CONGENITAL ABNORMALITIES

CONGENITAL ABNORMALITIES

Early in embryonic life there is a common chamber – the cloaca – into which the hind gut and the allantois open. This endoderm-lined chamber is separated from the surface ecto derm of the embryo by the cloacal membrane. The cloaca becomes divided into two parts – dorsal (rectum) and ventral (urogenital sinus) – by the downgrowth of a septum. The dorsal part of the cloacal membrane, kno wn as the anal membrane, is thus composed of an outer layer of ectoderm and an inner layer of endoderm. Resorption of this anal membrane by the eighth week of embryonic life creates the anal canal.