Foundations of Anatomical Pathology
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Explain Histopathology in your own words.
The microscopic examination of tissue to to determine the cause of disease
List some of the hazards associated with working in a Histopathology laboratory.
• Chemical: fixatives, stains, chemicals • Physical: sharps, radiation • Biological: cross infection • PPE must be worn
Explain what a fixative does and list some features of an ideal fixative.
• A fixative prevents a histological/cytological sample from decaying Features: • Will preserve tissue in life like manner • Will not add artefact material to tissue • Will not swell or shrink tissue • Will be safe for user and environment • Has convenient shelf life and storage • Is economical
What fixative/s can be used for Cytology smears?
Alcohol (ethanol and methanol)
List physical agents that can be used to assist in the fixation of tissues.
• Microwaves • Heat • Ultrasound
True or false: Autolysis represents the changes to tissue that occur before fixation due to bacterial contamination.
True
What type of fixative is Neutral Buffered Formalin classed as?
A formalin (formaldehyde) fixative
Why is Formalin Buffered to a neutral pH?
The further a fixative is from the pH of body tissues the more distortion you can get in the tissue at the cellular level.
Give an example of a Chemical Fixative that belongs to each of the following groups (one example for each group). Aldehydes, Oxidising Agents, Protein Coagulants, Uncertain Mechanism.
Aldehydes: - Formaldehyde, Glutaraldehyde Oxidising agents: - Osmium tetroxide, Potassium Dichromate Protein coagulants: - Ethanol, Methanol Uncertain mechanism: - Mercuric Chloride, Picric acid
What is the function of xylene in tissue processing?
It make the paraffin wax soluble so that the sample can be embedded in it and sections of the sample can be cut
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
List method/s used for the collection of Cytology samples.
• Pap Smears, Endoscopy samples, some FNA (fine needle aspiration) specimens
Compare the advantages and disadvantages of Histopathology with Cytopathology.
Cytology: • Less invasive process • Faster • Cheaper Histopathology: • Can observe tissue as a whole instead of individual cells to determine cause of disease • More detailed and easier to diagnose diseases from