Editing Amphibian (section)

=== Circulatory system ===
[[File:Juvenile Amphibian Circulatory System.svg|thumb|Juvenile amphibian circulatory systems are single loop systems which resemble fish. <!--
-->{{olist
    |Internal gills where the blood is reoxygenated
    |Point where the blood is depleted of oxygen and returns to the heart via veins
    |Two chambered heart
}} Red indicates oxygenated blood, and blue represents oxygen depleted blood.]]
Amphibians have a juvenile stage and an adult stage, and the circulatory systems of the two are distinct. In the juvenile (or tadpole) stage, the circulation is similar to that of a fish; the two-chambered heart pumps the blood through the gills where it is oxygenated, and is spread around the body and back to the heart in a single loop. In the adult stage, amphibians (especially frogs) lose their gills and develop lungs. They have a heart that consists of a single ventricle and two atria. When the ventricle starts contracting, deoxygenated blood is pumped through the [[pulmonary artery]] to the lungs. Continued contraction then pumps oxygenated blood around the rest of the body. Mixing of the two bloodstreams is minimized by the anatomy of the chambers.{{sfn | Dorit | Walker | Barnes | 1991 | p=306 }}