Question

Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because

• A. there is a negative intrapleural pressure pulling at the lung walls
• B. there is a negative pressure in the lungs
• C. pressure in the lungs is higher than the atmospheric pressure
• D. there is a positive intrapleural pressure

Answer 1

The correct option is A

there is a negative intrapleural pressure pulling at the lung walls

The correct option is A

Explanation of correct option:

The double-layered membrane that protects the lungs is the pleural membrane that has a negative pressure that is lower than the atmospheric pressure that pulls the air outside to the lungs.

Explanation of incorrect options

Option B

The negative pressure that is responsible for the inhalation of air is maintained by a pleural membrane that covers the lungs.

Option C

If the pressure inside the lungs is higher than the atmospheric pressure, air flows out from the lungs (exhalation).

Option D

If intrapleural pressure is positive, the further flow of air will be impossible.

Final answer: Lungs do not collapse between breaths, and some air always remains in the lungs, which can never be expelled because there is a negative intrapleural pressure pulling at the lung walls.