In the human blood circulation system, two characteristics are found :
(1) Oxygenated blood and deoxygenated blood never mix in the heart and blood vessels.
(2) Blood completes one full cycle in the body twice. Initially, impure blood from the entire body enters the right auricle and ventricle, goes to the lungs through the pulmonary arteries, and from the lungs, oxygenated blood enters the left auricle, ventricle, and through the aorta, circulates throughout the body.