Which lining lines cavities that open to the exterior, such as the respiratory and digestive tracts?

Which lining lines cavities that open to the exterior, such as the respiratory and digestive tracts?

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

Answer: (A)

Mucous membranes line surfaces that open to the outside, such as the respiratory and digestive tracts, because they remain moist and capable of secreting mucus. This mucus helps trap dust and microbes, keeps the tissue lubricated, and supports protection and absorption along the tract. Structurally, a mucous membrane has an epithelial layer supported by underlying connective tissue called the lamina propria, and many glands or goblet cells that produce mucus. In the airways, cilia and mucus work together to move particles out of the tract, while in the digestive tract mucus protects the lining and aids in passage and digestion. Serous membranes, by contrast, line closed body cavities and secrete lubricating serous fluid to reduce friction. Epithelial tissue is the general tissue type that covers many surfaces, but the specific lining that opens to the exterior is the mucous membrane. Connective tissue below provides support but does not serve as the surface lining.

Mucous membranes line surfaces that open to the outside, such as the respiratory and digestive tracts, because they remain moist and capable of secreting mucus. This mucus helps trap dust and microbes, keeps the tissue lubricated, and supports protection and absorption along the tract. Structurally, a mucous membrane has an epithelial layer supported by underlying connective tissue called the lamina propria, and many glands or goblet cells that produce mucus. In the airways, cilia and mucus work together to move particles out of the tract, while in the digestive tract mucus protects the lining and aids in passage and digestion.

Serous membranes, by contrast, line closed body cavities and secrete lubricating serous fluid to reduce friction. Epithelial tissue is the general tissue type that covers many surfaces, but the specific lining that opens to the exterior is the mucous membrane. Connective tissue below provides support but does not serve as the surface lining.