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What are the functions of epithelial tissue?
Protection, absorption, filtration, excretion, secretion, and nerve reception.
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What are the characteristics that distiguish epithelial tissue from other tissues?
- Polarity: free surface different from basal surface.
- Cellularity and Specialized Contacts: cells fit closely together to form membranes/sheets of cells and are bound by specialized junctions.
- Supported by connective tissue: basement membrane.
- AVascularity: have no blood supply of their own, depend on diffusion of nutrients from underlying connective tissues.
- Regeneration: well nourished cells can easily regenerate themselves.
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What is simple epithelium?
Singe layered cells attached to a basement membrane.
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What are simple cuboidal epithelium?
- Cubelike cells that line kidney tubles and glands.
- Secretes and reabsorbs water and small molecules.
- Highly specialized to remove materials from blood and manufacture them into new cells.
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What are simple squamous epithelium?
Lines blood vessels, air sacs of lungs, and heart. Permits exchange of nutrients, wastes, and gases.
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What are simple columnar epithelium?
- Lines most digetstive organs.
- Absorbs nutrients and goblet cells secrete mucus.
- May bear cilia for movement.
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What are stratified epithelium?
Consisting of two or more layers of cells attached to a basement membrane.
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What are pseudostratified epithelium?
- A simple layer of columnar cells, but vary in height and some not reaching free surface.
- Nuclei lie at different levels above the basement membrane. Often ciliated.
- Secretion of mucus and propulsion by ciliary action.
- Nonciliated located in male's sperm carrying ducts or ducts of large glands.
- Ciliated located in trachea and most of the upper respiratory system.
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What are transitional epithelium?
- Formed of round or "plump" cells with the ability to slide over one another to allow the organ to be stretched.
- Only found in urinary organs.
- Superficial cells are flattened (squamous) when organ is distended and round when organ is empty.
- Located in bladder and ureters.
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Skeletal Muscle
- Cells are long, cylindrical, multinucleate, striated.
- Voluntary Control: Requires nerve supply.
- The "meat" or flesh of body attached to skeleton.
- Contractions move limbs and other external body parts.
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Cardiac Muscle
- Have striations, branched, uninucleate cells that interdigitate (fit together) at junctions (intercalated discs).
- Intercalated discs allow cardiac muscle to act as a unit.
- Involuntary Control: Does not require nerve supply
- As it contracts, the heart acts as a pump, propelling blood into blood vessels.
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Smooth Muscle
- Spindle-shaped, nonstriated, uninucleate.
- Involuntary Control: Does not require nerve supply.
- Found mainly in hollow organs (digestive, urinary, uterus, blood vessels.)
- Contraction can constrict or dilate the lumen (cavity) and propel substances along predetermined pathways.
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What does squamous mean?
Scalelike
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What are stratified squamous epithelium?
- Protects against abrasion, drying out, and infection.
- Designed for "wear and tear."
- Located on outer layer of skin, mouth, vagina, and esophagus.
- May have keratinized cells on top layer.
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