Editing Reptile (section)

===Excretion===
[[Excretion]] is performed mainly by two small [[kidney]]s. In diapsids, [[uric acid]] is the main [[nitrogen]]ous waste product; turtles, like [[mammal]]s, excrete mainly [[urea]]. Unlike the [[mammalian kidney|kidneys of mammals]] and birds, [[Kidney (vertebrates)#Reptile kidney|reptile kidneys]] are unable to produce liquid urine more concentrated than their body fluid. This is because they lack a specialized structure called a [[loop of Henle]], which is present in the [[nephron]]s of birds and mammals. Because of this, many reptiles use the [[colon (anatomy)|colon]] to aid in the [[reabsorption]] of water. Some are also able to take up water stored in the [[Urinary bladder|bladder]]. Excess salts are also excreted by nasal and lingual [[salt gland]]s in some reptiles.

In all reptiles, the urinogenital ducts and the [[rectum]] both empty into an organ called a [[cloaca]]. In some reptiles, a midventral wall in the cloaca may open into a urinary bladder, but not all. It is present in all turtles and tortoises as well as most lizards, but is lacking in the [[monitor lizard]], the [[legless lizard]]s. It is absent in the snakes, alligators, and crocodiles.<ref>{{cite book |author=Rand, Herbert W. |year=1950 |title=The Chordates |publisher=Balkiston |url=https://archive.org/stream/chordates00rand/#page/276/mode/1up/search/bladder}}</ref>

Many turtles and lizards have proportionally very large bladders. [[Charles Darwin]] noted that the [[Galapagos tortoise]] had a bladder which could store up to 20% of its body weight.<ref>{{cite book |author=Bentley, P.J. |date=14 March 2013 |title=Endocrines and Osmoregulation: A comparative account in vertebrates |publisher=Springer Science & Business Media |isbn=978-3-662-05014-9 |url=https://books.google.com/books?id=U0D3BwAAQBAJ&pg=PA143}}</ref> Such adaptations are the result of environments such as remote islands and deserts where water is very scarce.<ref>{{cite conference |last=Paré|first=Jean |date=11 January 2006 |title=Reptile basics: Clinical anatomy&nbsp;101 |conference=North American Veterinary Conference |volume=20 |pages=1657–1660 |url=http://www.ivis.org/proceedings/navc/2006/SAE/600.pdf?LA=1}}</ref>{{rp|143}} Other desert-dwelling reptiles have large bladders that can store a long-term reservoir of water for up to several months and aid in [[osmoregulation]].<ref>{{Cite journal |last1=Davis |first1=Jon R. |last2=de&nbsp;Nardo |first2=Dale F. |date=2007-04-15 |title=The urinary bladder as a physiological reservoir that moderates dehydration in a large desert lizard, the Gila monster ''Heloderma suspectum'' |journal=Journal of Experimental Biology |language=en |volume=210 |issue=8 |pages=1472–1480 |doi=10.1242/jeb.003061 |issn=0022-0949 |pmid=17401130 |doi-access=free|bibcode=2007JExpB.210.1472D }}</ref>

Turtles have two or more accessory urinary bladders, located lateral to the neck of the urinary bladder and dorsal to the pubis, occupying a significant portion of their body cavity.<ref>{{Cite journal|last1=Wyneken|first1=Jeanette|last2=Witherington|first2=Dawn|date=February 2015|title=Urogenital System|url=http://www.ivis.org/advances/wyneken/16.pdf?LA|journal=Anatomy of Sea Turtles|volume=1|pages=153–165}}</ref> Their bladder is also usually bilobed with a left and right section. The right section is located under the liver, which prevents large stones from remaining in that side while the left section is more likely to have [[Bladder stone (animal)|calculi]].<ref>{{Cite book|title=Reptile Medicine and Surgery|last1=Divers|first1=Stephen J.|last2=Mader|first2=Douglas R.|publisher=Elsevier Health Sciences|year=2005|isbn=9781416064770|location=Amsterdam|pages=481, 597|url=https://books.google.com/books?id=7Ai4BKhi0VUC}}</ref>