Fixation Flashcards
What is the first and most critical step in histotechnology?
Fixation
The ideal volume of the fixative is _____ greater than the size or volume of the specimen.
10 to 20 times
What is the result of tissue digestion by lysosomes that are released when organelle membranes rupture?
Autolysis
What is the most common mechanism for fixation whereby the effect is induced by dehydrants, such as alcohol or acetone?
Denaturation
What type of physical fixation is the most widely used in routine laboratories?
Microwave fixation
What type of physical fixation involves freeze drying but is not usually applied to diagnostic tissue specimens?
Cryopreservation
What method of fixation involves immersing the specimen in the fixative solution?
Chemical fixation
What will happen to the tissues if it was immersed in a hypotonic solution?
Tissues will swell
What will happen to the tissues if it was immersed in a hypertonic solution?
Tissues will shrink
What is the usual range for the pH during fixation?
6-8
Enumerate the factors involved in fixation.
● Hydrogen ion concentration
● Temperature
● Thickness of section
● Concentration
● Duration of fixation
What is the preferred thickness of the section for tissue block for electron microscopy?
1-2 mm^2
What is the preferred thickness of the section for tissue block for light microscopy?
2 cm^2 (no more than 0.4 cm)
What is the usual duration for primary fixation in buffered formalin?
2-6 hours
- accentuate absorbance for the next procedure
- promote and hasten staining
accentuator
What are the 2 types of fixative according to composition?
- Simple fixative
- Compound fixative
What are the 2 types of fixative according to action?
- Microanatomical fixatives
- Cytological fixatives
What type of fixative according to action permits the general microscopy study of tissue structure without altering the structures?
Microanatomical fixatives
What type of fixative according to action preserves a specific part of the cell itself?
Cytological fixatives
What is formed from the precipitation of formaldehyde that is usually obtained as a fine white powder, which depolymerizes back to formalin when heated?
Paraformaldehyde