Yamasaki M
Department of Anatomy, Akita University School of Medicine, Japan.
Anat Anz. 1989;168(5):423-32.
2 cases of the defect of pectoralis major muscle observed in male cadavers allocated for routine dissection were investigated anatomically, especially on the nerve supply for the defected muscles. In both cases, one on the left and the other on the right side, pectoralis major muscle was defected, the clavicular portion and a small part of sternocostal portion only persisting. Meanwhile, the ipsilateral pectoralis minor muscle was defected in the first case to be a string-like muscle band and was missing in the second case substituted by a membrane which seemed not to be the degenerated same muscle. Both the lateral and medial pectoral nerves supplied the pectoral muscles in the first case. One of rami of the medial pectoral nerve was distributed unusually to the most lateral part of the persisted sternocostal portion. Only the lateral pectoral nerve existed in the second case. In both cases nerves derived from 2 caudal segments, C8 and Th1, were lacking or poor. However, it was suggested that the defect of the muscles was not due to the nonparticipation of these nerves but due to the failure of caudal growth of the pectoral premuscle mass in a five-week embryo (Lewis 1901).
对2例用于常规解剖的男性尸体中观察到的胸大肌缺损进行了解剖学研究，尤其关注缺损肌肉的神经供应情况。在这两例中，一例在左侧，另一例在右侧，胸大肌均有缺损，仅锁骨部及一小部分胸肋部留存。同时，第一例中同侧的胸小肌缺损为条索状肌束，第二例中胸小肌缺失，代之以一层膜，这层膜似乎并非退化的同一块肌肉。在第一例中，胸外侧神经和胸内侧神经均支配胸肌。胸内侧神经的一个分支异常分布于留存的胸肋部的最外侧部分。第二例中仅存在胸外侧神经。在这两例中，来自尾侧两个节段（C8和Th1）的神经均缺失或发育不良。然而，提示肌肉缺损并非由于这些神经未参与，而是由于五周胚胎期胸肌原基尾侧生长失败（Lewis，1901年）。
