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HT 12 Exam 1
| Question | Answer |
|---|---|
| surgery | tissue is removed in surgery, in the physician's office or at postmortem |
| grossing | the tissue is described and dissected, looking for abnormalities |
| fixation | stabilization of proteins to prevent autolysis and putrefaction |
| processing | dehydration-->clearing-->infiltration to embed the tissue in a solid medium firm to enable thin sections to be cut |
| embedding | orientation of the tissue in infiltration medium and allowing it to soldify |
| microtomy | the sectioning of tissue for examination by microscopy |
| cover-slipping | a mounting medium |
| purpose of fixation | a. Stabilization of proteins to prevent autolysis and putrefaction b. Maintain proper relationship between cells and extracellular material |
| Discuss the goal of tissue processing | To embed the tissue in a solid medium firm enough to support the tissue and give it sufficient rigidity to enable thin sections to be cut, and yet soft enough no to damage the knife or tissue |
| Define and discuss dehydration | the removal of free water from tissue |
| Define and discuss clearing | to remove the dehydrating fluid from the tissue |
| Define and discuss infiltration | Maintains structure of tissue for cutting |
| Define and describe embedding | Fixing the tissue specimen firmly into the embedding medium, allowing it to harden-->ready to cut |
| Describe microtomy and the use of a microtome | a. The sectioning of tissue for examination by microscopy b. Sections routinely cut at 4-6 microns (um) |
| Discuss staining as it applies to Histotechnology | Tissue is stained to aid in light microscopy |
| Discuss cover-slipping | Protection and for better viewing under the microscope |
| Pathology | study of disease |
| Histology | study of tissues |
| Cytology | study of cells |
| Histologist | a scientist who specializes in the study of tissues |
| Histotechnology | a technical histology concerned especially with preparing and processing histological specimens |
| Histotechnician/histotechnologist | a technician who specializes in histotechnology |
| Biopsy | removal of living tissue for examination under the microscope |
| Autolysis | cell breakdown |
| Putrefaction | rotting degradations from micro organs |
| Postmortem | an examination of a dead body to determine the cause of death |
| Miscible | forming a homogeneous mixture when added together |
| Microtome | an instrument used to cut a specimen, as of organic tissue, into thin sections for microscopic examination |
| define and describe embedding | Orientation of the tissue in infiltration medium and allowing it to solidify. Also known as casting or blocking. Areas of interest should be embedded down. |
| Describe the proper specimen orientation when embedding SKIN and other structures with a wall (layers) | Wall tissues must be embedded on edge (gallbladder, intestine, skin) |
| describe the proper specimen orientation when embedding tubular structures | tubular structures (with a LUMEN) are embedded in cross section (on end) |
| Describe proper specimen orientation when embedding bone. | Embedding at an angle. It allows knife edge to cut into a small area first and gradually cut through the remainder of the tissue (diagonal). |
| Describe double embedding | Tissues embedded in a medium and then re-embedded in paraffin. Used to orientate difficult specimens. |
| Demonstrate the use of quality control in embedding | Recording number of pieces and blocks submitted, plus any special instructions (stains, embedding instructions). Only embed one cassette at a time, ensure forceps are clean between embedding different tissues. |
| Define longitudinal section | cut that is parallel to the longest dimension |
| Define transverse section | a cut that is perpendicular to the longest dimension |
| Define oblique section | any cut made between the longitudinal plane and the transverse plane |
| Define tangential section | a cut that only touches or grazes the surface |
| Define sagittal section | a cut that divides into left and right |
| Define lumen | the space within an artery, vein, intestine or tube. |
| Describe proper embedding techniques of proper orientation, prevention of contamination and optimal tissue support. | Clean the forceps between embedding of different tissues to prevent cross contamination. Areas of interest should be tampered so that the tissues lays flat down ensuring the entire specimen is cut. Cooling the blocks as rapidly as possible. |
| Define use of tampers, base molds and cassettes. | Tampers are used to flatten tissue in the mold. Base molds form the shape of the block to be sectioned (reusable, disposable, and peel away). Cassettes hold and identify the specimen to be embedded. |
| Discuss the marking of specimens during grossing | Area of interest can be marked with a notch or ink. Some facilities use "ink side up" while others use "ink side down." India ink, Davidson Marking, tissue dyes, silver nitrate, and tattoo ink. |
| Discuss optimal temperatures for the embedding center components. | 2-4 C above melting point for the paraffin. |
| rotary microtome | embedded tissue passes over the knife edge cutting the section. each turn advances the number of micrometers. used in cryostats. (most common) |
| sliding microtome | block is held stationary and the knife travels over the specimen. block advances up to the knife at a preset distance. usually used for larger blocks in research |
| freezing microtome | knife moves over the specimen on a stage, advancing upward after each cut. liquid CO2 supplied to the tissue for freezing. sections floated in distilled water |
| sledge microtome | sample is placed into a fixed holder, which then moves backwards and forwards across a knife cuts sections of plastic, wood, and other hard materials cuts sections at 1-60 um biconcave knives |
