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GenPath Lab > Clearing > Flashcards

Clearing Flashcards

1
Q

Although dehydrated issue is now essentially water free it still cannot be infiltrated because _ are largely immiscible

A

Wax and ethanol

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2
Q

Is the process whereby alcohol or a dehydrating agent is removed from the tissue and replaced with a substance that will dissolve the wax in which issue is to be impregnated

A

clearing (de alcoholization)

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3
Q

Substance that will dissolve the wax with which the tissue is to be impregnated

A

Paraffin

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4
Q

Medium on which the tissue is to be mounted

A

Canada balsam

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5
Q

Aside from removing alcohol, a cleaning agent must also be miscible with

A

Canada balsam and other resins that are used for mounting sections

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6
Q

This stage in the process is called “clearing” because many (but not all) clearing agents impart an ___ or ___ to the tissue due to their relatively high refractive index

A

Optical clarity or transparency

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7
Q

Another important role of the clearing agent

A

remove a substantial amount of fat from the tissue

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8
Q

The most commonly used clearing agent for removing a substantial amount of fat from the tissue which otherwise presents a barrier to wax infiltration.

A

Xylene

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9
Q

used when the tissue is to be cleared directly from water, as in a frozen section.

A

Glycerin and gum syrup

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10
Q

A good clearing agent should be miscible with ___ to promote rapid removal of the dehydrating agent from the tissue.

A

Alcohol

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11
Q

A good clearing agent should be miscible with, and easily removed by ____ and/or by ____to facilitate impregnation and mounting of sections.

A

Melted paraffin wax, mounting medium

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12
Q

A good clearing agent should not produce excessive __, ___ or ___ of tissue

A

shrinkage, hardening or damage

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13
Q

A good clearing agent should not dissolve out

A

Aniline dyes

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14
Q

A good clearing agent should not _ in a water bath

A

Evaporate quickly

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15
Q

A good clearing agent should make tissues -

A

Transparent

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16
Q

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

A

Melted paraffin

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17
Q

has a lower boiling point than xylene in fact takes longer than the latter to clear.

A

Chloroform

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18
Q

also affects the speed of penetration of the clearing agent.

A

Viscosity

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19
Q

Prolonged exposure to most clearing agents causes the tissue to become ___ and therefore more difficult to cut.

A

Brittle

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20
Q

a colorless clearing agent that is most commonly used in histology laboratories.

A

Xylene

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21
Q

Clearing time for xylene/xylol is usually

A

1/2-1 hour

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22
Q

xylene/xylol is generally suitable for most routine histologic processing schedules of ___ hours, and when the tissue block size is ___ mm.

A

<24hours, <5 mm

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23
Q

is reasonably cost effective and works well for short-term clearing of small tissue blocks.

A

Xylene

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24
Q

is one of the routinely used chemical in histology and pathology laboratories because of its vital role in the paraffin wax tissue processing method.

A

Xylene

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25
Q

xylene It is mostly used as ____ during tissue processing and as a ___ during staining

A

clearing agent, dewaxing agent

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26
Q

several toxicities believed to be caused by intermediate products of xylene metabolism such as ___ have been reported.

A

methyl benzaldehyde

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27
Q

Xylene is the most rapid clearing agent, suitable for urgent biopsies which it clears within

A

15 -30 minutes (advantage)

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28
Q

xylene is miscible with ___ and __.

A

absolute alcohol and paraffin. (advantage)

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29
Q

xylene does not extract out

A

aniline dyes. (advantage)

30
Q

For mounting procedures, xylene does not dissolve ___ and can m therefore, be used for ___ sections.

A

celloidin, celloidin sections. (advantage)

31
Q

it makes tissue transparent

A

xylene (advantage)

32
Q

It evaporates quickly in ____ oven and can, therefore, be readily replaced by wax during impregnation and embedding.

A

paraffin oven (advantage), xylene

33
Q

it is cheap

A

xylene (advantage)

34
Q

it is highly inflammable and should be appropriately stored

A

xylene disadvantage

35
Q

if used longer than ___ it makes tissues excessively hard and brittle

A

3 hours, xylene (disadvantage)

36
Q

xylene causes considerable hardening and shrinkage of tissues; hence, is not suitable for ___ and ___

A

(disadvantage) nervous issues and lymph nodes

37
Q

Xylene becomes milky when an _______ is immersed in it.

A

incompletely dehydrated tissue

38
Q

may irritate eyes, nose and respiratory tract. It can be absorbed through the skin and cause dermatitis. At high concentrations, it is toxic and narcotic.

A

xylene disadvantage

39
Q

Keep container tightly closed to prevent xylene from ___ and entering the ____.

A

subliming, entering the atmosphere.

40
Q

Only _____ tools may be used to handle xylene.

A

non sparking

41
Q

Store xylene in a

A

flammable liquid storage cabinet.

42
Q

is better at preserving tissue structure and is more tolerant of small amounts of water left behind in the tissues than xylene.

A

toluene

43
Q

more expensive than xylene and more toxic, so it is less commonly used.

A

toluene

44
Q

may be used as a substitute for xylene or benzene for clearing both during embedding and mounting processes.

A

toluene

45
Q

Time recommended for clearing for toluene

A

1-2 hours

46
Q

it acts fairly rapidly and is recommended for routine purposes.

A

toluene (advantage)

47
Q

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

A

toluene (advantage)

48
Q

clears overnight

A

toluene (advantage)

49
Q

it is not carcinogenic

A

toluene advantage

50
Q

toluene is slower than ___ and ___ (disadvantage)

A

xylene and benzene (disadvantage)

51
Q

toulene tends to ___ in a partially filled vessel

A

acidify (disadvantage)

52
Q

Highly concentrated solutions will emit fumes that are toxic upon prolonged exposure.

A

toulene (disadvantage)

53
Q

it is more expensive

A

toluene (disadvantage)

54
Q

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

A

benzene

55
Q

used to be a popular routine clearing agent until recently when its highly carcinogenic properties were recognized.

A

benzene

56
Q

Its use for clearing purposes is therefore strongly discouraged.

A

benzene

57
Q

It is rapid acting, hence is recommended for urgent biopsies (15-60 minutes) and routine purposes.

A

benzene (advantage)

58
Q

volatilizes rapidly in paraffin oven and is therefore easily eliminated from the tissue.

A

benzene (advantage)

59
Q

Benzene is miscible with

A

Absolute alcohol

60
Q

causes minimum shrinkage

A

benzene (advantage)

61
Q

benzene is highly _

A

Flammable

62
Q

If a section is left in benzene for a long time, considerable ____ may be observed. Hence, tissues should be transferred to paraffin wax as soon as possible.

A

Tissue shrinkage

63
Q

Excessive exposure to benzene may be extremely toxic to man and may become carcinogenic or it may damage the bone marrow resulting in ____

A

Aplastic anemia

64
Q

If ever benzene is to be used for clearing, the laboratory should be _____.

A

Well ventilated

65
Q

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

A

Chloroform

66
Q

Thicker tissue blocks, even those up to I cm. in thickness, can be processed.

A

chloroflorm

67
Q

tissues placed in ___ do not become translucent.

A

chloroform

68
Q

It is recommended for routine work

A

Chloroform

69
Q

Chloroform is miscible with

A

absolute alcohol.

70
Q

It is recommended for tough tissues (e.g. skin, fibroid and decalcified tissues) for nervous tissues, lymph nodes and embryos because it causes minimum shrinkage and hardening of tissues.

A

Chloroform

GenPath Lab (5 decks)

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