Pleurae - pressure- intrapulmonary (intra-alveolar)...

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Pleurae : o parietal pleura o visceral (pulmonary) pleura : covers external lung surface o pleural fluid o pleurisy : inflammation of pleura; often caused by pneumonia less or more pleural fluid may be produced causing friction during breathing (less) or increased pressure (more) o pleural effusion : accumulation of fluid (pleural fluid, blood)in pleural space Mechanics of Breathing : - breathing (pulmonary ventilation) consists of: o inspiration : period when air flows into lungs o expiration : period when gases exit lungs - pressure relationships in thoracic cavity o respiratory pressures always described relative to atmospheric pressure atmospheric pressure (P atm ): pressure exerted by air (gases) surrounding body normal P atm at sea level is 760 mm Hg - negative respiratory pressure indicates pressure in that area is lower than atmospheric
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Unformatted text preview: pressure- intrapulmonary (intra-alveolar) pressure (P alv ) : pressure within alveoli of lungs o rises & falls with breathing, but always equalizes with P atm- intrapleural pressure (P ip ) : pressure within pleural cavity o also varies with breathing, but is always about 4 mm Hg less than P alv (negative with respect to both intrapulmonary & atmospheric pressures) o 2 forces lead to lung collapse: natural tendency of lungs to recoil surface tension of alveolar fluid (draws alveoli to smallest dimension) o these forces are opposed by the elasticity of chest wall (so thoracic cavity expands, preventing lung collapse) Kevin Kelleher, MTC Biology 211 Study Notes Exam 2 17 o any condition that equalizes intrapleural pressure with intrapulmonary or atmospheric pressure can cause immediate lung collapse o transpulmonary (transpulmonic) pressure : P alv - P ip keeps lungs from collapsing PAGE5...
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Pleurae - pressure- intrapulmonary (intra-alveolar)...

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