Classification of Epithelia The many types are identified structurally according to two criteria

Classification of Epithelia The many types are identified structurally according to two criteria

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Classification of Epithelia The many types are identified structurally according to two criteria: number of cell layers and shape of the cells Number of layers: two major varieties 1. Simple epithelia composed of a single layer of cells; found where absorption and filtration occur. 2. Stratified epithelia consists of layers of cells stacked one on top of the other; common in areas of high abrasion where protection is important. Shape of the cells: All cells have 6 somewhat irregular sides (polyhedral) which allows them to be closely packed. They vary in cell volume and consequently in cell height. On the basis of height; three cell types: 1. Squamous cells are flattened and scalelike. 2. Cuboidal cells are approximately as tall as they are wide. 3. Columnar cells are tall and column shaped. The nucleus of a squamous cells is disc shaped; that of a cuboidal cell is spherical; and a columnar cell nucleus is elongated and is usually located close to the cell base.
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Unformatted text preview: Maior Classification of Simple Epithelia : 1. simple squamous 2. simple cuboidal 3. simple columnar 4. pseudostratified-highly modified Maior Classification of Stratified Epithelia: 1. stratified squamous 2. stratified cuboidal 3. stratified columnar 4. transitional epitheliums In stratified epithelia, cell shape varies in the different layers. Thus stratified epithelia are named according to the shape of the cells at the free surface (also called the apical surface). Simple Epithelia Most concerned with absorption, secretion, and filtration.Very thin. Simple Squamous Flattened laterally, sparse cytoplasm, thin, often permeable, close-fitting cells resemble a tiled floor. Found where filtration or the exchange of substances by rapid diffusion is a priority. Two simple squamous epithelia have special names: endothelium- slick, friction reducing lining of vessels and heart; mesothelium- found in serous membranes lining body cavity...
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