On the Human Obliquus Abdominis Externus Profundus

The Obliquus abdominis externus profundus was found to be present in eleven cases among 50 sides examined in Japanese adult cadavers (frequency of occurrence 22%). This muscle originated at a level ranging from the fifth to seventh rib either by a single slip from one of these ribs (nine cases) or by two slips from two ribs (two cases), and ran medialwards almost horizontally to insert into the anterior lamina of the sheath of the Rectus abdominis. There was a fusion between this muscle and the Obliquus externus abdominis in four of the eleven cases. This muscle was supplied from its inner surface by the Ramus muscularis externus from the intercostal nerve of the corresponding segment. The identification, origin and insertion, nerve supply, and frequency of occurrence of this muscle were discussed.