Question: how do u breath?

Thomas Biggans answered on 23 Jun 2016:

So humans breath using our lungs. When we breath in our diaphragm (which is a dome shaped muscle underneath your lungs) goes flat which gives the lungs space to expand into and also decreases the pressure inside our chests. Now because our chest has a lower pressure than the atmospheric pressure outside our body, air is forced into our lungs and fills them up. Think about holding the end of a balloon full of air, if you open the end the air starts to come out of the balloon. That’s because the balloon has a higher pressure than the atmosphere. So its the same idea of pressure pushing air into our lungs.

The air collects in little pockets called alveoli. Blood that has been used by the body comes into the alveoli where the carbon dioxide waste is passed back into the air. Oxygen from the air passes into the blood which then leaves the alveoli and heads off to the heart where it’ll be pumped around the rest of the body.

Then your diaphragm goes back into its dome shape, reducing the amount of space and increasing the pressure on the lungs which forces the air back out into the atmosphere again the same way a balloon forces air back out.