Histotechnology - Fixation questions & answers graded A+ passed

Histotechnology - FixationWhat are the steps tissue must go through before it is viewed under a microscope? - correct answers 1. Fixation 2. Processing 3. Embedding 4. Microtomy 5. Staining 6. Coverslipping Define fixation. - correct answers The preservation of cells and tissue in as life-like a way as possible by stabilizing the protein so that it is resistant to further changes. What are the functions of fixation? - correct answers 1. To prevent putrefaction and autolysis 2. To help maintain proper relationships b/w cells and extracellular substances 3. To bring out diff's in refractive indexes, and to inc. visibility of or contrast b/w diff tissue elements 4. To enhance staining 5. To make cell constituents insoluble (spec. proteins) 6. To prevent dessication 7. To prevent osmotic swelling/shrinkage What are the considerations when choosing a fixative? - correct answers • Type of tissue • Substance examined • Size of tissue • Rate of action • Changes to tissue What are the two methods of fixation? - correct answers • Physical: via dry heat (coagulates proteins, melts lipids) or vapour (used for single cells) • Chemical: liquid fixation by direct immersion or perfusion (sending fixative through vessels in system) What effects does fixation have on tissue? - correct answers • Size dec. • Hardening • Inc. brittleness • Enhance or dec. stain • Some material loss • Cause chemical alterations • Can produce artifacts What factors affect the quality of fixation? - correct answers Temp, tissue size, volume ratio (ideal 20:1), time of fix'n (too long = brittle, too short = degredation), choice of fixative, pH, osmolality, and conc'n What are the 4 ways of classifying fixatives? - correct answers • By their chemical action on proteins • By their effect on microscopic appearance of tissue • By # of fixing reagents in fixing sol'n • By amt of time tissue can remain in fixative Explain the 2 classifications for fixatives that chemically act on proteins. - correct answers - Coagulant: destroys tertiary structure and organelles while turning protoplasm into a mesh that paraffin can easily penetrate; disadvantage is may be too coarse for good cell detail and may produce artifact - Non-coagulant: forms cross-links b/w proteins which takes up form of insoluble gel which will give bad consistency for embedding Explain the 3 classifications for fixatives that have an effect on the microscopic appearance of tissue. - correct answers - Microanatomical fixatives preserve the microarchitecture - Cytological fixatives preserve intracellular structures - Histochemical fixatives preserves a specific element to be demonstrated Explain the 2 classifications for fixatives that have a specific number of reagents in the fixing solution. - correct answers - Simple contains only 1 reagent