PLEURAL EFFUSION Hydrostatic pressure in the parietal pleura is similar to systemic circulation(30 cm H20),whereas that of the visceral pleura is similar to the pulmonary circulation(10 cm H20).Accordingly,most fluid in the pleural space is filtered from parietal pleura.Because the pressure within the pleural space itself is more subatmospheric at the apex than at the base,most of the fluid filters in from the less dependent upper lung zones. Fluid is drained out primarily through lymphatics in the parietal pleura.The fluid enters through lymphatic stomas (淋巴孔)on the surface of the parietal pleura,which are located beneath the mesothelial monolayer.The normal turnover of fluid within the pleural space is 10 to 20 mL/day.第 一 部 分 Hydrostatic pressure in the parietal pleura is similar to systemic circulation (30 cm H2O), whereas that of the visceral pleura is similar to the pulmonary circulation (10 cm H2O). Accordingly, most fluid in the pleural space is filtered from parietal pleura. Because the pressure within the pleural space itself is more subatmospheric at the apex than at the base, most of the fluid filters in from the less dependent upper lung zones. Fluid is drained out primarily through lymphatics in the parietal pleura. The fluid enters through lymphatic stomas （淋巴孔）on the surface of the parietal pleura, which are located beneath the mesothelial monolayer. The normal turnover of fluid within the pleural space is 10 to 20 mL/day. PLEURAL EFFUSION