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 these choices is correct.

Question

Quizplus · Accepted Answer

Air flows into and out of the lungs due to a pressure gradient established between the atmosphere and the alveoli. During inhalation, the diaphragm and intercostal muscles contract, which increases the volume of the thoracic cavity and decreases the pressure within the lungs. Air then flows from an area of high pressure (the atmosphere) to an area of low pressure (the lungs). During exhalation, the diaphragm and intercostal muscles relax, which decreases the volume of the thoracic cavity and increases the pressure within the lungs. Air then flows from an area of high pressure (the lungs) to an area of low pressure (the atmosphere).

For Air to Flow into or Out of the Lungs,there