DEHYDRATION

Question 1

Excessive dehydration causes tissues to become:

Answer 1

Hard
Brittle
Shrunken

Question 2

Ensures total dehydration making it the reagent of choice for electron microscopy

Answer 2

Ethanol

Question 3

Consists of ethanol plus 1% methanol, isopropyl alcohol, or a combination of alcohols
Used in the same manner as ethanol

Answer 3

INDUSTRIAL METHYLATED SPIRIT(DENATURED ALCOHOL)

Question 4

Clear, colorless, and flammable 
Highly toxic
Miscible with water
Can be substituted for ethanol
Used for dehydrating smears and tissue films

Answer 4

METHANOL

Question 5

Used in microwave processing schedules

Does not cause overhardening or shrinkage of tissues

Answer 5

PROPAN-2-OL

ISOPROPYL ALCOHOL

Question 6

Used primarily for plant and animal histology
Slow dehydrating agent
Less shrinkage and hardening

Answer 6

BUTANOLBUTYL ALCOHOL

Question 7

Clear, colorless and flammable liquid
Rapid in action
Poor penetration
Causes brittleness in tissues if used prolonged
Removes lipids during processing

Answer 7

ACETONE

Question 8

Produces less tissue shrinkage
Tissues can be left
Tissues tend to ribbon poorly
Expensive
Cumulative toxicity
Chromate fixated tissues should be washed thoroughly to remove chromate

Answer 8

DIOXANE

Question 9

DIOXANE METHODS:

Answer 9

GRAUPNER’S METHOD – 4H Dh + 3H impreg

WEISEBERGER’S METHOD – uses anhydrous calcium chloride to absorb water

Question 10

Dehydrate rapidly
Not harmful to tissues
Tissues may be transferred from water or normal saline and stored for months without hardening or distortion

Answer 10

CELLUSOLVE

ETHYLENE GLYCOL MONOETHYL ETHER

Question 11

Both rehydrates and clears
Dissolve many substances including fat
May be used for demixing, clearing and dehydrating paraffin sections before and after staining
Causes less shrinkage and easier cutting of sections with fewer artefacts
Does not dissolve aniline dyes
>6months exposure produces conjunctival irritation

Answer 11

TETRAHYDROFURAN

Question 12

ADDITIVE TO DEHYDRATING FLUIDS

Answer 12

GLYCEROL – softening agent for hard tissues

PHENOL – acts as a softening agent for hard tissues like tendons, nail, dense connective tissues, and keratin masses
4% solution is added to each 95% ethanol stations

Question 13

UNIVERSAL SOLVENTS

Answer 13

Dioxane
Tertiary butanol
Tetrahydrofuran