Question

Atmospheric air rushes in through trachea into the lungs due to ___.

• A. fall in pressure inside the lungs with decrease in the volume of the thoracic cavity
• B. fall in pressure inside the lungs with increase in the volume of the thoracic cavity
• C. increase in the pressure inside the lungs with increase in the volume of the thoracic cavity
• D. increase in the pressure inside the lungs with decrease in the volume of the thoracic cavity

Answer 1

The correct option is B

fall in pressure inside the lungs with increase in the volume of the thoracic cavity

During inspiration, the diaphragm contracts and pulls downward while the muscles between the ribs contract and pull upward. This increases the size of the thoracic cavity or lungs. Hence, there is decrease in the pressure inside the lungs and air rushes in and fills the lungs. In other words, the atmospheric air with high pressure or more gas molecules, moves to the low pressure or less gas molecules, in lungs.