Anatomy and Physiology
Epithelial Tissue
- If a tissue is a covering or lining on or inside the body, then its probably epithelial tissue. Epithelial tissue covers the skin. It also covers the cavities of the mouth and nose.
- Epithelial tissue lines the blood vessels, as well as the urinary and respiratory tracts.
- Epithelial tissue has no direct blood supply. It does, however, receive nutrients from blood vessels that run through the connective tissue beneath it.
Functions
- Epithelial tissue protects underlying tissues. It prevents dehydration, and prevents toxic substances from entering the body.
- Epithelial tissue also absorbs nutrients and other external substances required by the body. (This is what epithelial tissue does in the digestive system, for example.)
-Epithelial tissue secretes various necessary substances, such as enzymes and hormones. Epithelial tissue on the body surface secretes sweat. Inside the body, some epithelial tissues are involved in the secretion of wastes.
- A basement membrane (which consists of noncellular material) anchors the epithelial tissue to the underlying connective tissue. The basement membrane is made up of glycoproteins that are secreted by the epithelial cells. (Glycoproteins are combinations of proteins and carbohydrates.)
- Epithelial cells are packed closely together with tight junctions. These junctions cover the entire surface of a cell, forming a close cells with surrounding cells. There is little intracellular space in epithelial tissue.
- Epithelial tissue cells divide by mitosis.