Which type of collagen would you expect in basement membranes?

• A. Type II
• B. Type III
• C. Type IV
• D. Type V

Answer: (C)

Basement membranes are a specialized extracellular matrix that relies on a network-forming collagen to provide structure and support. The main collagen in this setting is type IV, which forms a distinctive non-fibrillar lattice that, together with laminin, creates the basal lamina underlying epithelial and endothelial cells. This network-type collagen is designed to create a thin, strong sheet that supports cell adhesion, filtration, and tissue organization.

In contrast, other collagens serve different roles: type II is the major cartilage collagen forming fibrils; type III forms reticular fibers in loose connective tissue and around vessels; type V is involved in fibril assembly with other collagens and is not the primary basement membrane component.