DEHYDRATION Flashcards
This is done in preparation for impregnation
dehydration
This process of removing intercellular and extracellular water from the tissue following fixation and prior to wax impregnation is known as
dehydration
the solution utilized for dehydration
dehydrating agents
many of the dehydrating agents are alcohols of various types that are used in _________ strengths
increasing
why are dehydrating agents used in increasing strengths
to remove aqueous tissue fluids with little disruption
to the tissue caused by diffusion currents.
the removal of water by evaporation from a solid, semi-solid or liquid.
drying
Note: SOLID TISSUES should NEVER be allowed to AIR DRY
involves slow substitution of the water in the tissue with an organic solvent
Dehydration
Most dehydrating agents are strong ____________ that bring about some ___________ and ________ of cell components.
organic solvents; shrinkage; extraction
how to counter the shrinkage and extraction of cell components when using dehydrating agents
To minimize these effects:
- dehydrating agents are used in a GRADED SERIES for SHORT PERIODS OF TIME
- water is GRADUALLY replaced so that violent osmotic changes do not produce distortions
an ideal dehydrating solution should dehydrate gradually without producing considerable shrinkage or distortion of tissues.
False. an ideal dehydrating solution should dehydrate RAPIDLY without producing considerable shrinkage or distortion of tissues
an ideal dehydrating solution should not evaporate very fast
True
an ideal dehydrating solution should be able to dehydrate even fatty tissues
True
an ideal dehydrating solution should harden tissues excessively
False. SHOULD NOT harden tissues excessively
an ideal dehydrating solution should be able to remove stains
False. should NOT remove stains
an ideal dehydrating solution should not be toxic to the body
True
an ideal dehydrating solution should not be toxic to the body
True
an ideal dehydrating solution should not be a fire hazard
True
whatever dehydrating agent is used, the amount in each step should not be less than 10 times the volume of the tissue in order to ensure
complete penetration of the tissue by the dehydrating solution.
True
Dehydration time must be as brief as possible to
minimize the risk of extracting cellular constituents
any water-miscible, anhydrous fluid can be used as a dehydrating agent providing that it
- does NOT damage the tissue PROTEINS
- is MISCIBLE with the fluids to be used subsequently
commonly used dehydrating agents
- alcohol (most common)
- Acetone
- Dioxane
- Cellosolve
- triethyl phosphate
- tetrahydrofuran
this is an alcohol recommended for routine dehydration
ethyl alcohol
the best dehydrating agent because it is fast-acting, it mixes with water and many organic solvents, and it penetrates tissues easily
ethanol
advantages of ethanol as a dehydrating agent
- fast-acting
- mixes with water and many organic solvents
- penetrates tissue easily
- not poisonous
- not very expensive
an alcohol dehydrating agent which is primarily employed for blood
and tissue films and for smear preparations
methyl alcohol
disadvantage of methyl alcohol
it is a toxic dehydrating agent
an alcohol dehydrating agent utilized in plant and animal micro-techniques
butyl alcohol
butyl alcohol is also a fast-acting dehydrating agent
False. butyl alcohol is a slow dehydrating agent
butyl alcohol produce less shrinkage and hardening than ethyl alcohol
true
this dehydrating agent is recommended for tissues which do not require rapid processing
butyl alcohol
why is it not advisable to transfer fixed tissues directly from water or aqueous fixative directly into absolute ethanol.
causes a rapid removal of water
which can distort the appearance of more delicate cells and structures
Hence:
-It is advisable to remove water gently and allow the tissue to slowly adjust to its removal.
-The more delicate the tissue, the more gently this should be done, but
there is no hard and fast rule
dehydration process
- 70% ethyl alcohol
- 95% ethyl alcohol
- 100% ethyl alcohol
