the hearts of other reptiles are designed to contain three sections including two atriums and ventricle. the right atrium, which collects the returned de-oxygenated blood and the left atrium which collects the oxygenated blood collected from pulmonary arteries of the lung, takes the blood to a common ventricle. when there is just one ventricle to receive and mix oxygenated and deoxygenated blood and pump it to the body, the mixture of blood the body receives has relatively less oxygen.