Which membrane surrounds the lungs?

• A. Alveoli
• B. Bronchioles
• C. Pleura
• D. Peritoneum

Answer: (C)

The surrounding membrane of the lungs is the pleura. It consists of two layers: the visceral pleura that clings to the lungs themselves and the parietal pleura that lines the inner chest wall and diaphragm. The space between these layers, the pleural cavity, contains a small amount of lubricating fluid that lets the lungs glide smoothly as you breathe and helps keep the lungs expanded. This setup is specific to the lungs; the other options are not membranes around the lungs—alveoli are the tiny air sacs where gas exchange occurs inside the lungs, bronchioles are small air passages, and the peritoneum lines the abdominal cavity.