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Histopathology (Lec & Lab) > CLEARING > Flashcards

CLEARING Flashcards

1
Q

The process whereby alcohol or a dehydrating agents is removed from the tissue and replaced by a fluid (clearing agent) that will dissolve the wax with which the tissue must be impregnated

A

Clearing

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2
Q

Other term of Clearing

A

DEALCOHOLIZATION

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3
Q

This must be miscible with the dehydrating agent, paraffin wax, and mounting medium

A

Clearing agent

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4
Q

Ideal amount of clearing agent:

A

Not less than 10x the volume of the
tissue

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5
Q

Excellent and true clearing agent

A

Xylene

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6
Q

These are used when tissue is to be cleared directly from water

A

Glycerin and gum syrup

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7
Q

No de-alcoholization is involved in this process

A

Frozen section

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8
Q

This is added to each of the 95% ethanol baths part of dehydration process, acts as a softener for hard tissue

A

Phenol (4%)

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9
Q

Hard tissues can immersed in a __________ mixture or in ___________

A

glycerol/alcohol; “Molliflex”

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10
Q

TRUE OR FALSE:
Clearing agent should not make tissues transparent

A

FALSE. It SHOULD make tissues transparent

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11
Q

TRUE OR FALSE:
Most clearing agents are flammable liquids.

A

TRUE

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12
Q

Clearing fluids with a low boiling point are generally more readily replaced by

A

melted paraffin

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13
Q

This also affects the speed of penetration of the clearing agent.

A

Viscosity

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13
Q

Among the Common Clearing Agents Used are:

A
  1. Xylene (most common)
  2. Toluene
  3. Benzene
  4. Chloroform
  5. Cedarwood oil
  6. Aniline oil
  7. Clove oil
  8. Carbon tetrachloride
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13
Q

This causes the tissue to become brittle and
therefore more difficult to cut.

A

Prolonged exposure to most clearing agents

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14
Q

Used for clearing both for embedding and mounting procedures.

A

Xylene (Xylol)

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15
Q

Xylene is generally suitable for most routine histologic
processing schedules of less than 24 hours, and
the tissue block size is __________ in thickness.

A

less than 5 mm

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16
Q

For mounting procedures, it does not dissolve celloidin

A

Xylene

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16
Q

Evaporates quickly in paraffin oven, and can readily replaced by wax during impregnation and embedding

A

Xylene

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17
Q

Becomes milky when
incompletely dehydrated tissue is immersed in it.

A

Xylene

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17
Q

Not suitable for nervous
tissues and lymph nodes

A

Xylene

17
Q

Used as a substitute for xylene or benzene

A

Toluene

18
Q

Not carcinogenic. Tissues do not become excessively hard
and brittle even if left in in this clearing agent for 24 hrs.

A

Toluene

19
Q

Tends to acidify in partially filled vessel. Highly concentrated solutions will emit fumes that are toxic upon prolonged exposure

A

Toluene

20
Q

Preferred by some as clearing agent in the embedding process of tissues because it penetrates and clears tissues rapidly

A

Benzene

21
Q

Excessive exposure may be extremely toxic to man and may become carcinogenic or it may damage the bone
marrow resulting in aplastic anemia.

A

Benzene

22
Q

Rapid acting, recommended for urgent biopsies and routine purposes.

A

Benzene

23
Q

Used for clearing of tissues during the embedding process, is slower in action than xylene, but causes less brittleness

A

Chloroform

24
Q

Recommended for routine work. Recommended for tough tissue and for nervous tissues, lymph nodes and embryos because it causes minimum shrinkage and hardening of tissues.

A

Chloroform

25
Q

Suitable for large tissue specimens

A

Chloroform

26
Q

Does not make tissues transparent, evaporates quickly from a water bath, and tissue tend to float in this clearing agent

A

chloroform

27
Q

Used to clear both paraffin and celloidin sections during the embedding process.

A

Cedarwood oil

28
Q

Recommended for central nervous system tissues and cytological studies, particularly smooth muscles and skin

A

Cedarwood oil

29
Q

Cedarwood oil requires ___________ in clearing solution, complete in 2-3 days

A

two changes

29
Q

IDENTIFY:
1. Very penetrating
2. Miscible with 96% alcohol which it removes readily
3. Clears celloidin in 5-6 days
4. Makes tissue transparent
5. Improves cutting of the sections.

A

Cedarwood oil

29
Q

Becomes milky upon prolonged storage and is very expensive

A

Cedarwood oil

30
Q

Hard to be eliminated from the tissues in paraffin bath (oil to benzene for ½ hour) and Quality is not always uniform and good

A

Cedarwood oil

31
Q

Not normally utilized as a routine clearing agent but is rather recommended for clearing embryos, insects and very delicate specimens, due to inability to clear 70% alcohol without excessive tissue shrinkage and hardening

A

Aniline oil

32
Q

This reagent causes minimum shrinkage of tissues. Quality is not guaranteed due to its tendency to become adulterated.

A

Clove oil

33
Q

Wax impregnation after clearing with clove oil is ________ and __________

A

slow; difficult

34
Q

In this clearing agent, tissues become brittle, aniline dyes are removed, and celloidin is dissolved

A

Clove oil

35
Q

Is used in clearing tissues for embedding. Its properties are very similar to chloroform although it is relatively cheaper.

A

Carbon tetrachloride

36
Q

Disadvantage is the same as that of chloroform.
Produces considerable tissue hardening, and is dangerous to inhale on prolonged exposure due to its highly toxic effects

A

Carbon tetrachloride

37
Q

These are slow-acting clearing agents
that can be used when double embedding techniques are required.

A

Methyl Benzoate/ Methyl Salicylate

38
Q

Cedarwood clearing time:

A

2-3 days

39
Q

Benzene clearing time:

A

15-60 minutes

40
Q

Toluene clearing time:

A

1-2 hours

41
Q

Xylene clearing time for urgent biopsies:

A

15-30 minutes

42
Q

Xylene usual clearing time:

A

1/2 to 2 hours

43
Q

Chloroform clearing time:

A

6-24 hours

Histopathology (Lec & Lab) (6 decks)

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