Which lining is commonly moist and lines cavities that communicate with the outside world?

Which lining is commonly moist and lines cavities that communicate with the outside world?

• A. Serous membrane
• B. Mucous membrane
• C. Epithelial tissue
• D. Connective tissue

Answer: (B)

The lining described is the mucous membrane, often called mucosa. These linings stay moist because they secrete mucus from goblet cells and glands, which helps protect surfaces, trap dust and microbes, and keep tissues from drying out. They line passages that connect the inside of the body to the outside world—such as the respiratory tract, digestive tract, urinary tract, and parts of the reproductive tract—where contact with air, food, or fluids is constant. This moisture and mucus aid in lubrication and defense, making mucous membranes well suited for surfaces that interface with the external environment. By contrast, serous membranes line closed cavities (like the chest or abdomen) and produce serous fluid for lubrication, not mucus, and epithelial or connective tissues are broader categories that don’t specifically describe this moist external-facing lining.

The lining described is the mucous membrane, often called mucosa. These linings stay moist because they secrete mucus from goblet cells and glands, which helps protect surfaces, trap dust and microbes, and keep tissues from drying out. They line passages that connect the inside of the body to the outside world—such as the respiratory tract, digestive tract, urinary tract, and parts of the reproductive tract—where contact with air, food, or fluids is constant. This moisture and mucus aid in lubrication and defense, making mucous membranes well suited for surfaces that interface with the external environment. By contrast, serous membranes line closed cavities (like the chest or abdomen) and produce serous fluid for lubrication, not mucus, and epithelial or connective tissues are broader categories that don’t specifically describe this moist external-facing lining.