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HISTOPATHOLOGY > MIDTERM LEC: DEHYDRATION > Flashcards

MIDTERM LEC: DEHYDRATION Flashcards

1
Q

Follows fixation, and decalcification (if applicable)

A

DEHYDRATION

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2
Q

It is the removal of water from tissue in preparation for impregnation

A

DEHYDRATION

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3
Q

Since most fixatives are aqueous solutions, placing the fixed tissue in molten paraffin will not achieve impregnation because paraffin wax and water (from fixative) do not mix. Hence, dehydration must be done.

A

DEHYDRATION

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4
Q

Done as brief as possible and at a tissue-to-fixative ratio of 1:10

A

DEHYDRATION

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5
Q

Common Dehydrating Agents:

A

I. Alcohol
II. Acetone
III. Dioxane
IV. Cellosolve
V. Triethyl phosphate
VI. Tetrahydrofuran

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5
Q

Characteristics of Ideal Dehydrating Agents:

A
  1. Rapid action, with minimal tissue shrinkage and distortion
  2. Should not evaporate fast
  3. Able to dehydrate even fatty tissues
  4. Should not harden tissues excessively
  5. Should not remove stains
  6. Non-toxic, and not a fire hazard
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6
Q

Done in ascending grades to avoid distortion of tissue: 70% ROH -> 90% ROH ->100% ROH

A

ALCOHOLS

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7
Q

For delicate tissues, start at 30%

A

ALCOHOLS

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8
Q

ALCOHOLS

Initial alcohol conc. depends on the size and nature of tissue and the fixative used:

A

 Strong initial conc.  shrinkage and brittleness
 Prolonged dehydration in less than 70% ROH  tissue maceration

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9
Q

ALCOHOLS

37C

A

will hasten dehydration rate (for urgent exams)

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10
Q

ALCOHOLS

To ensure complete dehydration:

A

Add atleast ¼ deep layer of anhydrous Cu2SO4 at bottom of container, and cover with filter paper

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11
Q

ALCOHOLS

indicates full saturation of dehydrating fluids with water, thus alcohol must be changed with
a fresh solution

A

Bluing of copper sulfate crystals

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12
Q

ALCOHOLS:

A
  1. Ethyl alcohol (Ethanol)
  2. Methanol
  3. Butanol
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13
Q

Best dehydrant because it is fast-acting, mixes with water and many organic solvents, and penetrates tissues easily

A

Ethyl alcohol (Ethanol)

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14
Q

Not poisonous and not very expensive

A

Ethyl alcohol (Ethanol)

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15
Q

Clear, colorless, flammable

A

Ethyl alcohol (Ethanol)

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16
Q

For blood & tissue films, smears

A

Methanol

17
Q

Plant and animal microtechniques

A

Butanol

18
Q

Less tissue shrinkage and hardening but slow

A

Butanol

19
Q

Fastest dehydrant (1/2 to 2 hours), thus for rapid biopsies

A

ACETONE

20
Q

Clear, colorless, and more miscible with epoxy resins than alcohol

A

ACETONE

21
Q

DADV: Flammable, extremely volatile, and not recommended for routine work because of considerable shrinkage and brittleness

A

ACETONE

22
Q

Lipids are removed from tissue

A

ACETONE

23
Q

Both a dehydrant and clearing agent

A

DIOXANE (DIETHYLENE DIOXIDE)

24
Q

ADV: Less tissue shrinkage, prolongation is possible

A

DIOXANE (DIETHYLENE DIOXIDE)

25
Q

DADV: extremely dangerous because of toxicity, and risk of explosion; expensive, tissues will have poor ribbons

A

DIOXANE (DIETHYLENE DIOXIDE)

26
Q

DIOXANE (DIETHYLENE DIOXIDE) Methods:

A
  1. Graupner’s
  2. Weiseberger’s
27
Q

pure dioxane -> paraffin

A

Graupner’s

28
Q

wrapping tissue in gauze and suspension
to bottle containing dioxane with anhydrous calcium oxide or quicklime

A

Weiseberger’s

29
Q

DIOXANE (DIETHYLENE DIOXIDE)

Note: Tissues treated with chromic acid must be ____

A

thoroughly washed with water prior to dioxane treatment

30
Q

ADV: no shrinkage in prolongation

A

CELLOSOLVE/ETHYLENE GLYCOL MONOGLYCOL ETHER

31
Q

DADV: Combustible at 110-120F, toxic to reproductive, fetal, urinary, and blood systems

A

CELLOSOLVE/ETHYLENE GLYCOL MONOGLYCOL ETHER

32
Q

If cannot be avoided, propylene-based glycol ethers should be used instead of ethylene-based

A

CELLOSOLVE/ETHYLENE GLYCOL MONOGLYCOL ETHER

33
Q

A:rapid, little distortion and hardening

A

TRIETHYL PHOSPHATE

34
Q

Both a dehydrant and clearing agent

A

TETRAHYDROFURAN

35
Q

Dissolves fats

A

TETRAHYDROFURAN

36
Q

Most staining procedures give improved results with THF

A

TETRAHYDROFURAN

37
Q

Has rather offensive odor, thus room must be well-ventilated

A

TETRAHYDROFURAN

38
Q

Toxic to eyes (conjunctival irritation) and skin (Teflon gloves may be used, but it is recommended to avoid THF use)

A

TETRAHYDROFURAN

39
Q

ADDITIVES:

A
  1. 4% phenol
  2. Molliflex (glycerol alcohol mixture)
40
Q

added to 95% ETOH; softener for hard tissues

A

4% phenol

41
Q

softener

A

Molliflex (glycerol alcohol mixture)

HISTOPATHOLOGY (13 decks)

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