dehydration Flashcards
preeminent type of tissue processing treatment considered to be the most suitable for routine preparation, sectioning, staining, and subsequent storage of large tissue samples.
Paraffin Wax Method
process that removes water from aqueous-fixed tissue to prepare it for further processing
Dehydration
step that makes tissue miscible with paraffin wax
Clearing
most common dehydrating agent used in tissue processing
Alcohol
ideal characteristics of a dehydrating solution
- Dehydrates rapidly without causing shrinkage or distortion.
- Does not evaporate too fast.
- Can dehydrate fatty tissues.
- Does not excessively harden tissues.
- Does not remove stains.
- non-toxic.
- not a fire hazard.
commonly used dehydrating agents aside from alcohol
Acetone, Dioxane, Cellosolve, Triethyl phosphate, Tetrahydrofuran
T/F Alcohol and paraffin wax are naturally miscible, so no additional step is needed after dehydration.
F (Clearing is required because alcohol & paraffin are not miscible)
T/F Common dehydrating agents like alcohol are preferred because they are non-toxic and not hazardous.
T
T/F Paraffin wax is used in tissue processing because it is unsuitable for large tissue samples.
F - considered most suitable for routine processing and large tissue samples
dehydrating fluid in paraffin wax method
alcohol
best dehydrating agent recommended for routine tissue dehydration
Ethyl alcohol (ethanol)
characteristics of ethyl alcohol used as a dehydrating agent
clear, colorless, and flammable
Odd One Out: Advantage of ethyl alcohol as a dehydrating agent
A) Fast-acting
B) Non-toxic
C) Expensive
D) Mixes with water and solvents
Expensive – Ethanol is not expensive.
alcohol primarily used for blood and tissue films and smear preparations but is toxic
Methyl alcohol (methanol)
T/F Butyl alcohol is a slow dehydrating agent used in both plant and animal micro-techniques.
True
Slow dehydrating agent producing less shrinkage and hardening than ethanol.
Butyl alcohol (butanol)
disadvantage of using butyl alcohol as a dehydrating agent
slow dehydrating agent -> unsuitable for rapid tissue processing.
In Paraffin Wax Method, what concentration of ethanol is used after initial dehydration with 60-70% ethanol?
90-95% ethanol
T/F For smaller, more delicate tissues, lower alcohol concentrations are required for dehydration.
T
T/F Unequal impregnation and poor sectioning happens when concentrated alcohols produce shrinkage and make the tissue hard, brittle and difficult to cut – making it unable to penetrate the deeper parts.
T
what happens to tissue stored for extended periods in alcohol concentrations below 70%?
macerates and becomes unsuitable for processing.
dehydration time will be hastened at __ C for urgent examinations
37°C
chemical added to the dehydrating fluid to remove water and ensure complete dehydration
Anhydrous Copper Sulfate
clear, colorless fluid that mixes with water, ethanol and most organic solvent
Acetone
Odd One Out: Acetone as a dehydrating agent
A) Cheap
B) Rapid-acting
C) Penetrates tissue well
D) Miscible with organic solvents
C) Penetrates tissue well – Acetone penetrates tissues poorly.
T/F Acetone is highly flammable and should be used with caution.
T
dehydrating agent that is an excellent clearing agent, produces less tissue shrinkage, but is toxic and expensive?
Dioxane (Diethylene Dioxide)
T/F Dioxane can be used routinely in tissue processing.
F - Dioxane is dangerous and should not be used routinely.
Time Schedule for dehydration with dioxane (Graupner’s Method)
(1st) Pure dioxane solution: __
(2nd) Pure dioxane solution: __
(3rd) Pure dioxane solution: __
(1st) Paraffin wax: __
(2nd) Paraffin wax: __
(3rd) Paraffin wax: __
Embed in mold and cool in water
1 hr - 1 hr - 2 hr - 15 min - 45 min - 2 min
dehydration method that uses dioxane and anhydrous calcium oxide to remove water from tissues
Weiseberg’s Method
Tissues treated with ______ fixatives must be washed thoroughly before being placed in dioxane.
chromate
Odd One Out: Advantage of dioxane
A) Produces less tissue shrinkage
B) Allows tissue to stay in solution for a long time
C) Cheap
D) Can be left without affecting staining properties
C) Cheap – Dioxane is expensive.
dehydrating agent that can store tissues for months without causing hardening or distortion?
Cellosolve
cellosolve utilizes what chemical
ethylene glycol monoethyl ether
T/F: Cellosolve is combustible and toxic, and should be handled with caution
T
safer alternative if ethylene-based glycol ethers like Cellosolve cannot be avoided
propylene-based glycol ethers
dehydrating agent that removes water readily and produces minimal distortion and shrinkage
Triethyl phosphate
agent in tissue processing that dehydrates sections and smears following certain stains.
triethyl phosphate
Odd One Out: Characteristic of triethyl phosphate
A) Removes water readily
B) Produces minimal shrinkage
C) Excessively hardens tissue
D) Dehydrates without distortion
C) Excessively hardens tissue – Triethyl phosphate does not excessively harden tissue.
dehydrating agent that also acts as a clearing agent, dissolves many substances including fats, and gives improved staining results
Tetrahydrofuran (THF)
Odd One Out: NOT an advantage of Tetrahydrofuran (THF)?
A) Dehydrates and clears tissues
B) Dissolves many substances, including fats
C) Non-toxic
D) Improves staining results
Non-toxic – THF is toxic.
T/F Tetrahydrofuran (THF) can be used in poorly ventilated rooms as long as it is handled with care.
False – only used in well-ventilated rooms due to toxicity.
fixative that requires tissue to be transferred directly to 90% or higher ethanol for dehydration
Carnoy’s fluid and other alcoholic fixatives
For soft tissues like embryos, what is the first concentration of alcohol used to prevent shrinkage?
50% alcohol, followed by graded alcohol treatments.
T/F Tissues fixed in Susa fluid are transferred to 90% alcohol to avoid swelling of fibrous tissues.
T
typical dehydration sequence for specimens not more than 4 mm thick
70% ethanol: 15 min
90% ethanol: 15 min
100% ethanol: 15 min
100% ethanol: 15 min
100% ethanol: 30 min
100% ethanol: 45 min
chemical used to check the quality of absolute alcohol by detecting water contamination?
Anhydrous copper sulfate
What color does anhydrous copper sulfate turn if the absolute alcohol is contaminated with water?
blue
T/F Dehydration can be performed automatically in tissue processors (HP).
T
T/F Prolonged storage of tissues in alcohol concentrations below 70% tends to macerate the tissue.
T
T/F Tissues fixed in Susa fluid are transferred to 9% alcohol because lower grades of alcohol may cause swelling of the fibrous tissues
False – 90% alcohol.
Odd One Out: Factors to consider in choosing strength of initial alcohol
a) size
b) weight
c) nature of the tissue
d) fixative used.
b) Weight
conc. ranging from 70-80% alcohol at very long periods of time might interfere with the _____ properties of the specimen.
staining
acetone is more miscible when _____ than alcohol
epoxy resins
