Ba-boom, ba-boom, ba-boom . . . your incredible heart beats more than once every second, no matter what you’re doing. And your lungs pull in up to 145 gallons of oxygen each day. So how are your heart and lungs connected, and what do they do? Join the Stickmen as they explore your body to find out how your heart pumps blood, how oxygen travels through your body, and how your body fights off germs. You’ll discover why you need two trillion red blood cells, how exercise affects the body, and what exactly is inside your lungs. Colorful diagrams and fascinating text show how your circulatory system works to keep you fit, warm, and alive!