Whenever you inhale your lungs fill with oxygen. That oxygen goes to your heart and acts as a fuel to make blood. You're heart then pumps it to everywhere in your body through your veins and takes back the used blood. When returned to the heart, the oxygen refreshes the red blood cells to make them usable again! When you exhale, you get rid of the Carbon Dioxide, which is basically used up oxegen, so it's useless. After you exhale, you inhale again and the process starts over again!
} I hope this helped! {
> Sorry the question was long