For air to flow into or out of the lungs, there must be
A) a volume gradient established between the atmosphere and the alveoli.
B) a temperature gradient between the atmosphere and the alveoli.
C) a pressure gradient established between the atmosphere and the alveoli.
D) a diffusion gradient between the atmosphere and the alveoli.
E) None of the choices are correct.

Question

Quizplus · Accepted Answer

Air flows into or out of the lungs due to a pressure gradient between the atmosphere and the alveoli. When the pressure inside the alveoli is lower than the atmospheric pressure, air flows into the lungs (inhalation). Conversely, when the alveolar pressure is higher than atmospheric pressure, air flows out of the lungs (exhalation).

For Air to Flow into or Out of the Lungs