Editing Reptile (section)

===Respiratory system===
[[File:X-ray video of a female American alligator (Alligator mississippiensis) while breathing - pone.0004497.s009.ogv|right|thumb|X-ray [[fluoroscopy]] videos of a female American alligator showing contraction of the lungs while breathing]]
All reptiles breathe using [[lung]]s. Aquatic [[turtle]]s have developed more permeable skin, and some species have modified their [[cloaca]] to increase the area for [[gas exchange]].<ref>{{cite book | last=Orenstein | first=Ronald | title=Turtles, Tortoises & Terrapins: Survivors in Armor | publisher=Firefly Books | year=2001 | isbn=978-1-55209-605-5 | url-access=registration | url=https://archive.org/details/turtlestortoises0000oren }}</ref> Even with these adaptations, breathing is never fully accomplished without lungs. Lung ventilation is accomplished differently in each main reptile group. In [[squamata|squamates]], the lungs are ventilated almost exclusively by the axial musculature. This is also the same musculature that is used during locomotion. Because of this [[Carrier's constraint|constraint]], most squamates are forced to hold their breath during intense runs. Some, however, have found a way around it. Varanids, and a few other lizard species, employ [[buccal pumping]] as a complement to their normal "axial breathing". This allows the animals to completely fill their lungs during intense locomotion, and thus remain aerobically active for a long time. [[Tupinambis|Tegu lizards]] are known to possess a proto-[[thoracic diaphragm|diaphragm]], which separates the pulmonary cavity from the visceral cavity. While not actually capable of movement, it does allow for greater lung inflation, by taking the weight of the viscera off the lungs.<ref>{{cite journal | last=Klein | first=Wilfied |author2=Abe, Augusto |author3=Andrade, Denis |author4= Perry, Steven | title=Structure of the posthepatic septum and its influence on visceral topology in the tegu lizard, ''Tupinambis merianae'' (Teidae: Reptilia) | journal=Journal of Morphology | volume=258 | issue=2 | year=2003 | pages=151–157 | doi=10.1002/jmor.10136 | pmid=14518009| s2cid=9901649 }}</ref>

[[Crocodilia]]ns actually have a muscular diaphragm that is analogous to the mammalian diaphragm. The difference is that the muscles for the crocodilian diaphragm pull the pubis (part of the pelvis, which is movable in crocodilians) back, which brings the liver down, thus freeing space for the lungs to expand. This type of diaphragmatic setup has been referred to as the "[[Liver|hepatic]] [[piston]]". The [[Bronchus|airways]] form a number of double tubular chambers within each lung. On inhalation and exhalation air moves through the airways in the same direction, thus creating a unidirectional airflow through the lungs. A similar system is found in birds,<ref>{{cite journal|last=Farmer|first=CG|author2=Sanders, K |title=Unidirectional airflow in the lungs of alligators|journal=Science|year=2010|volume=327|issue=5963|pages=338–340|doi=10.1126/science.1180219|pmid=20075253|bibcode=2010Sci...327..338F|s2cid=206522844}}</ref> monitor lizards<ref>{{cite journal | last1 = Schachner | first1 = E.R. | last2 = Cieri | first2 = R.L. | last3 = Butler | first3 = J.P. | last4 = Farmer | first4 = C.G. | year = 2013 | title = Unidirectional pulmonary airflow patterns in the savannah monitor lizard | doi = 10.1038/nature12871 | journal = [[Nature (journal)|Nature]] | pmid = 24336209| volume=506 | issue = 7488 | pages=367–370| bibcode = 2014Natur.506..367S | s2cid = 4456381 | url = http://nrs.harvard.edu/urn-3:HUL.InstRepos:32631102 | url-access = subscription }}</ref> and iguanas.<ref>{{cite journal |author1=Cieri, Robert L. |author2=Craven, Brent A. |author3=Schachner, Emma R. |author4=Farmer, C.G. |year=2014 |title=New insight into the evolution of the vertebrate respiratory system and the discovery of unidirectional airflow in iguana lungs |journal=[[Proceedings of the National Academy of Sciences]] |volume=111 |issue=48 |pages=17218–17223 |pmid=25404314 |pmc=4260542 |doi=10.1073/pnas.1405088111 |bibcode=2014PNAS..11117218C |doi-access=free }}{{open access}}</ref>

