<prompt> During inspiration when the diaphragm contracts, the intrapleural pressure becomes:More negativeLess negativePositiveEqual to the intra alveolar pressure  <response>: The intrapleural pressure is always negative to the atmospheric pressure. During inspiration it is -6mHg and during expiration it is -2mmHg. Intrapleural pressure prevents collapse of lungs.Intra alveolar pressure is -4mm during inspiration and 4mm Hg during expiration. It helps in flow of air in and out of alveoli and helps in exchange of gases. 