The cloaca is the terminal portion of the hindgut. It is an embryonic structure (weeks 4-7) in which the distal ends of the gastrointestinal tract and urogenital system share a common channel. The most distal aspect of the cloaca is termed the cloacal membrane.
The cloaca, or portions of it, can persist after birth and contribute to congenital urinary anomalies. This developmental anomaly occurs in females only.
History and etymology
"Cloaca" derives from the Latin word for "sewer" or "drain".