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Groups of cells are held together by
Cell to cell junctions and the binding of cells to the basal lamina
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Parenchyma and Stroma
- Parenchyma is the epithelial layer of the inner organs/cells of an organ that provide function
- Stroma is the supporting connective tissue of an organ. Support, structure, and protection of epithelial cells
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Functions of epithelium
- Covering of body surfaces/Lining of body cavities
- Secretion
- Absorption
- Sensation
- Contractility
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Different cell shapes
Squamous, Columnar, cuboidal
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Epithelium specializations
cilia, microvilli, goblet cells, keratinization
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Types of layers of epithelium
simple, stratified, pseudostratified
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functions of epithelium
glandular, covering, secretory
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basal lamina
separates epithelium from support tissues, identifies orientation of cells above. Diffusion barrier, cell differentiation and organization controller, pathway for migration during development/healing
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simple squamous epithelium location
lung, blood vessels, lining of body cavities
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function of simple squamous epithelium
active and passive transport of substances
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simple cuboidal location/function
kidney/ovary/thyroid, secretion/active and passive molecule transport
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simple columnar function/location
intestine/gallbladder, absorption/protection/secretion/lubrication
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function of stratified squamous keratinized
they help in areas of high friction. They secrete, prevent water loss, protect. located in epidermis
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Stratified squamous non-keratinized location/function
- areas subjected to repeated friction forces. (mouth, esophagus, vagina, anal canal)
- protection/secretion/water loss prevention
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pseudostratified columnar location/function/specializations
- intestines/respiratory epithelium
- absoroption/secretion/protection/trap airborne particles
- cilia, micovilli, goblet cells
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Goblet cells
- mucus secreting epithelial cells
- found in intestinal tract and respiratory tracts
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transitional epithelium function/location
protects, distends to take on more liquid. (bladder, ureters) Facet cells change shape depending on distention
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biology of epithelial cells (innervation/renewal)
- rich capillary beds and innervation from plexuses via lamina propria
- cells are continuously renewed (slowly in liver/pancreas, quickly in epidermis/intestine)
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order of epithelial connections
tight/occluding junctions, adhering belts, gap/communicating junctions, desmosomes, hemidesmosomes
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communicating junctions
they use connexons to communicate inter-cellularly. Coordinated synchronized cell excitation
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occluding junctions
tight junctions that seal off cells from molecules. Prevents diffusion
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hemidesmosomes/desmosomes
attach cells to other cells (intermediate filaments) or extracellular matrix. Hemidesmosomes attach to basal lamina
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