Fixation Flashcards
Mechanism in fixation wherein the fixing agent is not incorporated into the tissue
Non-additive fixation
Mechanism in fixation wherein the fixing agent is taken in and becomes part of the tissue
Additive fixation
Inadequate or poor fixation will result in?
Poorly processed tissue
Disadvantage of liquid nitrogen
Soft tissue is liable to crack
Fixation helps preserve ____, ____, ____, and _____ of tissue
Shape, structure, intercellular relationship, and chemical constituents
Generally used in histochemistry and during operative procedures
Liquid nitrogen
Leaving the tissue in water will result in?
Cell shrinkage
Amount of fixative to be used for maximum effectiveness of fixation is?
20x the tissue volume
The following are additive fixatives except:
A. Formalin
B. Mercury
C. Alcohol
C. Alcohol
Types of fixative according to composition
Simple fixative and compound fixative
Type of fixative which permits the general microscopic study of tissue structures without altering the structural pattern and normal intercellular relationship of tissue in question
Microanatomical fixative
Type of fixative which has been added together to obtain optimal combined effect of their individual actions
Compound fixative
Type of cytological fixative which preserves the nuclear structures and usually contains glacial acetic acid as primary component
Nuclear fixative
The following are nuclear fixative except for two A. Flemming’s fluid B. Orth’s fluid C. Heidenhain’s susa D. Regaud’s fluid E. Bouin’s fluid
B and D. Orth’s and Regaud’s fluids are cytoplasmic fixatives
Leaving the tissue in air for prolonged period of time will cause?
Drying out and will further result in distortion of its morphologic appearance.
Type of cytological fixative which preserves cytoplasmic structures and does not contain glacial acetic acid
Cytoplasmic fixative
Most widely used fixative
Formaldehyde
pH of nuclear fixative
4.6 or less
Type of cytological fixative which preserves the chemical constituent of cells and tissues
Histochemical fixative
True or false:
10% formalin is achieved by mixing 10ml of formalin with 90ml of water
True
True or false:
10% neutral buffered formalin is recommended for preservation and storage of surgical , post mortem, and research specimen
True
True or false:
Fixation time needed for 10% neutral buffered formalin is 1/2hr - 3hrs
False. Fixation time is 4-24hrs
Two of the following statements about glutaraldehyde are incorrect
- Glutaraldehyde is made up of formaldehyde residues linked by 3 carbon chains
- Specimen vial need not be refrigerated during fixation
- Fixation time is 1-2hrs
2 and 3 are incorrect.
Specimen should be refrigerated and fixation time is 1/2hr - 2hrs
Two aldehyde fixative mixture useful for electron cytochemistry
Karnovsky’s paraformaldehyde- glutaraldehyde
Types of cytological fixatives
Nuclear, cytological, and histochemical
Give 5 characteristics of a good fixative
- Must be cheap, stable, and safe to handle
- Must be isotonic
- Must inhibit bacterial decomposition
- Must permit rapid and even penetration of tissues
- Must produce minimum shrinkage of tissue
Practical considerations of fixation
- Speed
- Penetration
- Volume
- Duration/ time
Diffusion time of formalin into tissue
1mm/hr
Fixation time can be cut down by using?
Heat, vacuum, agitation, or microwave
Give 5 effects of fixative
- Hardens soft tissues and make the handling and cutting of sections easier
- Inhibit bacterial decomposition
- Increase the optical diff of cells and tissues
- Make cells resistant to damage and distortion
- Acts as mordant or accentuators
Types of coagulant fixatives
- Dehydrant
- Acidic
- Cross-linking
- Compound fixative
Type of coagulant fixative which changes the charges of the ionizable side chains of proteins and disrupt electrostatic and hydrogen bonding
Acidic coagulant
Microwave heating reduces time of fixation from more than 12hrs to less than _____
20minutes
The following are histochemical fixatives except? A. Formol saline 10% B. Absolute ethyl alcohol C. Newcomer’s fluid D. Acetone E. Carnoy’s fluid
E. Carnoy’s fluid is a nuclear fixative
Most useful fixatives for preserving glycogen?
- Rossman’s fluid
2. Cold absolute alcohol
Generally recommended for glycogen fixation
Alcoholic fixative
The following are simple fixatives except? A. Mercuric chloride B. Formaldehyde C. Glutaraldehyde D. All are simple fixatives
D.
Most common metallic fixative
Mercuric chloride
Two mechanisms involved in fixation are_____ and _____
- Additive
2. Non-additive
