What is called double circulation?

(N/A) Double circulation is a process in which the blood flows through the heart twice during each complete cycle of the body. In humans,the blood passes through the heart in two distinct circuits: the pulmonary circulation (deoxygenated blood to the lungs) and the systemic circulation (oxygenated blood to the body tissues). Because the oxygenated and deoxygenated blood are kept separate and pass through the heart separately,this mechanism is known as double circulation.