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What are the functions of epithelial tissue?
Protection, absorption, filtration, excretion, secretion, and nerve reception.
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.
What is simple epithelium?
Singe layered cells attached to a basement membrane.
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.
What are simple squamous epithelium?
Lines blood vessels, air sacs of lungs, and heart. Permits exchange of nutrients, wastes, and gases.
What are simple columnar epithelium?
- Lines most digetstive organs.
- Absorbs nutrients and goblet cells secrete mucus.
- May bear cilia for movement.
What are stratified epithelium?
Consisting of two or more layers of cells attached to a basement membrane.
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.
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.
- 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.
- 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.
- 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.
What does squamous mean?
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.