02 Clearing

Question 1

the process whereby alcohol or a dehydrating agent is removed from the tissue

Answer 1

clearing

Question 2

in the clearing process, the tissue has a ___ appearance when dehydrating agent has been replaced by the solvent

Answer 2

translucent

Question 3

function of the clearing agent:

when used after alcohol dehydration

Answer 3

mix with alcohol and remove it from the tissue

Question 4

function of the clearing agent:

when used after tissue section has been stained

Answer 4

make microscopic tissue preparation transparent

Question 5

function of the clearing agent:

when the tissue is to be cleared directly from water

Answer 5

improve refractive index of the tissue

Question 6

T/F: when the function of the clearing agent is for the tissue to be cleared directly from water, dealcoholization is one of the most important process

Answer 6

F (no dealcoholzation required)

Question 7

in clearing, those with low boiling point are ___ (more/less) readily replaced by melted paraffin

Answer 7

more

Question 8

in clearing, the viscosity of the agent affects the ___ of penetration

Answer 8

speed

Question 9

prolonged exposure to clearing agent causes the tissue to become ___

Answer 9

brittle

Question 10

clearing agent:

colorless and most commonly used

Answer 10

xylene

Question 11

clearing time of xylene

Answer 11

1/2-1 hour

Question 12

clearing agent:

used for clearing, both for embedding and mounting procedures

Answer 12

xylene

Question 13

clearing agent:

generally suitable for routine histologic processing schedules of less than 24 hours and when tissue block is less than 5mm in thickness

Answer 13

xylene

Question 14

clearing agent:

most rapid

Answer 14

xylene

Question 15

clearing agent:

makes the tissue excessively hard if used over 3 hours

Answer 15

xylene

Question 16

clearing agent:

causes considerable shrinkage and hardening on lymph nodes

Answer 16

xylene

Question 17

clearing agent:

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

Answer 17

toluene

Question 18

clearing time of toluene

Answer 18

1-2 hours

Question 19

clearing agent:

miscible with both absolute alcohol and paraffin

Answer 19

toluene

Question 20

clearing agent:

acts fairly rapidly; recommended for routine purposes

Answer 20

toluene

Question 21

clearing agent:

does not make tissues excessively hard and brittle if left for 24 hours

Answer 21

toluene

Question 22

T/F: toluene is a faster clearing agent than xylene and benzene

Answer 22

F (slower)

Question 23

clearing agent:

preferred by some in the embedding process because it penetrates and clears tissues rapidly

Answer 23

benzene

Question 24

clearing agent:

rapid acting; for urgent biopsies (15-60 mins) and routine purposes

Answer 24

benzene

Question 25

T/F: benzene causes shrinkage if the tissue is exposed for too long

Answer 25

T

Question 26

T/F: chloroform is used for clearing and is slower than xylene

Answer 26

T

Question 27

clearing agent:

can be used for large and thicker tissue blocks - up to 1cm

Answer 27

chloroform

Question 28

T/F: tissues in chloroform easily become translucent

Answer 28

F (do not become translucent)

Question 29

clearing agent:

used for routine work (6-24 hours)

Answer 29

chloroform

Question 30

clearing agent:

used for tough tissues such as skin, dibroid, decalcified tissues, and for nervous tissues, lymph nodes, and embryos

Answer 30

chloroform

Question 31

clearing agent:

used to clear both paraffin and celloidin sections during the embedding process

Answer 31

cedarwood oil

Question 32

clearing agent:

especially recommended for CNS tissues and cytological studies

Answer 32

cedarwood oil

Question 33

cedarwood oil requires __ changes in clearing solution

Answer 33

2

Question 34

clearing time of cedarwoord oil

Answer 34

2 days

Question 35

cedarwood oil is ___ miscible with alcohol, which removes readily

Answer 35

96

Question 36

clearing agent:

tissues may be left indefinitely without causing considerable damage and distortion

Answer 36

cedarwood oil

Question 37

clearing agent:

not normally utilized as a routine clearing agent

Answer 37

cedarwood oil

Question 38

clearing agent:

recommended for clearing embryos, insects, and very delicate specimens

Answer 38

cedarwood oil

Question 39

clearing agent:

has the ability to clear 70% alcohol without excessive shrinkage and hardening

Answer 39

cedarwood oil

Question 40

clearing agent:

has a tendency to be adulterated; therefore the quality is not guaranteed

Answer 40

clove oil

Question 41

clearing agent:

has similar properties with chloroform

Answer 41

carbon tetrachloride

Question 42

clearing agent:

can be used when double embedding techniques are required

Answer 42

methyl benzoate/methyl salicylate

Question 43

clearing agent:

causes greater shrinkage than xylene does

Answer 43

dioxane

Question 44

a popular clearing agent is ___ and multiple changes are required to completely displace ethanol

Answer 44

xylene

Question 45

xylene substitute:

isoprene polymers found in essential oils originally derived from plants

Answer 45

terpenes

Question 46

xylene substitute:

a volatile oil found in citrus peels which goes by several trade names

Answer 46

limonenes

Question 47

xylene substitute:

offer the clearing action with the lowest hazard rating of all xylene alternatives

Answer 47

orange oil-based

Question 48

xylene substitute:

excellent in preserving fine tissue structure, and can often be used in place of xylene with not alteration of protocol

Answer 48

orange oil-based

Question 49

xylene substitute:

can be effective solvents, but they are considered toxic chemicals, posing serious health risks

Answer 49

chlorinated hydrocarbons

Question 50

xylene substitute:

non-hazardous, less expensive and causes less shrinkage of the tissue; can be used as a dealcoholization agent in the histopathological laboratory, without losing the quality of the histological details

Answer 50

coconut oil

Question 51

xylene substitute:

gives good tissues, sections, and histological slides; non-toxic, non-hazardous, non-flammable, biodegradable, economic, easy to handle, and readily available

Answer 51

bleached palm oil