Question

Expiration involves

• A. Relaxation of diaphragm and contraction of intercostal muscles.
• B. Contraction of Diaphragm and intercostal muscles.
• C. Contraction of diaphragm muscles.
• D. Contraction of intercostal muscles.

Answer 1

The correct option is A Relaxation of diaphragm and contraction of intercostal muscles.

• During expiration, the contracted intercostal muscles and diaphragm tend to relax.
• The lungs can contract by themselves like a deflating balloon. Therefore, when the muscles that expand the thorax are relaxed, the lungs contract under their own elastic recoil forces so that the breath is expired.

So the answer is- relaxation of the diaphragm and intercostal muscles.