The circulatory system is made up of the heart and blood vessels, including arteries, veins, and capillaries. The heart pumps blood through the arteries and returns it via the veins. Arteries carry oxygenated blood away from the heart while veins carry deoxygenated blood back to the heart. Capillaries link the arteries and veins and allow for the exchange of oxygen, carbon dioxide, nutrients, and waste between the blood and body cells. The main components of blood are plasma, red blood cells, white blood cells, and platelets. Red blood cells carry oxygen, white blood cells protect against disease, and platelets help the blood to clot.