Histopathology Final Exam Review UPDATED
QUESTIONS AND CORRECT ANSWERS
L 11 & 12 Fixation and Processing - CORRECT ANSWER Lecture 11 and 12
Histopathology importance - CORRECT ANSWER - The 'Gold Standard' in the
diagnosis of numerous diseases
- Plays a key role in determining treatment and prognosis
- Techniques play a key role in research
Histopathology definition - CORRECT ANSWER The study of tissues to determine
the manifestations of disease with the inclusion of microscope examination
Why is tissue fixation necessary? - CORRECT ANSWER - Cells are dependent upon
the blood stream
- Cells deprived of oxygen will ultimately die
3 types of tissue changes can be seen - CORRECT ANSWER 1. Pressure
changes/abnormal metabolism
2. Autolysis (self digestion)
3. Putrefaction (decomposition)
Features of putrefaction - CORRECT ANSWER - Discoloration of tissue
- Disfiguration - gases
- Dissolution - liquefaction
Post mortem changes - CORRECT ANSWER - Pressure changes: example of dead
body where all is red except where pressure was which remains the skin color. Fixed 10-
12hrs
- Autolysis
- Putrefaction
,Why is it necessary to fix tissue? - CORRECT ANSWER -Is a sample removed from
life support
To stop:
- Tissue metabolism (pressure changes)
- Autolysis
- Putrefaction
To preserve the tissue as life like as possible for as long as possible. Tissue should be in its
most stable form.
Techniques to 'fix' tissue and so preserve it - CORRECT ANSWER - Mummification
*most common fixatives are toxic chemicals (ie. alcohol and acetic acid)
- Formaldehyde (HCHO) -most commonly used.
*a toxic gas soluble in water
* Solid as a 40% solution of Formaldehyde in water = Formalin
* Routinely used as a 4% solution of Formaldehyde (one part formalin to 9 parts water)
* Formalin fixation
Properties of an ideal fixative - CORRECT ANSWER 1. Penetrate tissue quickly and
evenly
2. Kill cells quickly and evenly, stopping abnormal metabolism
3. Prevent autolysis
4. Prevent putrefaction
5. Not add any endogenous material to the tissue
6. Not swell or shrink the tissue 7. Prepare the tissue for later treatments such as staining and
not prevent any other
investigations that may be required
8. Prevent desiccation and drying of tissue which would cause shrinkage and distortion 9. Be
safe to use (non toxic and flammable)
, 10. Be reasonably priced
11. Be convenient to use (shelf life, storage)
Formaldehyde (HCHO) fixes by creating 'cross links' - CORRECT ANSWER - In
aqueous solution forms methylene glycol
- The glycol adds onto proteins to form single & double addition
- Slow acting fixative
Advantages or Formaldehyde - CORRECT ANSWER - Fixed tissue remains soft and
pliable
- Tissue cannot be over fixed
- Natural color is maintained
- Allows for staining and further techniques to be carried out on the tissue
- Some reversal by washing the specimen in water
Disadvantages of formaldehyde - CORRECT ANSWER - Cytoplasmic staining is
duller
- Toxic: causes formalin dermatitis
- Is a suspected cancer agent as well as been a respiratory poison
- Not good at fixing fat
- Antigen masking
Gluteraldehyde - CORRECT ANSWER - Fixes by forming cross links
- Contains 2 aldehyde groups so can form cross links twice as fast as formalin
- Has limited penetration so can only be used on small specimens
Advantages of Gluteraldehyde - CORRECT ANSWER - Good penetration in small
samples. rapid cross link formation
- Good for small specimens
- Excellent morphology
QUESTIONS AND CORRECT ANSWERS
L 11 & 12 Fixation and Processing - CORRECT ANSWER Lecture 11 and 12
Histopathology importance - CORRECT ANSWER - The 'Gold Standard' in the
diagnosis of numerous diseases
- Plays a key role in determining treatment and prognosis
- Techniques play a key role in research
Histopathology definition - CORRECT ANSWER The study of tissues to determine
the manifestations of disease with the inclusion of microscope examination
Why is tissue fixation necessary? - CORRECT ANSWER - Cells are dependent upon
the blood stream
- Cells deprived of oxygen will ultimately die
3 types of tissue changes can be seen - CORRECT ANSWER 1. Pressure
changes/abnormal metabolism
2. Autolysis (self digestion)
3. Putrefaction (decomposition)
Features of putrefaction - CORRECT ANSWER - Discoloration of tissue
- Disfiguration - gases
- Dissolution - liquefaction
Post mortem changes - CORRECT ANSWER - Pressure changes: example of dead
body where all is red except where pressure was which remains the skin color. Fixed 10-
12hrs
- Autolysis
- Putrefaction
,Why is it necessary to fix tissue? - CORRECT ANSWER -Is a sample removed from
life support
To stop:
- Tissue metabolism (pressure changes)
- Autolysis
- Putrefaction
To preserve the tissue as life like as possible for as long as possible. Tissue should be in its
most stable form.
Techniques to 'fix' tissue and so preserve it - CORRECT ANSWER - Mummification
*most common fixatives are toxic chemicals (ie. alcohol and acetic acid)
- Formaldehyde (HCHO) -most commonly used.
*a toxic gas soluble in water
* Solid as a 40% solution of Formaldehyde in water = Formalin
* Routinely used as a 4% solution of Formaldehyde (one part formalin to 9 parts water)
* Formalin fixation
Properties of an ideal fixative - CORRECT ANSWER 1. Penetrate tissue quickly and
evenly
2. Kill cells quickly and evenly, stopping abnormal metabolism
3. Prevent autolysis
4. Prevent putrefaction
5. Not add any endogenous material to the tissue
6. Not swell or shrink the tissue 7. Prepare the tissue for later treatments such as staining and
not prevent any other
investigations that may be required
8. Prevent desiccation and drying of tissue which would cause shrinkage and distortion 9. Be
safe to use (non toxic and flammable)
, 10. Be reasonably priced
11. Be convenient to use (shelf life, storage)
Formaldehyde (HCHO) fixes by creating 'cross links' - CORRECT ANSWER - In
aqueous solution forms methylene glycol
- The glycol adds onto proteins to form single & double addition
- Slow acting fixative
Advantages or Formaldehyde - CORRECT ANSWER - Fixed tissue remains soft and
pliable
- Tissue cannot be over fixed
- Natural color is maintained
- Allows for staining and further techniques to be carried out on the tissue
- Some reversal by washing the specimen in water
Disadvantages of formaldehyde - CORRECT ANSWER - Cytoplasmic staining is
duller
- Toxic: causes formalin dermatitis
- Is a suspected cancer agent as well as been a respiratory poison
- Not good at fixing fat
- Antigen masking
Gluteraldehyde - CORRECT ANSWER - Fixes by forming cross links
- Contains 2 aldehyde groups so can form cross links twice as fast as formalin
- Has limited penetration so can only be used on small specimens
Advantages of Gluteraldehyde - CORRECT ANSWER - Good penetration in small
samples. rapid cross link formation
- Good for small specimens
- Excellent morphology
