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Histopath LAB > DEHYDRATION > Flashcards

DEHYDRATION Flashcards

1
Q

Percent and Time

A

70 - 15mins
90 - 15mins
95 - 30mins
100 - 30mins
100 - 45mins

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2
Q

removal of water before infiltration

A

Dehydration

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3
Q

melted paraffin wax is_______

(mao na need i dehydrate)

A

hydrophobic

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4
Q

Dehydration

Immersing the specimen in a series of

A

increasing concentrations of alcohol

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5
Q

The most common manner of carrying it out is by immersing specimens in a series of_______ solutions of increasing concentration until pure, water-free alcohol is reached.

A

ethanol (alcohol)

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6
Q

is miscible with water in all proportions so that the water in the specimen is progressively replaced by the it

A

Ethanol

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7
Q

A series of increasing concentrations is used to avoid…

A

excessive distortion of the tissue

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8
Q

As a general rule, it is relevant to keep contact time with chemicals as brief as possible to limit_______ and to minimize the_________

A

tissue distortion

risk of extracting cellular constituents

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9
Q

The ideal amount of dehydrating agent, whatever type it may be, should also be maintained at a fluid to tissue ratio of_____ to achieve adequate dehydration

A

10:1

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10
Q

Dehydrating agent CHARACTERISTICS

A

a. Dehydrate rapidly without producing considerable tissue shrinkage;

b. Not evaporate too fast;

c. Not harden tissues excessively;

d. Not remove stains;

e. Not be a fire hazard;

f. Not be toxic to the handler (e.g. histotechnologist);

g. Be able to dehydrate a wide range of tissue types.

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11
Q

Dehydrating Agents

A

• Alcohols
• Glycol-Ethers
• Acetone
• Tetrahydrofuran

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12
Q

Alcohols

A
  • Ethanol
  • Methanol
  • Isopropanol
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13
Q

Glycol-Ethers

A
  • 2-ethoxyethanol / ethylene glycol monoethyl ether (cellosolve)
  • Dioxane
  • Polyethylene glycols
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14
Q
  • clear, colorless, flammable, hydrophilic liquid
  • miscible with water
  • when anhydrous, miscible with most organic solvents
A

Alcohols

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15
Q

Alcohols

also acts as…

A

secondary coagulant fixatives

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16
Q

Examples of alcohol

A

Ethanol
Methanol
Isopropanol

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17
Q

is probably the most commonly used dehydrating agent in histology.

A

Ethanol

18
Q

It is a rapid, efficient and widely applicable agent.

A

Ethanol

19
Q

It is normally a poor lipid solvent except under microwave processing conditions.

A

Ethanol

20
Q

It dissolves nitrocellulose slowly unless combined in equal proportions 1:1 (or better, 1:2) with diethyl ether

A

Ethanol

21
Q

Processing times in absolute ethanol should be minimal.

Minimal processing time

A

Ethanol

22
Q

Progressive removal of bound water from carbohydrates and proteins during prolonged immersion in absolute ethanol causes tissues to harden excessively and become brittle.

A

Ethanol

23
Q

Colloid, blood, collagen and yolky tissues are particularly affected. The problem is exacerbated by heat during wax infiltration.

A

Ethanol

24
Q

is a good ethanol substitute but rarely used for routine processing because of its volatility, flammability and cost

A

Methanol

25
Q

• poor lipid solvent
• does not dissolve nitrocellulose (unless mixed with acetone)

A

Mathanol

26
Q

In microwave processing it tends to harden tissues more than ethanol.

A

Methanol

27
Q

Ethanol

It dissolves nitrocellulose slowly unless combined in equal proportions (or better, 1:2) with______

A

diethyl ether

28
Q

Methanol

It is a poor lipid solvent, and will not dissolve nitrocellulose unless mixed with______.

A

acetone

29
Q

was first suggested as an ethanol substitute during the prohibition era in the United States.

A

Isopropanol

30
Q

It is a universal solvent

A

Isopropanol

31
Q

slightly slower in action and not as hydroscopic as ethanol

A

Isopropanol

32
Q

a far superior lipid solvent

A

Isopropanol

33
Q

• completely miscible with water and most organic solvents

• fully miscible with melted paraffin wax

• readily expelled from tissues and water baths

A

Isopropanol

34
Q

It shrinks and hardens tissues less than ethanol and is used to dehydrate hard, dense tissues, which can remain in the solvent for extended periods without harm.

A

Isopropanol

35
Q

To minimize shrinkage, fixed tissues are transferred via 60%-70% isopropanol or ethanol to absolute isopropanol.

A

Isopropanol

36
Q

is a solvent for some lipid-soluble dyes, but is not used in staining work stations as many other dyes are insoluble in this solvent.

A

Isopropanol

37
Q

Unlike the alcohols, these reagents do not act as secondary fixatives, and apart from solvent effects do not appear to alter tissue reactivity

A

GLYCOL-ETHERS

38
Q

is a colorless flammable liquid with sharp characteristic ketonic odor, low toxicity and is freely miscible with water and organic solvents

A

ACETONE

39
Q

is a colorless, highly volatile and flammable universal solvent with an offensive ethereal odor.

A

TETRAHYDROFURAN

40
Q

What makes ethanol the most common choice for a dehydrating agent?

A

Ethanol is miscible with water in all proportions so that the water in the specimen is progressively replaced by the alcohol. A series of increasing concentrations is used to avoid excessive distortion of the tissue.

41
Q

What is the purpose of subjecting formalin-fixed tissues to an ascending order of graded alcohol?

A

The graded series of alcohols ensures that the tissue is not extremely distorted due to the constant use of the alcohol.

Histopath LAB (12 decks)

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