GPHT LAB - FIXATION Flashcards
Makes tissues harder
fixation
preserves morphology and chemical constituents of cells and tissues
fixation
prevents decomposition and putrefaction of tissues
fixation
destroys any microorganisms present in tissue
fixation
2 Goals of Fixation
preserves morphology and chemical constituents of cells and tissues
harden the tissues for further processing
mechanisms of fixation (2)
additive
non-additive
mechanisms of fixation
fixative becomes part of tissue by forming crosslinks or bridges
these bridges stabilize proteins, thus fixing the tissue
additive
mechanisms of fixation
fixative does not become part of the tissue
works by removing water present
non-additive
ex of additive fixatives
aldehydes, mercury, osmium tetroxide
ex of non-additive fixatives
alcoholic fixatives
tradition temp of fixation
RT
Autotech temp of fixation
40C
Rapid fixation
60C
What must be the volume of fixative for max effectiveness
20x that of tissue
ideal tissue:fixative ratio
1:20
ideal fixative:tissue ration
20:1
if expensive fixatives are used like osmium tetroxide, what must be the volume
5-10x that of tissue
most common fixative, an aldehyde fixative
10% Formalin
ratio used in preparing 10% Formalin
1:9
how is 10% Formalin prepared
1 part stock solution 37-40% Formalin
9 parts water
an aldehyde fixative, addition of phosphate buffer adjusted to pH 7
10% Neutral buffered formalin
why is 10% Neutral buffered formalin better than 10% formalin
neutral pH = less chance of developing formalin artifacts
disadv of formalin (2)
irritating to nose (rhinitis), eyes (excessive lacrimation), skin (allergic dermatitis)
formalin pigment production
brownish pigments due to action of formic acid with blood
formalin pigments
brownish pigments w/c can interfere with different processes
formalin pigments
formalin pigments happens when tissue sample is ___
bloody
an aldehyde fixative whose action is similar with formalin
glutaraldehyde
a more pleasing aldehyde fixative because it does not cause irritation
glutaraldehyde
disadv of glutaraldehyde
expensive
an aldehyde fixative useful for preserving specimen for electron microscopy
glutaraldehyde
most common metallic fixative
mercuric chloride
metallic fixative very useful to visualize cell detail used in tissue photography
mercuric chloride
ex of mercuric chloride fixatives [4]
Zenker’s
Zenker’s Formol
B5 Fixative
Heidenhain Susa
a mercuric chloride fixative for bone marrow
B5 Fixative
a mercuric chloride fixative for skin tumor biopsy
Heidenhain Susa
disadv of mercuric chloride
tends to form black granular deposits except in Heidenhain Susa
all mercuric chloride fixatives tends to form black granular deposits except in ______
Heidenhain Susa
black granular deposits are removed using __
iodine
metallic fixative for preserving cho
Strong oxidizing agents
chromic fixatives
metallic fixative for acid mucopolysaccharides
lead fixatives
used in preserving glycogen and embryos
picric acid fixatives
disadv of picric acid fixatives
1) yellowing of tissues
2) explosive when dry
metallic fixative that must be used wet or in solution
picric acid fixatives
ex of picric acid fixatives
Bouin’s
Brasil’s
fixative for nucleoproteins
usually added to nuclear fixatives
glacial acetic acid
fixative not suitable for cytoplasmic fixation because cells will swell and burst
glacial acetic acid
2 purposes of alcoholic fixatives
fixative
dehydrating agent
ex. of alcoholic fixatives
ethanol
methanol
isopropyl alcohol
most rapid fixative (among all types of fixative)
Carnoy’s
fixative used at ice-cold temperatures to preserve enzymes
acetone
fixative used for brain tissues for Rabies diagnosis
Acetone
fixative and decalcifying agent
trichloroacetic acid
2 main uses of osmium tetroxide or osmic acid
fix and stain fats permanently
fixative for EM
disadv of osmium tetroxide or osmic acid
expensive
not for routine histopath
corneal blindness
why osmium tetroxide or osmic acid not for routine histopath
inhibits hematoxylin, a common stain
ex of osmium tetroxide or osmic acid
Flemming’s Fixative
type of fixation for bacteriologic smears
heat fixation
