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Pleura
  In our body's respiratory system, the Pleura is the thin serous membrane enveloping the lungs and lining the thoracic body cavity (chest cavity), consisting of two layers, the inner visceral pleura lying next to the pulmonary parenchyma and the outer parietal pleura, between the two layers is the pleural cavity which contains the pleural fluid, a thin film of liquid (serous fluid).
  In our body's thoracic cavity (chest cavity), each lung is enclosed by a double-layered serous membrane, called the pleura. The visceral pleura is firmly attached to the surface of the lung, at the hilum, the visceral pleura is continuous with the parietal pleura that lines the wall of the thorax.
  In and on our body's lungs, the small space between the visceral and parietal pleurae is the pleural cavity, which contains a thin film of <serous fluid produced by the pleura.
The fluid acts as a lubricant to reduce friction as the two layers slide against each other, and it helps to hold the two layers together as the Lungs inflate and deflate.
The pleura includes:

visceral pleura (inner pleura)
parietal pleura (outer pleura)
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