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What is epthelial tissues? Explain its types

Answer» \tIt consists of cells which form membranes.\tThis membrane covers the body surface and the glands.\tThe covering or protective tissues in the animal body are epithelial tissues.\tEpithelium covers most organs and cavities within the body.\tIt also forms a barrier to keep different body systems separate.\tThe skin, the lining of the mouth, the lining of blood vessels, lung alveoli and kidney tubules are all made of epithelial tissue.\tThe cells are tightly packed and form a continuous sheet.\tThey have only a small amount of cementing material between them and almost no intercellular spaces.\tThese are divided into four types:-\xa0\xa0SIMPLE\tThe cells are extremely thin and flat and form a delicate lining.\tThe lining of oesophagus and the mouth are covered with squamous epithelium.STRATIFIED\tThe cells are arranged in many layers to prevent wear and tear.\tSince they are arranged in a pattern of layers, the epithelium is called stratified squamous\tThe skin, which protects the body, is made of squamous epithelium.COLUMNAR\tThe columnar (meaning ‘pillar-like’) epithelium facilitates movement across the epithelial barrier.\tIt is present where absorption and secretion occur, as in the inner lining of the intestine, tall epithelial cells are present.\tIn the respiratory tract, the columnar epithelial tissue also has cilia, which are hair-like projections on the outer surfaces of epithelial cells.\tThese cilia can move, and their movement pushes the mucus forward to clear it. This type of epithelium is thus ciliated columnar epithelium.CUBOIDAL\tCuboidal epithelium (with cube-shaped cells) forms the lining of kidney tubules and ducts of salivary glands, where it provides mechanical support.\tEpithelial cells often acquire additional specialisation as gland cells, which can secrete substances at the epithelial surface.\tSometimes a portion of the epithelial tissue folds inward and a multicellular gland is formed.\tThis is glandular epithelium.


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