Dehydration & Clearing - Histo Flashcards
process of removing intracellular and extracellular water from the tissue following fixation and prior to wax impregnation
Dehydration
Alcohol increasing concentration used for dehydration
70% —> 95% —> 100%
give few characteristics of an ideal dehydrating solution
- Dehydrates rapidly without producing considerable shrinkage or distortion in tissues
- should not evaporate fast
- dehydrate even fatty tissues
- not harden tissues excessively
- not remove stains
- should not be toxic to the body
- not a fire hazard
enumerate the commonly used dehydrating agents.
- Alcohol (most common)
- Acetone
- Dioxane
- Triethyl phosphate
- Tetrahydrofuran
it is important to keep dehydration times as ______ as possible to minimize risk of extracting cellular constituents
brief
what is the general rule in tissue dehydration process?
Whatever dehydrating agent is used, the amount of each stage should not be less than 10 times the volume of the tissue to ensure complete penetration
most commonly used dehydrating agent
Alcohol
an alcohol recommended for routine process, fast-acting and it easily penetrates tissue, also relatively cheap
Ethyl alcohol (ethanol)
a toxic dehydrating agent used for blood and tissue film smear prep
Methyl alcohol (methanol)
a slow dehydrating agent, used in plants and animal micro-tech
Butyl alcohol (butanol)
initially, very concentrated alcohol is used that eventually results in a relatively unequal impregnation of tissue consequently leading to poor cutting of sections
what is the remedy?
Start at 70% or lower concentrations of alcohol, then gradually increasing to 95%
what will happen to the tissue if its storage is prolonged in lower concentrations?
Tends to macerate tissues
what temp hastens dehydration time when using alcohol as the dehydrating agent?
37C
rapid yet poorly penetrates tissue, more miscible to epoxy, removes lipids, extreme volatility and flammability, not reco as routine
Acetone
excellent dehydrating and clearing agent, readily miscible with water, alcohol, xylol, and melted paraffin. extremely dangerous, expensive
dioxane