna
Artery	radial recurrent artery
Nerve	musculocutaneous nerve
Action	flexion at elbow joint

The brachialis (brachialis anticus) is a muscle in the upper arm that flexes the elbow joint. It lies just deep of the biceps brachii, and is a synergist that assists the biceps brachii in flexing at the elbow. It makes up part of the floor of the region known as the cubital fossa.

Origin and insertion

The brachialis originates from the lower half of the front of the humerus, near the insertion of the deltoid muscle, which it embraces by two angular processes. Its origin extends below to within 2.5 cm of the margin of the articular surface of the humerus at the elbow joint. It also arises from the intermuscular septa of the arm, but more extensively from the medial than the lateral; it is separated from the lateral below by the brachioradialis and extensor carpi radialis longus muscles.

Its fibers converge to a thick tendon, which is inserted into the tuberosity of the ulna and the rough depression on the anterior surface of the coronoid process of the ulna.

Innervation

The brachialis muscle is innervated by the musculocutaneous nerve, which runs on its superficial surface, between it and the biceps brachii. Part of it is also innervated by the radial nerve which allows it to be split during certain approaches to the arm. The divide between the two innervations is at the insertion of the deltoid.

Actions

The brachialis is the strongest flexor of the elbow. Unlike the biceps, the brachialis does not insert on the radius, and therefore cannot participate in pronation/supination of the forearm.

Pronation/supination of the forearm does not affect its action.

Variations

Occasionally doubled; additional slips to the supinator, pronator teres, biceps brachii, lacertus fibrosus, or radius are more rarely found.

Additional images

Left humerus. Anterior view.

Bones of left forearm. Anterior aspect.

Nerves of the left upper extremity.

External links

• LUC brac
• UWASH brachialis
• -1777991623 at GPnotebook
• Muscles/Brachialis at exrx.net

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.