Fixation (Part 1) Flashcards
Step in tissue processing that involves preservation
FIXATION
Primary goal of fixation
To preserve tissues as close to the original as possible
Secondary goal of fixation
- Harden the tissue to facilitate easy cutting (into thin slices)
- Protect the tissue from trauma of further handling that might be caused by different reagents used in tissue processing
If processing lung specimen (which is thicker than other specimen), the required size is
1-2 cm
pH of fixatives
should be 6-8
The osmolality of fixative should be
Slightly hypertonic but practically, we use isotonic
Hypotonic fixative will cause
swelling
Hypetonic fixative will cause
Shrinking
Why do we not use concentrated solutions?
It will damage the tissue
Maximum effectiveness of fixative
20x the volume of the specimen
Ratio of fixative to tissue
15-20:1
When do preservation of tissue happens?
When the fixative penetrates the tissue
Penetration rate of formalin
1mm per hour
few fixatives used for Electron Microscopy; used 5-10x the volume of the specimen
Osmium tetroxide
Time and Duration of fixation
Should be 24-48 hours