The most crucial step
Fixation
A process of preserving cells and tissue
Fixation
2 important goals of fixation
- Preserve the morphological and chemical integrity of the cell.
- Harden the tissue for easy handling
Two mechanisms of action in fixation
- Additive fixation
2. Non-additive fixation
A mechanism of action that does not incorporate the fixative to the tissue
Non-additive fixation
A mechanism of action that make the fixative a part of the tissue
Additive fixation
Factors involved in fixation
- pH
- Temperature
- Thickness
- Osmolality
- Concentration
- Time duration
pH in fixation must be
6-8
Traditional tempersture in fixation
Room temp or 22-25C
Time duration in fixation
2-6 hrs
Types of fixative
- Simpke fixatives
2. Compount fixative
A type of fixative that has 2 or more fixative
Compount fixative
Type of fixative with 1 component
Simpke fixative
Fixative classifications according to action
- Microanatomical
2. Cytological
Aldehyde fixatives
- Formaline (formaldehyde)
- Formol Corrosive (formol sublimate)
- Glutaraldehyde
- 10% Formol saline
- 10% Neutral Buffered Formalin/ PO4 Buffered formalin
- Gendre’s/ alcoholic formalin
- Paraformaldehyde
An aldehyde fixative eith mercuric chloride
Formol corrosive (formol sublimate)
An aldehyde fixative for routine histopath
10% Neutral Buffered formalin or PO4 buffered formalin
An aldehyde fixative that us a polymer of formalin in white powder form
Paraformaldehyde
Fixation time using formalin
12-24 hours
The black/brown precipitate formed by blood using Formalin
Acid formaldehyde hematein
Metallic Fixatives
A. Mercuric chloride
- Zenker’s
- Zenker’s formol (Helly’s sol’n)
- Heidenhan’s susa
- B5
B. Chromate fixative
- Potassium dichromate
- Regaud’s (Muller’s)
- Orth’s fluid
C. Lead fixatives
Most common metallic fixative
Mercuric chloride
Also known as Helly’s solution
Zenker formol
A metallic fixative for BM biopsies
B5 fixative
