A thin layer of tissue covering the lungs and the wall of the chest cavity to protect and cushion the lungs A small amount of fluid that acts as a lubricant allows the lungs to move smoothly in the chest cavity during breathing SOURCE : http: //cancernet nci nih gov/dictionary html
– double membrane lining the lung, the layer of tissue lining the inside of the chest wall is called the parietal pleura and the outside of the lung the visceral pleura