Deep muscles of the chest and front of the arm, with the boundaries of the axilla. (Brachialis visible at bottom right.)
Position of brachialis (shown in red).
|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.
The muscle is occasionally doubled; additional slips to the supinator, pronator teres, biceps brachii, lacertus fibrosus, or radius are more rarely found. (A "slip" in this context refers to an accessory or variant part of a muscle that has an unusual trajectory in growth relative to the normal fibers' direction of growth.)
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.
The brachialis muscle  and brachial muscle  can be considered as the anglicized variant of the Latin expression musculus bracchialis. In classical Latin bracchialis means of or belonging to the arm, and is derived from classical Latin bracchium,"arm". The expression musculus brachialis is used in the current official anatomic nomenclature Terminologia Anatomica.
Horizontal section through the middle of upper arm. (Brachialis labeled at center left.)
- Drake, Richard L.; Vogl, Wayne; Tibbitts, Adam W.M. Mitchell; illustrations by Richard; Richardson, Paul (2005). Gray's anatomy for students. Philadelphia: Elsevier/Churchill Livingstone. p. 662,672. ISBN 978-0-8089-2306-0.
- Dirckx, J.H. (Ed.) (1997).Stedman’s concise medical dictionary for the health professions. (3rd edition). Baltimore: Williams & Wilkins.
- Anderson, D.M. (2000). Dorland’s illustrated medical dictionary (29th edition). Philadelphia/London/Toronto/Montreal/Sydney/Tokyo: W.B. Saunders Company.
- Triepel, H. (1910). Die anatomischen Namen. Ihre Ableitung und Aussprache. Mit einem Anhang: Biographische Notizen.(Dritte Auflage). Wiesbaden: Verlag J.F. Bergmann.
- Lewis, C.T. & Short, C. (1879). A Latin dictionary founded on Andrews' edition of Freund's Latin dictionary. Oxford: Clarendon Press.
- Federative Committee on Anatomical Terminology (FCAT) (1998). Terminologia Anatomica. Stuttgart: Thieme
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