EPITHELIAL TISSUE OR EPITHELIA

Epithelium term coined by Ruysh, it was applied originally to thin skin covering the nipple. (G.epi = upon, thele = nipple)

Epithelial tissues evolved first and are also formed first in the embryo.

• Epidermis of the skin from the ectoderm.
• Coelomic epithelium from the mesoderm.
• Epithelial lining of alimentary canal (= gut) from the endoderm.

Epithelial cells rest upon nonecellular Basal lamina or Basement membrane, but in transitional epithelium, basal lamina is absent.

Blood vessels and lymph vessels are absent in epithelial tissues.

The epithelial tissues have a good power of repair (regeneration) after injury.

CLASSIFICATION OF EPITHELIAL TISSUE -