The biceps brachii muscle (biceps muscle of the arm) is a strong biarticular muscle bridging the shoulder and elbow joint. In contrast to humans, it only possesses one tendon of origin in domestic mammals, that begins on the supraglenoid tubercle of scapula. It passes over the extensor side of the shoulder joint through the intertubercular groove and tends distally along the craniomedial aspect of the humerus.
At the level of the elbow joint, the muscle splits into two parts: the stronger part inserts on the radial tuberosity and the other ont the proximal ulna. Some fibres (lacertus fibrosus), extend further distally to radiate into the extensor carpi radialis and the fascia of forearm.
In carnivores, the biceps brachii muscle invaginates the capsule of the shoulder joint cranially, thus forming a synovial sheaths in the region of the intertubercular groove. A transverse band (transverse retinaculum of humerus) between the lesser and the greater humeral tubercle holds the muscle in place.
Origin: supraglenoid tubercle of the scapula
Insertion: Radial tuberosity and ulnar tuberosity.
Action: Flexion of the elbow joint, extensor of shoulder joint, stabiliser of the shoulder and carpal joint