Final answer:
The thin slippery outer membrane that covers the lungs is known as the pleura, comprising two layers, the visceral and parietal pleura, which enclose the pleural cavity containing pleural fluid.
Step-by-step explanation:
The thin slippery outer membrane that covers the lungs is referred to as the pleura. This serous membrane is composed of two layers: the visceral pleura that is directly on top of the lungs and extends into the lung fissures, and the parietal pleura, which is the outer layer that attaches to the thoracic wall, mediastinum, and diaphragm.
The space between these two layers is known as the pleural cavity, which contains a small amount of pleural fluid that serves two main functions; it acts as a lubricant to reduce friction during breathing, and as an adhesive to maintain the connection between the lungs and the thoracic wall, allowing the lungs to move during ventilation.