Question

Expiration involves

• A. Relaxation of diaphragm and 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 intercostal muscles

When the diaphragm relaxes, air is exhaled by elastic recoil of the lung and the tissues lining the thoracic cavity in conjunction with the abdominal muscles which act as an antagonist paired with the diaphragm's contraction. The internal intercostals assist in expiration by pulling the ribcage down.