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Histopath Lec > Fixation > Flashcards

Fixation Flashcards

(70 cards)

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1
Q

first and most critical step in histotechnology

A

fixation

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2
Q

Primary aim of fixation

A

to preserve the morphologic and chemical integrity of the cell in as life
like manner as possible.

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3
Q

Secondary goal of fixation

A
  • to harden and protect the tissue from the trauma of further handling,
    – so it is easier to cut during gross examination
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4
Q

Fixation prevents __________ of tissues after removal from the body

A

degeneration, decomposition, putrefaction and
distortion

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5
Q

Fixatives stops all cellular activities

A

To preserve the tissue

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6
Q

Fixation prevents autolysis by inactivating the lysosomal
enzymes or by chemically altering, stabilizing and making the
tissue components insoluble

A

To prevent breakdown of cellular elements

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7
Q

2 Basic Mechanisms

A
  • Additive fixation
  • Non-additive fixation
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8
Q

example of additive fixation

A

Formalin, mercury, osmium
tetroxide

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9
Q

example of Non-additive fixation

A

Alcoholic fixative

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10
Q

Effects of Fixatives

A

*Preserve the morphologic and chemical integrity of the cell
*Harden soft & friable tissues
* Inhibit bacterial decomposition
*Act as mordants or accentuators

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11
Q

Main Factors Involved in Fixation

A

Osmolality
Concentration
Duration of fixation
Hydrogen ion concentration
Temperature
Thickness of section

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12
Q

ideal conc in Immuno EM

A

0.25%

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13
Q

temperature for electron microscope & Histochemistry

A

0-4⁰C

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14
Q

Formalin Heated to 60⁰C

A

rapid fixatio

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15
Q

Formalin at 100⁰C

A

fix tissues with tuberculosis

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16
Q

thickness of section

A

– 1-2 mm² for electron microscopy
– 2 cm² for light microscopy

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17
Q

example of Large solid tissue

A

Uterus
BRain

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18
Q

Practical Considerations of Fixation

A

Speed
Penetration
Volume
Duration of Fixation

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19
Q

Characteristics of fixation

A

*Cheap, stable, safe to handle
*Must be isotonic
* Inhibit bacterial decomposition
*Must permit rapid and even penetration of tissues
*Must make cellular components insoluble to hypotonic
solutions.

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20
Q

Types of Fixatives according to composition and according to action

A

according to composition:
- simple fixative
- compound fixative

according to action
- microanatomical fixative
- cytological fixative
- histochemical fixative

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21
Q

Simple Fixatives

A
  • aldehyde
  • metallic fixative
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22
Q

fixative under aldehyde

A
  • formaldehyde
  • glutaraldehyde
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23
Q

fixative under metallic

A

ØMercuric chloride
ØChromate fixatives
ØLead fixatives
ØHeat

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24
Q

fixative under Chromate fixatives

A

ØPotassium dichromate
ØChromic acid

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25
fixative under Lead fixatives
ØAcetone ØAlcohol ØPicric acid ØAcetic acid ØOsmium tetroxide (Osmic acid)
26
Permit general microscopic study of tissue structures
Microanatomical Fixatives
27
Preserve specific parts Nuclear Cytoplasmic
Cytological Fixatives
28
Preserve the chemical constituents of cells and tissues
Histochemical Fixatives
29
Microanatomical Fixatives
1. 10% Formol Saline 2. 10% Neutral Buffered Formalin 3.Heidenhein’s susa 4.Zenker’s solution 5.Zenker’s formol (Helly’s solution) 6.Bouin’s solution 7.Brasil soln
30
preserve nuclear structure (chromosomes). Contain glacial aa, pH 4.6 or less
Nuclear fixatives
31
preserve cytoplasmic structure, no glacial aa, pH > 4.6
Cytoplasmic Fixatives
32
Nuclear fixative
1. Flemming’s Fluid 2. Carnoy’s Fluid 3. Bouin’s Fluid 4. Newcomer’s Fluid 5. Heidenhain susa
33
Cytoplasmic fixative
1.Flemming’s Fluid without acetic acid 2.Helly’s Fluid 3.Regaud’s Fluid (Muller’s fluid) 4.Orth’s Fluid
34
Histochemical Fixatives
1.Formol Saline 10% 2.Absolute Ethyl Alcohol 3.Acetone 4.Newcomer’s Fluid
35
most widely used aldehyde fixative
10% Formaldehyde (formalin)
36
unsatisfactory for routine fixation
Pure stock solution of 40%
37
A gas produced by the oxidation of methyl alcohol
formaldehyde
38
Preserves fats, glycogen and mucin
formaldehyde
39
Recommended for nervous tissue preservation
formaldehyde
40
Recommended for fixation of central nervous tissues and general postmortem tissues for histochemical examination
1-% formol saline
41
Physical methods include
heating, microwaving and cryo-preservation (freeze drying)
42
May cause sinusitis, allergic rhinitis, excessive lacrimation or allergic dermatitis
formaldehyde
43
Preserves enzymes and nucleoproteins
10% formol saline
44
Recommended for preservation and storage of surgical, post-mortem and research specimen
10% NBF or phosphate bufferd formalin
45
recommended for routine postmortem tissues
Formol – Corrosive or Formol – Sublimate
46
Penetration is slow
- Formol – Corrosive or Formol – Sublimate - Glutaraldehyde - Methyl Alcohol
47
Demonstrates fats and mucins
10% formol saline
48
Penetration is poor
- Zenker’s Fluid - trichloroacetic acid
49
Best fixative for tissues containing iron pigments and for elastic fibers
10% NBF or phosphate bufferd formalin
50
Excellent for many staining procedures including silver reticulum methods
Formol – Corrosive or Formol – Sublimate
51
Considered as the most rapid fixative
carnoy's fluid
52
Used to fix sputum since it coagulates mucus
Alcoholic Formalin or Gendre’s Fixative
53
For routine light microscopic work
Glutaraldehyde
54
Very expensive
- glutaraldehyde - osmium tetroxide
55
Reduces PAS positivity of reactive mucin
-10% Neutral buffered formalin or Phosphate-buffered formalin - Regaud’s Fluid or Muller’s Fluid
56
Recommended for renal tissues, fibrin, connective tissues and muscles
Mercuric Chloride
57
Permits brilliant staining of nuclear and connective tissue fibers
Zenker's fluid
57
Recommended mainly for tumor biopsies especially of the skin
Heidenhain’s Susa Solution
58
Commonly used for bone marrow biopsies
B-5 fixative
59
Preserves lipids Preserves mitochondria
Potassium Dichromate
60
Hardens tissues better and more rapidly than Orth’s fluid
Regaud’s Fluid or Muller’s Fluid
61
Demonstrates Rickettsiae and other bacteria
Orth's fluid
62
Suitable for Aniline stains
Picric Acid
63
Does not need washing out
Bouin’s Solution
64
Recommended for fixation of embryos and pituitary biopsies.
Bouin’s Solution
65
Suitable only for small pieces of tissues or bones
trichloroacetic acid
66
Can irritate the eyes producing conjunctivitis
osmium tetroxide
67
Permanently fixes fat
Flemming’s Solution
68
Recommended for the study of water diffusible enzymes especially phosphatases and lipases
acetone
69
Highly explosive when dry
Picric Acid

Histopath Lec (17 decks)

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