ABSTRACT
The pleura consist of two membranes: the visceral covering the lung and the parietal pleura covering the diaphragm and the chest wall. Between these two membranes there is a potential space named pleural space, which is filled with a thin film of fluid, called pleural fluid. The pleural fluid is a filtrate of the parietal pleura capillaries. The main function of the pleural fluid is to eliminate friction forces (acting as a lubricant) allowing extensive movement of the lung to the chest wall during respiratory movements. The visceral pleura also contributes to the shape of the lung, provides a limit to expansion, and contributes to the work of deflation (1,2). Pleural space also provides a protecting mechanism against the development of pneumothorax and alveolar edema. During edema, excess fluid could escape the lung by entering the pleural space (3). The continuous submesothelial tissue with the connective tissue of the lung parenchyma prevents the overdistension of alveoli at the pleura surface (4).
