Blue staining in the umbilical cord tissue indicates the presence of which substance?

• A. Collagen
• B. Connective tissue mucin
• C. Elastic fibers
• D. Keratin

Answer: (B)

Blue staining reflects the presence of acidic mucopolysaccharides (mucin) because stains like Alcian blue specifically bind these substances and turn them blue. The umbilical cord’s Wharton’s jelly is rich in mucopolysaccharides, so blue staining indicates connective tissue mucin in that tissue. This helps distinguish it from other components: elastic fibers and keratin are revealed by different stains and appearances (elastic fibers often show up black with special stains, keratin staining highlights cytokeratin rather than mucin), and collagen is typically demonstrated with other stains that don’t specifically indicate mucin.