Biceps brachii muscle

Origin and insertion

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

• long head: originates at the supraglenoid tubercle above the glenoid cavity 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 apex of the coracoid process of the scapula where it partly blends with the origin tendon of the coracobrachialis.

Memorising the origins of the biceps brachii muscle is very easy if you use a mnemonic! Here's an easy one for you.

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• Short head originates from Coracoid process.
• Long head originates from the Supraglenoid cavity.

Both heads unite to one large muscle belly 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.

Learn the main muscles of the upper limb with the following quiz. 

Did you know that we have an upper limb muscle anatomy chart which you can use to quickly learn the attachments, innervations and functions of the biceps brachii muscle? 

Relations

The biceps brachii lies superficial to the brachialis and coracobrachialis muscles, and essentially forms the anterior side of the arm. 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.

Innervation

The biceps brachii muscle is supplied by the musculocutaneous nerve (C5-C6), a branch of the brachial plexus.

Blood supply

Arterial supply to the biceps brachii muscle varies considerably, coming from up to eight vessels originating from the brachial artery in the middle third of the arm.

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. Its antagonist is the triceps brachii in the posterior compartment of the arm.