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characteristics of epithelium
- -polarity: basal, apical
- -sheets: high cell/extra-cellular space ratio
- -avascular: which limits thickness
- -origins: ectoderm, mesoderm, endoderm
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intercellular juntions in epithelium
zonula - strip
macula/plaque - spot
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epithelial classifications:
simple, layered, pseudostrafied, transitional
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epithelial surface specializations
- cilia-movement
- microvilli-increase the surface area of cells
- keratin-form a dense meshwork of filaments throughout the cytoplasm of epithelial cells
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functions of epithelial tissue
- -protection
- -regulation of materials into/out of organs or tissues
- -produce secretions: endocrine/exocrine glands
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types of secretions
- serous-minimizes friction between surfaces in interior cavities (tears, digestive juices, milk, sweat)
- mucous-protects, lines cavities that conncect to exterior ( mouth, mucous)
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modes of secretion
–Merocrine: exocytosis (tear glands)
–Apocrine: sweat glands and mammary glands
–Holocrine: mixture of cell fragments and sustances synthesized in the cells (oil glands on scalp
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exocrine
secretion exits via ducts
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endocrine
ductless glands; release shit straight into bloodstream
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epithelial overview/review
- -lines every body surface and cavitiy
- -external and internal lining of many organs
- -constitutes the majority of glands
- -polarized cells
- -high cell/ecm ratio
- -avascular: no blood vessels penetrate an epithelium
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