Cloaca 518211 225672686 2008-07-14T20:56:27Z VolkovBot 3035831 robot Adding: [[la:Cloaca (anatomia)]] {{for|other meanings|Cloaca (disambiguation)}} [[Image:Avian cloaca.jpg|thumb|An avian cloaca or vent; in this example, a [[Red-tailed Hawk|red-tailed hawk]] (''Buteo jamaicensis'').]] [[Image:American Coots mating.jpg|thumb|Two [[American Coot]]s engaged in a "cloacal kiss"]] In zoological anatomy, a '''cloaca''' is the posterior opening that serves as the only such opening for the [[alimentary tract|intestinal]], [[urinary tract|urinary]], and (usually) [[Sex organ|genital tracts]] of certain animal species. The word comes from Latin, and means ''[[sewer]]''. All [[bird]]s, [[reptile]]s, and [[amphibian]]s possess this orifice, from which they excrete both urine and [[feces]], unlike placental mammals, which possess two separate orifices for evacuation. [[Marsupial]]s and [[monotreme]]s also possess one (in marsupials and a few birds, the genital tract is separate). In contrast, each individual among most species of [[placental mammal]]s and bony fishes has, in lieu of a cloaca, a specialized opening for at least one of these tracts. This is one of the features of marsupials and monotremes which suggest their primitivity, as the reptiles from which mammals evolved possessed a cloaca, and the earliest animals to diverge into the [[mammalia|mammalian class]] would have had this feature too. In [[bird]]s the cloaca is also referred to as the ''vent'', and among [[Falconry|falconers]] the word ''vent'' is also a verb meaning "to defecate". Birds also reproduce with this organ, this is known as a cloacal kiss. Excretory systems with analogous purpose in certain [[invertebrate]]s are also sometimes referred to as "cloacae". One study has looked into birds that use their cloaca for cooling (see [[Urohydrosis]]).<ref>[http://jeb.biologists.org/cgi/content/full/210/5/i Journal of Experimental Biology 210, 0i (2007) by Yfke Hager]</ref> In [[bird]]s the reproductive system must be re-engorged 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 if the first is taken away (they have the ability to produce more). For some birds, such as some species of swans and ducks, the males do not use the cloaca for reproduction but have a [[penis]]. The cloacal region is also often associated with a secretory organ, the cloacal gland, which has been implicated in the scent marking behavior of some reptiles, amphibians and monotremes. Some [[turtle]]s, especially those specialized in diving, are highly reliant on cloacal [[Respiration (physiology)|respiration]] during dives. <ref>[http://www.deh.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=1761#Movements Australian Government - Department of Environment and Heritage - Fitzroy Tortoise]</ref> They accomplish this by having a pair of accessory air bladders connected to the cloaca which can absorb oxygen from the water. <ref>[http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab-9a/Reptiles/Chelonians/chelonians.htm University of Wisconsin-La Crosse - Zoo Lab - Chelonians]</ref><ref>[http://www.vhs.com.au/pages/Turtlecare1.html Victorian Herpetological Society - Caring For Australian Freshwater Turtles In Captivity]</ref> [[Sea cucumber]]s also extract oxygen from water in a pair of 'lungs' or respiratory 'trees' that branch off the cloaca just inside the anus. There are also a variety of [[fish]]es, as well as [[polychaete]] worms and even [[crab]]s, that are specialized to take advantage of the constant flow of water through the cloacal respiratory tree of [[sea cucumbers]] while simultaneously gaining the protection of living within the sea cucumber itself. At night many of these species emerge from the anus of the sea cucumber in search of food. <ref>[http://www.advancedaquarist.com/issues/mar2003/invert.htm Aquarium Invertebrates by Rob Toonen, Ph.D.]</ref> == In humans == Human beings only have an [[embryonic cloaca]], which is split up into separate tracts during the [[development of the urinary and reproductive organs]]. However, a few human [[congenital disorder]]s result in persons being born with a cloaca, including [[persistent cloaca]] and [[Sirenomelia]] (''mermaid syndrome''). == References == <references/> [[Category:Animal anatomy]] [[Category:Bird anatomy]] [[cs:Kloaka]] [[de:Kloake (Biologie)]] [[es:Cloaca (zoología)]] [[eo:Kloako (biologio)]] [[hr:Kloaka]] [[id:Kloaka]] [[la:Cloaca (anatomia)]] [[lt:Kloaka]] [[nl:Cloaca (anatomie)]] [[ja:総排出腔]] [[no:Kloakk (zoologi)]] [[pl:Kloaka (biologia)]] [[pt:Cloaca]] [[ro:Cloaca]] [[ru:Клоака]] [[sl:Kloaka]] [[sr:Клоака]] [[su:Kloaka]] [[fi:Kloaakki]] [[sv:Kloaköppning]] [[tr:Kloak]] [[uk:Клоака]] [[zh:泄殖腔]]