Why is epithelium avascular, and how does it receive nutrients?

• A. Lacks blood vessels; receives nutrients via diffusion from underlying connective tissue capillaries and lamina propria
• B. Contains abundant blood vessels; nutrients diffuse from the bloodstream
• C. Is formed of cartilage; nutrients diffuse through the matrix
• D. Receives nutrients from underlying muscle tissue via diffusion

Answer: (C)

Epithelium is avascular, meaning it has no blood vessels running through its layers. It gets nutrients and oxygen by diffusion from capillaries in the underlying connective tissue, such as the lamina propria, across the basement membrane to the epithelial cells. This vascular network beneath provides the nourishment, while the epithelial cells stay thin and tightly packed. The idea that epithelium contains cartilage or that nutrients come from muscle tissue isn’t correct for epithelial tissue—the nourishment comes from the vascularized connective tissue beneath, not from cartilage.