Biceps brachii muscle

Author: Achudhan Karunaharamoorthy, MD • Reviewer: Dimitrios Mytilinaios, MD, PhD
Last reviewed: October 30, 2023
Reading time: 11 minutes

Biceps brachii muscle (Musculus biceps brachii)

The biceps brachii muscle is one of the chief muscles of the arm.

The origin at the scapula and the insertion into the radius of the biceps brachii means it can act on both the shoulder joint and the elbow joint, which is why this muscle participates in a few movements of the arm.

It derives its name from its two heads which merge in one unique distal body, defining the unusual structure of the muscle.

Key facts about the biceps brachii muscle
Origin	Short head - Apex of the Coracoid process of the scapula Long head - Supraglenoid tubercle of the scapula Mnemonic: 'You walk Shorter to a street Corner. You ride Longer on a Superhighway'
Insertion	Radial tuberosity of the radius Deep fascia of forearm (insertion of the bicipital aponeurosis)
Innervation	Musculocutaneous nerve (C5- C6)
Blood supply	Branches of brachial artery
Function	Flexion and supination of the forearm at the elbow joint, weak flexor of the arm at the glenohumeral joint

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

Contents

Origin and insertion
Relations
Innervation
Blood supply
Function
Frequent questions
Clinical notes
Sources

+ Show all

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.

You walk Shorter to a street Corner. You ride Longer on a Superhighway

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.

Frequent questions

Where is the biceps brachii located?

The biceps brachii is a muscle situated in the anterior compartment of the arm, lying superficial to the brachialis muscle. It becomes easily visible and palpable when the elbow is flexed, which is its primary function.

What bone is the origin of the biceps brachii?

The biceps brachii has two heads, both of which originate from the scapula. The long head originates from the supraglenoid tubercle of the scapula and the short head originates from the coracoid process of the scapula.

What is the insertion of the biceps brachii?

The biceps brachii inserts on the radial tuberosity and the bicipital aponeurosis, a fibrous sheet that integrates with the deep fascia of the forearm. It functions to flex the elbow, supinate the forearm when the elbow is flexed, and assists in shoulder flexion.

What is the action of the biceps brachii muscle?

The contraction of the biceps brachii flexes the forearm at the elbow joint and supinates the forearm (rotates the forearm so the palm faces upward). It is also a weak flexor of the arm at the shoulder joint.

Which muscle is an antagonist to the biceps brachii muscle?

The triceps brachii muscle serves as an antagonist to the biceps brachii. While the triceps brachii extends the forearm at the elbow joint, the biceps brachii flexes it. This is primarily due to the anatomical positioning of these muscles. The triceps brachii is the sole muscle located in the posterior compartment of the arm, whereas the biceps brachii is part of the anterior compartment. Their locations result in their muscle fibers and tendons crossing the elbow joint on opposite sides, leading to their opposing actions.

What nerve innervates the biceps brachii?

The biceps brachii is innervated by the musculocutaneous nerve (C5-C6 | lateral cord of the brachial plexus). That same nerve innervates the other muscles in the anterior compartment of the arm, like the brachialis and coracobrachialis muscles.

Is the brachialis deep to the biceps brachii?

Yes, the brachialis muscle lies deep to the biceps brachii in the anterior compartment of the arm. The biceps brachii muscle is the most superficial muscle of that compartment, while the brachialis muscle lies underneath it.

Which type of lever is exemplified by the flexing of the forearm by the biceps brachii muscle?

The flexing of the forearm by the biceps brachii muscle represents a third-class lever. In that example, the fulcrum or pivot is the elbow joint, the force is applied by the muscle at its insertino on the radial tuberosity and the load or resistance is the is the weight of the forearm and any objects that are being held in the hand. The effort (the force) is applied between the fulcrum and the load, which is exactly what happens in our example.

What is the origin and insertion of the long head of biceps brachii?

The long head of the biceps brachii muscle originates from the supraglenoid tubercle of the scapula. Its tendon passes through the shoulder joint capsule and travels along the intertubercular groove (bicipital groove) of the humerus, where it is secured by the transverse humeral ligament. Despite having different origins, the short and long heads share a common insertion at the radial tuberosity of the radius.

Clinical notes

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 tendinitis involving the rotator cuff, more rarely through overuse. In severe cases the tendon can even tear apart completely (biceps tendon rupture).

Sources

All content published on Kenhub is reviewed by medical and anatomy experts. The information we provide is grounded on academic literature and peer-reviewed research. Kenhub does not provide medical advice. You can learn more about our content creation and review standards by reading our content quality guidelines.

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

Illustrators:

Biceps brachii muscle (lateral-right) - Yousun Koh

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