Air enters the nostrils
passes through the nasopharynx,
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
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!).