FIXATION Flashcards
Post martem devomposition or autolysis occurs due to the action of what enzyme
Hydrolytic enzymes
Fixation prevents autolysis by inactivating by what enzyme
Lysosomal enzyme
2 types of mechanism
Additive fixation
Non additive fixation
Mechanism whereby the chemical constituent of the the fixative is taken in
Forming crosslinks or molecular complexes
Additive fixation
Mechanism whereby altering the tissue composition
Upon removal of water to to hbonds, new cross links are established
Acetone and alcohon fixatives are examples
Non-Additive fixation
Formalin heated at 60C
Rapid fixation for very urgent biopsy specimens
Formalin heated at 100C
For tuberculosis
Volume of fixative used
10-25 times the volume of the tissus
Maximum effectiveness
- 20 times the volume of specimen
For museum
- not less than 50-100 times the specime
Penetration of fixatives in the tissue at the rate of
1mm/hour
Intensifies hematoxylin staining?
Inhibits?
Formaldehyde
Osmium tetroxide
Fixative that react with viruses
Mercuric chloride
Commonly used fixatives for nucleic acids
MEC
methanol
Ethanol
Carnoys
Involves thermal coagulation
For frozen tissue sections (urgent biopsies)
Preparation of bacteriologic smear
Heat fixation
Process of placing an already fixed tissue in a second fixative
Acting as a mordant
Secondary fixation
Stain MASSON’S TRICHROME
for connective tissue