Every part of the body needs to be fed by a constant supply of oxygen and nutrients to survive. Oxygen and nutrients are delivered by the blood, a fluid that circulates continuously throughout the body.
Blood picks up oxygen, becomes oxygenated in the lungs, then loses oxygen and picks up carbon dioxide in the organs and tissues of the body.
The heart is the organ responsible for maintaining this vital circulation of blood. The heart has dual responsibilities of pumping oxygenated blood to the body and pumping oxygen-poor blood to the lungs for reoxygenation.