Biceps brachii

Musculus biceps brachii

A two-headed muscle in the anterior compartment of the upper arm. The long head originates from the supraglenoid tubercle of the scapula, and the short head from the coracoid process. Both heads insert on the radial tuberosity and bicipital aponeurosis.

Type Muscle
Body System Muscular
Body Region Upper Arm
Parent Structure forelimb stylopod muscle
Latin Name Musculus biceps brachii
FMA ID 37670

Function

Primary supinator of the forearm and powerful flexor of the elbow. Also assists in shoulder flexion. The long head assists in shoulder joint stabilization.

Clinical Significance

Biceps tendon ruptures cause a visible bulge (Popeye deformity). Bicipital tendinitis causes anterior shoulder pain. The biceps reflex tests the C5-C6 nerve roots.

Frequently Asked Questions

What are the primary functions of the biceps brachii muscle?
The biceps brachii serves as the primary supinator of the forearm—rotating the palm upward—and a powerful flexor of the elbow joint. It also assists in shoulder flexion, and its long head contributes to stability of the glenohumeral (shoulder) joint by running within the bicipital groove of the humerus.
What is the Popeye deformity and what causes it?
The Popeye deformity is a visible bulge in the upper arm caused by proximal biceps tendon rupture. When the long head of the biceps tendon tears—most commonly at its attachment to the supraglenoid tubercle of the scapula—the muscle belly retracts distally, creating a characteristic rounded bulge resembling the cartoon character's arm.
Which nerve roots does the biceps reflex test?
The biceps reflex tests the integrity of the C5 and C6 nerve roots. A clinician strikes the biceps tendon at the elbow with a reflex hammer; the expected response is elbow flexion. An absent or diminished reflex may indicate pathology at the C5 or C6 spinal levels, while an exaggerated reflex may suggest an upper motor neuron lesion.
What is bicipital tendinitis and how does it present?
Bicipital tendinitis is inflammation of the long head of the biceps tendon, usually where it runs through the bicipital groove of the humerus. It presents as anterior shoulder pain that worsens with overhead activities, lifting, or resisted forearm supination. It often accompanies rotator cuff pathology.
Why is the biceps brachii considered a two-joint muscle?
The biceps brachii crosses both the shoulder and elbow joints. Proximally, it attaches via two heads—the long head to the supraglenoid tubercle and the short head to the coracoid process of the scapula—and distally to the radial tuberosity and bicipital aponeurosis. This dual-joint architecture allows it to act on both joints simultaneously.

Related Structures

anterior internodal tract anterior internodal fasciculus aponeurosis aponeuroses atrioventricular node A-V node Bachmann's bundle anterior interatrial band bundle of His A-V bundle cardiac muscle tissue of myocardium cardiac Purkinje fiber cardiac Purkinje fiber cartilage tissue cartilage

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Educational Disclaimer

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Data sources: Terminologia Anatomica, Foundational Model of Anatomy, Wikidata.