Asvat R, Candler P, Sarmiento E E
Department of General Anatomy, University of the Witwatersrand School of Dentistry, Johannesburg, South Africa.
J Anat. 1993 Feb;182 ( Pt 1)(Pt 1):101-4.
Three different origins were found for the third head of the biceps brachii: (1) an origin from the humeral shaft inferior to and in common with the insertion area for the coracobrachialis; (2) a brachial origin in which the muscle originated distally from the medial humeral shaft, adjacent to and in common with the brachialis muscle; (3) a dual origin in which the medial fibres originated from the short head of biceps and the lateral fibres from the deltoid fascia and the insertion area of this muscle. In all cases, the third head inserted together with the other 2 heads of biceps brachii into the bicipital aponeurosis and the radial tuberosity. The third head receives its innervation from the musculocutaneous nerve, as do the other 2 heads of biceps. When there is a dual origin, partial innervation from the axillary nerve is possible since the fibres of the third head intermingle with those of the deltoid. There was a 20.5% incidence of the third head in South African blacks and only an 8.3% incidence in South African whites. Statistical analysis showed the difference between South African whites and blacks to be significant (P < 0.05). Not all of the blacks, however, had a higher incidence, since the Zulus showed a significant absence (P < 0.05) of the third head when compared with the other black populations.
(1) 起于肱骨干，位置低于肱肌的止点且与之共用同一区域；(2) 臂部起源，即肌肉起于肱骨干内侧远端，与肱肌相邻且共用同一区域；(3) 双重起源，即内侧纤维起于肱二头肌短头，外侧纤维起于三角肌筋膜及该肌的止点区域。在所有病例中，第三头与肱二头肌的另外两个头一起止于肱二头肌腱膜和桡骨粗隆。第三头与肱二头肌的另外两个头一样，由肌皮神经支配。当存在双重起源时，由于第三头的纤维与三角肌的纤维相互交织，故可能有部分神经由腋神经支配。在南非黑人中，第三头的发生率为20.5%，而在南非白人中仅为8.3%。统计分析表明，南非白人和黑人之间的差异具有显著性（P<0.05）。然而，并非所有黑人的发生率都更高，因为与其他黑人种群相比，祖鲁人第三头的发生率显著缺失（P<0.05）。
