Which type of collagen is found in smooth muscle?

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

Answer: (D)

Collagen types have tissue-specific roles that shape how the extracellular matrix supports different tissues. In smooth muscle, the matrix around the muscle cells needs to be carefully organized to allow contraction and maintain tensile strength. Type V collagen is a minor fibrillar collagen that co-assembles with type I collagen and helps regulate fibril diameter and organization. This control over the fiber architecture is important for the proper mechanical properties of smooth muscle tissue and its surrounding connective tissue, including vessel walls.

Other collagen types are more characteristic of different structures: Type I forms the strong fibers of bone, skin, and tendon; Type II is principal in cartilage; Type III forms reticular networks in soft tissues; Type IV is a basement membrane component.