Your Circulatory System
Your body needs oxygen to survive. Getting oxygen to all parts of your body is the job of the circulatory system. It includes your heart, several quarts of blood, and more than 60,000 miles of blood vessels.
Heart
This fist-sized muscle pumps nonstop. Each heartbeat forces two ounces of blood into the arteries. Some goes to the lungs to pick up oxygen. The rest transports oxygen to other parts of the body.
Lungs
These two organs take oxygen from the air you breathe. The blood that is pumped to the lungs then picks up the oxygen.