- Definition and Origin
- Cloaca is the rear orifice for digestive, reproductive, and urinary tracts
- Word comes from Latin "cluo" meaning "cleanse"
- Vertebrate Variations
- Found in amphibians, reptiles, birds, and some mammals
- True cloaca present only in elasmobranchs and lobe-finned fishes
- Most mammals lack cloaca, except monotremes and marsupial moles
- Embryonic cloaca divides into separate tracts in mammals
- Birds and Reptiles
- Birds use cloaca for mating through cloacal kiss
- Reptiles have urodeum, proctodeum, and coprodeum
- Some reptiles modify cloacae for gas exchange
- Special Functions
- Some turtles use cloacal respiration during diving
- Sea cucumbers use cloacal respiration for specialized species
- Cloacal gland associated with scent-marking in reptiles and mammals