Doncouse_Jeremy_Week4

Doncouse_Jeremy_Week4 - Running head Chapter 4 1 Week 4...

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Running head: Chapter 4 1 Week 4 Written Assignment: Chapter 4 Jeremy Doncouse Mountain State University
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Running head: Chapter 4 2 Chapter 4: Tissue: The Living Fabric Epithelial Tissue 1. List several structural and functional characteristics of epithelial tissue. Epithelium covers a body surface or cavity and occurs as 1) a covering and lining epithelium and 2) glandular epithelium. The first forms the outer layer of skin, lines the open cavities of the cardiovascular, digestive, and respiratory systems, and covers the organs of the ventral body cavity. The former makes the glands of the body. Epithelium is used as 1) protection, 2) absorption, 3) filtration, 4) excretion, 5) secretion, and 6) sensory reception. There are also five characteristics of epithelium that distinguish them from other tissues types. First, epithelium is polarized. The top surface is the apical surface which is attached to the lower surface, or basal surface. The apical surface is sometimes smooth but most have microvilli which greatly increase their surface area. Some epithelia have cilia which propel substances along their free surface. Next to the basal surface is the basal lamina, a noncellular adhesive sheet which is a selective filter for diffusion and also allows the migration of epithelial cells for wound repair. Second, covering and lining epithelium have specialized contacts that fit closely together and are bound together at many points by tight junctions and desmosomes. The tight junctions keep proteins separate proteins in the apical region from diffusing into the basal region. Third, epithelia are supported by connective tissue. Deep to the basal lamina is the reticular lamina, which contains collagen protein fibers. The basal lamina and reticular lamina together form the basement membrane. This region reinforces the epithelial sheet, helping to resist stretching and tearing, and define the epithelial boundary. Fourth, epithelia are avascular but innervated. Meaning that there are no blood vessels but there are nerve fibers. The tissue is nourished by diffusion from blood vessels in the underlying connective tissue.
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Running head: Chapter 4 3 Finally, epithelium regenerates rapidly. Because the tissues are exposed to a lot of wear and tear the cells begin to reproduce themselves when their apical-basal polarity and lateral contacts are destroyed.
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