Which tissues can be used as a second control to demonstrate epithelial mucins?

• A. Small bowel and appendix
• B. Brain and Lung
• C. Stomach and Colon
• D. Spleen and Pancreas

Answer: (A)

Epithelial mucins are produced by goblet cells in mucosal lining, so a good second control for demonstrating mucins must be a tissue with robust, well-defined mucin-producing epithelium. The small intestine and appendix fit this role perfectly because their mucosal surfaces are rich in goblet cells that secrete mucins. When you apply mucin stains, these tissues reliably show positive staining, confirming that the stain and technique are working across mucin-producing epithelium. Using a second control from these sites helps validate the assay beyond a single tissue.

Brain and lung aren’t ideal here because brain lacks mucin-producing epithelium, and while lung has goblet cells in the airways, its mucin expression isn’t as consistently representative as that of the intestinal mucosa. Stomach and colon do have mucins, but the combination of small bowel and appendix provides a clear, strong demonstration across two distinct mucin-rich intestinal epithelia. Spleen and pancreas do not have the mucin-rich epithelial lining needed for this purpose.