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Biceps brachii muscle

The biceps brachii muscle is one of the chief muscles of the arm. Its origin and insertion acts on both the shoulder joint and the elbow joint, which is why this muscle participates in the mare than few movements of the arm.

It derives its name from its two heads which insert on the coracoid apex and the supraglenoid tubercle.

So basically, the biceps muscle has a double origin, but an unique insertion. This defines the structure of the muscle so it has the two heads that merge in one unique distal body.

Key Facts
Origin Long head: supraglenoid tubercle of the scapula
Short head: coracoid process of the scapula
Insertion Radial tuberosity of the humerus
Vascularisation Brachial artery
Innervation Musculocutaneous nerve (branch of the brachial plexus)
Antagonist muscle Triceps brachii muscle

In this article, we're going to discuss the attachments, innervation and functions of the biceps muscle.  

Anatomy

Origins and Insertions

The biceps brachii muscle (biceps) is a large, thick muscle of the upper arm consisting of two heads.

  • long head: originates at the supraglenoid tubercle above the socket of the scapula. It lies within the intracapsular space but it still remains extrasynovial. The long biceps tendon makes a sharp turn at the humeral head and continues its course in the bicipital groove (intertubercular sulcus). This turning point is secured by ligaments at the capsular area (=biceps pulley).
  • short head: arises at the coracoid process of the scapula where it partly blends with the origin tendon of the coracobrachialis.

Both heads unite to one large muscle at the anterior side of the humerus and attach to the radial tuberosity. A fibrous membrane emerging from the distal part of the muscle (bicipital aponeurosis, also called lacertus fibrosus) inserts at the deep fascia of forearm.

Innervation

In terms of innervation, this muscle is supplied by the musculocutaneous nerve (C5-C6), a branch of the brachial plexus.

Musculocutaneous nerve - ventral view

Musculocutaneous nerve - ventral view

Surface Anatomy

The surface anatomy of the anterior side of the upper arm is essentially formed by the biceps. While both its origin tendons are covered by the deltoid its insertion tendon can be easily seen and palpated at the crook of the arm. The space between the biceps and triceps forms two grooves (medial and lateral bicipital grooves). Within the medial bicipital groove course the brachial artery and both the ulnar and median nerves. The lateral bicipital groove contains the radial nerve.

Recommended video: Biceps brachii muscle
Origin, insertion, innervation and functions of the biceps brachii muscle.

Function

The biceps is a two-joint muscle. In the shoulder joint both muscle heads partially enforce opposite movements. The long head pulls the arm away from the trunk (abduction) and turns it inwards (inward rotation) whereas the short head pulls the arm back towards the trunk (adduction). When both heads contract simultaneously it leads to an arm bend (flexion).

In the elbow joint the muscle bends the forearm (flexion) and rotates it outwards (supination). The supination is most powerful in a flexed elbow. In addition to the movement functions, the biceps has the important task to support the humeral head within the shoulder joint.

Clinical Aspects

In physical examination, the biceps plays an important role. It provides an orientation for the palpation of the brachial artery. Hereby the artery is pushed with the fingertips against the humerus in the medial bicipital groove. Furthermore it serves as a reference muscle for the nerve roots C5 and C6. In this exam the biceps reflex is tested by striking the insertion tendon with a hammer and thus activating a contraction of the muscle.

Due to the close relationship between the long biceps tendon and the rotator cuff, inflammatory and degenerative processes often affect each other. Common consequences are a pulley lesion or biceps tendinitis. A pulley lesion is characterized by damage to the biceps pulley complex through which the long biceps tendon is no longer secured in the shoulder joint and thus slips out of the intertubercular sulcus. A biceps tendinitis is an inflammation of the long biceps tendon often caused by a bursitis or other tendinitides involving the rotator cuff, more rarely through overuse. In severe cases the tendon can even tear apart completely (biceps tendon rupture).

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Show references

References:

  • M. Schünke/E. Schulte/U. Schumacher: Prometheus – LernAtlas der Anatomie – Allgemeine Anatomie und Bewegungssystem, 2.Auflage, Thieme Verlag (2007), S.304-305
  • J. E. Muscolino: The muscular system manual – The skeletal muscles of the human body, 2.Auflage, Elsevier Mosby (2005), S.518, 548-550
  • J. R. Doyle/M. J. Botte: Surgical anatomy of the hand and upper extremity, Lippincott Williams and Wilkins (2003), S.98-101
  • V. Echtermeyer/S. Bartsch: Praxisbuch Schulter, 2.Auflage, Thieme Verlag (2005), S.159-160

Author:

  • Achudhan Karunaharamoorthy

Illustrators:

  • First Illustration Gallery - Yousun Koh
  • Second Illustration Gallery - Yousun Koh
  • Musculocutaneous nerve - ventral view - Yousun Koh
  • Third Illustration Gallery - Paul Kim
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Related Atlas Images

Muscles of the arm and the shoulder

Main muscles of the upper extremity

Biceps brachii muscle level

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