Define Histopathology
the study of changes in tissues caused by disease.
the study of changes in cells caused by disease.
Select Three hazards associated with working in a Histopathology laboratory.
- Chemical: fixatives, stains, chemicals
– Biological: cross infection
– Physical: sharps, radiation
- Safety: slips, trips, falls
Explain what a fixative does
preservation of tissue specimen
decontaminates all viruses associated with the tissue specimen
List Six features of an ideal fixative
• Will not swell or shrink tissue
• Is economical
• Has convenient shelf life and storage
• Will be safe for user and environment
• Will preserve tissue in life like manner
• Will not add artefact material to tissue
• Will add artefact material to tissue
Select Three fixative/s that can be used for Cytology smears?
Spray fixed with aerosol of propanol and acetone+ Poly ethylene glycol- a water soluble wax
Methanol
Ethanol
Xylene
Sodium dihydrogen phosphate monohydrate 4g
Select Three physical agents that can be used to assist in the fixation of tissues.
Microwave
Heat
Ultrasound
Freeze
True or false: autolysis represents the changes to tissue that occur before fixation due to bacterial contamination.
What type of fixative is Neutral Buffered Formalin classed as?
Universal fixative
Fixative used for specific purposes
Why is Formalin Buffered to a neutral pH?
because the further a fixative is from the pH of body tissues the more distortion you can get in the tissue at the cellular level.
because the further a fixative is from the pH of body tissues the less distortion you can get in the tissue at the cellular level.
What is the function of xylene in tissue processing?
To cut sections, the tissue has to be embedded in paraffin wax, but wax is not soluble in water or alcohol. However, it is soluble in a paraffin solvent called 'xylene'.
Cleaning up the lab station to prevent contamination of other specimens and users of the facilities
Why is the histological section cut to approximately 5µm thick?
- Sample needs to be thin enough for light microscopy (about 1 cell layer thick) - makes it easier to evaluate tissue and look at its morphology
- Provides enough thickness to account for cell to cell ratio
List method/s used for the collection of Cytology samples.
- Pap Smears, Endoscopy samples, some FNA (fine needle aspiration) specimens
- Blood test, saliva test, sputum collection
Give an example of a Chemical Fixative that belongs to Aldehydes
- Formaldehyde, Glutaraldehyde
- Ethanol, Methanol
Give an example of a Chemical Fixative that belongs to Oxidising agents
- Osmium tetroxide, Potassium Dichromate
Give an example of a Chemical Fixative that belongs to Protein coagulants
- Mercuric Chloride, Picric acid
Give an example of a Chemical Fixative that belongs to Uncertain mechanism
