Dehydration Flashcards

1
Q

Process of removing intercellular & extracellular water from the tissue following fixation & prior to wax impregnation

A

dehydration

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2
Q

Characteristics of an Ideal Dehydrating Solution:

A
  • It must dehydrate rapidly
  • It should not remove stains
  • Not evaporate very fast
  • not toxic
  • be able to dehydrate fatty tissues
  • Not be a fire hazard
  • It should not harden the tissue
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3
Q
  • Best dehydrating agent - fast acting
  • not expensive
  • not poisonous
A

ethyl alcohol

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4
Q
  • Primarily employed for blood and tissue
    films and for smear preparation
  • toxic
A

methyl alcohol

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5
Q
  • slow dehydrating agent
  • recommended for tissues which do not require rapid processing
A

butyl alcohol

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6
Q

produces less shrinkage and hardening than ethyl alcohol

A

butyl alcohol

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7
Q

Factors to considered in dehydration:

A
  • Size and nature of tissue
  • type of fixative used
  • temperature
  • ratio
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8
Q

alcohol concentration:
make tissues hard brittle and
difficult to cut

A

above 80%

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9
Q

alcohol concentration:
liable to produce considerable
shrinkage and hardening of tissues leading
to distortion

A

85-95%

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10
Q

tend to harden only the surface of the tissue while the deeper parts are not completely penetrated

A

95% or absolute alcohol

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11
Q

Gen. Schedule for Alcohol Dehydration

A

70% alcohol - 6 hrs
95% alcohol - 12 hrs
100% alcohol - 2 hrs
100% alcohol - 1 hr
100% alcohol - 1 hr

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12
Q

dehydration sequence for
specimens not more than 4mm thick

A

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

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13
Q

Cheap, rapid acting dehydrating agent.

A

acetone

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14
Q

Expensive and extremely dangerous

A

dioxane (diethyl dioxide)

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15
Q

dehydrates in 30 mins to 2 hours

A

acetone

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16
Q

Used to dehydrate sections and smears

A

triethyl phosphate

17
Q

It may be used for demixing, clearing and dehydrating paraffin sections
before and after staining

A

tetrahydrofuran

18
Q

Clear, colorless highly flammable and extremely volatile fluid

A

acetone

19
Q

Not recommended for routine dehydration purposes

A

acetone

20
Q

Tissues can be left for long periods of time without affecting the
consistency or staining properties of the specimen

A

dioxane

21
Q

The tissue may be transferred from water or normal saline directly to cellosolve and stored in it for months without producing hardening or distortion

A

cellosolve

22
Q

combustible at 110°F to 120°F and is toxic

A

ethylene glycol

23
Q

Triethyl Phosphate is soluble in

A
  • water
    -alcohol
  • ether
  • benzene
  • chloroform
  • acetone
  • xylene
24
Q

removes water

A

triethyl phosphate

25
Q

instead of ethylene glycol ether you can use

A

propylene based glycol

26
Q

It both dehydrates and clears tissues since it is miscible in water and
paraffin

A

tetrahydrofuran (THF)

27
Q

Additives to Dehydrating Agentsd

A
  • 4% Phenol
  • glycerol alcohol mixture or in “Molliflex)
28
Q

Tissue processing for transmission electron microscopy

A

ethanol - dehydrating solvent
propylene oxide - transition fluid

29
Q

good substitute for propylene

A

Acetonitrile

30
Q

non-carcinogenic, less toxic and not as flammable as propylene oxide

A

Acetonitrile