HISTOPATHOLOGY CLEARING & IMPREG Flashcards
appearance of tissue after it has been treated by the fluid chosen to remove the dehydrating agent
Clearing
IN Clearing, Most of these tissues have similar refractive index to that of protein therefore the tissue is left ___________
translucent
Clearing agent is required when the dehydrating agent is not ______ with the ___________ medium.
miscible ; impregnating
It is essential for a clearing agent to be miscible both in _________ agent as well as ___________ agent.
dehydrating ; embedding
Commonly used clearing agents are as follows :
Xylene
Toluene and Benzene
Chloroform
Carbon tetrachloride
Cedar wood oil (Histological)
a clearing agent; It has a rapid action. Biopsy specimens of 3-4 mm thickness
are cleared in 2-4 hours.
Xylene
In xylene, Immersion time must not be prolonged otherwise the tissue become _______
brittle.
a clearing agent; that are similar in properties to xylene but are less damaging to the tissues on prolonged exposure.
Toluene and Benzene
a clearing agent; It is slower in action but it causes less brittleness therefore tissue can be left in it overnight.
Chloroform
a clearing agent; does not affect the refractive index of the tissue is not
rendered translucent and is expensive and inflammable.
Chloroform
a clearing agent; It is good for treatment of delicate tissues as it has the least hardening effect.
Cedar wood oil (Histological):
a clearing agent; is very slow in action and is very expensive.
Cedar wood oil (Histological):
In Cedar wood oil (Histological), care should be taken not to confuse it with ____________- used with oil immersion lens.
cedar wood oil (microscopic)
Techniques of clearing
If the tissue is being cleared in _______ or _________ it may be left overnight.
chloroform ; carbon tetrachloride
Techniques of clearing
In automatic tissue processor ____ changes of ____ hour each are usually satisfactory.
three ; one
Techniques of clearing
In _______, _______, ______ one change after 30-60 minutes is satisfactory to give a clear translucent appearance to the tissue.
Xylene, benzene or toluene
It is the complete removal of clearing reagents by substitution of paraffin or any such similar media.
Impregnation
Impregnation with paraffin wax takes place in an oven heated to _________ depending upon the melting point of the wax in use.
56-60°C
Frequent check of the temperature of paraffin baths is required since temperature 5°C above the melting point of the paraffin will cause tissue _________ and __________
shrinkage and hardening
Properties of paraffin wax
- Easy to prepare large number of tissue blocks in comparatively _____ time.
- Minimum _______ is required
- It is ______ than other impregnating media
- During staining there is very little ________ than other media.
short ; supervision ; cheaper ; difficulty
(Points to be remembered during use of paraffin wax)
- It should be free from ____, ____ and other foreign matter.
dust ; grit
(Points to be remembered during use of paraffin wax)
- It should not contain ______, which causes it to crystallize and turn it
white.
water
(Points to be remembered during use of paraffin wax)
- The wax has to be _______ before use by use of ordinary filter paper.
filtered
(Points to be remembered during use of paraffin wax)
- ______ melting point waxes are hard to ribbon.
Higher
For impregnation the wax oven has to be kept at high temperature,
making the tissue hard, too low melting point wax may not be hard enough to support the tissue during cutting.
yes
If the wax is overheated and remains in that state for a long time, it tends to ______ and become _______.
crystallize ; useless
his is mixture of highly purified paraffin and several plastic polymers.
Paraplast
Paraplast has greater elasticity than __________, therefore, the results are superior.
normal paraffin wax
Paraplast ribbons well allowing almost wrinkle free serial sections to be cut with ease at ______ thickness.
4 micron
should not be used for thin walled structures as it prevents complete expansion of the specimen.
Paraplast
Good embedding medium in which thin walled structures can be sectioned satisfactorily.
Bioloid
(Technique of impregnation)
The tissue is transferred from clearing agent to ___________-.
molten paraffin wax
(Technique of impregnation)
The amount of wax should be ______ times the volume of tissue.
25-50
(Technique of impregnation)
The tissue must be submitted to ___ changes in wax.
3
(Technique of impregnation)
The temperature of the wax bath should be ______ above the melting point of wax.
2-3°C
Time of impregnation
Depends on the following 3 factors
- The size and type of tissue
- The clearing agent employed
- The use of vacuum embedding oven.
- Size and type of tissue:
The _____ the tissue the _____ will be the time required for wax to
penetrate to the centre in addition a thick tissue has more of clearing agent so more changes of wax are necessary to remove it.
thicker ; longer
- Size and type of tissue:
If even small amounts of clearing agents remains with the wax this will cause ________ and produce ______ of the sections during cutting.
crystallization ; crumbling
- Size and type of tissue:
The type of tissue is also important since ____, _____, _____ needs twice as long as soft tissue like liver or kindly.
bone, skin, CNS
- Size and type of tissue:
Tissue like muscle and fibrous tissue tends to overharden and become brittle in wax bath so the time for impregnation must be kept to a ______.
minimum
- Size and type of tissue:
The reduction of time can be achieved by using ________________.
vacuum embedding medium
- Clearing agent employed
Some clearing agents are more rapidly and easily cleared than other e.g. _____, _______ and ______ are easiest to remove, and ____ change of wax is normally sufficient; whereas for chloroform and carbon tetrachloride _____ changes are needed.
Xylene, benzene and toluene ; one ; 2-3
- Use of vacuum embedding oven
With the use of normal paraffin oven, ___ changes of paraffin wax for a
period of ______ are needed but by using vacuum embedding oven this time may be halved
2 ; 4 hours
