Write a note on pleura.

Pleura : Pleura is the double membrane structure that surrounds the lungs. The space inbetween the two membranes is filled with pleural fluid. 

The outer pleural membrane is in close contact with the thoracic lining whereas the inner pleural membrane is in contact with the lung surface. 

The pleural membrane protects the lungs and the pleural fluid reduces friction on the lung-surface.