Five-headed biceps brachii muscle with a rare origin from the tendon of pectoralis major muscle.

We found a five-headed biceps brachii (BB) muscle associated with the pectoralis major muscle in a 43-year-old Korean male cadaver during a routine dissection course. A supernumerary head originated from the anterior surface of the distal tendinous part of the pectoralis major muscle, lay in the sulcus between the short and long heads of BB muscle, and terminated at their point of union. The additional two accessory heads originated from the body of the humerus between the insertion site of the coracobrachialis muscle and the origin site of the brachialis muscle and inserted into the distal part of the united muscle belly of the BB muscle. The additional accessory heads were supplied by branches of the musculocutaneous nerve. Although a supernumerary head of BB muscle originated from the pectoralis major is a peculiar finding, morphological details on the presence of another combined variation might be essential for clinicians as well as anatomists.