Long head of biceps brachii

At a glance

English

Long head of biceps brachii

Latin (TA2)

Caput longum musculi bicipitis brachii

System

Muscle

Region

Upper limb

Side

Paired, left and right

About the long head of biceps brachii

Biceps brachii is the two-headed muscle on the front of the arm. Its long head is the lateral of the two and has the more unusual course, because its tendon begins inside the shoulder joint. The short head lies medial to it, and the two bellies unite in the lower arm before reaching the forearm.

The long head arises from the supraglenoid tubercle of the scapula, just above the glenoid cavity, and from the top of the glenoid labrum. Its rounded tendon arches over the humeral head within the joint capsule, wrapped in a sleeve of synovial membrane, and leaves the joint through the intertubercular groove, where the transverse humeral ligament holds it in place. In the arm it forms a fleshy belly that meets the short head. The common tendon passes in front of the elbow and attaches to the back of the radial tuberosity, and a fibrous sheet, the bicipital aponeurosis, fans medially into the forearm fascia.

Biceps is the strongest supinator of the forearm, especially when the elbow is bent, and it is a powerful elbow flexor. The long head also helps flex the shoulder and, by pressing down on the humeral head, steadies it in the socket when the arm is raised. It is supplied by the musculocutaneous nerve. Its blood comes from muscular branches of the brachial artery and from the anterior circumflex humeral artery near the groove.

The long head's tendon is a frequent site of trouble. It can become inflamed in its groove, slip out of it, or tear, usually in older people, leaving a low bulging belly sometimes called a Popeye sign. Injuries of its anchor on the labrum are known as SLAP lesions.

Attachments, action and supply

Origin

Supraglenoid tubercle of the scapula and the upper glenoid labrum.

Insertion

Radial tuberosity through the common biceps tendon, and the forearm fascia through the bicipital aponeurosis.

Action

Supinates the forearm and flexes the elbow; assists shoulder flexion and steadies the humeral head.

Nerve supply

Musculocutaneous nerve (C5, C6).

Blood supply

Muscular branches of the brachial artery and the anterior circumflex humeral artery.