Question

During inspiration, air passes into lungs due to

• A. Increase in volume of thoracic cavity and fall in lung pressure
• B. Fall in pressure inside the lungs
• C. Increased volume of thoracic cavity
• D. Muscular expansion of lungs

Answer 1

Answer: (A)

Increase in volume of thoracic cavity and fall in lung pressure

Inspiration leads to increase in the volume of the lungs which is caused due to contraction of the diaphragm. The intercoastal muscles lift the ribcage. During inspiration, air flows into the alveoli because atmospheric pressure is greater than alveolar pressure. Increasing thoracic volume results in decreased pleural pressure. Increased alveolar volume, decreases alveolar pressure. Thus air moves into the lungs.

So, the correct answer is option A.