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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
Examples of cytological fixatives
Nuclear- bouin’s fluid, flemming’s fluid, heidenhain sua Cytoplasmic- flemmings’s fluid w/o acetic acid, helly’s fluid, orth’s fluid
26
Preserve chemical constituents of cells
Histochemical
27
Example of histochemical fixatives
10% formol saline Acetone Newcomer’s fluid
28
Effective for preservation of lipid, fixatives containing mercuric chloride and potassium dichromate
Frozen section
29
Most useful for glycogen, glycogen fixation
Alcoholic fixative
30
The most common used for amino acid histochemistry
Formaldehyde
31
For routine paraffin section, for electron microscopy, for histochemical and enzyme studies
Aldehyde fixatives
32
Most common and widely used fixative
Formaldehyde (formalin)
33
Troubleshoot for formaldehyde
Filter or add 10% methanol
34
2 concentrations of formaldehyde
40% formaldehyde 10% formaldehyde (working solution)
35
Made up of 2 formaldehyde residues linked by 3 carbon chain, for LM and EM
Glutaraldehyde
36
2.5 glutaraldehyde
Small tissues for fine needle biopsy
37
4% glutaraldehyde
Larger tissues
38
Recommended for CNS tissues, made up of formaldehyde diluted to 10% NaCl
10% formol saline
39
For preservation and storage of surgical, post mortem and research specimen
10% neutral buffered formalin
40
For routine post-mortem tissues
Formol-corrosive
41
Preservation of lipids (phospholipids), HCHO+ CaCl
Formol calcium
42
Alternatives to mercuric chloride formulations, HCHO+ zinc sulfate
Unbuffered zinc formalin
43
Can be used to fix sputum, coagulates mucus
Alcoholic formalin (Gendre’s)
44
Removal of formalin pigment
Kardasewitch’s method- 70% ETOH and 28% ammonia Lilie’s method- acetone, H2O2, 28% ammonia Picric acid method- saturated alcoholic picric acid
45
Most common metallic fixative, recommended for renal tissue, fibrin, connective tissue and muscle
Mercuric chloride
46
Troubleshoot for mercuric chloride
Remove by 0.5% iodine solution in 70% ethanol the decolorize iodine using absolute alcohol
47
Recommended for liver, spleen, ct fibers, nuclei, also for trichome staining
Zenker’s fluid
48
Fixative for pituitary, BM, spleen, liver, brown pigment is produced
Zenker’s formol
49
For skin biopsies, excellent cytological fixative
Heidenhain’s Susa
50
For making smears of loose cells on slides
Schaudinn’s Fluid
51
Chromate fixative for carbohydrate
1-2% chromic acid
52
Chromate fixatives for lipids and mitochondria
Potassium dichromate
53
Chromate fixative for rickettsiae, bacteria and myelin
Orth’s fluid
54
Chromate fixative for golgi, rbc, colloid
Moller’s fluid
55
For acid MPS, fixes connective tissue mucin (umbilical cord or Wharton’ s Jelly)
Lead fixatives
56
Highly explosive when dry, used in strong aqueous solution, excellent for glycogen demonstration
Picrate fixatives
57
Troubleshoot for picrate fixatives
Remove color by dipping 70% ETOH followed by 5% sodium thiosulfate and running water
58
Can be use for embryos and glycogen
Bouin’s fluid
59
Good for glycogen
Brasil’s alcoholic picroformol
60
Use for GIT specimen, endocrine, tissues
Hollande’s fixative
61
Fixes nucleoproteins, detroys the mitochondria, causes tissue to swell
Glacial acetic acid
62
Acts as both fixative and dehydrating agent, precipitates protein
Alcoholic fixatives
63
Slow, form BM/ blood smears
Methanol
64
Used cyto smear fixative, best example of alchol fixative, strong reducing agent
Ethanol
65
Used for fixation of chromosome
Carnoy’s fluid
66
For sputum
Alcoholic formalin
67
For MPS
Newcomer’s fluid
68
For frozen section and smear
Clarke’s solution
69
Fixes fats, expensive, produces black precipitate
Osmium tetroxide fixatives
70
Troubleshoot for osmium tetroxide fixatives
Add saturated aqueous mercuric chloride or putting a cold water
71
Other alcoholic fixative
Trichloroacetic acid- weak decalcifying agent Acetone- for enzyme studies, fixes brain tissue for rabies diagnosis
72
A type of heat fixation that has an optimum temp of 45-55c
Microwave fixations
73
Process of placing a fixed tissue in a second fixative
Secondary fixation
74
Form of secondary fixation which utilizes, potassium dichromate as mordant
Post-chromatization
75
It is a process of removing excess fixative
Washing out

Histopath (8 decks)

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