MIDTERM LEC: DEHYDRATION Flashcards
Follows fixation, and decalcification (if applicable)
DEHYDRATION
It is the removal of water from tissue in preparation for impregnation
DEHYDRATION
Since most fixatives are aqueous solutions, placing the fixed tissue in molten paraffin will not achieve impregnation because paraffin wax and water (from fixative) do not mix. Hence, dehydration must be done.
DEHYDRATION
Done as brief as possible and at a tissue-to-fixative ratio of 1:10
DEHYDRATION
Common Dehydrating Agents:
I. Alcohol
II. Acetone
III. Dioxane
IV. Cellosolve
V. Triethyl phosphate
VI. Tetrahydrofuran
Characteristics of Ideal Dehydrating Agents:
- Rapid action, with minimal tissue shrinkage and distortion
- Should not evaporate fast
- Able to dehydrate even fatty tissues
- Should not harden tissues excessively
- Should not remove stains
- Non-toxic, and not a fire hazard
Done in ascending grades to avoid distortion of tissue: 70% ROH -> 90% ROH ->100% ROH
ALCOHOLS
For delicate tissues, start at 30%
ALCOHOLS
ALCOHOLS
Initial alcohol conc. depends on the size and nature of tissue and the fixative used:
Strong initial conc. shrinkage and brittleness
Prolonged dehydration in less than 70% ROH tissue maceration
ALCOHOLS
37C
will hasten dehydration rate (for urgent exams)
ALCOHOLS
To ensure complete dehydration:
Add atleast ¼ deep layer of anhydrous Cu2SO4 at bottom of container, and cover with filter paper
ALCOHOLS
indicates full saturation of dehydrating fluids with water, thus alcohol must be changed with
a fresh solution
Bluing of copper sulfate crystals
ALCOHOLS:
- Ethyl alcohol (Ethanol)
- Methanol
- Butanol
Best dehydrant because it is fast-acting, mixes with water and many organic solvents, and penetrates tissues easily
Ethyl alcohol (Ethanol)
Not poisonous and not very expensive
Ethyl alcohol (Ethanol)
Clear, colorless, flammable
Ethyl alcohol (Ethanol)