What is the Purpose of Epithelial Tissue? What are the Types of Epithelial Tissues? What Do They Look Like?

Epithelial tissues line and cover body surfaces. For example, they line the stomach, line the ducts of glands, and cover our body. Because of the location of epithelial tissues, each type has a free surface (that faces open space) and a basement membrane (where they are connected to the body). Epithelial tissues are used for protection, absorption, secretion, filtration, and diffusion. The cells in epithelial tissue are very close together. The cells may be found in layers (stratified). Alternatively, the tissue may be only one cell layer thick (simple). Epithelium does not contain blood vessels, the tissue must get its nutrients from underlying connective tissue. We will consider six types of epithelium. Each type has a different structure and function. Students should be able to find and identify these tissues and their characteristic structure.

Table 1. Structure, Function and Location of Epithelial Tissue Types
Tissue	Structure	Function	Representative Locations
Simple Squamous Epithelium	Very thin, flat cells, one cell layer thick	Diffusion, osmosis, filtration	Air sacs in lungs, line blood vessels, capillaries, intestine surface
Simple Columnar Epithelium	Single layer of very tall cells, some are goblet cells	protection, secretion, absorption	lines stomach and intestines, uterus
Pseudostratified Columnar Epithelium with cilia	simple tissue but varying location of nuclei gives the appearance of striations, goblet cells, cilia	protection, secretion, movement of cells and particles	trachea, fallopian tubes
Simple Cuboidal Epithelium	simple tissue, cells are cube shaped with nucleus in the middle	secretion, absorption	lines ducts of glands, lines kidney tubules
Stratified Squamous Epithelium	many layers of cells with the cells towards the surface being flat and the deeper cells more cuboidal	protection	skin - keratinized, lining of oral cavity, vagina - nonkeratinized
Transitional Epithelium	appears to have many layers when the tissue is not stretched; appears to have fewer layers when the tissue is stretched	as the bladder empties and fills, it's able to adapt.	lines urinary bladder, urethra

The following video also discusses the types of epithelial tissues.

Video 2. View the Epithelial Tissues video on YouTube (opens in a new window)

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