C4_Dr.-Faller-Tissues.pdf - Tissues and Histology • Tissues...

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Tissues and HistologyTissuesare a group of cells with similar structureand function that have similar extracellularsubstances located between them.Histologyis the microscopic study of tissuestructures located between them.Cells are organized to become tissues to becomeorgans, then organ systems, and lastly thecomplete organism.Four Basic Tissue Types:1. Epithelial2. Connective3. Muscle4. NervousEPITHELIUM OR EPITHELIAL TISSUECovers external and internal surfaces throughoutthe bodyAlso forms most glandsConsists almost entirely of cells with very littleextracellular material between them.Most epithelia have a free surface, which is not acontact with other cells, and basal surfaceadjacent to a cell membrane, which attaches theepithelial cells to underlying tissues.Basement membranes is secreted partly byepithelial cells and partly by the cells of theunderlying tissues.Functions of Epithelia1. Protecting underlying structures2.Acting as a barrier3.Permitting the passage of substances4. Secreting substances5. Absorbing substancesClassification of EpitheliumNumber of Layersor CategoryShape of CellsSimple(singlelayer of cells)SquamousCuboidalColumnarStratified (morethan one layer ofcells)SquamousNonkeratinized(moist)KeratinizedCuboidal(veryrare)Columnar(veryrare)Pseudostratified(modification ofsimpleepithelium)ColumnarTransitional(modification ofstratifiesepithelium)Roughlycuboidalto columnar whennot stretched andsquamous-likewhen stretchedClassification of Epithelia1. Simple Epithelium
2. Stratified Cuboidal EpitheliumConsists of more than one layer of cuboidalepithelial cellsRelatively rareFound in sweat gland ducts, ovarian follicularcells and the salivary glandsFunction: absorption, secretion and protectionCell Layers and Cell ShapesThe number in a specific type of epithelium reflectthe function it performs.Two Important Functions:1. Controlling the passage of materialsthrough the epithelium.2.Protecting the underlying tissuesDifferences in function are also reflected in cellshapeFlat and thin when the function is diffusion (aveoliin the lungs) or filtration (glomeruli in the kidneys)Shape and number of layers can change if theyare subjected to long-term irritation or otherabnormal conditions (cases of cigarette smoking)Free SurfacesCharacteristics reflects its functionCan be smooth (reduces friction as materialmoves across it) or lined with microvilli or cilia.

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Term
Spring
Professor
N/A
Tags
Chronic Inflammation, Classification of Connective Tissue

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