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Fixation data

Chapter 1

QuestionAnswer
A chemical that alters tissue by stabilizing protein in such a way that the tissue is resistant to further change is the definition of...? Fixation
A fixative must change the soluble/insoluble contentsof the cell into soluble/insoluble substances so that those substances are not lost during subsequent processing steps? ...change the soluble contents into insoluble substances...
List 5 functions of a fixative? Prevent putrefaction, prevent autolysis, maintain the proper relationship between cells and extracellular substances, enhance the refractive index, enhance staining.
List the actions of a fixative? Render enzymes inactive, kill bacteria and molds, make tissue receptive to dyes, modify tissue for the maximum retention of form, stabilize tissue elements so subsequent procedures will have minimal effect.
Name the two methods of stabilizing proteins (fixation)? Physical Method and Chemical Method
Name two different types of the Physical Method of fixation? Heat (microwave)and Desiccation (air-drying)
What is the primary method of protein stabilization (fixation)? Chemical Fixation
List the factors that influence fixation? Temperature (increase in temp.increases rate which increases autolysis) , size of tissue (3mm thick), volume ratio 15-20 times tissue volume), time (length of time from incision to fixative submersion time before processing)
What is the volume ratio between fixative and tissue? 15 to 20 times the tissue volume.
List four things to consider when choosing a fixative? Penetration, tissue storage, pH, osmoality.
Fixation begins at the periphery of the tissue and proceeds inward/outward? Inward
What fioxative penetrates faster than any other common fixative ingredient? Formaldehyde
How long can tissue remain in NBF? Indefinitely
Tissue is stored wet or dry? Wet
What can be the effect on tissue if the solution drops below pH 4.0? A pigment may be produced.
What is the pH range of most fixatives? 4 to 9
What is the physiological range of pH used for EM fixation? 7.2 to 7.4
Solutions with a pH value above 7.0 are considered alkali (base),acidic, or neutral? Alkali (base)
Solutions with a pH below 7.0 are considered alkali (base), acidic, or neutral? Acidic
Soultions that have a pH of 7.0 are considered alkali (base), acidic, or neutral? Neutral
Is the pH of a solution more important for light microscopy or electron microscopy? Very important for electron microscopy and not very important for light microscopy.
Reference to the number of particles in a solution? Osmolality
What is the osmolality of body fluids? 340 mOsm
If a cell in in a solution that is more concentrated than the cell cytosol(contains more particles) is this solution considered hypertonic, hypotonic or isotonic to the cell? Hypertonic (water leaves the cell and the cell shrinks)
If a cell is in a solution that is less concentrated than the cell cytosol(contains less particles) is this solution considered hypertonic, hypotonic or isotonic to the cell? Hypotonic (water enters the cell and swells)
Fluids into which normal cells can be placed without causing either swelling or shrinkageare considered what? Isotonic
A 0.9% solution fo sodium chloride (saline) or a 5% glucose solution are considered approximately what? Isotonic
This classification of a fixative changes the tertiary structure of a protein? Additive Fixative
Chemicals combine with the protein molecules to change them. This means the protein is made insoluble by the addition of the fixative and then becomes immobilized, remaining at its original location in the cell. What is this the defintion of? An Additive Fixative
This classification of fixative are predominantly organic compounds that act on tissue without chemically combining with it? Nonadditive Fixatives
This classification of fixatives precipitate or coagulate protein but do not add to the tissue. The primary mechanism by which these fixatives act is to dissociate bound water molecules from tissue protein groups? Nonadditive Fixatives
Created by: Pixel
 

 



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