Multiple choice

In normal expiration, the diaphragm is

  1. Arched

  2. Flattened

  3. Perforated

  4. None of these

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

During inhalation, the diaphragm contracts, thus enlarging the thoracic cavity (the external intercostal muscles also participate in this enlargement). This reduces intra-thoracic pressure: in other words, enlarging the cavity creates suction that draws air into the lungs.