bíceps

Bíceps, known in anatomy as the biceps brachii, is a two-headed muscle of the upper arm. It lies on the anterior aspect of the arm and crosses the shoulder and elbow joints, enabling forearm movements and contributing to shoulder stability.

Anatomy: The long head originates from the supraglenoid tubercle of the scapula, while the short head arises from the coracoid process. The two heads converge into a common tendon that inserts on the radial tuberosity, with the bicipital aponeurosis extending into the forearm fascia. The long head tendon also traverses the shoulder joint, aiding in glenohumeral stability.

Function: The primary actions are elbow flexion and forearm supination, especially when the forearm is fully supinated. The biceps also assists with shoulder flexion and helps stabilize the humeral head during arm movements.

Nerve and blood supply: The muscle is innervated by the musculocutaneous nerve (C5–C7). Blood supply comes from branches of the brachial artery, including muscular branches to the muscle. The proximal region receives most vascular input.

Clinical notes: Variations include a third (accessory) head in some individuals. Common injuries involve proximal long head tendinopathy or rupture; distal ruptures can occur with rapid loading. Injury can weaken elbow flexion and forearm supination, and treatment ranges from conservative rehabilitation to surgical repair or tenodesis when necessary.