Malignant Pleural Mesothelioma : What is the Pleural ?

The lungs are in a cavity that is protected by the ribs.  The glue, so to speak, that keeps the lungs inflated is called the “pleura.” The pleura are two thin linings or membranes that protect and cushion the lungs.

One lining covers the lungs. It is called the visceral pleura—the other lining covers the chest wall. It is called the parietal pleura. 

Between these two linings there is a small amount of fluid (pleural fluid) that lubricates the surface of the linings, so the two surfaces glide smoothly over each other. 

It might be helpful to think of the linings as two pieces of glass placed on top of each other, one representing the lung pleura and the other piece being the chest wall pleura. If you set these pieces of glass one on top of the other they can easily be separated. But if you lightly coat the inside glass with water (pleural fluid) the pieces slide easily over each other and are very difficult to separate. 

When there is extra fluid in the pleural space, as in Malignant Pleural Mesothelioma, breathing becomes difficult, as the excess fluid does not allow the lungs to fill with the needed oxygen.