4. CellsAndTissues - Tissues-four primary tissue types 1...

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Tissues -four primary tissue types: 1. Epithelial 2. Connective 3. Muscle 4. Neural
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Epithelial Tissue = lining epithelium & glands multiple functions of epithelial tissues: 1.protection - from dehydration, pathogens 2.synthesis – e.g. vitamin D 3. regulation - e.g. body temperature 4. excretion - e.g. waste 5. immune response 6. control of permeability – every substance must cross an epithelial membrane first 7. sensitivity – epithelial membranes are well-innervated lining epithelium = line body surfaces and cavities glandular epithelium = secretion
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Epithelial characteristics Mostly cells (lecture exam) 1.Cellularity 2.Polarity 3.Attachment 1. to each other 2. to connective tissue 4.Avascularity 5.Regeneration
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Epithelial characteristics 1. Cellularity: composed almost entirely of cells held together by cell junctions -very little extracellular matrix 2. Polarity: possesses an exposed surface the faces the exterior of the body - apical face (top) -also has an attached base which is anchored to other tissues basal face -the organelles are not uniformly distributed EPITHILIUM (has basal face) -> CONNECTIVE TISSUE -> MUSCLE OR BONE
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3. Attachment: attached to underlying tissues via the basement m EPITHELIUM (BASEMENT MEMBRANE) -> CONNECTIVE TISSUE Epithelial characteristics -BM is produced by the basal surface of the cells & connective tissue -the BM is comprised of two layers a. closest to epithelial cell = basal lamina (glycoproteins, laminin and actin) -acts as a barrier to transport b. furthest from the epithelial cell = reticular lamina -collagen IV bundles produced by the underlying connective tissue cells -provides strength
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Epithelial characteristics 1. Tight junctions: lipid portions of PMs are bound together by interlocking membrane proteins -very tight union - prevents passage of water and solutes between the two cells 3. Attachment: also form extensive connections between each other Epithelial characteristics - HOMEWORK
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2. Desmosomes: comprised of a. plaque of proteins inside the plasma membrane -the plaque attaches to the intermediate filaments of the cytoskeleton ( keratin ) b. cellular adhesion proteins/CAMs called cadherins
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Epithelial characteristics 3. Gap junctions: two cells held together by proteins called connexons -connexons are channel proteins -materials can freely move between the two cells -passage of materials helps to coordinate the activities of the adjacent cells e. g beating rhythm of cilia Epithelial characteristics
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4. Avascularity: do not contain blood vessels -must obtain nutrients via diffusion or absorption 5. Regeneration: damaged cells are replaced through differentiation of stem cells located deep within the tissue -rate of renewal depends on rate of cell death -stem cells = germinative cells -these cells are found closest to the basement membrane -migrate towards the surface and differentiate into epithelial cells Epithelial characteristics
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Classification of Epithelia A. # of layers simple = 1 layer stratified = multiple **pseudo = 1 layer B. Cell shape columnar cuboidal squamous catagorizing epithelial tissue types
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Classification of Epithelia NO stratified cuboidal & columnar, only squamous
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