Asked by  | 20th May, 2009, 09:33: PM

Expert Answer:

The respiratory tract includes the nasal passages, pharynx, larynx, trachea, the primary bronchi, and lungs.

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 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

Answered by  | 21st May, 2009, 08:35: PM

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