Dehydration & Clearing - Histo Flashcards

1
Q

process of removing intracellular and extracellular water from the tissue following fixation and prior to wax impregnation

A

Dehydration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Alcohol increasing concentration used for dehydration

A

70% —> 95% —> 100%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

give few characteristics of an ideal dehydrating solution

A
  1. Dehydrates rapidly without producing considerable shrinkage or distortion in tissues
  2. should not evaporate fast
  3. dehydrate even fatty tissues
  4. not harden tissues excessively
  5. not remove stains
  6. should not be toxic to the body
  7. not a fire hazard
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

enumerate the commonly used dehydrating agents.

A
  1. Alcohol (most common)
  2. Acetone
  3. Dioxane
  4. Triethyl phosphate
  5. Tetrahydrofuran
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

it is important to keep dehydration times as ______ as possible to minimize risk of extracting cellular constituents

A

brief

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the general rule in tissue dehydration process?

A

Whatever dehydrating agent is used, the amount of each stage should not be less than 10 times the volume of the tissue to ensure complete penetration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

most commonly used dehydrating agent

A

Alcohol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

an alcohol recommended for routine process, fast-acting and it easily penetrates tissue, also relatively cheap

A

Ethyl alcohol (ethanol)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

a toxic dehydrating agent used for blood and tissue film smear prep

A

Methyl alcohol (methanol)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

a slow dehydrating agent, used in plants and animal micro-tech

A

Butyl alcohol (butanol)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

initially, very concentrated alcohol is used that eventually results in a relatively unequal impregnation of tissue consequently leading to poor cutting of sections

what is the remedy?

A

Start at 70% or lower concentrations of alcohol, then gradually increasing to 95%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what will happen to the tissue if its storage is prolonged in lower concentrations?

A

Tends to macerate tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what temp hastens dehydration time when using alcohol as the dehydrating agent?

A

37C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

rapid yet poorly penetrates tissue, more miscible to epoxy, removes lipids, extreme volatility and flammability, not reco as routine

A

Acetone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

excellent dehydrating and clearing agent, readily miscible with water, alcohol, xylol, and melted paraffin. extremely dangerous, expensive

A

dioxane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

dehydrates rapidly, stored for mos without producing hardening or distortion, combustible at 110-120F, toxic by inhalation (vulnerable particularly are reproductive, fetal, urinary, and blood systems)

A

Cellosolve (ethylene glycol monoethyl ether)

17
Q

If the use of cellosolve cannot be avoided, what can be used instead?

A

propylene-based glycol ethers

18
Q

tissues are fixed, washed, and transferred directly into this dehy agent, it removes water readily with little distortion, dehydrates sections and smears

A

Triethyl phosphate

19
Q

Dehydrates and clears, miscible with water and paraffin, toxic when inhaled of ingested

A

Tetrahydrofuran (THF)

20
Q

acts as softener for hard tissues e.g. nails, tendons, fibrous tissues

A

Phenol 4%

21
Q

Hard tissues can be immersed in this mixture of glycerol and alcohol

A

Molliflex

22
Q

Process whereby alcohol or a dehydrating agent is removed from tissues and replaced with a substance that will dissolve the wax with which the tissue is to be impregnated

A

Clearing

23
Q

aka de-alcoholization

A

Clearing

24
Q

Used when tissue is to be cleared directly from water, as in frozen section

A

Glycerin and gum syrup

25
Q

Give few characteristics of a good clearing agent.

A
  1. Miscible with alcohol
  2. Miscible with, and easily removed by melted paraffin, and/or by mounting medium
  3. not produce excessive shrinkage, hardening, or damage to tissues
  4. not dissolve out aniline dyes
  5. not evaporate quickly in a water bath
  6. should make tissues transparent
26
Q

most common clearing agent

A

Xylene

27
Q

For urgent biopsies, clears 15-30mins, highly flammable, milky in incomp dehy tissue, cheap

A

Xylene (most common)

28
Q

Reco as routine, fairly rapid, emits fumes if highly concentrated, relatively slower than benzene and xylene, used as substitute for xylene, clears 1-2hrs, expensive

A

Toluene

29
Q

Preferred by some, urgent biopsies 15-60mins, highly flammable, carcinogenic, dmg BM results to aplastic anemia

A

Benzene

30
Q

Reco for routine work, slower than xylene but less brittle, can process up to 1cm thickness, for tough tissues, does not make tissue transparent or translucent, toxic to liver, tissues tend to float, difficult to remove from paraffin

A

Chloroform

31
Q

Extremely slow, not reco for routine, clears both paraffin and celloidin (5-6days), reco for CNS and cytological studies, 2-3 days, improves cutting of sections, milky upon prolonged use, quality not uniform, also tissue initially float

A

Cedarwood oil

32
Q

Reco for embryos, insects, very delicate spx,.. not normally utilized, able to clear 70% alcohol without excessive shrinkage or damage

A

Aniline oil

33
Q

Unsuitable for routine clearing, wax impregnation after using this clearing agent is slow and difficult,.. quality not guaranteed due to its tendency to become adulterated

A

Clove oil

34
Q

clearing agent used for tissue embedding, very similar with chloroform but relatively cheaper, highly toxic

A

Carbon tetrachloride

35
Q

Slow-acting dehydrating agents, used when double embedding is required

A

Methyl benzoate and methyl salicylate