what do you mean by when air is taken in and let out , the lungs always contain a residual volume of air
Answers
The mechanics of breathing follow Boyle’s Law which states that pressure and volume have an inverse relationship.
The process of inhalation occurs due to an increase in the lung volume (diaphragm contraction and chest wall expansion) which results in a decrease in lung pressure in comparison to the atmosphere; thus, air rushes in the airway.
The process of exhalation occurs due to an elastic recoil of the lung tissue which causes a decrease in volume, resulting in increased pressure in comparison to the atmosphere; thus, air rushes out of the airway.
There is no contraction of muscles during exhalation; it is considered a passive process.
The lung is protected by layers of tissue referred to as the visceral pleura and parietal pleura; the intrapleural space contains a small amount of fluid that protects the tissue by reducing friction.