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MCAT Question A Day - 6/16/13 - Answer!

Surfactant is a secretion in the lungs that prevents alveoli from collapsing. Without this substance, what problem(s) might occur?

A.  The diameter of the bronchioles would remain constant.
B.  Inhalation would have to be more forceful.
C.  Exhalation would have to be more forceful.
D.  All of the above

The correct answer is (B). If alveolar walls collapse onto themselves (like inner walls of a balloon sticking together prior to inflation), it would take very forceful inhalation to fill them with air. Exhalation would not be as difficult, and the diameter of the bronchioles is irrelevant.