CLEARING

Question 1

The process whereby alcohol or a dehydrating agents is removed from the tissue and replaced by a fluid (clearing agent) that will dissolve the wax with which the tissue must be impregnated

Answer 1

Clearing

Question 2

Other term of Clearing

Answer 2

DEALCOHOLIZATION

Question 3

This must be miscible with the dehydrating agent, paraffin wax, and mounting medium

Answer 3

Clearing agent

Question 4

Ideal amount of clearing agent:

Answer 4

Not less than 10x the volume of the
tissue

Question 5

Excellent and true clearing agent

Answer 5

Xylene

Question 6

These are used when tissue is to be cleared directly from water

Answer 6

Glycerin and gum syrup

Question 7

No de-alcoholization is involved in this process

Answer 7

Frozen section

Question 8

This is added to each of the 95% ethanol baths part of dehydration process, acts as a softener for hard tissue

Answer 8

Phenol (4%)

Question 9

Hard tissues can immersed in a __________ mixture or in ___________

Answer 9

glycerol/alcohol; “Molliflex”

Question 10

TRUE OR FALSE:
Clearing agent should not make tissues transparent

Answer 10

FALSE. It SHOULD make tissues transparent

Question 11

TRUE OR FALSE:
Most clearing agents are flammable liquids.

Answer 11

TRUE

Question 12

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

Answer 12

melted paraffin

Question 13

This also affects the speed of penetration of the clearing agent.

Answer 13

Viscosity

Question 13

Among the Common Clearing Agents Used are:

Answer 13

1. Xylene (most common)
2. Toluene
3. Benzene
4. Chloroform
5. Cedarwood oil
6. Aniline oil
7. Clove oil
8. Carbon tetrachloride

Question 13

This causes the tissue to become brittle and
therefore more difficult to cut.

Answer 13

Prolonged exposure to most clearing agents

Question 14

Used for clearing both for embedding and mounting procedures.

Answer 14

Xylene (Xylol)

Question 15

Xylene is generally suitable for most routine histologic
processing schedules of less than 24 hours, and
the tissue block size is __________ in thickness.

Answer 15

less than 5 mm

Question 16

For mounting procedures, it does not dissolve celloidin

Answer 16

Xylene

Question 16

Evaporates quickly in paraffin oven, and can readily replaced by wax during impregnation and embedding

Answer 16

Xylene

Question 17

Becomes milky when
incompletely dehydrated tissue is immersed in it.

Answer 17

Xylene

Question 17

Not suitable for nervous
tissues and lymph nodes

Answer 17

Xylene

Question 17

Used as a substitute for xylene or benzene

Answer 17

Toluene

Question 18

Not carcinogenic. Tissues do not become excessively hard
and brittle even if left in in this clearing agent for 24 hrs.

Answer 18

Toluene

Question 19

Tends to acidify in partially filled vessel. Highly concentrated solutions will emit fumes that are toxic upon prolonged exposure

Answer 19

Toluene

Question 20

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

Answer 20

Benzene

Question 21

Excessive exposure may be extremely toxic to man and may become carcinogenic or it may damage the bone marrow resulting in **aplastic anemia.**

Answer 21

Benzene

Question 22

Rapid acting, recommended for **urgent biopsies** and **routine purposes.**

Answer 22

Benzene

Question 23

Used for clearing of tissues during the embedding process, is **slower in action** than xylene, but **causes less brittleness**

Answer 23

Chloroform

Question 24

Recommended for routine work. Recommended for **tough tissue** and for **nervous tissues**, **lymph nodes** and **embryos** because it causes minimum shrinkage and hardening of tissues.

Answer 24

Chloroform

Question 25

Suitable for large tissue specimens

Answer 25

Chloroform

Question 26

Does **not** make tissues transparent, evaporates quickly from a water bath, and tissue tend to float in this clearing agent

Answer 26

chloroform

Question 27

Used to **clear both paraffin and celloidin sections** during the embedding process.

Answer 27

Cedarwood oil

Question 28

Recommended for c**entral nervous system tissues** and **cytological studies**, particularly **smooth muscle**s and **skin**

Answer 28

Cedarwood oil

Question 29

Cedarwood oil requires ___________ in clearing solution, complete in 2-3 days

Answer 29

two changes

Question 29

IDENTIFY: 1. Very penetrating 2. Miscible with 96% alcohol which it removes readily 3. Clears celloidin in 5-6 days 4. Makes tissue transparent 5. Improves cutting of the sections.

Answer 29

Cedarwood oil

Question 29

Becomes **milky upon prolonged storage** and is very expensive

Answer 29

Cedarwood oil

Question 30

Hard to be eliminated from the tissues in paraffin bath (oil to benzene for ½ hour) and **Quality is not always uniform and good**

Answer 30

Cedarwood oil

Question 31

Not normally utilized as a routine clearing agent but is rather recommended for **clearing embryos, insects and very delicate specimens,** due to inability to clear 70% alcohol without excessive tissue shrinkage and hardening

Answer 31

Aniline oil

Question 32

This reagent causes minimum shrinkage of tissues. Quality is not guaranteed due to its tendency to become **adulterated**.

Answer 32

Clove oil

Question 33

Wax impregnation after clearing with clove oil is ________ and __________

Answer 33

slow; difficult

Question 34

In this clearing agent, tissues become brittle, **aniline dyes are removed, and celloidin is dissolved**

Answer 34

Clove oil

Question 35

Is used in clearing tissues for embedding. Its properties are very **similar to chloroform** although it is relatively cheaper.

Answer 35

Carbon tetrachloride

Question 36

Disadvantage is the same as that of chloroform. **Produces considerable tissue hardening**, and is dangerous to inhale on prolonged exposure due to its highly toxic effects

Answer 36

Carbon tetrachloride

Question 37

These are **slow-acting clearing agents** that can be used when **double embedding techniques** are required.

Answer 37

Methyl Benzoate/ Methyl Salicylate

Question 38

Cedarwood clearing time:

Answer 38

2-3 days

Question 39

Benzene clearing time:

Answer 39

15-60 minutes

Question 40

Toluene clearing time:

Answer 40

1-2 hours

Question 41

Xylene clearing time for urgent biopsies:

Answer 41

15-30 minutes

Question 42

Xylene usual clearing time:

Answer 42

1/2 to 2 hours

Question 43

Chloroform clearing time:

Answer 43

6-24 hours