What is the peritoneum?

• A. The membrane covering the heart
• B. Double-layered membrane surrounding the abdominal organs
• C. The serous membrane lining the thoracic cavity
• D. The lining of the joint capsule

Answer: (B)

The peritoneum is a serous membrane that lines the abdominal cavity and covers the abdominal organs. It is essentially a continuous, double-layered sheet: the parietal peritoneum lines the cavity, the visceral peritoneum covers the organs, and the two layers fold back on themselves to form mesenteries and omenta. This arrangement creates a potential space—the peritoneal cavity—filled with a small amount of serous fluid that lets abdominal organs glide smoothly against each other as they move. When you hear “double-layered membrane surrounding the abdominal organs,” that captures the core idea: a continuous serous membrane that both lines the cavity and covers the organs within it. In contrast, membranes around the heart are the pericardium, those lining the thoracic cavity are pleura, and the lining of a joint capsule is the synovial membrane, so they are located in different regions and serve related but distinct roles.