Week 4: Fixations Flashcards
This is done to
prevent the decomposition and drying
of tissue samples so that it can be
processed in the laboratory.
Fixation
This process is also considered
the first and most critical step
in histotechnology.
Fixation
o Heating (blue flame),
microwaving, cryopreservation
(freeze-drying)
Physical fixation
o Achieved by immersing the specimen in a fixative or by perfusing the vascular system with fixative o For specialized histochemical procedures, fixatives can be applied in vapor form
Chemical fixation
Fixatives chemically link/add
themselves on to the tissue
giving stability to the protein
Additive fixation
Example of additive fixation
formalin, mercury, osmium
tetroxide
Example of non-additive fixation
acetone, alcohols
Fixation ph
6-8
What happens in tissue hypoxia?
Lower the pH of the solution
What temperature is sufficient to maintain excellent
morphology of tissues
room temperature
What temperature is used for regular tissue processing
40°C
What temperature is used for electron microscopy and
some histochemistry
0-4°C
What fixative is used for osmolarity?
Normal phosphate buffered
saline (PBS)
Concentration of fixative in routine laboratory
10% formaldehyde
Concentration of fixative in immune electron microscopy
3%
glutaraldehyde, 0.25%
glutaraldehyde
commonly used in
routine laboratory
formalin
Made up of only one component substance (e.g. Formaldehyde, HgCl, acetone, alcohol, glutaraldehyde)
Simple