Epithelial Tissue

The epithelium is a sheet of aggregated cells of similar type that covers body surfaces, lines hollow organs or modified to form glands or neuroepithelium.

General Features of Epithelium

  • It may originate from all three embryonic germ layers (ectoderm, mesoderm and endoderm).
  • It is composed of high number of closely applied cells with very little intercellular substances.
  • It is separated from the underlying connective tissue by a basement membrane.
  • It is avascular, blood and lymph vessels do not penetrate the basement membrane. Thus, it receives its nutritional support by diffusion.
  • The epithelial cells have high capacity for regeneration.
  • The epithelium can change from one form to another in a process called metaplasia.

  • It performs many functions such as protection, secretion, excretion, absorption and sensory reception.