The pleura is a thin membrane that surrounds the lungs and lines the chest cavity. It consists of two layers: the visceral pleura, which is attached to the lungs, and the parietal pleura, which is attached to the chest wall. This structure helps reduce friction between the lungs and the chest wall during breathing. The pleura also plays a role in creating a pressure gradient that aids in lung expansion. It contains pleural fluid, which lubricates the surfaces and allows smooth movement. Conditions affecting the pleura, such as pleurisy or pleural effusion, can lead to pain and breathing difficulties.