How do the pleural membranes cover the lungs and chest wall?

The pleura is a continuous serous membrane that forms a closed, protective sac around each lung. It consists of two distinct layers that are in direct continuity at the hilum, the area where airways and vessels enter the lungs:12

• Parietal pleura: This layer lines the inner surface of the thoracic cavity, including the chest wall, the diaphragm, and the mediastinum.123
• Visceral pleura: This layer closely covers the surface of the lungs.12

In a healthy state, these two membranes are in close contact, separated only by a thin film of extracellular fluid. This fluid acts as a lubricant, allowing the lungs to move smoothly against the chest wall during breathing. The lungs are maintained in apposition to the thoracic wall by negative pressure within the potential space between these membranes, known as the pleural cavity.123