In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, urinary, and genital tracts of certain animal species. The word comes from Latin, and means "sewer". All birds, reptiles, and amphibians possess this orifice, by which they simultaneously evacuate both urine and feces. Monotremes also possess one. In contrast, each individual among most species of placental mammals and bony fishes has, in lieu of a cloaca, a specialized opening for at least one of these tracts. For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and... The urinary system is a system of organs, tubes, muscles, and nerves that work together to create, store, and carry, urine. ... A sex organ, or primary sexual characteristic, narrowly defined, is any of those anatomical parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in a complex organism; namely: Male: penis (notably the glans... Orders Many - see section below. ... Orders See text. ... Subclasses and Orders Order Temnospondyli- extinct Subclass Lepospondyli- extinct Subclass Lissamphibia   Anura   Caudata   Gymnophiona Amphibians (class Amphibia) are a taxon of animals that include all tetrapods (four-legged vertebrates) that do not have amniotic eggs. ... Families Kollikodontidae(extinct) Ornithorhynchidae- Platypus Tachyglossidae- Echidnas Steropodontidae(extinct) Monotremes (monos, single + trema, hole; refers to the cloaca) are mammals that lay eggs, instead of giving birth to live young like marsupials (Metatheria) and placental mammals (Eutheria). ... Eutheria is a classification system nearly synonymous with Placentalia. ...

Excretory systems with analogous purpose in certain invertebrates are also sometimes referred to as "cloaca". Invertebrate is a term coined by Jean-Baptiste Lamarck to describe any animal without a spinal column. ...

In birds the reproductive system must be regrown prior to the mating season of each species. Such regeneration usually takes about a month. Birds generally produce one batch of eggs per year, but they will produce another batch if the first is taken away (they have the ability to produce more). Some birds, such as soem species of swans and ducks, do not use the cloaca for reproduction, but have a penis. Orders Many - see section below. ... Estrus (also spelled œstrus) or heat in female mammals is the period of greatest female sexual responsiveness usually coinciding with ovulation. ...

The cloacal region is also often associated with a secretory organ, the cloacal gland, which has been implicated in the scent marking behaviour of some reptiles, amphibians and monotremes.

Some turtles, especially those specialized in diving, are highly reliant on cloacal respiration during dives. ^[1] They accomplish this by having a pair of accessory air bladders connected to the cloaca which can absorb oxygen from the water. ^[2][3] Suborders Cryptodira Pleurodira See text for families. ... Respiration is the process by which an organism obtains energy by reacting oxygen with glucose to give water, carbon dioxide and ATP (energy). ...

References

1. ^ Australian Government - Department of Environment and Heritage - Fitzroy Tortoise
2. ^ University of Wisconsin-La Crosse - Zoo Lab - Chelonians
3. ^ Victorian Herpetological Society - Caring For Australian Freshwater Turtles In Captivity