Question

Breathing is affected by

• A. Expansion of lungs
• B. Contraction of lungs
• C. Both A and B
• D. Heart beat

Answer 1

Answer: (C)

Both A and B

Breathing involves expansion and contraction off lungs to adjust the partial pressure of relative gases for exchange. The process of inhalation occurs due to an increase in the lung volume (diaphragm contraction and chest wall expansion) which results in a decrease in lung pressure in comparison to the atmosphere. Thus, air rushes in the airway. The process of exhalation occurs due to an elastic recoil of the lung tissue which causes a decrease in volume, resulting in increased pressure in comparison to the atmosphere. Thus, air rushes out of the airway.

Therefore, the correct answer is option C.