embryonic cloaca
Endoderm-lined chamber that develops as pouch-like dilation of the caudal end of the hindgut and receives the allantois ventrally and two mesonephric ducts laterally; caudally it ends blindly at the cloacal membrane formed by the union of proctodeal (anal pit) ectoderm and cloacal endoderm, with no intervening mesoderm[MP].