WEEK 4 THE PROPER FIXATION OF TISSUE SAMPLES PART...

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MLS 410-LAB | HISTOPATHOLOGY LABWEEK 4: THE PROPER FIXATION OF TISSUE SAMPLES PART 1DR. VICHERYL LOPEZFIXATION● Acritical step in the preparation of histologicalsections so the quality of the section on the slide isonly as good as the quality of the fixed tissuespecimen.● If fixation is not adequate the other processes thatfollowsuch as dehydration, clearing, infiltration,embedding,microtomy,andstaining will also beinadequate.● A poorly processed tissue will make it difficult forthe pathologist to render a proper diagnosis.● First and most critical step in histotechnology.Preventorarrestthegenerativeprocesseswhich begin as soon as a tissue is deprived of itsblood supply. These processes includes:Autolysis-lysisordissolvingofcellsbyenzymaticactionasaresultofruptureoflysosome.It is the enzymatic digestion of cellsby the action of its own enzymes. Auto = self,lysis = breakdown.Putrefaction- breakdown of tissue by bacterialaction.OtherwiseknownasBacteriadecomposition.BothAutolysisandPutrefactionmustbeprevented. Fixation should be carried out assoon as possible after removal of the tissue inthe case of surgical pathology or soon afterdeathinthecaseofautopsytopreventautolysis and putrefaction● Acomparisonbetweenawell-preservedsmallintestine and an autolyzed small intestine.Note thedisruption of the normal morphology of the liningepitheliumofthesmallintestine,someofthenucleiarefadedandhavealmosttotallydisappeared in this section of the intestine, othernuclei are pyknotic- there is nuclear shrinkage andthosefeaturesmaybeseeninanautolyzedsample.● Another image showing autolysis and putrefactioninatissuesection.Thereisawashedoutappearancewithswellingofthecytoplasm,convertingitto a granular homogeneous masswhich fails to take up stains. Nuclei show loss ofchromatin,othersarefadingandothershavecompletelydisappeared.Thisareashowsthepresence of bacteria, indicating putrefaction. Bothautolysisandputrefactionshouldbepreventedwith the use of adequate fixativesPRIMARY GOALPreservethemorphologicandchemicalintegrity of the cell with the alteration from theliving statewith the use of fixatives.● With fixation the shape, structure, the intercellularrelationshipandthechemicalcomponentsoftissues are preservedSECOND GOAL● Harden and protect the tissue from the traumaof further handling, so that it is easier to cutand process for microscopy.● Increases the mechanical strength or stability ofthe treated tissues.● Allows the tissue to be more properly oriented inthe cassette in preparation for paraffin embeddingand microtomy.● Fixativesrenderthespecimeninsensitivetosubsequenttreatmentasmay be necessary topermit microscopic examination.OBJECTIVES● To Preserve the TissueoBy stopping all cellular activities so that thecells can be viewed under the microscope asif they are still in their original living state.

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Term
Summer
Professor
N/A
Tags
Histology, Histopathology lab, Dr Vicheryl Lopez

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