Question

Air moves out of the lungs when the pressure inside the lungs is ___.

• A. less than the pressure in the atmosphere
• B. greater than the pressure in the atmosphere
• C. equal to the pressure in the atmosphere
• D. greater than the intra-alveolar pressure

Answer 1

The correct option is B

greater than the pressure in the atmosphere

The movement of air into and out of the lungs occurs because of a pressure gradient between the lungs and the atmosphere. Inspiration can occur if the pressure within the lungs (intrapulmonary pressure) is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure. Similarly, expiration takes place when the intrapulmonary pressure is higher than the atmospheric pressure.