Which type of membrane lines body cavities that open to the exterior?

• A. Serous
• B. Mucus
• C. Synovial
• D. Cutaneous

Answer: (B)

The correct type of membrane that lines body cavities opening to the exterior is mucus. Mucous membranes, also known as mucosae, are specialized epithelial tissues that secrete mucus, which serves various functions such as lubrication, protection, and secretion. These membranes are found in areas such as the respiratory tract, gastrointestinal tract, and urogenital tract, where they play a critical role in maintaining moisture and providing a barrier against pathogens.

In contrast, serous membranes line body cavities that do not open to the exterior, such as the pleura around the lungs and the peritoneum around the abdominal cavity. Synovial membranes line the cavities of joints and are involved in the production of synovial fluid, which lubricates the joints. Cutaneous membranes refer to the skin, which serves as a protective barrier for the body but does not line any internal body cavities. Understanding the different functions and locations of these membrane types is crucial for recognizing their roles in overall body function.