urorectal septum


ur·o·rec·tal sep·tum

in embryos, a partition dividing the cloaca into a dorsal, rectal portion and a ventral portion called the urogenital sinus; reaching the cloacal membrane at about the time of its disintegration, the urorectal septum divides the cloacal exit into an anal and a urogenital orifice. Synonym(s): urorectal fold