Five Heads of the Biceps Brachii Muscle in Thai : A Case Report

Abstract

Background : Anatomical variations are possible to in all aspects of human body and should be recognized. Variations of form and origin of the biceps brachii muscle have been reported.  The origin of the biceps brachii muscle are classicall described as being a long head from the supraglenoid tubercle and a short head from the coracoid process of the scapula.  These two heads unite and insert into the radial tuberosity and the bicipital aponeurosis.  Occasionally, the presence of a third head of the biceps brachii muscle have been well documented in the avilable literatures.  There have been no previous report of five heads in the literature.

Objective : To study the anatomy of the biceps brachii muscle with five heads.

Results : Five distinct origins of the biceps brachii muscle were dissected carefully in the right arm of a 67 year old female cadaver.  The long head arises from supraglenoid tubercle of the scapula, the short head and the third hdad arise from coracoid process of the scapula.  The origin of the fourth head and the fifth heath are the humeral shaft between the insertion of the coracobrachialis and the origin of the brachialis muscles.  Distally all bellies of this muscle unite and insert through a biceps tendon into radial tuberosity together with bicipital aponeurosis, except the fourth head which inserts into the fifth head.  All five heads of this muscle receive their innervation from the musculocutaneous nerve and the arterial supply from the brachial artery.

Conclusions : This report has emphasized that the biceps brachii muscle with five heads was found in Thai female cadaver in Gross Anatomy Laboratory, Faculty of Medicine, Khon Kaen University.  This variation may occur during embryological development.  The five heads of the biceps brachii muscle may enhance the strength of elbow flexion and forearm supination and stability of elbow joint.