The circulatory system, also called the cardiovascular system, transports blood throughout the body to provide nutrients and oxygen to tissues and remove waste. It has three main parts: the pulmonary circulation to the lungs, the coronary circulation to the heart, and the systemic circulation to the rest of the body. Each part must work independently for the overall system to function properly. Centered on the heart, the circulatory system is a complex network of blood vessels that pumps approximately 5 liters of blood to fuel all body tissues and remove waste through the entire body.