Pleural anatomy and physiology
The pleural space is a potential space that contains 2 to 10 mL of pleural fluid between the visceral and parietal pleural layers that essentially represents interstitial fluid from the parietal pleura (an ultrafiltrate of plasma). The pleural space is contiguous with the interlobar fissures of the lungs. The pleura is a thin, serous layer that covers the lungs (visceral pleura) and is reflected onto the chest wall and pericardium (parietal pleura). The visceral pleura is supplied by the pulmonary arterial system and drains into the pulmonary venous system, whereas the parietal pleura is supplied by the systemic arterial system and drains into the systemic venous system. Figure 21-1 shows the normal appearance of the pleura on chest radiography.