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Histopath > Fixation > Flashcards

Fixation Flashcards

1
Q

Process by which the constituents of cells and tissues are fixed in a physical and chemical state with various reagents

A

Fixation

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2
Q

Achieved by exposing the tissues to chemical compounds called

A

Stabilization

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3
Q

Primary purpose of fixation

A

Preserve chemical integrity of the cell

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4
Q

Secondary purpose of fixation

A

Harden and protect the tissue

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5
Q

Correct fixative ratio

A

20:1 - 10: 1

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6
Q

Usual fixation time

A

24hrs

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7
Q

Usual temp for surgical specimen

A

Room temp

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8
Q

Effects of fixatives

A

Makes cells resistant
Inhibit bacterial decomposition
Reduce the risk of infection

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9
Q

Characteristic of a good fixative

A

Cheap
Stable
Isotonic
Safe to handle

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10
Q

Hydrogen ion concentration

A

Satisfactory fixation occurs between 6-8pH
Nuclear < 4.6
Cytoplasmic > 4.6

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11
Q

Temperature

A

EM: 0-4 degrees

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12
Q

Osmolality

A

Hypertonic: shrink
Hypotonic: swell
Ideal: 400-450msOm

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13
Q

Thickness of the section

A

Em- 1-2mm^2
Light microscopy- 2cm^2

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14
Q

Concentration

A

10%
Stock- -40%

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15
Q

Duration of fixation without agitation

A

24hrs

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16
Q

Practical considerations of fixation

A

Speed- fixed immediately
Penetration- 1mm/hr
Volume
Duration of fixation varies with different type of tissues

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17
Q

Other factors that affect fixation

A

Retardation- presence of mucus, fats, blood
Acceleration- agitation

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18
Q

Fixative becomes a part of the tissue by formation of cross links or complexes, stabilizes the tissue proteins

A

Additive fixation

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19
Q

The fixative does not become part of the tissue, stabilizes the tissue by removing of the bound water.

A

Non-additive fixation

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20
Q

Types of fixative according to composition

A

Simple- one component
Compound- 2 or more ex: mercuric chloride, glacial HAC

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21
Q

Types of fixative according to action

A

Microanatomical
Cytological
Histochemical

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22
Q

Without altering the structural and normal intracellular relationship of tissues

A

Microanatomical

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23
Q

Examples of microanatomical fixatives

A

10% formol saline
10% NBF
Heidenhain Susa

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24
Q

Preserve specific parts elements of the cell

A

Cytological

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25
Q

Examples of cytological fixatives

A

Nuclear- bouin’s fluid, flemming’s fluid, heidenhain sua
Cytoplasmic- flemmings’s fluid w/o acetic acid, helly’s fluid, orth’s fluid

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26
Q

Preserve chemical constituents of cells

A

Histochemical

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27
Q

Example of histochemical fixatives

A

10% formol saline
Acetone
Newcomer’s fluid

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28
Q

Effective for preservation of lipid, fixatives containing mercuric chloride and potassium dichromate

A

Frozen section

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29
Q

Most useful for glycogen, glycogen fixation

A

Alcoholic fixative

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30
Q

The most common used for amino acid histochemistry

A

Formaldehyde

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31
Q

For routine paraffin section, for electron microscopy, for histochemical and enzyme studies

A

Aldehyde fixatives

32
Q

Most common and widely used fixative

A

Formaldehyde (formalin)

33
Q

Troubleshoot for formaldehyde

A

Filter or add 10% methanol

34
Q

2 concentrations of formaldehyde

A

40% formaldehyde
10% formaldehyde (working solution)

