This lesson focuses on the respiratory system. As you're probably aware, it's the group of organs that allow you to get that crucial substance, oxygen, to all the cells in your body. You'll learn about the anatomy of your respiratory organs and which muscles are crucial for breathing. You'll also become aware of the differences between ventilation, external respiration, internal respiration, and cellular respiration. You'll also learn about illnesses that can affect the respiratory system, compromising a person's ability to breathe.