What are The Pleural Membranes

The pleura is a membrane lining the inside of the chest similar to the peritoneum which lines the abdomen. After lining the inside of the chest, just like wall paper lines the walls of the inside of a room, a continuation of the same membrane is reflected over the entire surface of the lungs, just as if you were also to line the back of your bookcase with pleura over the lungs creates a narrow space all around the lungs between lung and chest wall, all lined with the same pleural membrane.

This space is called the "pleural cavity," When this pleural membrane is inflamed the condition is called "pleurisy"