35
Q

Made up of 2 formaldehyde residues linked by 3 carbon chain, for LM and EM

A

Glutaraldehyde

36
Q

2.5 glutaraldehyde

A

Small tissues for fine needle biopsy

37
Q

4% glutaraldehyde

A

Larger tissues

38
Q

Recommended for CNS tissues, made up of formaldehyde diluted to 10% NaCl

A

10% formol saline

39
Q

For preservation and storage of surgical, post mortem and research specimen

A

10% neutral buffered formalin

40
Q

For routine post-mortem tissues

A

Formol-corrosive

41
Q

Preservation of lipids (phospholipids), HCHO+ CaCl

A

Formol calcium

42
Q

Alternatives to mercuric chloride formulations, HCHO+ zinc sulfate

A

Unbuffered zinc formalin

43
Q

Can be used to fix sputum, coagulates mucus

A

Alcoholic formalin (Gendre’s)

44
Q

Removal of formalin pigment

A

Kardasewitch’s method- 70% ETOH and 28% ammonia
Lilie’s method- acetone, H2O2, 28% ammonia
Picric acid method- saturated alcoholic picric acid

45
Q

Most common metallic fixative, recommended for renal tissue, fibrin, connective tissue and muscle

A

Mercuric chloride

46
Q

Troubleshoot for mercuric chloride

A

Remove by 0.5% iodine solution in 70% ethanol the decolorize iodine using absolute alcohol

47
Q

Recommended for liver, spleen, ct fibers, nuclei, also for trichome staining

A

Zenker’s fluid

48
Q

Fixative for pituitary, BM, spleen, liver, brown pigment is produced

A

Zenker’s formol

49
Q

For skin biopsies, excellent cytological fixative

A

Heidenhain’s Susa

50
Q

For making smears of loose cells on slides

A

Schaudinn’s Fluid

51
Q

Chromate fixative for carbohydrate

A

1-2% chromic acid

52
Q

Chromate fixatives for lipids and mitochondria

A

Potassium dichromate

53
Q

Chromate fixative for rickettsiae, bacteria and myelin

A

Orth’s fluid

54
Q

Chromate fixative for golgi, rbc, colloid

A

Moller’s fluid

55
Q

For acid MPS, fixes connective tissue mucin (umbilical cord or Wharton’ s Jelly)

A

Lead fixatives

56
Q

Highly explosive when dry, used in strong aqueous solution, excellent for glycogen demonstration

A

Picrate fixatives

57
Q

Troubleshoot for picrate fixatives

A

Remove color by dipping 70% ETOH followed by 5% sodium thiosulfate and running water

58
Q

Can be use for embryos and glycogen

A

Bouin’s fluid

59
Q

Good for glycogen

A

Brasil’s alcoholic picroformol

60
Q

Use for GIT specimen, endocrine, tissues

A

Hollande’s fixative

61
Q

Fixes nucleoproteins, detroys the mitochondria, causes tissue to swell

A

Glacial acetic acid

62
Q

Acts as both fixative and dehydrating agent, precipitates protein

A

Alcoholic fixatives

63
Q

Slow, form BM/ blood smears

64
Q

Used cyto smear fixative, best example of alchol fixative, strong reducing agent

65
Q

Used for fixation of chromosome

A

Carnoy’s fluid

66
Q

For sputum

A

Alcoholic formalin

67
Q

For MPS

A

Newcomer’s fluid

68
Q

For frozen section and smear

A

Clarke’s solution

69
Q

Fixes fats, expensive, produces black precipitate

A

Osmium tetroxide fixatives

70
Q

Troubleshoot for osmium tetroxide fixatives

A

Add saturated aqueous mercuric chloride or putting a cold water

71
Q

Other alcoholic fixative

A

Trichloroacetic acid- weak decalcifying agent
Acetone- for enzyme studies, fixes brain tissue for rabies diagnosis

72
Q

A type of heat fixation that has an optimum temp of 45-55c

A

Microwave fixations

73
Q

Process of placing a fixed tissue in a second fixative

A

Secondary fixation

74
Q

Form of secondary fixation which utilizes, potassium dichromate as mordant

A

Post-chromatization

75
Q

It is a process of removing excess fixative

A

Washing out

Histopath (8 decks)

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