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epithelium

Wednesday 1 March 2017

Plur. epithelia ; Adj. epithelial (epi- + thele + -ium)

WKP

Definition: Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of blood vessels and organs throughout the body.

There are three principal shapes of epithelial cell: squamous cells , columnar cells, and cuboidal cells.

These can be arranged in a single layer of cells as simple epithelium, either squamous, columnar, cuboidal, pseudo-stratified columnar or in layers of two or more cells deep as stratified epithelium (layered epithelium ), either squamous epithelium , columnar epithelium or cuboidal epithelium .

All glands are made up of epithelial cells. Functions of epithelial cells include secretion, selective absorption, protection, transcellular transport, and sensing.

Epithelial layers contain no blood vessels, so they must receive nourishment via diffusion of substances from the underlying connective tissue, through the basement membrane. The cell junctions are well-employed in epithelial tissues.

Types

- cuboidal epithelium
- squamous epithelium
- columnar epithelium
- columnar ciliated epithelium

Pathology

-  epithelial anomalies
- epithelial tumors

See also

-  mucosa