What are the two layers of the membrane surrounding each lung commonly referred to as?

• A. Pleura
• B. Mediastinum
• C. Pericardium
• D. Endothelium

Answer: (A)

The two layers of the membrane surrounding each lung are referred to as the pleura. This pleural membrane consists of two distinct layers: the visceral pleura, which adheres directly to the lung surface, and the parietal pleura, which lines the thoracic cavity. These layers create a pleural cavity filled with pleural fluid, which serves to reduce friction between the lungs and the chest wall during respiration, allowing for smooth movement as the lungs expand and contract. The pleura also plays a role in maintaining negative pressure within the thoracic cavity, which is essential for effective lung inflation.

The other options refer to different anatomical structures. The mediastinum is the area between the lungs that contains the heart, great vessels, and other structures but is not a membrane layer. The pericardium is a membrane surrounding the heart, and the endothelium refers to the thin layer of cells lining blood vessels, neither of which has any relation to the lungs' surrounding membranes.