The ridge of mesoderm covered with endoderm that in the early developing embryo partitions the endodermal cloaca into the primary urogenital sinus (ventrally) and the anorectal canal of the hindgut (dorsally); the urorectal septum eventually fuses with the cloacal membrane, dividing it into a dorsal anal membrane and a larger ventral urogenital membrane - this area of fusion is represented in the adult by the perineal body[MP]. [ ]

This is just here as a test because I lose it

Term information



depicted by

editor note

todo - use to define cloacal septation in GO

external definition

A ridge of mesoderm covered with endoderm that in the early developing embryo divides the endodermal cloaca into the urogenital sinus and the rectum. [TFD][VHOG]

has exact synonym

urorectal membrane
urorectal fold
septum urorectale

has related synonym

cloacal septum

homology notes

In mammals the lowly monotremes still have a cloaca. Higher types have done away with this structure and have a separate anal outlet for the rectum. The monotreme cloaca shows the initiation of this subdivision. The cloaca has such includes only the distal part, roughly comparable to the proctodeum. The more proximal part is divided into (1) a large dorsal passage into which the intestine opens, the coprodeum, and (2) a ventral portion, the urodeum with which the bladder connects. (...) the development of the placental mammals recapitulates in many respects the phylogenetic story. In the sexually indifferent stage of placental mammal there is a cloaca. While the indifferent stage still persists, a septum develops, and extends out to the closing membrane. This divides the cloaca into two chambers: a coprodeum continuous with the gut above, and a urodeum or urogenital sinus below.[well established][VHOG]