Figure 4.

Simplified schematic of pleural space anatomy. Note the anatomic features of the parietal pleura, which suggest its central role in pleural fluid flow, including capillaries close to the pleural space, a thin pleural lining, and the presence of lymphatic stomata. Normal pleural fluid originates from parietal pleural microvascular filtrate and is drained from the pleural space by the hydraulic pumping action of parietal pleural lymphatics. Pleural fluid can also develop from movement across the visceral pleura in settings of elevated left atrial pressure and interstitial pulmonary edema.