A histological section of small intestine stained with PAS shows a magenta-stained brush border along the luminal surface of columnar absorptive cells. Which structure accounts for this PAS-positive staining?

• A Terminal web of actin filaments beneath the membrane
• B Glycosaminoglycan layer overlying true cilia
• C Glycocalyx rich in glycoproteins on the tips of microvilli ✓
• D Zonula occludens complex at the apical pole

Explanation

Microvilli of the striated border are covered by a fuzzy glycocalyx composed of glycoproteins and glycolipids that stains intensely with PAS. Cilia are not present on absorptive enterocytes, which eliminates option B. The terminal web is intracellular and does not itself give the luminal PAS reaction.

Reference: Junqueira's Basic Histology: Text and Atlas, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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