The Pathway of Oxygen
• Air enters the nostrils.
• Passes through the nasopharynx,
• Then, in the oral pharynx.
• Through the glottis.
• Into the trachea.
• Into the right and left bronchi, which branches and rebranches into.
• Bronchioles, each of which terminates in a cluster of
• Alveoli. Only in the alveoli does actual gas exchange takes place. There are some 300 million alveoli in two adult lungs. These provide a surface area of some 160 m2 (almost equal to the singles area of a tennis court and 80 times the area of our skin).