What is the name of the continuous double sac that covers each lung?

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

Answer: (A)

The pleura is the continuous double-layer serous membrane that surrounds each lung. It has an inner layer, the visceral pleura, that clings to the lung surface, and an outer layer, the parietal pleura, that lines the chest wall and diaphragm. The small gap between these layers, the pleural cavity, contains fluid that allows the lungs to glide smoothly during breathing and helps keep them expanded. The other terms refer to membranes in different parts of the body: the peritoneum lines the abdominal cavity, the pericardium surrounds the heart, and the endometrium lines the uterus.