| Namespace | MPheno.ontology | Obsolete | false |
| description | failure or anomaly in the formation of a pouch-like dilation of the caudal end of the hindgut by the process of folding of the caudal region of the embryonic disk; during the tail-fold process, the posteriorly placed allantois, or allantoic diverticulum of the yolk sac, becomes an anterior extension of the cloaca; soon after the cloaca forms, it receives posterolaterally the caudal ends of the paired mesonephric ducts and hence becomes a junctional cistern for the allantois, the hindgut, and the ducts; a cloacal membrane, composed of ectoderm and endoderm, is the caudal limit of the primitive gut and temporarily separates the cloacal cavity from the extraembryonic confines of the amniotic cavity; subsequent growth of the urorectal septum eventually subdivides the once single cloaca chamber into the primitive urogenital sinus (ventrally) and the anorectal canal of the hindgut (dorsally) |
