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

Answer 1

The correct option is A There is a negative pressure in the lungs.

Lungs do not collapse between breaths and some air always remains in the lungs which can be never expelled because there is a negative intrapleural pressure pulling at the lung walls. The alveoli are the functional units of the lungs. The outer wall of alveoli has the presence of lipid surfactants that cause the expansion of alveoli. Due to this expansion, the negative pressure inside the alveoli increases. This prevents the lungs from collapsing.

So, option A is the correct option.