The positive control tissue commonly used for mucin staining is which?

• A. Small intestine
• B. Heart
• C. Brain
• D. Skin

Answer: (A)

Mucin staining relies on tissues that naturally produce abundant mucin so the stain reliably lights up. The small intestine fits this perfectly because its lining has many goblet cells that secrete mucus rich in mucopolysaccharides. When a mucin stain is applied, these goblet cells show strong, consistent staining, confirming the stain is working.

The other tissues don’t provide that reliable mucin signal: the heart and brain have little or no mucin-producing goblet cells, and while skin contains some mucous components, it doesn’t offer the abundant, uniform mucin signal that goblet cells in the intestine do. So the small intestine is the best positive control for mucin staining.