Your respiratory system is working with each breath in and out. But it's more complex than just breathing. The information inside this book covers the structure and function of the respiratory system, as well as the importance of maintaining healthy lungs. The air that enters our lungs when we breathe in contains oxygen, which our bodies need to help turn food into energy. When we breathe out, carbon dioxide is removed from the body. Colorful photographs and in-depth diagrams display how this essential life process functions ceaselessly each day.