The membrane that lines the inside of the chest cavity is the pleura.
The pleura is a thin, slippery serous membrane arranged in two continuous layers. The parietal pleura lines the inner surface of the chest wall, diaphragm, and central region around the lungs. The visceral pleura tightly covers the outer surface of each lung. Between them is the pleural cavity, containing a small amount of lubricating fluid that lets the lungs move smoothly as they expand and contract.
This arrangement also helps maintain a pressure relationship that keeps the lungs closely apposed to the chest wall. If air enters the pleural space, a pneumothorax can occur and part or all of a lung may collapse. Inflammation of the membrane is called pleurisy or pleuritis and can cause sharp pain that worsens with breathing.
The pleura is easy to confuse with nearby membranes. The pericardium surrounds the heart, the peritoneum lines much of the abdominal cavity, and the meninges surround the brain and spinal cord. The word pleura comes from Greek for “side” or “rib,” reflecting its location along the thorax.