Your diaphragm, and muscles between your ribs, make air move in and out of your lungs. It travels through the trachea, bronchi, and bronchioles to alveoli. In the alveoli, oxygen diffuses into the blood and carbon dioxide leaves. This is gas exchange.
Air enters the lungs and leaves it as a result of the relaxation and contraction of the diaphragm and the muscles between the ribs. When both the muscles and the diaphragm relax, air enters from the trachea and travels through the bronchi and the bronchioles to the alveoli, where the oxygen in the air diffuses into the blood and carbon dioxide diffuse in the opposite direction. The entire process is known as gas exchange.
