title: Does the urorectal septum fuse with the cloacal membrane?
abstract: OBJECTIVE
  Traditional theories of cloacal embryogenesis assume that the urorectal septum fuses with the cloacal membrane before the anal membrane disintegrates. However, recent observations in humans and other species raise doubt about this assumption. We determined whether urorectal septum fusion occurs in rats.
  
  
  METHODS
  Rat embryos were harvested at specific times between days 11 and 16 of gestation. We evaluated the morphology, growth and relationship of the urorectal septum to the cloacal membrane on serial histological sections.
  
  
  RESULTS
  The urorectal septum consistently fused with the cloacal membrane on day 15 of gestation before the cloacal membrane began to disintegrate.
  
  
  CONCLUSIONS
  In rats the urorectal septum fuses with the cloacal membrane, after which the urogenital membrane and anal membrane disintegrate by a process of apoptosis.
authors.affiliation: Department of Paediatric Surgery, Christchurch Hospital, Christchurch, New Zealand.
authors.forename: B Q
authors.initials: BQ
authors.lastname: Qi
authors.forename: S W
authors.initials: SW
authors.lastname: Beasley
authors.forename: A K
authors.initials: AK
authors.lastname: Williams
authors.forename: F
authors.initials: F
authors.lastname: Frizelle
mesh_terms: D000818:Animals; D002988:Cloaca / Q000196:embryology*; D005260:Female; D005865:Gestational Age; D051381:Rats; D017207:Rats, Sprague-Dawley; D012007:Rectum / Q000196:embryology*; D014566:Urogenital System / Q000196:embryology*