A. Preallantoic hind gut
Structure is urinary bladder
Postallantoic part of hind gut is the dilated endodermal cloaca, which is separated from the surface by cloacal mambrane.
Urorectal septum divides endodermal cloaca into :-
i. Anterior part, known as primitive urogenital sinus, which develops into urinary bladder and urethra.
ii. Posterior part, known as primitive rectum, which gives rise to lower part of rectum and upper part of anal canal.
- URINARY BLADDER (except TRIGONE) is derived from Vesicourethral canal, cranial part of urogenital sinus(endodermal).
- TRIGONE is derived from absorbed part of Wolffian duct/ mesonephric duct(mesodermal).