Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because
there is a negative pressure in the lungs
there is negative intrapleural pressure pulling at the lung walls
there is a positive intrapleural pressure
pressure in the lungs is higher than the atmospheric pressure
Lungs do not collapse between breaths, and some air always remains in the lungs, which can never be expelled due to the negative intrapleural pressure that pulls at the lung walls.