Le site de vulgarisation scientifique de l’Université de Liège. ULg, Université de Liège
Cloaca

Posterior opening which serves as the sole orifice for the intestinal, urinary and genital tracts of certain animal species. All the birds, reptiles and amphibians have such an orifice, through which they simultaneously expel urine and excrement (the snake’s tail begins just behind the cloaca). On the other hand the majority of placentary mammals and bony fish have, in the place of the cloaca, a specialised orifice for at least one of these three tracts.

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