Brachialis muscle

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Deep muscles of the chest and front of the arm, with the boundaries of the axilla. (Brachialis visible at bottom right.)
Brachialis muscle11.png
Position of brachialis (shown in red).
Latin musculus brachialis
Gray's p.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 (C5, C6)
Actions flexion at elbow joint
Anatomical terms of muscle

The brachialis (brachialis anticus) is a muscle in the upper arm that flexes the elbow joint. It lies deeper than 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.


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.


The muscle is occasionally doubled; additional nip to the supinator, pronator teres, biceps brachii, lacertus fibrosus, or radius are more rarely found.


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 (proprioceptive branch) 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.


Unlike the biceps, the brachialis does not insert on the radius, and therefore cannot participate in pronation and supination of the forearm. It flexes the elbow joint.



The brachialis muscle [1] and brachial muscle [2] can be considered as the anglicized variant of the Latin expression musculus bracchialis.[3] In classical Latin bracchialis means of or belonging to the arm,[4] and is derived from classical Latin bracchium,"arm".[4] The spelling brachium is less correct,[4] and bracchialis is preferred above brachialis.[4] The expression musculus brachialis is however used in the current official anatomic nomenclature Terminologia Anatomica.[5]

Although bracchium in general can refer to the arm,[4] more specifically it can refer to the forearm.[6][7] Latin encyclopedist Aulus Cornelius Celsus defined the bracchium as: "constat ex ossibus duobos, quae sunt radius et cubitus",[6] (consists of two bones, that are the radius and the ulna) with cubitus in the nomenclature of Celsus referring to the ulna.[6] Confusingly the brachialis muscle actually more resides at the upperarm than at the forearm.

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  4. ^ a b c d e Lewis, C.T. & Short, C. (1879). A Latin dictionary founded on Andrews' edition of Freund's Latin dictionary. Oxford: Clarendon Press.

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