The human musculus obliquus externus abdominis innervated by ramus muscularis externus of intercostal nerves.

Each of the uppermost slips of the bilateral M. obliquus externus abdominis originated from the fifth rib and was innervated from its inner surface by the Ramus muscularis externus of the fifth intercostal nerve, in one corpse. Furthermore, the slip originating from the sixth rib of the right M. obliquus externus abdominis was innervated not only by the lateral cutaneous branches of the sixth and seventh intercostal nerves from its outer surface, but also by the Ramus muscularis externus of the sixth intercostal nerve from its inner surface. The slip originating from the fifth rib was given us an aspect in appearance as if it were the uppermost slip of origin of this muscle, but its true nature is considered to be the M. obliquus abdominis externus profundus from the viewpoint of its innervating nerve and pattern. In addition, the slip originating from the sixth rib is considered to be a substance formed by the dorsal adhesion of the M. obliquus abdominis externus profundus originating from the sixth rib to the slip of the M. obliquus externus abdominis originating from the same rib.