The human circulatory system consists of the heart, blood vessels, and blood. The heart is a muscular organ located in the chest that pumps blood through the entire body using the blood vessels. It has four chambers - the right and left atria receive blood while the right and left ventricles pump blood out of the heart. The heart pumps deoxygenated blood to the lungs and oxygenated blood to the rest of the body. Maintaining a healthy heart is important to prevent diseases like heart attacks and strokes.