It is the process of removal of water and fixative from the tissue
Why is dehydration required during processing
Paraffin wax is used for impregnation and embedding which is not miscible with water. Most of the fixatives are aqueous. Hence fixatives should be removed from tissue, for which dehydration is required
How is the dehydration achieved
Dehydration is achieved by placing the tissue in graded alcohols to avoid damage to the tissues.
For example: It starts with 70% alcohol, than 90-95% and then 100% alcohol.
What happens if the tissue is placed directly in 100% alcohol
Rapid removal of water causes shrinkage
What should be the volume of dehydrating agent
It should be 10times more than tissue size
What are the features of ideal dehydrating agent
An ideal dehydrating agent
Should be rapid in dehydrating
Should not produce much shrinkage or distortion
Should not evaporate fastly
Should dehydrate fat tissue
Should not harden tissue excessively
List out various dehydrating agents
Ethyl alcohol
Isoprophyl alcohol
Methanol
Butyl alcohol
Acetone
Cellosolve
Dimethoxy propane (or) Diethoxy propane
Dioxane
Tetrahydrofuran
Name the commonly used dehydrant
Ethyl alcohol
Which dehydrant is used for fatty tissue samples
Acetone
What is cellosolve
It is ethylene glycol or poly ethylene glycol monoethyl ether (PEG)
What are the advantages of cellosolve
Tissue can be kept in cellosolve for months without distortion
It is especially used for preceding ester wax embedding
Name the dehydrant which can be used both for clearing and dehydration
Dioxane (diethylene dioxide)
Tetrahydrofuran
What substance is used to test water content in alcohol used for dehydration
Anhydrous copper sulphate is used. It is placed in jar of absolute alcohol. As the water content in alcohol increases anhydrous copper sulphate absorbs water and becomes bluish in colour. Then the alcohol has to be damaged
Reference
Cullings. Histotecniques. In: Lynch Medical Laboratory technology by Mathew J. Lynch, Stanely S. Raphael. Saunders publication 1983