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Histopathology > Fixation, Decalcification, Dehydration, Clearing > Flashcards

Fixation, Decalcification, Dehydration, Clearing Flashcards

1
Q

Amount of fixing fluid should be:

A

10-20 times the volume of the specimen

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2
Q

Nuclear fixatives usually contain ____ as their primary component due to its affinity for nuclear chromatin.

A

Glacial acetic acid

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3
Q

Added as a preservative to formaldehyde; prevents decomposition to formic acid

A

Methanol

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4
Q

Concentrations solutions must never be neutralized since this might precipitate violent explosions.

A

Formaldehyde

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5
Q

Dark brown artifact pigment granules from unbuffered formalin can be removed by:

A

Picric acid

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6
Q

Mercuric chloride pigment may be removed by:

A

Iodine-sodium thiosulfate sequence

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7
Q

Fixatives that give the best results with metachromatic staining

A

Mercurial

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8
Q

Highly explosive when dry

A

Picric acid

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9
Q

Demonstrates Rickettsiae and other bacteria

A

Orth’s fluid

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10
Q

Recommended for fixation of embryos

A

Bouin’s solution

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11
Q

Used in fixing brain tissues for diagnosis of rabies

A

Acetone

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12
Q

Considered the most rapid fixative; fixes and dehydrates at the same time

A

Carnoy’s fluid

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13
Q

Chemical reactions are rapid at ___C.

A

60-65

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14
Q

Thickness of section for light microscopy

A

2 cm^2

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15
Q

Brain is suspended whole in ____ for 2-3 weeks to ensure hardening prior to sectioning.

A

10% buffered formalin

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16
Q

Recommended osmolality for fixation

A

400-500 mOsm

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17
Q

Fixation inn buffered formalin is carried out for ___ hours.

A

2-6

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18
Q

Fixatives diffuse into tissue at the rate of ___ per hour and slows down as its goes deeper into the tissue.

A

1 mm

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19
Q

If the fixative is osmium tetroxide, it should be ___ times the tissue volume.

A

5-10

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20
Q

TRUE or FALSE: Fibrous organs take longer than small or loosely textured tissues.

A

True

21
Q

Microanatomical vs Cytologic: fixatives that preserve specific parts and particular microscopic elements of the cell

A

Cytologic

22
Q

Why must cytoplasmic fixatives not contain glacial acetic acid?

A

It destroys mitochondria and Golgi bodies

23
Q

pH required for nuclear fixatives

A

<4.6

24
Q

Removes chromates, formalin, osmic acid

A

Tap water

25
Q

Removes picric acid

A

50-70% alcohol/ethanol or lithium carbonate

26
Q

Removes excess mercuric fixative

A

Alcoholic iodine (Dezenkerization)

27
Q

Form of secondary fixation whereby primarily fixed tissue is placed in a 2.5-3% potassium dichromate for 24 hours

A

Post-chromatization

28
Q

Most reliable method of determining the extent of decalcification due to its ability to detect even the smallest focus of calcium

A

Radiological method

29
Q

Recommended ratio of fluid to tissue volume for decalcification

A

20:1

30
Q

Ideal time for decalcifying tissue

A

24-48 hours

31
Q

After decalcification, acid must be removed by ___ changes of 70-90% ethanol.

A

3

32
Q

Decalcifying agent and tissue softener at the same time

A

Perenyi’s fluid

33
Q

Decal agent recommended for teeth and small bone pieces

A

Von Ebner’s fluid

34
Q

Ammonium form of polystyrene resin that hastens decalcification by removing calcium ions from formic acid

A

Ion exchange resin

35
Q

Whatever dehydrating agent is used, the amount in each stage should be:

A

> 10x the tissue volume

36
Q

Toxic dehydrating agent, primarily employed or blood and tissue films and for smear preparations

A

Methyl alcohol

37
Q

Most rapid and most commonly used clearing agent in histology laboratories

A

Xylene

38
Q

Most probably cause when clearing agent turns milky as soon as the tissue is placed in it

A

Incomplete dehydration

39
Q

Dehydrating agent recommended for routine dehydration of tissues

A

Ethanol

40
Q

Method of dioxane dehydration which uses pure dioxane and paraffin

A

Graupner’s

41
Q

Method of dioxane dehydration where tissues are wrapped in a gauze and submerged in dioxane with calcium oxide

A

Weiseberg’s

42
Q

TRUE or FALSE: Dioxane is a dehydrating but not a clearing agent.

A

False

43
Q

Dehydrating agent that is combustible at 110-120F

A

Cellosolve

44
Q

A blue discoloration of ____ crystals will indicate full saturation of dehydrating fluid with water.

A

Copper sulfate

45
Q

Clearing agent should be miscible with ____ and ____.

A

Alcohol; paraffin wax

46
Q

Amount of clearing agent should be ____ times the tissue volume.

A

> 10

47
Q

Clearing agent used as a substitute for xylene or benzene

A

Toluene

48
Q

Clearing agent recommended for CNS tissues and cytological studies; turns milky upon prolonged storage

A

Cedarwood oil

49
Q

Clearing agent recommended for clearing embryos, insects, and delicate specimens

A

Aniline oil

Histopathology (3 decks)

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