The serous membrane that lines the thoracic cavity and surrounds the lungs is the

• A. Meninges
• B. Pleura
• C. Pericardium
• D. Peritoneum

Answer: (B)

Serous membranes produce a slippery fluid and form two layers that slide past each other to reduce friction as organs move. In the chest, the membrane that lines the thoracic cavity and covers the lungs is the pleura—consisting of a parietal layer lining the chest wall and a visceral layer covering the lungs, with a narrow pleural space between them that contains fluid to help the lungs expand smoothly during breathing. The other membranes have different roles: the meninges protect the brain and spinal cord, the pericardium surrounds the heart, and the peritoneum lines the abdominal cavity.