Which tissue partitions the cloaca into separate outlets?

Which tissue partitions the cloaca into separate outlets?

• A. Dorsal mesentery
• B. Urorectal septum
• C. Cloacal membrane
• D. Ventral aorta

Answer: (B)

During embryonic development, a single cloacal chamber must be divided into separate outlets for the urinary/genital and digestive tracts. This separation is achieved by the urorectal septum, a wedge of mesoderm that grows downward between the hindgut and the urogenital sinus and meets the cloacal membrane. As it expands, the urorectal septum splits the cloaca into an anterior compartment (the urogenital sinus) and a posterior compartment (the anorectal canal), establishing distinct openings for the urinary/genital tract and the rectum. The anal opening forms later when the anal membrane ruptures, and the urogenital opening forms from the urogenital membrane. Other structures listed do not perform this partitioning.

During embryonic development, a single cloacal chamber must be divided into separate outlets for the urinary/genital and digestive tracts. This separation is achieved by the urorectal septum, a wedge of mesoderm that grows downward between the hindgut and the urogenital sinus and meets the cloacal membrane. As it expands, the urorectal septum splits the cloaca into an anterior compartment (the urogenital sinus) and a posterior compartment (the anorectal canal), establishing distinct openings for the urinary/genital tract and the rectum. The anal opening forms later when the anal membrane ruptures, and the urogenital opening forms from the urogenital membrane. Other structures listed do not perform this partitioning.