How is the Volume Of The Lungs Increased?
The volume of the lungs is increased during inspiration (The process of breathing in). During inspiration; • The diaphragm contracts and flattens which increases the vertical dimension of the thoracic cavity. • The chest wall lifts up and out increasing the horizontal dimension of the thoracic cavity. • In turn the pleural cavity increases causing a drop in intrapleural pressure. Therefore the parietal pleura are pulled outwards by the expanding thoracic cavity. • The parietal pleura also pull the visceral pleura and the lungs out with them. The net result is that the pressure in the lungs drops to 758mmHg, which is lower than the 760mmHg air pressure. As air flows from a region of high pressure to a region of low pressure, inspiration takes place. Air continues to flow into the lungs as long as the pressure difference exists. Once the pressure equalises the inspiration muscles relax and expiration can begin.
