Neutral mucin is present in which structures?

• A. Basement membrane
• B. Thyroid colloid
• C. Surface epithelium of stomach goblet cells
• D. All of the above

Answer: (D)

Neutral mucin is a neutral glycoprotein component found in several tissue contexts, not just in secretions. In the basement membrane, the extracellular matrix contains mucin‑type glycoproteins that contribute to its gel-like properties, so neutral mucin can be present there. In thyroid colloid, glycoprotein components of thyroglobulin carry carbohydrate residues that can be neutral mucin–like in nature. In the stomach, the surface epithelium has mucus-secreting cells that produce neutral mucin to form a protective gel over the mucosa. Because neutral mucin can be present in all of these structures, the best answer is that it is present in all of the above.