FIXATION Flashcards
most critical step in routine histopathology
fixation
goals of fixation
- preserve morphological and chemical integrity of the cell
2. harden and preserve tissue
action of fixatives
- preserves the tissue by stopping all cellular activities
2. prevent autolysis by inactivating lysosomal enzymes
fixation pH
6-8
fixation osmolality
slightly hypertonic
fixation rate of penetration
1 mm/hour
rapid fixation temp
60 C
routine histopath fixation temp
22-25 C
electron microscopy and histochem fixation temp
0-4 C
autotechnicon fixation temp
40 C
tb patients fixation temp
100 C
mercury refrigerator fixation temp
4 C
buffered formalin duration
2-6 hours
electron microscopy duration
3 hours
hastens fixation
small and loose tissues, agitation, heat, microwave, vacuum
retards fixation
fibrous tissues, blood, mucus, fats, and cold temp
routine histopath fixation volume
10-20x of the tissue
usually, 20:1
expensive fixation volume
5-10x of the tissue
museum fixation volume
50x of the tissue
brain special consideration (spc)
- tied at the circle of willis
2. fixed for 2-3 weeks in 10% neutral buffered formalin
large solid tissues (uterus) spc
cut open and sliced thinly
hollow organs spc
place cotton inside or open organs entirely
air filled lungs spc
covered with gauze
eyes spc
fixative is injected
hard tissues (nails) spc
immersed in tissue softeners
fixative that forms cross-links with the tissue
additive fixatives
fixative that removes water in the tissue
alcoholic/dehydrating agents
cytological fixative that preserves nucleus and chromatin. also contains glacial acetic acid
nuclear fixative
cytological fixative that preserves membrane bound organelles. should not contain glacial acetic acid.
cytoplasmic fixative
cytological fixative that preserves biochemical components (fats, enzymes).
histochemical
microanatomical fixative (7) 1010 hfb zb
10% formol saline 10% BNF heidenhain's susa formol sublimate bouin's zenker's brasil's
nuclear fixative (5) fch nb
flemming's carnoy's heidenhain's susa newcomer's bouin's
cytoplasmic (5)
fk fro
flemming's w/o hoac helly's formalin regaud's (moller's) orth's
histochemical (4)
10 aan
10% formol saline
absolute ethanol
acetone
newcomer’s
fixation of CNS tissue, post-mortem tissues, and silver impregnation techniques
10% formol saline
routine histopath fixative, also for tissues with iron pigments and elastic fibers
10% BNF
fixative for silver reticulin methods and post-mortem tissues
formol sublimate
fixative for glycogen and sputum
alcohol formalin (gendre’s fixative)
fixative for enzyme histochem and electron microscopy, has 2 concs
glutaraldehyde
2.5% - small tissue fragments and needle biopsy
4% - larger tissue specimens
aldehyde fixative for ultrathin sections
paraformaldehyde
most common metallic fixative
mercuric chloride