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Transpulmonary pressures during expiration. 0. mid expiration. air. 1. -5. 0. start expiration. air. end expiration. 0. +2. +6. -7. 0. -5. Ptp. +9. +5. What keeps the lung inflated at end-expiration?. The negative Ppl. end expiration. 0. -5.
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Transpulmonary pressures during expiration 0 midexpiration air 1 -5 0 startexpiration air end expiration 0 +2 +6 -7 0 -5 Ptp +9 +5
What keeps the lung inflated at end-expiration? • The negative Ppl
end expiration 0 -5 Lungs collapse if chest is opened
What keeps the lung inflated at end-expiration? • 2. Alveolar surfactant • (phospholipid secreted by alveolar type II cells)
alveolar space type II cell type I cell The alveolar air-water interface Type I water Type II
Type I Laplace: If Palv constant, T 1 water Alveolar radius Type II Air-water interfacial tension T Palv T air water
T 1 Alveolar radius Alveolar surfactant decreases air-water tension Type I T Palv T air Type II water
Lung volumes total lung capacity residual volume 1.5 L 6 L inspiratory volume functional residual capacity inspiration expiration 3 L tidal volume (500 ml)
