Epithelium Tissue: Epithelium Tissue is the simplest animal tissue that forms the continuous sheet of closely packed cells that covers all external and internal surface of the animal body. Thus, it is also known as covering tissue.
Structure of Epithelium Tissue
Epithelium Tissue is formed from a tightly fitted continuous layer of cells. One surface of the epithelial tissue is exposed to either the external environment or the body fluid. The other surface is attached to tissue by a membrane, which consists of fibres and polysaccharides secreted by epithelial cells.
There is little intercellular material present between cells. There are specialised junctions present between the cells of the epithelium that link individual cells.
Tight junctions- prevent leakage across tissues
Adhering junctions- keep the neighbouring tissues well cemented together
Gap junctions- facilitate the movement of ions and molecules across the tissue
Epithelial cells form membranes. The epithelial membrane consists of a layer of epithelial tissue and has underlying connective tissue. There are two types of epithelial membranes, mucous membrane and serous membrane.
Mucous membrane: It is also known as mucosa. There are goblet cells present, which secrete mucus. The mucus helps in lubrication, protection and easy movement of materials. It prevents tissues from drying. It lines the body cavities such as respiratory and digestive tracts, which open outside the body.
Serous membrane: The serous membrane lines the body cavities, which do not open outside the body, such as the lining of the pleural cavity, pericardial membranes. These membranes secrete the fluid inside the cavity and are made up of simple squamous epithelium.
Glands are made up of epithelial cells. There are two types of glands, exocrine and endocrine. Exocrine glands secrete their product into a duct, e.g. goblet cells, sweat glands. Endocrine glands are called ductless glands and they release their product directly into the blood or intestinal fluid, e.g. hormones.
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By Team Learning Mantras