Does the nerve supply to both the superficial and deep surfaces of pectoralis major imply two separate developmental origins?
The nature of the nerve supply to the "pocket' of pectoralis major was examined on 7 randomly selected sides of 5 embalmed cadavers. The pocket was a U-shaped muscular fold, opening cranially. The anterior limb and inner surface of the fold were supplied by nerve branches that originated from the middle segment of the pectoral nerve loop and penetrated pectoralis minor. The outer surface of the posterior limb was supplied by one or two branches that extended from the caudal segment of the pectoral nerve loop. If the muscular U-shaped fold is unfolded, it becomes obvious that the posterior wall of the pocket forms the most caudal part of pectoralis major and is supplied from both the superficial (anterior) and deep (posterior) surfaces. This dual surface supply does not suggest any aspect of the developmental origin of the pocket but may simply be due to the relative positions of the pectoralis major and its nerve.
Shinohara
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Division of Human Sciences, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Japan.
D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010369:Pectoralis Muscles / Q000033:anatomy & histology* / Q000196:embryology; D013900:Thoracic Nerves / Q000033:anatomy & histology*