Biseps

Biseps is a term sometimes used to refer to the biceps brachii, the two-headed muscle of the upper arm. In standard medical usage, the form biceps is preferred, while biseps may appear as a transliteration in some languages or as a common misspelling.

Anatomy and structure: The biceps brachii has two heads—the long head originates from the supraglenoid tubercle of the scapula, and the short head from the coracoid process. The two heads merge to form a single muscle belly, whose distal tendon attaches to the radial tuberosity and, via the bicipital aponeurosis, to the fascia of the forearm. The long head tendon passes through the intertubercular groove of the humerus and may traverse the shoulder joint capsule.

Function: The primary action of the biceps is elbow flexion and forearm supination. It also assists with shoulder flexion and helps stabilize the upper arm during movement, particularly when the forearm is supinated.

Innervation and blood supply: The muscle is innervated by the musculocutaneous nerve (C5–C6). Blood supply predominantly comes from branches of the brachial artery.

Clinical significance: Common injuries include bicipital tendinopathy and ruptures of either the proximal (long head) or distal biceps tendon, causing pain and weakness. Distal ruptures can produce a visible bulge in the arm, sometimes described as a Popeye deformity. Diagnosis typically involves physical examination and imaging such as ultrasound or MRI.

See also: Biceps, musculocutaneous nerve, forearm supination, tendinopathy.