Urogenital sinus

The urogenital sinus (also known as the persistent cloaca) is a part of the human body only present in the development of the urinary and reproductive organs. It is the ventral part of the cloaca, formed after the cloaca separates from the rectum. It eventually becomes, among other things, the bladder.

Pathology
A urogenital sinus anomaly is also a rare birth defect in women where the urethra and vagina both open into a common channel.