Step 1-
Your diaphragm moves down as it contracts. Your ribs move outward. These movements make the space inside the chest larger.
Step 2-
Air rushes in through the nose and mouth and passes through the throat. Air then moves past the epiglottis which is open into the trachea.
Step 3
Air moves into your bronchi. The bronchi branch out and end in tiny air sacs, called alveoli.
Step 4
Air moves into your alveoli. Oxygen moves through the walls of alveoli and capillaries, entering the blood.
Step 5
Carbon dioxide moves from the blood through the walls of capillaries and alveoli in order to be expelled by the lungs.
Step 6
Your diaphragm moves up as it relaxes. Your ribs move inward. These movements make the space inside the chest smaller.
Step 7
Your lungs are squeezed and air is pushed out of the alveoli. The air travels back through your bronchi, trachea, and nose and mouth.