Clearing

Question 1

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

Answer 1

Wax and ethanol

Question 2

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

Answer 2

clearing (de alcoholization)

Question 3

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

Answer 3

Paraffin

Question 4

Medium on which the tissue is to be mounted

Answer 4

Canada balsam

Question 5

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

Answer 5

Canada balsam and other resins that are used for mounting sections

Question 6

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

Answer 6

Optical clarity or transparency

Question 7

Another important role of the clearing agent

Answer 7

remove a substantial amount of fat from the tissue

Question 8

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

Answer 8

Xylene

Question 9

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

Answer 9

Glycerin and gum syrup

Question 10

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

Answer 10

Alcohol

Question 11

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

Answer 11

Melted paraffin wax, mounting medium

Question 12

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

Answer 12

shrinkage, hardening or damage

Question 13

A good clearing agent should not dissolve out

Answer 13

Aniline dyes

Question 14

A good clearing agent should not _ in a water bath

Answer 14

Evaporate quickly

Question 15

A good clearing agent should make tissues -

Answer 15

Transparent

Question 16

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

Answer 16

Melted paraffin

Question 17

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

Answer 17

Chloroform

Question 18

also affects the speed of penetration of the clearing agent.

Answer 18

Viscosity

Question 19

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

Answer 19

Brittle

Question 20

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

Answer 20

Xylene

Question 21

Clearing time for xylene/xylol is usually

Answer 21

1/2-1 hour

Question 22

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

Answer 22

<24hours, <5 mm

Question 23

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

Answer 23

Xylene

Question 24

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

Answer 24

Xylene

Question 25

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

Answer 25

clearing agent, dewaxing agent

Question 26

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

Answer 26

methyl benzaldehyde

Question 27

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

Answer 27

15 -30 minutes (advantage)

Question 28

xylene is miscible with ___ and __.

Answer 28

absolute alcohol and paraffin. (advantage)

Question 29

xylene does not extract out

Answer 29

aniline dyes. (advantage)

Question 30

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

Answer 30

celloidin, celloidin sections. (advantage)

Question 31

it makes tissue transparent

Answer 31

xylene (advantage)

Question 32

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

Answer 32

paraffin oven (advantage), xylene

Question 33

it is cheap

Answer 33

xylene (advantage)

Question 34

it is highly inflammable and should be appropriately stored

Answer 34

xylene disadvantage

Question 35

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

Answer 35

3 hours, xylene (disadvantage)

Question 36

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

Answer 36

(disadvantage) nervous issues and lymph nodes

Question 37

Xylene becomes milky when an _______ is immersed in it.

Answer 37

incompletely dehydrated tissue

Question 38

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.

Answer 38

xylene disadvantage

Question 39

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

Answer 39

subliming, entering the atmosphere.

Question 40

Only _____ tools may be used to handle xylene.

Answer 40

non sparking

Question 41

Store xylene in a

Answer 41

flammable liquid storage cabinet.

Question 42

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

Answer 42

toluene

Question 43

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

Answer 43

toluene

Question 44

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

Answer 44

toluene

Question 45

Time recommended for clearing for toluene

Answer 45

1-2 hours

Question 46

it acts fairly rapidly and is recommended for routine purposes.

Answer 46

toluene (advantage)

Question 47

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

Answer 47

toluene (advantage)

Question 48

clears overnight

Answer 48

toluene (advantage)

Question 49

it is not carcinogenic

Answer 49

toluene advantage

Question 50

toluene is slower than ___ and ___ (disadvantage)

Answer 50

xylene and benzene (disadvantage)

Question 51

toulene tends to ___ in a partially filled vessel

Answer 51

acidify (disadvantage)

Question 52

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

Answer 52

toulene (disadvantage)

Question 53

it is more expensive

Answer 53

toluene (disadvantage)

Question 54

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

Answer 54

benzene

Question 55

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

Answer 55

benzene

Question 56

Its use for clearing purposes is therefore strongly discouraged.

Answer 56

benzene

Question 57

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

Answer 57

benzene (advantage)

Question 58

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

Answer 58

benzene (advantage)

Question 59

Benzene is miscible with

Answer 59

Absolute alcohol

Question 60

causes minimum shrinkage

Answer 60

benzene (advantage)

Question 61

benzene is highly _

Answer 61

Flammable

Question 62

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.

Answer 62

Tissue shrinkage

Question 63

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

Answer 63

Aplastic anemia

Question 64

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

Answer 64

Well ventilated

Question 65

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

Answer 65

Chloroform

Question 66

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

Answer 66

chloroflorm

Question 67

tissues placed in ___ do not become translucent.

Answer 67

chloroform

Question 68

It is recommended for routine work

Answer 68

Chloroform

Question 69

Chloroform is miscible with

Answer 69

absolute alcohol.

Question 70

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.

Answer 70

Chloroform