Our respiratory system is responsible for cleaning the air that we breathe, supplying our bodies with oxygen, and getting rid of carbon dioxide. Did you know that you breathe in and out about 22,000 times a day? Or that your left lung is slightly smaller than your right? That leaves room in your chest for your heart! Learn all this and more in . ABOUT THE SERIES: The human body is a complex ⹀ and remarkable ⹀ machine. Digesting our food. Pumping our blood. Walking, running, and dancing. It takes our many body systems working together to keep us alive and living our lives to the fullest. This set of A True Books offers an in-depth look at our amazing bodies ⹀ one system at a time. Interesting information is presented in a fun, friendly way ⹀ and in the simplest terms possible ⹀ giving students a "behind-the-scenes" look at how their bodies work.