"It takes our many body systems working together to keep us alive and living our lives to the fullest. This set of True Books offers an in-depth look at our amazing bodies--one system at a time"-- "Discover the main systems of our amazing human body with this new series of books! Our muscular system covers our bodies from head to toe. It helps keep us upright and gives us the power to stand, sit, run, smile, and more. Did you know that your muscles...