Sawada M, Ishibashi Y, Suzuki T, Chiba S
Department of Anatomy, Hirosaki University School of Medicine, Japan.
Kaibogaku Zasshi. 1991 Apr;66(2):99-105.
Each one case of the pectoralis quartus and the pectoralis intermedius muscles was found on the left thoracic wall in a 73 year old male and on the right thoracic wall in a 57 year old female respectively. The pectoralis quartus was a thin muscle of triangular shape, the base of which was the origin arising from the left thoracic wall at the level of the 6th rib between the pectoralis major and the latissimus dorsi, being separated from both margins of the muscles. The aberrant muscle ascended left-upwards about 10 cm to insert to the inner surface of the pectoralis major near its lower margin. The muscle was innervated by the most caudal pectoral nerve, passing around the lower margin of the pectoralis minor. The pectoralis quartus is extremely rare in man, and only two cases were reported by Bluntschli (1906) and Frey (1921). From the comparative anatomical point of view, the pectoralis quartus muscle was supposed to be a remnant of the ventral part of the subcutaneous trunci muscle in lower mammals, differing from the ordinary muscular arch of the axilla which was believed to derive from the dorso-cranial part of the muscle. The pectoralis intermedius was located in the deep layer of the right pectoralis major, lying about 2 cm below the lower margin of the pectoralis minor. It arose in the 4th and 5th ribs and extended right-upwards, running almost parallel with the pectoralis minor. The origin of the pectoralis minor shifted cranially to the 2nd and 3rd ribs.(ABSTRACT TRUNCATED AT 250 WORDS)
在一名73岁男性的左胸壁和一名57岁女性的右胸壁上分别发现了一例胸四头肌和胸中间肌。胸四头肌是一块薄的三角形肌肉，其基部起自左胸壁第6肋水平，位于胸大肌和背阔肌之间，与这两块肌肉的边缘均分开。这块异常肌肉向左上方上升约10厘米，插入胸大肌下缘附近的内表面。该肌肉由最尾侧的胸神经支配，该神经绕过胸小肌下缘。胸四头肌在人类中极为罕见，Bluntschli（1906年）和Frey（1921年）仅报告过两例。从比较解剖学的角度来看，胸四头肌被认为是低等哺乳动物皮下躯干肌腹侧部分的残余，不同于被认为源自该肌肉背颅部的普通腋窝肌弓。胸中间肌位于右胸大肌深层，位于胸小肌下缘下方约2厘米处。它起自第4和第5肋，向右上方延伸，几乎与胸小肌平行。胸小肌的起点向头侧移至第2和第3肋。（摘要截短至250字）
