What is the function of epithelial tissues?
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Answers
Epithelial tissue covers the outside of the body and lines organs, vessels (blood and lymph), and cavities. Epithelial cells form the thin layer of cells known as the endothelium, which is contiguous with the inner tissue lining of organs such as the brain, lungs, skin, and heart. The free surface of epithelial tissue is usually exposed to fluid or the air, while the bottom surface is attached to a basement membrane.
The cells in epithelial tissue are very closely packed together and joined with little space between them. With its tightly packed structure, we would expect epithelial tissue to serve some type of barrier and protective function and that is certainly the case. For example, the skin is composed of a layer of epithelial tissue (epidermis) that is supported by a layer of connective tissue. It protects the internal structures of the body from damage and dehydration.
Epithelial tissue also helps to protect against microorganisms. The skin is the body's first line of defense against bacteria, viruses, and other microbes.
Epithelial tissue functions to absorb, secrete, and excrete substances. In the intestines, this tissue absorbs nutrients during digestion. Epithelial tissue in glands secrete hormones, enzymes, and other substances. Epithelial tissue in the kidneys excrete wastes, and in the sweat glands excrete perspiration.
Epithelial tissue also has a sensory function as it contains sensory nerves in areas such as the skin, tongue, nose, and ears.