Generalized Functions of Epithelial TissueĮpithelial tissues provide the body’s first line of protection from physical, chemical, and biological wear and tear. Sloughing off of damaged or dead cells is a characteristic of surface epithelium and allows our airways and digestive tracts to rapidly replace damaged cells with new cells. Many epithelial tissues are capable of rapidly replacing damaged and dead cells. For instance, no blood vessels cross the basement membrane to enter the tissue, and nutrients must come by diffusion or absorption from underlying tissues or the surface. The basal lamina attaches to a reticular lamina, which is secreted by the underlying connective tissue, forming a basement membrane that helps hold it all together.Įpithelial tissues are nearly completely avascular. The basal lamina, a mixture of glycoproteins and collagen, provides an attachment site for the epithelium, separating it from underlying connective tissue. The epithelial cells exhibit polarity with differences in structure and function between the exposed or apical facing surface of the cell and the basal surface close to the underlying body structures. Adjoining cells form a specialized intercellular connection between their cell membranes called a cell junction. This tissue is highly cellular, with little or no extracellular material present between cells. The epithelium that lines vessels in the lymphatic and cardiovascular system derives from the mesoderm and is called an endothelium.Īll epithelia share some important structural and functional features. Cells lining the airways and most of the digestive system originate in the endoderm. The epithelia lining the skin, parts of the mouth and nose, and the anus develop from the ectoderm. Hollow organs and body cavities that do not connect to the exterior of the body, which includes, blood vessels and serous membranes, are lined by endothelium (plural = endothelia), which is a type of epithelium.Įpithelial cells derive from all three major embryonic layers. Other areas include the airways, the digestive tract, as well as the urinary and reproductive systems, all of which are lined by an epithelium. Skin is not the only area of the body exposed to the outside. Epithelium also forms much of the glandular tissue of the body. Most epithelial tissues are essentially large sheets of cells covering all the surfaces of the body exposed to the outside world and lining the outside of organs. Describe the structure and function of endocrine and exocrine glands and their respective secretions.Distinguish between simple epithelia and stratified epithelia, as well as between squamous, cuboidal, and columnar epithelia.Distinguish between tight junctions, anchoring junctions, and gap junctions.Explain the structure and function of epithelial tissue.
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