Each lung is surrounded by a separate pleural (relating to the ribs) cavity formed by the pleural serous membranes. The parietal pleura covers the inner thoracic wall, diaphragm, and mediastinum. The parietal pleura is continuous with the visceral pleura, which covers the surface of the lung.
Each pleural cavity is lined by a single layer of flat cells, mesothelium, and an associated layer of supporting connective tissue; together, they form the pleura.
The pleura is divided into two major types, based on location:
- pleura associated with the walls of a pleural cavity is parietal pleura;
- pleura that reflects from the medial wall and onto the surface of the lung is visceral pleura , which adheres to and covers the lung
Each pleural cavity is the potential space enclosed between the visceral and parietal pleurae. Theynormally contain only a very thin layer of serous fluid. As a result, the surface of the lung, which is covered by visceral pleura, directly opposes and freely slides over the parietal pleura attached to the wall