What are the principal components of the basement membrane?

• A. Basal lamina and reticular lamina
• B. Basal lamina only
• C. Basal lamina, reticular lamina, and proteoglycans
• D. Reticular lamina only

Answer: (C)

The basement membrane is a thin, specialized extracellular matrix that anchors the epithelium to the underlying connective tissue. It consists of two layers: the basal lamina on the epithelial side and the reticular lamina produced by connective tissue. The basal lamina is a dense mesh built mainly from laminin and type IV collagen, and it also includes proteoglycans such as perlecan. The reticular lamina lies beneath and is composed by connective tissue components like collagen type III and other matrix molecules, linking to the basal lamina to form a continuous barrier.

Proteoglycans are essential parts of this matrix; their long GAG chains attract water and provide charge, helping with hydration, resilience, filtration, and sequestration of signaling molecules. Because proteoglycans are integrated into the basement membrane’s network, all three components—basal lamina, reticular lamina, and proteoglycans—collectively define its principal makeup.