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Histopath Lec > Clearing > Flashcards

Clearing Flashcards

1
Q

the transition step between
dehydration and infiltration with the
embedding medium

A

clearing

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2
Q

Process whereby alcohol is removed from the tissue & replaced with a substance that will dissolve the wax with which the tissue is impregnated (Paraffin) or the medium on which the tissue is to be mounted.

A

de-alcoholization or clearing

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2
Q

Does not dissolve aniline dyes

A
  • cedarwood oil
  • ## xylene
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3
Q

Most commonly used clearing agents are

A

Xylene, dioxane, chloroform and cedarwood oil

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4
Q

The clearing agent will make microscopic tissue preparations transparent due to

A

high index refraction

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5
Q

Characteristics of a Good Clearing Agent

A
  • Miscible with alcohol to promote rapid removal for the dehydrating agent
  • Should be miscible with and easily removed by melted 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
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6
Q

Xylene clearing time

A

30 mins to 1 hr

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7
Q

Makes tissues transparent

A
  • xylene
  • benzene
  • cedarwood oil
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8
Q

Colorless clearing agent that is most commonly used. Most rapid clearing agent,

A

xylene

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9
Q

Not suitable for nervous tissues and lymph nodes

A

xylene

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10
Q

Tissues do not become excessively hard and brittle even if left for 24 hrs

A

toluene

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11
Q

suitable for urgent biopsies

A

xylene

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12
Q

Expensive

A
  • toluene
  • cedarwood oil
  • clove oil
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13
Q

What is the clearing time of toluene

A

1- 2 hours

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14
Q

It is preferred as clearing agent in the embedding process of tissue

A

benzene

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15
Q

Slower in action than xylene but causes less brittleness

A

chloroform

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16
Q

Acts fairly rapidly and is recommended for routine purpose

A

toluene

17
Q

Does not make tissues hard and brittle but it causes minimum shrinkage

A

benzene

18
Q

highly flammable

A
  • xylene
  • benzene
19
Q

clearing time of benzene

A

15 mins to 1 hr

20
Q

not carcinogenic / toxic

A
  • ## toluene
21
Q

becomes milky when an incompletely dehydrated tissue is
immersed in it

A

xylene

22
Q

carcinogenic / toxic

A
  • benzene
  • chloroform
  • carbon tetrachloride
23
Q

does not make tissues transparent

A
  • ## chloroform
24
Q

It may damage the bone marrow resulting in aplastic anemia

A

benzene

25
Q

Suitable for large tissue specimens. Thicker tissue blocks (up to 1 cm) are can be
processed

A

chloroform

26
Q

chloroform clearing time

A

6-24 hours

27
Q

not recommended for routine purposes

A
  • cedarwood oil
  • aniline oil
  • clove oil
28
Q

Relatively toxic to the liver after prolonged inhalation

A

chloroform

29
Q

Difficult to remove from paraffin sections because it is not very volatile

A

chloroform

30
Q

Recommended for clearing embryos, insects and very
delicate specimens due to its ability to clear 70% alcohol
without excessive tissue shrinkage and hardening

A

aniline oil

31
Q

Complete clearing is difficult to evaluate

A

chloroform

32
Q

cedarwood clearing time

A

2-3 days

33
Q

Very penetrating clearing agent

A

cedarwood oil

34
Q

Recommended for central nervous system tissues and cytological studies

A

cedarwood oil

35
Q

Becomes milky upon prolonged storage and should be filtered before use

A

cedarwood oil

36
Q

its quality is not guaranteed due to its tendency to become adulterated

A

clove oil

37
Q

Tissues become brittle, aniline dyes are removed and celloidin is
dissolve

A

clove oil

38
Q

produces considerable tissue hardening and dangerous to
inhale on prolonged exposure due to its highly toxic effect

A

Carbon Tetrachloride

39
Q

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

A

Methyl Benzoate and
Methyl Salicylate

Histopath Lec (7 decks)

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