dehydration and clearing Flashcards
process of removing intercellular and extracellular water from the tissue following fixation and prior to wax impregnation
dehydration
removal of water by evaporation from solid, semi-solid, or liquid state
drying
10% formalin and Bouin’s
1) 70% - 100& alcohol III = __ - __ hours
2) xylol I = __ - __ hours
3) xylol II = __ hour
1) 3-12 hours
2) 1-2 hours
3) 1 hour
characteristics of an ideal dehydrating agent
- should dehydrate rapidly without shrinkage or distortion of tissue
- should not evaporate very fast
- should be able to dehydrate even fatty tissue
- should not harden tissues excessively
- should not remove stains
- should not be toxic to the body
- should not be a fire hazard
commonly used dehydrating agents
alcohol - most commonly used
acetone
dioxane
cellosolve
triethyl phosphate
tetrahydrofuran
____ ____is the recommended dehydrating agent for routine dehydration. considered to be the best dehydrating agent because it is ___ ___.
ethyl alcohol, fast-acting
___ toxic dehydrating agent, primarily employed for blood and tissue films and for smear preparation
methyl alcohol
___ is a slow dehydrating agent, produce less shrinkage and hardening than ethyl alcohol. recommended for tissues that do not require rapid processing
butyl alcohol
___ is a cheap dehydrating agent utilized for urgent biopsies which dehydrate in 1/2 to 2 hours. It is a clear, colorless fluid that mixes with water, ethanol, and most organic solvents
acetone
___ is a excellent dehydrating and clearing agent that is readily miscible in water, melted paraffin, alcohol, and xylol.it produces less tissue shrinkage than alcohol. however, it is extremely dangerous
dioxane
___ dehydrates rapidly. tissues may be transferred from water or saline directly to cellosolve and stored for months without producing hardening or distortion.
cellosolve
___ removes water readily and produce very little distortion and hardening of tissue
triethyl phosphate
___ reagent that both dehydrates and clears tissue since it is miscible in both water and paraffin.
tetrahydrofuran
two types of clearing agents: ___ and ___
organic solvents and oils
___ clearing of choice
xylol
characteristics of a good clearing agent
should be miscble with alchol
should be miscible with paraffin wax
should not produce excessive shrinkage, hardening, or damage of tissue
should not dissolve out aniline dyes
should not evaporate quickly in a water bath
should make tissues transparent
__ most commonly used in histology laboratories. clearing time is usually __ - __ hour/s. used for clearing, embedding, and mounting procedures.
xylene, 1/2 - 1 hour
___ is used as an substitute for xylne or benzene for clearing both during embedding and mounting process. time recommended for clearing is __ - __ hours
toluene. 1-2 hours
__ preferred by some since it penetrates and clear tissues rapidly. recommended for urgent biopsies and routine purposes
benzene
___ is slower than xylene but causes less brittleness. thicker tissue blocks can be processed. used when tough tissues like skin, fibroid, and decalcified tissues.
chloroform
___ used to clear both paraffin and celloidin sections. recommended for CNS tissues and cytological studies particularly smooth muscles and skin. clearing is usually complete in __ - __ days
cedarwood oil, 2-3 days
not normally utilized but is recommended for embryos, insects and delicate specimens due to its ability to clear 70% alcohol without excessive tissue shrinkage and hardening.
aniline oil
__ quality is not guaranteed due to tendency to become adulterated.
clove oil
similar to chloroform but cheaper. dangerous to inhale on prolonged exposure
carbon tetrachloride
slow acting clearing agent that can be used when double embedding techniques are required
methyl benzoate and methyl salicylate
