The classification considers the following:

• functional specialization of epithelial tissues
• in surface epithelial tissues:
  • proportion of cells that are attached to basement membrane
• in simple epithelial tissues:
  • localization of cell nuclei within the epithelial layer
  • cell shape
  • morphological features of apical cell surfaces
• in stratified epithelial tissues:
  • cell shape in the outermost layer
  • keratinization potential
• certain structural features originating from cell precursors in surface epithelial tissues (relevant for epithelial tissues of glands)

Structural diversity of certain epithelial types is described in details in the section on histological slides.