circulatory systems in amphibians
two atria and a single ventricle. The atrium receives deoxygenated blood from the blood vessels (veins) that drain the various organs of the body. The left atrium receives oxygenated blood from the lungs and skin (which also serves as a gas exchange organ in most amphibians). when the ventricle contracts, oxygenated blood from the left atrium is sent, relatively pure, into the carotid arteries taking blood to the head (and brain); deoxygenated blood from the right atrium is sent, relatively pure, to the pulmocutaneous arteries taking blood to the skin and lungs where fresh oxygen can be picked up. Only the blood passing into the aortic arches has been thoroughly mixed, but even so it contains enough oxygen to supply the needs of the rest of the body. in contrast to the fish, both the gas exchange organs and the interior tissues of the body get their blood under full pressure.