Surface epithelium

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Surface epithelia form the outer covering of organs and surfaces, which means they have a barrier function. They also allow regulated transport between the respective organs and their environment.

Surface epithelium is a specialized layer of tissue formed by closely aggregated cells that are linked to one another via cell contacts. Cells in epithelial tissue are directional, meaning that one can distinguish an apical pole from a basal pole. The basal pole lies on the basement membrane, which represents the transition from epithelial to connective tissue.

Epithelial tissue can be further divided according to shape, arrangement and surface differentiation:

• The shape of the cells can be squamous, cuboidal and columnar. 
• Depending on the number of layers, the tissue is divided into simple epithelium for a single cell layer or stratified epithelium for multiple cell layers. Furthermore, there is pseudostratified epithelium where all cells touch the basement membrane, but not all reach the lumen.
• Finally, there are special surface differentiations that only occur in certain organs. These include microvilli, kinocilia, cornifications and glomerular cells.

Watch the following video to learn more about the structures and types of simple epithelia:

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Review all of the structures and types of surface epithelia you learned today in the image gallery below:

Ready to look at the structures of stratified epithelium? Browse the image gallery below: