Cloaca
총배설강
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<speciesfyi-glossary slug="cloaca"></speciesfyi-glossary>Definition
A single posterior opening in reptiles and amphibians serving as the exit for the digestive, urinary, and reproductive tracts.
Detailed Explanation
The cloaca's multipurpose function is a reflection of ancestral vertebrate anatomy — early tetrapods had a single posterior opening. In reptiles, cloacal scent glands secrete pheromones used in sex recognition and territorial marking. Cloacal bursae in some aquatic turtles allow gas exchange during winter submergence, functioning as a supplementary respiratory organ. Birds retain the cloaca — reproduction, excretion, and egg-laying all involve this single opening.