DEHYDRATION

Question 1

Percent and Time

Answer 1

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

Question 2

removal of water before infiltration

Answer 2

Dehydration

Question 3

melted paraffin wax is_______

(mao na need i dehydrate)

Answer 3

hydrophobic

Question 4

Dehydration

Immersing the specimen in a series of

Answer 4

increasing concentrations of alcohol

Question 5

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.

Answer 5

ethanol (alcohol)

Question 6

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

Answer 6

Ethanol

Question 7

A series of increasing concentrations is used to avoid…

Answer 7

excessive distortion of the tissue

Question 8

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

Answer 8

tissue distortion

risk of extracting cellular constituents

Question 9

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

Answer 9

10:1

Question 10

Dehydrating agent CHARACTERISTICS

Answer 10

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.

Question 11

Dehydrating Agents

Answer 11

• Alcohols
• Glycol-Ethers
• Acetone
• Tetrahydrofuran

Question 12

Alcohols

Answer 12

• Ethanol
• Methanol
• Isopropanol

Question 13

Glycol-Ethers

Answer 13

• 2-ethoxyethanol / ethylene glycol monoethyl ether (cellosolve)
• Dioxane
• Polyethylene glycols

Question 14

• clear, colorless, flammable, hydrophilic liquid
• miscible with water
• when anhydrous, miscible with most organic solvents

Answer 14

Alcohols

Question 15

Alcohols

also acts as…

Answer 15

secondary coagulant fixatives

Question 16

Examples of alcohol

Answer 16

Ethanol
Methanol
Isopropanol

Question 17

is probably the most commonly used dehydrating agent in histology.

Answer 17

Ethanol

Question 18

It is a rapid, efficient and widely applicable agent.

Answer 18

Ethanol

Question 19

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

Answer 19

Ethanol

Question 20

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

Answer 20

Ethanol

Question 21

Processing times in absolute ethanol should be minimal.

Minimal processing time

Answer 21

Ethanol

Question 22

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

Answer 22

Ethanol

Question 23

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

Answer 23

Ethanol

Question 24

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

Answer 24

Methanol

Question 25

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

Answer 25

Mathanol

Question 26

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

Answer 26

Methanol

Question 27

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

Answer 27

diethyl ether

Question 28

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

Answer 28

acetone

Question 29

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

Answer 29

Isopropanol

Question 30

It is a universal solvent

Answer 30

Isopropanol

Question 31

slightly slower in action and not as hydroscopic as ethanol

Answer 31

Isopropanol

Question 32

a far superior lipid solvent

Answer 32

Isopropanol

Question 33

• completely miscible with water and most organic solvents • fully miscible with melted paraffin wax • readily expelled from tissues and water baths

Answer 33

Isopropanol

Question 34

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.

Answer 34

Isopropanol

Question 35

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

Answer 35

Isopropanol

Question 36

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.

Answer 36

Isopropanol

Question 37

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

Answer 37

GLYCOL-ETHERS

Question 38

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

Answer 38

ACETONE

Question 39

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

Answer 39

TETRAHYDROFURAN

Question 40

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

Answer 40

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.

Question 41

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

Answer 41

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