clearing Flashcards
process by which alcohol or a dehydrating agent is removed from the tissue and replaced with a substance to dissolve wax or mounting medium
Clearing
why is alcohol dissolved during the clearing process
paraffin (wax used for tissue impregnation) does not mix with alcohol.
T/F The first step of clearing involves replacing water in the tissue with alcohol during dehydration
True
most commonly used clearing agent to dissolve alcohol in tissues
Xylene
function of a clearing agent used after alcohol dehydration
mixes with alcohol and removes it from the tissue
what happens when the clearing agent is used after tissue section staining?
makes the tissue preparation transparent for microscopic examination.
when tissue is cleared directly from water, what is the role of the clearing agent?
improves the refractive index of the tissue without dealcoholization
Odd One Out: Characteristic of a good clearing agent
A) Miscible with alcohol
B) Dissolves aniline dyes
C) Makes tissues transparent
D) Easily removed by paraffin wax
B) Dissolves aniline dyes – a good clearing agent should not dissolve aniline dyes.
Odd One Out: acceptable property of a clearing agent
A) Causes excessive shrinkage
B) Miscible with alcohol
C) Easily removed by paraffin
D) Makes tissues transparent
A) Causes excessive shrinkage – A good clearing agent should not cause excessive shrinkage.
T/F: A good clearing agent should evaporate quickly in a water bath.
False – should not evaporate quickly in a water bath.
How does the boiling point of a clearing agent affect the process?
Clearing agents with low boiling points are more readily replaced by melted paraffin wax.
T/F Clearing agents with high viscosity can slow the penetration of the clearing agent into the tissue.
T
effect of prolonged exposure to a clearing agent on the tissue?
cause the tissue to become brittle.
Odd One Out: NOT a factor in choosing clearing agent
A) Cost and convenience
B) Processor system used
C) Ability to dissolve paraffin
D) Type of tissue and processing method
C) Ability to dissolve paraffin – The clearing agent should not dissolve paraffin, but it should be easily removed by it.
T/F: The ease of removing the clearing agent by molten paraffin wax is a key consideration when selecting a clearing agent.
T
commonly used clearing agent in tissue processing
A) Benzene
B) Cedarwood Oil
C) Xylene
D) All of the above
D) All of the above
Odd One Out: Which of the following is NOT a commonly used clearing agent?
A) Xylene
B) Carbon tetrachloride
C) Methanol
D) Toluene
C) Methanol – Methanol is a dehydrating agent, not a clearing agent.
most commonly used clearing agent, suitable for tissue blocks less than 5 mm in thickness
Xylene (Xylol)
T/F: Xylene is used for both embedding and mounting procedures in routine histologic processing.
T
typical clearing time for Xylene?
½ to 1 hour
Odd One Out: Advantage of Xylene
A) Miscible with alcohol and paraffin
B) Most rapid clearing agent
C) Extracts aniline dyes
D) Evaporates quickly in a paraffin oven
C) Extracts aniline dyes – Xylene does not extract aniline dyes.
disadvantage of using Xylene for more than 3 hours
makes tissue excessively hard
Odd One Out: Disadvantage of Xylene
A) Highly inflammable
B) Not suitable for nervous tissues
C) Expensive
D) Makes tissue hard if used over 3 hours
C) Expensive – Xylene is cheap.
used as a substitute for Xylene and Benzene, and is less likely to make tissues hard and brittle
Toluene
clearing time for Toluene
1-2 hours
Odd One Out: Advantage of Toluene
A) Miscible with alcohol and paraffin
B) Does not make tissues excessively hard
C) Slow clearing agent
D) Acts fairly rapidly for routine purposes
C) Slow clearing agent – Slower than xylene and benzene.
T/F Toluene is slower than Xylene and Benzene, and it acidifies in a partially filled vessel.
T
Odd One Out: Disadvantages of Toluene
A) Emits toxic fumes upon prolonged exposure
B) Acidifies in a partially filled vessel
C) Makes tissue brittle after 24 hours
D) More expensive
C) Makes tissue brittle after 24 hours – does not make tissues brittle after 24 hours.
preferred by some in the
embedding process because it
penetrates and clears tissues
rapidly
Benzene
clearing agent that volatilizes rapidly in a paraffin oven, does not make tissues hard and brittle, and causes minimum shrinkage
Benzene
T/F Benzene is highly inflammable and may cause tissue shrinkage if left in benzene for a long time.
