Amphibian circulation has a more complex arrangement of blood vessels, forming a double-circuit circulation. The three chambered amphibian heart consists of the right and left atria and a single ventricle. In the amphibian heart, oxygenated and deoxygenated blood are kept somewhat separate, largely as a result of the timing of the contractions of the left and right atria. First the blood returning from the right atrium is pumped by the ventricle into pulmonary circulation. After most of the deoxygenated blood has left the ventricle, oxygenated blood is pushed in and pumped through the amphibian body.
