Cheatography
https://cheatography.com
To help study for the ASCP cert exam.
This is a draft cheat sheet. It is a work in progress and is not finished yet.
Fixation
Additive |
chemically linked |
Non-Additive |
not chemically linked |
Coagulant |
creates mesh |
Non-coagulant |
creates gel |
Fixatives
Formaldehyde |
Additive |
Non-coagulant |
Gluteraldehyde |
Additive |
Non-coagulant |
Osmium tetroxide |
Additive |
Non-coagulant |
Potassium dichromate |
Additive |
Non-coagulant |
Mercuric chloride |
Additive |
Coagulant |
Chromic acid |
Additive |
Coagulant |
Picric acid |
Additive |
Coagulant |
Zinc salts |
Additive |
Coagulant |
Alcohol |
Non-additive |
Coagulant |
Acetone |
Non-additive |
Coagulant |
Acetic acid |
Non-additive |
Coagulant |
|
|
Factors Affecting Fixation
Temperature increase |
speeds up fixation and autolysis |
Temperature decrease |
slows down fixation and autolysis |
Size (Electron microscopy) |
1 mm thick |
Size (Routine surgical) |
4 mm thick, 20 mm width, 30 mm length |
Volume of fixative |
15-20x greater than tissue |
Time |
At least 24 hours |
Penetration (Fast) |
Alcohol, acetic acid, acetone |
Penetration (Slow) |
Osmium tetroxide, gluteraldehyde |
pH (Formalin fixed) |
6.8-7.2 |
Fixation Accelerators
|
What accelerates fixation? Heat, agitation, and vacuum
|
Cell Reaction with Fixative
Nucleus |
No reaction |
Protein |
Stabilized |
Lipid |
Only fixed with osmium tetroxide and chromic acid, not aldehydes |
Carbohydrates |
Some loss during fixation |
|
|
|
