What is the main reason for expiration to occur?

What is the main reason for expiration to occur?
  1. Negative pressure in the lungs with respect to atmospheric pressure
  2. Intra-pulmonary pressure is less than atmospheric pressure
  3. Intra-pulmonary pressure is greater than atmospheric pressure
  4. Positive pressure in the lungs with respect to atmospheric pressure

Solution

Expiration takes place when the intra-pulmonary pressure is higher than the atmospheric pressure.

Asked in: NCERT

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