The pleura includes two thin layers of tissue that protect and cushion the lungs. The inner layer (visceral pleura) wraps around the lungs and is stuck so tightly to the lungs that it cannot be peeled off. The outer layer (parietal pleura) lines the inside of the chest wall. The very thin space between the layers is called the pleural cavity. A liquid, called pleural fluid, lubricates the pleural cavity so that the two layers of pleural tissue can slide against each other.