describe double circulation of blood in human beings why is it necessary

Double circulation in human beings refers to the process where blood passes through the heart twice in one complete cycle of circulation. This involves two separate circuits: the pulmonary circulation and the systemic circulation. In pulmonary circulation, deoxygenated blood from the body enters the right atrium, moves to the right ventricle, and is then pumped to the lungs through the pulmonary artery for oxygenation. Oxygen-rich blood returns to the left atrium of the heart, moves to the left ventricle, and is pumped out to the body through the aorta in systemic circulation. This system ensures the separation of oxygenated and deoxygenated blood. Double circulation is necessary because it prevents the mixing of oxygenated and deoxygenated blood, allowing the body tissues to receive pure oxygenated blood. This efficient oxygen supply supports higher metabolic activity and energy production, which is crucial for warm-blooded animals like humans to maintain their body temperature and perform energy-intensive functions. It also allows the heart to pump blood at different pressures to the lungs and body, protecting delicate lung tissues while ensuring adequate blood flow to the body tissues.