Editing Amphibian (section)

=== Respiratory system ===
[[File:Axolotl ganz.jpg|thumb|left|alt=Axolotl|The [[axolotl]] (''Ambystoma mexicanum'') retains its larval form with gills into adulthood]]
The lungs in amphibians are primitive compared to those of amniotes, possessing few internal [[alveolar septum|septa]] and large [[Pulmonary alveolus|alveoli]], and consequently having a comparatively slow diffusion rate for oxygen entering the blood. Ventilation is accomplished by [[buccal pumping]].<ref>{{cite journal|last1=Brainerd|first1=E. L. |title=New perspectives on the evolution of lung ventilation mechanisms in vertebrates |journal=Experimental Biology Online |year=1999 |volume=4 |issue=2 |pages=1–28 |doi=10.1007/s00898-999-0002-1 |bibcode=1999EvBO....4b...1B |s2cid=35368264 }}</ref> Most amphibians, however, are able to exchange gases with the water or air via their skin. To enable sufficient [[cutaneous respiration]], the surface of their highly vascularised skin must remain moist to allow the oxygen to diffuse at a sufficiently high rate.{{sfn | Dorit | Walker | Barnes | 1991 | p=847 }} Because oxygen concentration in the water increases at both low temperatures and high flow rates, aquatic amphibians in these situations can rely primarily on cutaneous respiration, as in the [[Telmatobius culeus|Titicaca water frog]] and the [[Cryptobranchus|hellbender salamander]]. In air, where oxygen is more concentrated, some small species can rely solely on cutaneous gas exchange, most famously the [[Plethodontidae|plethodontid salamanders]], which have neither lungs nor gills. Many aquatic salamanders and all tadpoles have gills in their larval stage, with some (such as the [[axolotl]]) retaining gills as aquatic adults.{{sfn | Dorit | Walker | Barnes | 1991 | p=847 }}