MEDL 310: Module 13: Fixatives General Latest Questions & Answers Verified 100% Correct

how does delayed fixation affect tissues? - ️️result in drying and decomposition of tissues. loss of nuclear detail, disappearance of cells, cell shrinkage, etc. what is a fixative? - ️️substance that alters tissues through the stabilization of proteins so that it is resistant to changes in subsequent treatments of the tissues. what is a preservative? - ️️does not alter the tissue structure, so it will not protect it from changes in subsequent treatments of the tissue functions of a fixative are - ️️prevent autolysis (breakdown by enzymes within the cells), prevent putrefraction (breakdown by bacteria), stabilize tissues, lessen shrinkage, enhance staining, etc. additive fixatives - ️️change the tissue by its addition - formaldehyde, gultaraldehyde, etc. coagulant fixatives - ️️produce aggregation of protein molecules, granulation and precipitation - mercuric chloride, picric acid non-coagulant fixatives - ️️form a gel which is difficult for subsequent reagents to penetrate factors affecting fixation - ️️time, temperature, pH, volume of fixative to tissues, osmolality how does insufficient fixation affect tissues? - ️️poor processing and staining results. tissue structure may be lost. how does prolonged fixation affect tissues? - ️️results in brittle, shrunken tissues if the fixative is intolerant, leading to hard to cut tissues = poor product how does room temperature affect fixation? - ️️it will take longer to fix how does warmer temperatures (45C) affect fixation? - ️️increased rate of fixation but also increases rate of autolysis what is the thickest a tissue can be for fixation? - ️️3mmvolume of fixative to tissue volume affects fixation? - ️️15 to 20 times greater fixative volume than the tissues. how does pH affect fixation? - ️️light mircoscopy = variations will not affect tissues electron microscopy = pH must be controlled to 7.2-7.4 to preserve ultrastructure hypertonic cells - ️️cells will shrink hypotonic cells - ️️cells will swell fixative used for frozen sections - ️️none