The process by which blood containing O2 from the heart passes through the blood vessels to different parts of the body and blood containing CO2 from different parts of the body returns to the heart is called blood circulation. Liver has the highest blood flow (1350 ml/min). Blood flows in the second volume (1100 ml/min) to the kidney and in the third volume (700 ml/min) to the brain.
The process of blood circulation in the human body is completed in four stages. Systemic circulation, pulmonary circulation, coronary circulation and portal circulation.