Humans inhale air that is rich in oxygen and exhale air that is rich in carbon dioxide. The pathway that air takes in the human body begins with the nose and ends with the alveoli in the lungs.
Air enters the nose of humans as they inhale. Next, it passes through the nasopharnyx at the back of the throat. Then, air reaches the oral pharynx in the throat and passes through the glottis. Next, air passes into the trachea. Then, it reaches the lungs by passing into the right and left bronchi. The bronchi branch into bronchioles. Each of the bronchioles terminates with a small cluster of blood vessels and alveoli. Air reaches the alveoli and gas exchange occurs here.