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• Histotechnology, also known as microtome automatic tissue processor, involves the use of a microscope, a microtome, and essential tools such as a blow holder, knife carrier, pawl rachet feed wheel and adjustment screw, and clearance angle.
• The bevel angle for a microtome is 27-32 C, with a perfect optimum angle of 15C, and a clearance angle of 0-50C.
• Types of microtome include the rocking (Cambridge) microtome invented by Pladwell Trefall in 1881, the rotary (minot) microtome invented by Minot on 1885-1886, the sliding microtome invented by Adams in 1789, the freezing microtome invented by Queckett in 1848, the cryostat/cold microtome, the fresh tissue microtome, and the ultra-thin microtome for electron microscopy.
• Conventional knives used in a microtome include the plain concave knife with a length of 25mm, the more concave knife with a length of 120mm, the plane wedge knife with a length of 100mm, and the biconcave knife with a length of 120mm.
• Honing, also known as hard sharpening, is a type of sharpening that removes irregularities from the edge of a knife, while stropping, also known as polishing, is a type of sharpening that removes burrs from the cutting edge.
• Disposable blades are cheaper and most commonly used, eliminating the need for honing and stroping process.
• Diamond knives are used for ultrathin sections, while magnetic knives are used for cryostat.
• The histotechnology station involves 10% formalin, ascending grades of ethyl alcohol from 70% to 95%, and two changes of acetone.
• The dehydration and clearing process involves somatic death, which can be primary or secondary, and histological staining, which is done using H&E stain.
• The practical exam for histotechnology involves the use of a microscope, a microtome, and histological staining.
• The written exam for histotechnology covers the topics of histotechnology, dehydration and clearing, somatic death, and H&E stain.
• The practical exam for histotechnology includes a quiz every meeting, a long quiz before the exam, and 30 points for the exam.
• The midterm topic coverage for histotechnology includes histotechnology, dehydration and clearing, somatic death, and H&E stain.
• The practical exam for histotechnology involves a written exam and a practical exam, with 10 points awarded for each discussion and 30 points for the exam.
• Toluene is a clearing agent that clears in 1 to 2 hours and may be used as a substitute to xylene or benzene.
• Isophrophyl alcohol (IPA) is an ethanol substitute used in microwave processing.
• Temperature for wax infiltration: 45-50 c.
• Benzene is a rapid acting clearing agent that clears in 15 to 60 minutes and may be carcinogenic, causing aplastic anemia.
• Methyl alcohol is toxic and primarily used for blood and tissue films preparation.
• Incomple dehydration is the most common processing problem, it results for making tissue soft and non receptible to infiltration.
• Xylene (xylool) is the most commonly used clearing agent, it clears in 15 to 30 minutes and becomes milky when an incompletely dehydrated tissue is immerse in it.
• Nervous changes include loss of coordination in body function.
• Dring temperature for wax infiltration is 56-60 c for 2 hrs.
• Clearing is the process where alchohol dehydrating fluid is removed from tissue and replaced with intermediate solvent, the clearing agent should be atleast 10x the volume of tissue.
• Application of clearing includes making tissue, embryo and parasite transparent, dealcoholization of tissue preparatory to wax impregnation, and dealcoholization of stain section prior to mounting, Canada balsam.
• Alcohol is the most common dehydrating agent, a temperature of 37 c will hasten dehydration time.
• Butyl alchohol (tertiary butanol) acts as dehydrating and clearing.
• Chloroform is used for tough tissue (skin, decalcified tissue).
• Cedarwood oil is recommended for cns.
• Respiratory changes due to absence of oxygen.
• Somatic death refers to the death or complete cessation of metabolic functional activities.
• A small amount of detergent added to water to reduce surface tension.
• Denatured (industrial methylated spirit) is a raw material in making shabu methamphetamine.
• B.oven paraffin is used in the infiltration process.
• Dioxane (diethylene dioxide) is an excellent dehydrating and clearing agent, miscible in water, xylol, paraffin and alchohol.
• C.)staining equipment includes Coplin jars with 5 to 9 slides, slotted staining with 5 to 19 slides, and metal glass with 10 to 30 slides.
• Dehydration is the process of removing tissue following fixation in preparation for wax impregnation, usually occurs placing fix tissue in ascending grade of dehydrating fluid.
• Ethyl alcohol is clear, colorless, flammable and most commonly used, recommended for routine dehydration.
• Primary changes in circulatory system include immediate death, for medico legal purpose.
• Pentanol (AMYL Alchohol) is used for plants and animals.