Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled becauseA. there is a negative pressure in the lungsB. there is a negative intrapleurai pressure pulling at the lungs wallsC. there is a positive intrapleural pressureD. pressure in the lungs is higher than the atmospheric pressure

Lungs do not collapse between breaths and some air always remains in t

1.	Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled becauseA. there is a negative pressure in the lungsB. there is a negative intrapleurai pressure pulling at the lungs wallsC. there is a positive intrapleural pressureD. pressure in the lungs is higher than the atmospheric pressure
Answer» Correct Answer - B Lungs do not collapse between breaths and some air always remain in the lungs, which can be never expelled, because there is a negative inrapleural pressure pulling the lung walls. Alveoli are basic funcational unit of lungs. The outer alveolar wall surface have cells, which secrets DPPC also called as lipid surfactant. The surfactant expands the alveoli. Due to which the negative pressure inside the alveoli increase. this prevents the alveoli from collapsing .