The human body contains approximately 6 quarts (5.6 liters) of blood. Blood acts as your body’s transportation system—in one day, your blood travels nearly 12,000 miles (19,312 kilometers). Pumped along by your heart, blood takes oxygen from the air you breathe and nutrients from the food you eat to all the cells of your body. (Your heart pumps 1 million barrels of blood during your lifetime—enough to fill three supertankers.) Blood also keeps cells clean and healthy by transporting waste products away after the nutrients and oxygen have been used for processes such as growth and repair. In addition, blood transports hormones—chemicals made in glands that control a variety of processes—throughout your body.