Contents

Brachialis muscle

Flexor muscle in the upper arm

Brachialis

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).

Anterior surface of the humerus, particularly the distal half of this bone

Coronoid process and the tuberosity of the ulna

Radial recurrent artery, brachial artery

Musculocutaneous nerve (C5-C7) and radial nerve (C5, C6)

Flexionatelbow joint

musculus brachialis

A04.6.02.018

2469

37667

The brachialis (brachialis anticus) is a muscle in the upper arm that flexes the elbow. It lies beneath the biceps brachii, and makes up part of the floor of the region known as the cubital fossa (elbow pit). It originates from the anterior aspect of the distal humerus;^[1] it inserts onto the tuberosity of the ulna. It is innervated by the musculocutaneous nerve,^[2] and commonly also receives additional innervation from the radial nerve.^[3] The brachialis is the prime mover of elbow flexion generating about 50% more power than the biceps.^{[dubious – discuss][1]}

Structure[edit]

Origin[edit]

The brachialis originates from the anterior surface of the distal half of the humerus,^[1] 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.^[2]

Insertion[edit]

Its fibers converge to a thick tendon which is inserted into the tuberosity of the ulna,^[2] and the rough depression on the anterior surface of the coronoid process of the ulna.^{[citation needed]}

Innervation[edit]

The brachialis muscle is innervated by the musculocutaneous nerve, which runs on its superficial surface, between it and the biceps brachii.^[2] However, in 70-80% of people, the muscle has double innervation with the radial nerve (C5-T1). The divide between the two innervations is at the insertion of the deltoid.^[3]

Blood supply[edit]

The brachialis is supplied by muscular branches of the brachial artery and by the recurrent radial artery.^[4]

Variation[edit]

The muscle is occasionally doubled; additional muscle slips to the supinator, pronator teres, biceps brachii, lacertus fibrosus, or radius are more rarely found.^{[citation needed]}

Function[edit]

The brachialis flexes the arm at the elbow joint.^[2] Unlike the biceps, the brachialis does not insert on the radius, and does not participate in pronation and supination of the forearm.^[2]

History[edit]

Etymology[edit]

The brachialis muscle^[5]Inclassical Latin bracchialis means of or belonging to the arm,^[6] and is derived from classical Latin bracchium, "arm".^[6] The expression musculus brachialis is used in the current official anatomic nomenco Terminologia Anatomica.^[7]

Additional images[edit]

• 
  Position of brachialis (shown in red). Animation.
• 
  Still image.
• 
  Horizontal section through the middle of upper arm. (Brachialis labeled at center left.)
• 
  Muscles of forearm, including insertion of brachialis tendon. Cross section. (Brachialis labeled at bottom left.)
• 
  Left humerus. Anterior view.
• 
  Bones of left forearm. Anterior aspect.
• 
  Nerves of the left upper extremity.
• 
  Brachialis muscle (labeled in green text)

See also[edit]

References[edit]

This article incorporates text in the public domain from page 444 of the 20th edition of Gray's Anatomy (1918)

External links[edit]

Wikimedia Commons has media related to Brachialis muscles.

• Illustration: brachialis from The Department of Radiology at the University of Washington