Brachialis muscle

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Brachialis
Brachialis.png
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).
Details
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, brachial artery
Nerve Musculocutaneous nerve (C5-C7) and radial nerve (C5, C6)
Actions Flexion at elbow joint
Identifiers
Latin musculus brachialis
TA98 A04.6.02.018
TA2 2469
FMA 37667
Anatomical terms of muscle

The brachialis (also brachialis anticus or Casserio muscle) 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]

Contents

Structure

Origin

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

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. [4]

Innervation

The brachialis muscle is innervated by the musculocutaneous nerve (also Casserio 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

The brachialis is supplied by muscular branches of the brachial artery and by the recurrent radial artery. [5]

Variation

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

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

Etymology

The brachialis muscle [6] and brachial muscle [7] can be considered as the anglicized variant of the Latin expression musculus bracchialis. [8] In classical Latin bracchialis means of or belonging to the arm, [9] and is derived from classical Latin bracchium,"arm". [9] The expression musculus brachialis is used in the current official anatomic nomenclature Terminologia Anatomica . [10]

Additional images

See also

References

PD-icon.svgThis article incorporates text in the public domain from page 444 of the 20th edition of Gray's Anatomy (1918)

  1. 1 2 3 Saladin, Kenneth S, Stephen J. Sullivan, and Christina A. Gan. Anatomy & Physiology: The Unity of Form and Function. 2015. Print.[ page needed ]
  2. 1 2 3 4 5 6 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.
  3. 1 2 "Brachialis Muscle." Kenhub. Kenhub, Aug. 2001
  4. ↑ White, Tim D.; Black, Michael T.; Folkens, Pieter A. (2012). Human Osteology. doi:10.1016/C2009-0-03221-8. ISBN   978-0-12-374134-9.[ page needed ]
  5. ↑ "Brachialis." UW Department of Radiology. University of Washington, Nov. 2005
  6. ↑ Dirckx, J.H. (Ed.) (1997).Stedman’s concise medical dictionary for the health professions. (3rd edition). Baltimore: Williams & Wilkins.
  7. ↑ Anderson, D.M. (2000). Dorland’s illustrated medical dictionary (29th edition). Philadelphia/London/Toronto/Montreal/Sydney/Tokyo: W.B. Saunders Company.[ page needed ]
  8. ↑ Triepel, H. (1910). Die anatomischen Namen. Ihre Ableitung und Aussprache. Mit einem Anhang: Biographische Notizen.(Dritte Auflage). Wiesbaden: Verlag J.F. Bergmann.[ page needed ]
  9. 1 2 Lewis, C.T. & Short, C. (1879). A Latin dictionary founded on Andrews' edition of Freund's Latin dictionary. Oxford: Clarendon Press.[ page needed ]
  10. ↑ Federative Committee on Anatomical Terminology (FCAT) (1998). Terminologia Anatomica. Stuttgart: Thieme.[ page needed ]
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