Mechanism of Breathing · NCERT Biology

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

  1. Lower than atmospheric
  2. Higher
  3. Equal to atmospheric
  4. Zero or negligible
Show answer and explanation

Correct answer: Higher

Expiration occurs when the relaxation of the diaphragm and intercostal muscles reduces the thoracic volume. This increase in intra-pulmonary pressure to a level slightly above atmospheric pressure forces air out of the lungs.

Difficulty: Medium Question 4 of 20

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