Fixation Flashcards
Formalin (10 percent neutral buffered)
Most common fixative
A solution of formaldehyde gas in a pH balanced aqueous solution
Direct contact with the liquid or the fumes that rise from it will cause harm
Factors that affect fixation
- Heat- accelerates it, Cooling- slows it
- Dense tissue - slows it, tissues with an open, loose arrangement - penetrated quickly
- Ratio of fixative to tissue volume (must be 10:1)
Glutaraldehyde
Aldehyde fixative
Essentially two formaldehyde molecules linked together
Used for tissue samples that are destined for electron microscope examination (small) and is used sometimes to sterilize instruments
Getting rid of formalin
Must be recycled through specialized filtration equipment or treated with a neutralizing product to stabilize and the dispose of it through sewer system
Alcohol
Ethyl alcohol and methyl alcohol
Rarely used on their own as a fixative
Do not penetrate well and cause the tissues to become very hard and brittle
Can cause shrinkage of tissues if used on their own
Very volatile and very flammable
Acetic acid
Rarely used on its own
Causes slight swelling of tissues
Can be used with alcohol to counteract shrinkage
Picric acid (trinitrophenol)
Potentially explosive
Must be kept wet to avoid explosion
Never used on own because it causes shrinkage and penetrates poorly
Powerful yellow dye
Bouin’s fixative
Formaldehyde, acetic acid and water
Used for liver biopsies for glycogen studies
Mercuric chloride
Extremely toxic
Rarely used anymore
Highly corrosive
Used with other fixatives
B-5 fixative
Contains formaldehyde, mercuric chloride, a bigger salt and water
Used for bone marrow biopsies or lymph nodes for special studies
Must be freshly mixed before use
12-24 hours of fixation is allowed
B-5 substitute
Mercury free version
Contains zinc salt, formaldehyde, buffer salt and water
Some controversy over the success of this substitute
Katnovskys fixative
Popular for renal studues
