Which components form the basement membrane?

• A. Basal lamina produced by epithelial cells and reticular lamina produced by connective tissue.
• B. Tight junctions and gap junctions.
• C. Connective tissue reticular fibers only.
• D. Basal lamina and lamina propria.

Answer: (B)

The basement membrane is a specialized extracellular matrix that sits between epithelium and connective tissue. It is formed from two layers: the basal lamina, produced by epithelial cells, and the reticular lamina, produced by connective tissue cells. The basal lamina provides a supportive scaffold rich in laminin and type IV collagen that helps epithelial cells attach, polarize, and organize their structure. The reticular lamina, made by fibroblasts in the underlying connective tissue, anchors the basement membrane to the deeper tissues through components like type III collagen. Together, these two layers create a continuous sheet that strengthens the epithelium and regulates exchange between tissues.

Tight junctions and gap junctions are types of cell junctions between neighboring epithelial cells and are not part of the basement membrane. A description mentioning connective tissue fibers alone misses the epithelial-derived basal lamina, and lamina propria refers to a broader connective tissue layer beneath mucous membranes, not the basement membrane itself.