Most reptiles lack a [[secondary palate]], meaning that they must hold their breath while swallowing. Crocodilians have evolved a bony secondary palate that allows them to continue breathing while remaining submerged (and protect their brains against damage by struggling prey). Skinks (family [[Skink|Scincidae]]) also have evolved a bony secondary palate, to varying degrees. Snakes took a different approach and extended their trachea instead. Their tracheal extension sticks out like a fleshy straw, and allows these animals to swallow large prey without suffering from asphyxiation.<ref>{{Cite journal|last1=Chiodini|first1=Rodrick J.|last2=Sundberg|first2=John P.|last3=Czikowsky|first3=Joyce A.|date=January 1982|editor-last=Timmins|editor-first=Patricia|title=Gross anatomy of snakes.|url=https://www.researchgate.net/publication/241830127|journal=Veterinary Medicine/Small Animal Clinician|via=ResearchGate}}</ref>

====Turtles and tortoises====
[[File:Tortue de Floride Amiens.jpg|thumb|[[Red-eared slider]] taking a gulp of air]]

How [[turtle]]s breathe has been the subject of much study. To date, only a few species have been studied thoroughly enough to get an idea of how those turtles [[Breathing|breathe]]. The varied results indicate that turtles have found a variety of solutions to this problem.

The difficulty is that most [[turtle shell]]s are rigid and do not allow for the type of expansion and contraction that other amniotes use to ventilate their lungs. Some turtles, such as the Indian flapshell (''[[Indian flapshell turtle|Lissemys punctata]]''), have a sheet of muscle that envelops the lungs. When it contracts, the turtle can exhale. When at rest, the turtle can retract the limbs into the body cavity and force air out of the lungs. When the turtle protracts its limbs, the pressure inside the lungs is reduced, and the turtle can suck air in. Turtle lungs are attached to the inside of the top of the shell (carapace), with the bottom of the lungs attached (via connective tissue) to the rest of the viscera. By using a series of special muscles (roughly equivalent to a [[thoracic diaphragm|diaphragm]]), turtles are capable of pushing their viscera up and down, resulting in effective respiration, since many of these muscles have attachment points in conjunction with their forelimbs (indeed, many of the muscles expand into the limb pockets during contraction).<ref>{{cite journal |first1=Tyler R. |last1=Lyson |first2=Emma R. |last2=Schachner |first3=Jennifer |last3=Botha-Brink |first4=Torsten M. |last4=Scheyer |first5=Markus |last5=Lambertz |first6=G.S. |last6=Bever |first7=Bruce S. |last7=Rubidge |first8=Kevin |last8=de Queiroz |year=2014|title=Origin of the unique ventilatory apparatus of turtles |journal=Nature Communications |volume=5 |number=5211 |page=5211 |doi=10.1038/ncomms6211 |doi-access=free |pmid=25376734 |bibcode=2014NatCo...5.5211L |url=http://www.zora.uzh.ch/id/eprint/100716/7/LysonEtAl_NatCommun2014_Vol5_OriginVentilationApparatusTurtles_Supplem_s1.pdf}}{{open access}}</ref>

Breathing during locomotion has been studied in three species, and they show different patterns. Adult female green sea turtles do not breathe as they crutch along their nesting beaches. They hold their breath during terrestrial locomotion and breathe in bouts as they rest. North American box turtles breathe continuously during locomotion, and the ventilation cycle is not coordinated with the limb movements.<ref name=Landberg>{{cite journal | last=Landberg | first=Tobias |author2=Mailhot, Jeffrey |author3=Brainerd, Elizabeth | title=Lung ventilation during treadmill locomotion in a terrestrial turtle, ''Terrapene carolina'' | journal=Journal of Experimental Biology | volume=206 | issue=19 | year=2003 | pages=3391–3404| doi=10.1242/jeb.00553| pmid=12939371| doi-access=free | bibcode=2003JExpB.206.3391L }}</ref> This is because they use their abdominal muscles to breathe during locomotion. The last species to have been studied is the red-eared slider, which also breathes during locomotion, but takes smaller breaths during locomotion than during small pauses between locomotor bouts, indicating that there may be mechanical interference between the limb movements and the breathing apparatus. Box turtles have also been observed to breathe while completely sealed up inside their shells.<ref name=Landberg/>