T
Odd One Out: Advantage of Benzene
A) Rapid acting
B) Does not make tissues hard
C) Causes minimum shrinkage
D) Suitable for thicker tissue blocks
D) Suitable for thicker tissue blocks – Benzene is used for thinner tissue blocks.
serious health risk associated with prolonged exposure to Benzene
extremely toxic to humans upon excessive exposure
agent that when used for clearing in
embedding process, it’s slower than
xylene and causes less brittleness
Chloroform
T/F Chloroform can be used for thicker tissue blocks (up to 1cm)
T
clearing agent suitable for large tissue specimens, nervous tissues, and lymph nodes, and is not inflammable?
Chloroform
Odd One Out: Disadvantage of Chloroform
A) Toxic to the liver
B) Tends to float tissues
C) Makes tissues transparent
D) Wax impregnation is slow after clearing
C) Makes tissues transparent – Chloroform does not make tissues transparent
Odd One Out: Disadvantage of Chloroform
A) Complete clearing is difficult to evaluate
B) Evaporates quickly from a water bath
C) Wax impregnation is slow
D) Attacks rubber seals in vacuum baths
B) Evaporates quickly from a water bath – Chloroform evaporates slowly from a water bath.
typical clearing time for Cedarwood Oil
2-3 days
Odd One Out: Disadvantage of Cedarwood Oil
A) Becomes milky upon prolonged storage
B) Causes extensive tissue shrinkage
C) Hard to eliminate from tissues in paraffin bath
D) Expensive
B) Causes extensive tissue shrinkage – minimal shrinkage.
T/F: Aniline Oil is commonly used in routine clearing for large tissue samples.
F - not used routinely
Clearing agent that causes minimal tissue shrinkage but is unsuitable for routine clearing due to its tendency to adulterate and make tissues brittle
Clove Oil
Odd One Out: Disadvantage of Clove Oil
A) Expensive
B) Causes tissues to become brittle
C) Removes aniline dyes
D) Makes tissues transparent
D) Makes tissues transparent – Clove Oil does not make tissues transparent.
clearing agent that has properties similar to chloroform but produces considerable tissue hardening and is highly toxic
Carbon Tetrachloride
T/F: Carbon Tetrachloride is associated with health hazards similar to chloroform, including toxicity upon prolonged exposure.
T
what is double embedding, and why are Methyl Benzoate/Methyl Salicylate used for it
It uses two embedding media (e.g., celloidin and paraffin) and these agents are ideal because they act slowly.
clearing agent that has the ability to perform both dehydration and clearing at the same time and is non-toxic but has an offensive odor
Tetrahydrofuran
T/F: Tetrahydrofuran is toxic and should be handled with caution.
False – non-toxic, but has an offensive odor
significant health risk associated with Dioxane
toxic to liver
Odd One Out: Disadvantage of Dioxane
A) Causes greater shrinkage than xylene
B) Toxic to the liver
C) Fast-acting in embedding
D) Slow tissue impregnation
D) Slow tissue impregnation – fast because it allows tissues to be embedded within 4 hours
done to xylene containers to prevent it from entering the atmosphere and sublimating
keep it tightly closed (wow ang oa)
T/F: Xylene should be stored in a flammable liquid storage cabinet, away from incompatible substances
T
T/F: Coconut Oil is commonly used in the histopathological laboratory as a dealcoholization agent without compromising histological quality.
T
Odd One Out: NOT a less-toxic substitute for xylene
A) Limonene reagents
B) Vegetable oils
C) Coconut oil
D) Alcohol
D) Alcohol – not a substitute for xylene
offer the lowest hazard rating among xylene alternatives and preserve fine tissue structure.
ORANGE OIL BASED CLEARING AGENTS
isoprene polymers found in essential oils originally derived from plants.
Terpenes
Which of the following is NOT a source of terpenes that can be used as a clearing substitute?
A) Oil of bergamot
B) Cedarwood oil
C) Olive Oil
D) Oil of sandalwood
C) Olive Oil – not a terpene; panluto yn tanga
oil considered as an efficient substitute for xylene due to being nonhazardous and less expensive
Coconut Oil
volatile oil found in citrus peels, such as lemons and oranges
Limonene
T/F Orange oil can often be used in place of xylene without altering the protocol.
T
effective solvents but are considered toxic chemicals that pose serious health risks
Chlorinated Hydrocarbons
Odd One Out: Which of the following is NOT an advantage of Coconut Oil?
A) Nonhazardous
B) Causes significant shrinkage
C) Less expensive
D) Good for dealcoholization
B) Causes significant shrinkage – Coconut Oil causes less shrinkage of tissue.
provides good tissue sections and is non-toxic, nonhazardous, and nonflammable
Bleached Palm Oil
T/F: Bleached Palm Oil is not biodegradable.
F - biodegradable.
Odd One Out: Characteristic of Bleached Palm Oil
A) Easy to handle
B) Highly toxic
C) Economic
D) Readily available
B) Highly toxic – non-toxic.
