Epithelial tissue

It covers external surfaces and internal cavities and organs. Glands are also composed of epithelial tissue.

-         Epithelia forms boundaries. Most substances that move into or out of the body must pass through epithelial tissue.

-         One surface of the tissue is free (no contact with other tissue) and the other adheres to a basement membrane.

-         Some epithelial cells may have cilia.

Functions

-         Protection for dehydration

-         Absorption
-         Reduce friction

-         Secretion:

o       Endocrine glands secrete hormones directly into the extracellular space.

o       Endocrine glands often secrete through ducts, mucus, saliva, was, milk.

Layers of epithelial tissue

-         Simple epithelium is one cell thick

-         Stratified epithelium has more than one layers. It is found in areas of high abrasion such as the skin or the lining of the mouth.

Shape

-         Squamous (flat)

 -         Cuboidal (cube-shaped)

-         Elongated (columnar)