Which two components comprise the basement membrane?

• A. Basal lamina and reticular lamina
• B. Endothelium and mesothelium
• C. Keratin and collagen
• D. Basement membrane and submucosa

Answer: (A)

Basement membranes are thin, specialized extracellular sheets that anchor epithelia to the underlying connective tissue. They are composed of two layers: the basal lamina, laid down by epithelial cells and rich in laminin and type IV collagen, and the reticular lamina, produced by the surrounding connective tissue and containing different collagens and matrix components. The basal lamina provides a close, supportive surface for epithelial attachment and a selective barrier, while the reticular lamina links to the connective tissue, adding structural support. Together, these two layers form the basement membrane that stabilizes tissue architecture and regulates exchange between tissues. Endothelial and mesothelial cells are unrelated cell types lining vessels and cavities, keratin and collagen refer to structural proteins found in various tissues, and basement membrane with submucosa describes broader tissue regions rather than the two-layer structure itself.