Epithelial tissue is avascular, which means it does not contain blood vessels. Instead, it receives its nutrients and oxygen through diffusion from underlying connective tissues.
This characteristic is significant because it affects how epithelial tissue functions and heals. Since epithelial cells are tightly packed, forming barriers and protective layers, they rely heavily on the connective tissues beneath them to supply essential substances. This lack of direct blood supply means that any damage to the epithelium may take longer to heal compared to vascular tissues, which can often repair more quickly due to their blood supply.
Furthermore, the avascular nature of epithelial tissue plays a role in its function in various organs. For example, in the lungs, the thin epithelial lining facilitates gas exchange efficiently, while in the skin, it provides a barrier to protect from external factors, despite having no direct blood supply.