TISSUE PROCESSING: FIXATION Flashcards
Historically, FIXATION is defined as ________, ________ and, _______ of tissues
Killing,Penetration and Hardening
This tissue processing is currently defined as the alteration of tissues by stabilizing protein
Fixation
FUNCTIONS OF FIXATION:
1. Change the _________ contents of cells into ______ structures
- Soluble ; Insoluble
What do fixation stops?
Autolysis, putrefaction and decay
FUNCTIONS OF FIXATION:
3. ____________ to maintain the proper relationship pf cells and their ______.
Stabilize structures; stroma
What do fixation affects?
Refraction index
What are the mechanism fixatives of Fixation?
A. Additive
B. Non-additive
C. Coagulant
D. Non-coagulant
E. Cytologic
F. Histochemical
G. Microanatomical
H. Chemical Composition of Fixatives
This chemically alters the issue by bonding with it and adding themselves to the tissue
Additive fixative
Give examples of Additive fixative.
Formaldehyde
Mercuric chloride
Chromium trioxide
Picric acid
Glutaraldehyde
Osmium tetroxide
Zinc sulfate
This act on tissue without chemically combining with it.
Non-additive fixatives
Give example of Non-additive fixatives
Acetone and alcohol
This acts by creating a network that allows a solution to readily penetrate the anterior of the tissue.
Coagulant fixatives
This creates a gel that makes it difficult to penetrate by subsequent solutions. This should be cut thinly
Non-coagulan fixatives
This preserves specific cellular constituents
Cytologic fixatives
Which of the following has an acetic acid? What is their pH?
Nuclear fixatives: with acetic acid <4.6pH
Cytoplasmic fixative: without acetic acid >4.6pH
This preserves the chemical constituents of cells and tissues
Histochemical
This permits the general microscopic study of tissue structure altering the structural
Microanatomical
What are the factors that affect fixations?
- Temperature
- Specimen size
- Volume ratio
- Type of tissue or Organ
- Time
- Penetration
- pH
- Osmolality
Fixation is mostly done at?
20-22’C
Heat fixation is done at what sample?
Blood smear and bacteriologic smears
What is the temp. Of DNA and RNA?
RNA: 45’C
DNA: 65’C
What is the temp of formalin Incase of urgent biopsy and tissue with TB.
UB: Formalin is heated at 60’C
TB: Formalin is heated at 100’C
What is the specimen size of the ff?
RECOMMENDED: 2cm2 x 4mm
Electron microscopy: 1 to 2 mm2
Lung edeme: 1 to 2cm
What is the ideal fixative ratio?
15-20:1
What is the volume ratio of Osmium tetroxide and Museum material?
OT: 5-10:1
MM: 50-100:1
Give examples of hollow organs
Colon, Intestines and Gallbladder
Intravascular Perfusion: ____________
Ringer’s lactate
This refers to the interval between interruption of blood supply and time tissue is immersed in the fixative.
Cold Ischemia Time
This refers to the time period the tissue is exposed to formalin
Fixation time
What is the ideal time to perform fixation?
20-30 mins
How long a tissue must be immersed?
No longer than 60 mins
What is the minimum and maximum time of fixation?
6 - 48 hrs
What is the fastest penetrating fixative?
Formalin
If the formalin the fastest penetrating fixative. In an hour and 4 hours how much did the formalin penetrate?
1hr: 3.6mm
4hrs: 7.2 mm (@25’C, pH 7)
Cross linking is complete in _______?
48 hours
What is the recommended pH?
6-8 pH
At low pH, what does Formalin produce to obscure cellular detail?
Dark pigment
What solution is used as a holding solution for frozen section and kidney biopsy?
Isotonic solution
