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Write a short note on different types of epithillial tissues and its functions

Answer» Epithelial TissueThe\xa0covering or protective tissues\xa0in the animal body are epithelial tissues.\xa0Epithelium\xa0covers most organs and cavities within the body. It also forms a barrier to keep different body systems separate. The skin, the lining of the mouth, the lining of blood vessels, lung alveoli and kidney tubules are all made of epithelial tissue.\xa0Epithelial tissue\xa0cells are tightly packed and form a continuous sheet. They have only a small amount of cementing material between them and almost no intercellular spaces. Obviously, anything entering or leaving the body must cross at least one layer of epithelium. As a result, the\xa0permeability of the cells\xa0of various epithelia play an important role in regulating the exchange of materials between the body and the external environment and also between different parts of the body. Regardless of the type, all\xa0epithelium\xa0is usually separated from the underlying tissue by an extracellular fibrous basement membrane.Different epithelia show differing structures that correlate with their unique functions. For example, in cells\xa0lining blood vessels\xa0or\xa0lung alveoli, where transportation of substances occurs through a selectively permeable surface, there is a simple flat kind of epithelium. This is called the simple\xa0squamous epithelium. Simple squamous epithelial cells are extremely thin and flat and form a delicate lining. The oesophagus and the lining of the mouth are also covered with squamous epithelium. The skin, which protects the body, is also made of squamous epithelium.\xa0Skin epithelial cells\xa0are arranged in many layers to prevent wear and tear. Since they are arranged in a pattern of layers, the epithelium is called\xa0stratified squamous epithelium.Where absorption and secretion occur, as in the inner lining of the intestine,\xa0tall epithelial cells\xa0are present. This\xa0columnar\xa0(meaning �pillar-like�)\xa0epithelium\xa0facilitates movement across the epithelial barrier. In the respiratory tract, the\xa0columnar epithelial tissue\xa0also has\xa0cilia,\xa0which are hair-like projections on the outer surfaces of epithelial cells. These cilia can move, and their movement pushes the mucus forward to clear it. This type of epithelium is thus\xa0ciliated columnar epithelium.Cuboidal epithelium\xa0(with cube-shaped cells) forms the lining of kidney tubules and ducts of salivary glands, where it provides mechanical support. Epithelial cells often acquire additional specialisation as gland cells, which can secrete substances at the epithelial surface. Sometimes a portion of the epithelial tissue folds inward, and a\xa0multicellular gland\xa0is formed. This is\xa0glandular epithelium.


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