Clearing

Question 1

the transition step between
dehydration and infiltration with the
embedding medium

Answer 1

clearing

Question 2

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.

Answer 2

de-alcoholization or clearing

Question 2

Does not dissolve aniline dyes

Answer 2

• cedarwood oil
• ## xylene

Question 3

Most commonly used clearing agents are

Answer 3

Xylene, dioxane, chloroform and cedarwood oil

Question 4

The clearing agent will make microscopic tissue preparations transparent due to

Answer 4

high index refraction

Question 5

Characteristics of a Good Clearing Agent

Answer 5

• 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

Question 6

Xylene clearing time

Answer 6

30 mins to 1 hr

Question 7

Makes tissues transparent

Answer 7

• xylene
• benzene
• cedarwood oil

Question 8

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

Answer 8

xylene

Question 9

Not suitable for nervous tissues and lymph nodes

Answer 9

xylene

Question 10

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

Answer 10

toluene

Question 11

suitable for urgent biopsies

Answer 11

xylene

Question 12

Expensive

Answer 12

• toluene
• cedarwood oil
• clove oil

Question 13

What is the clearing time of toluene

Answer 13

1- 2 hours

Question 14

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

Answer 14

benzene

Question 15

Slower in action than xylene but causes less brittleness

Answer 15

chloroform

Question 16

Acts fairly rapidly and is recommended for routine purpose

Answer 16

toluene

Question 17

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

Answer 17

benzene

Question 18

highly flammable

Answer 18

• xylene
• benzene

Question 19

clearing time of benzene

Answer 19

15 mins to 1 hr

Question 20

not carcinogenic / toxic

Answer 20

• ## toluene

Question 21

becomes milky when an incompletely dehydrated tissue is
immersed in it

Answer 21

xylene

Question 22

carcinogenic / toxic

Answer 22

• benzene
• chloroform
• carbon tetrachloride

Question 23

does not make tissues transparent

Answer 23

• ## chloroform

Question 24

It may damage the bone marrow resulting in aplastic anemia

Answer 24

benzene

Question 25

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

Answer 25

chloroform

Question 26

chloroform clearing time

Answer 26

6-24 hours

Question 27

not recommended for routine purposes

Answer 27

- cedarwood oil - aniline oil - clove oil

Question 28

Relatively toxic to the liver after prolonged inhalation

Answer 28

chloroform

Question 29

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

Answer 29

chloroform

Question 30

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

Answer 30

aniline oil

Question 31

Complete clearing is difficult to evaluate

Answer 31

chloroform

Question 32

cedarwood clearing time

Answer 32

2-3 days

Question 33

Very penetrating clearing agent

Answer 33

cedarwood oil

Question 34

Recommended for central nervous system tissues and cytological studies

Answer 34

cedarwood oil

Question 35

Becomes milky upon prolonged storage and should be filtered before use

Answer 35

cedarwood oil

Question 36

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

Answer 36

clove oil

Question 37

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

Answer 37

clove oil

Question 38

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

Answer 38

Carbon Tetrachloride

Question 39

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

Answer 39

Methyl Benzoate and Methyl Salicylate