What happens to the pressure inside the lungs while a person inhales?
AIt rises above atmospheric pressure
BIt stays equal to atmospheric always
CIt rises to about 60 mm Hg gauge
DIt drops below atmospheric pressure
Answer & Solution
Correct answer: D. It drops below atmospheric pressure
1. Air flows from higher pressure toward lower pressure.
2. To draw air in, the lungs must be at a lower pressure than the outside air.
3. Muscles in the diaphragm and rib cage increase the volume of the lungs, which lowers the pressure inside them below atmospheric, a negative gauge pressure.
4. On exhaling the pressure rises above atmospheric instead, which is a positive gauge pressure, so the two must not be swapped.
5. A steady match with atmospheric pressure would mean no air moved at all.
_Source: OpenStax College Physics (CC BY 4.0), Ch 11 "Fluid Statics", section 11.9 Pressures in the Body_
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