Answer
There are several types of epithelium but they have several features and functions in common: First, epithelial cells usually present in closely packed sheets. These tissues are usually not covered by any other tissue, so they have a free space/surface, whether it is the environmental exterior, a body cavity, a duct ,or lumen of a vessel. Epithelial cells are usually held tightly together by tight junctions , gap junctions, adherens junctions, and desmosomes, so that there is very little lateral intercellular space between the plasma membranes of the cells.. Epithelial tissues are usually located as coverings , for example the skin; as linings , for example linings of digestive respiratory, and the cardiovascular system, or as glandular epithelia, for example, in the thyroid gland, the adrenals and the sweat glands. Epithelial tissues have nerve supply, but they usually lack a blood supply. They are dependent on the underlying connective tissue layer to supply nutrients and remove waste and toxins through its rich vascular supply. The connective tissue layer not only nourishes epithelial tissue, it anchors the epithelium. A basement membrane is interposed between the basal surface of the epithelium and the connective tissue, The basement membrane comprises a basal lamina, and a reticular lamina. These arrangement is usually found in epithelial tissue.
Work Step by Step
Epithelia form coverings and linings, but they have important protective functions. In the several parts of the body epithelium protects the body from the damage of abrasions , for example in the GI tract , the vagina and the epidermis of the skin. The Epithelium also has an important filtering function, for example, in Bowman's capsule of the kidneys . it also protects the organism by trapping microbes in mucous secretions in the GI and respiratory tracts.
