how does delayed fixation affect tissues? - ️️result in drying and decomposition of
tissues. loss of nuclear detail, disappearance of cells, cell shrinkage, etc.
what is a fixative? - ️️substance that alters tissues through the stabilization of
proteins so that it is resistant to changes...
MEDL 310: Module 13: Fixatives General
how does delayed fixation affect tissues? - ✔️✔️result in drying and decomposition of
tissues. loss of nuclear detail, disappearance of cells, cell shrinkage, etc.
what is a fixative? - ✔️✔️substance that alters tissues through the stabilization of
proteins so that it is resistant to changes in subsequent treatments of the tissues.
what is a preservative? - ✔️✔️does not alter the tissue structure, so it will not protect it
from changes in subsequent treatments of the tissue
functions of a fixative are - ✔️✔️prevent autolysis (breakdown by enzymes within the
cells), prevent putrefraction (breakdown by bacteria), stabilize tissues, lessen shrinkage,
enhance staining, etc.
additive fixatives - ✔️✔️change the tissue by its addition
- formaldehyde, gultaraldehyde, etc.
coagulant fixatives - ✔️✔️produce aggregation of protein molecules, granulation and
precipitation
- mercuric chloride, picric acid
non-coagulant fixatives - ✔️✔️form a gel which is difficult for subsequent reagents to
penetrate
factors affecting fixation - ✔️✔️time, temperature, pH, volume of fixative to tissues,
osmolality
how does insufficient fixation affect tissues? - ✔️✔️poor processing and staining
results. tissue structure may be lost.
how does prolonged fixation affect tissues? - ✔️✔️results in brittle, shrunken tissues if
the fixative is intolerant, leading to hard to cut tissues = poor product
how does room temperature affect fixation? - ✔️✔️it will take longer to fix
how does warmer temperatures (45C) affect fixation? - ✔️✔️increased rate of fixation
but also increases rate of autolysis
what is the thickest a tissue can be for fixation? - ✔️✔️3mm
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