| ultra microtome | ultra thin sections of specimens are cut. uses glass/diamond knives. 0.5-2 um |
| rocking microtome | 6-20 um. performs repetitive rocking motions while advancing towards a fixed knife. biconcave knives. |
| vibrating microtome | accurately cut tissue without freezing or embedding. cutting using a vibrating blade. used for difficult biological samples. 30-50 um for live tissue. 10-500 um for fixed tissue. maintains cell morphology. |
| steel knives | rust resistant, free from impurities and contain anti-corrosives. heat treated to harden the edge |
| disposable blades | most common. superior edges. refined, thickened razor blades. high and low profile. |
| tungsten carbide | nonmagnetic and 100x harder than hardened tool steel. excellent resistance to wear but are brittle because of extreme hardness. |
| glass knives | used for ultramicrotomy. hard but brittle. |
| diamond knives | expensive but extremely durable due to hardness. used for ultramicrotomy |
| bioconcave | concave on both sides. used on rocking or sledge type microtomes. rarely used in U.S. |
| planoconcave | concave on one side only. used for celloidin or plastic resin sectioning. |
| plano-wedge (wedge) | used for paraffin sectioning on a rotary microtome, for cryostat sectioning. easiest knives to sharpen |
| chatter | parallel tears or fractures in tissue |
| serial section | all consecutive sections from a block are saved |
| levels (steps/step sections) | block is trimmed, sections are cut and picked up, the more of the block is trimmed away, and more sections are cut and picked up |
| coarse trimming | using a blade to manually trim away excess material |
| washboarding | aka: udulations- parallel blinds of varied thickness |
| clearance angle | the angle between a plane containing the end surface of a cutting tool and a plane passing through the cutting edge in the direction of cutting motion |
| microtome saftey | always lock the handwheel, use of blade guard, do not rock the handwheel |
| how to prevent repetitive motion injury (RMI) | taking breaks using an automated rotary microtome |
| identify problem and the appropriate corrective action: compression | cause: knife too dull or dirty remedy: sharpen/replace blade cause: too little knife tilt remedy: increase knife angle cause: block too warm remedy: chill block |
| identify problem and the appropriate corrective action: split ribbons | cause: dull knife remedy: sharpen knife/change blade cause: knife angle too little remedy: adjust knife tilt cause: warm room/paraffin too soft remedy: chill block |
| identify problem and the appropriate corrective action: length wise scratches | cause: defect in the knife edge or hard particle in the tissue/dirty knife remedy: move or change blade |
| identify problem and the appropriate corrective action: gouging (overlapping) | cause: knife too dull or dirty remedy: sharpen knife or replace cause: too little knife tilt remedy: increase knife angle |
| identify problem and the appropriate corrective action: crooked ribbons | cause: horizontal edges of block not parallel remedy: trim block until parallel, reposition specimen holder cause: blade blunt in one area remedy: move blade or replace cause: tissue varies in consistency remedy: rotate block |
| identify problem and the appropriate corrective action: chatter | cause: over dehydration remedy: rehydrate cause: too much knife tilt remedy: adjust knife angle cause: dull knife remedy: sharpen knife or replace blade |
| identify problem and the appropriate corrective action: lifting sections | cause: dull knife remedy: sharpen or change blade |
| identify problem and the appropriate corrective action: udulations/washboarding | cause: knife angle too great remedy: decrease knife tilt cause: loose block or knife remedy: tighten block or knife cause: hard tissue remedy: use very sharp knife |
| identify problem and the appropriate corrective action: holes in sections | cause: block faced too aggressively remedy: face block less aggressively cause: excessive dehydration remedy: rehydrate |
| identify problem and the appropriate corrective action: lack of ribbon forming | cause: dull knife remedy: replace knife cause: paraffin too hard remedy: warm paraffin, re-embed cause: too much knife tilt remedy: adjust knife angle cause: room temp too low remedy: adjust room temp, warm knife/block |
| identify problem and the appropriate corrective action: thick and thin sections | cause: block or blade loose remedy: tighten cause: too little knife tilt remedy: increase clearance angle cause: wax too soft remedy: cool block or change to higher melting point wax |
| describe the effects of speed on microtomy | whether fast or slow a constant speed is necessary to avoid uneven sections one revolution of the hand-wheel per second smooth even revolutions |
| describe "tricks" for obtaining optimal microtomy sections | breathe on the block to provide heat, moisture, reduce static. softening paraffin embedded tissue by trimming the block until the tissue is exposed and then soaking the block in H2O or glycerol. tissues containing keratin can be soften by a depilatory |
| describe routine mircrotome maintenance | keep covered when not in use. thorough cleaning after use. lubrication as recommended. routine preventative maintenance. |
| Optimal temperature for the flotation bath? | 5-10 C below melting point of paraffin (which is 58 C) |
| Describe the need for distilled or deionized water | deoionized water prevents static and contamination |
| Describe the use of additives and adhesives in the flotation bath | Alcohol, detergent, photo-flo can be added to the flotation bath to lower the surface tension. |
| Identify the need for drying slides | Water is not miscible with the solvent used for deparaffinizing slides for staining |
Created by:
deeloused
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