Tissue Examination Flashcards
What is tissue procurement?
Tissue procurement is used to collect a tissue sample. This can be surgical, scraping, needle, or transvascular (insert tool into blood vessel, then travel via vessels to the target site).
What is the purpose of fixation in tissue preparation?
Fixation is used to prevent the tissue sample from degrading and ‘stiffens’ the biopsy by using formalin solution.
What is formalin and its role in fixation?
Formalin contains formaldehyde which forms cross-links between proteins to preserve tissue structure.
What is the process of embedding in tissue preparation?
Embedding uses an increasing % of alcohol to dehydrate, then adds a solvent like toluene which allows heated paraffin wax to enter the tissue.
What is the final step in the embedding process?
The sample is placed in a mould and more wax is added to let it solidify overnight.
What is FFPE?
FFPE stands for Formalin-Fixed, Paraffin-Embedded tissue.
Why can’t most stains penetrate wax in FFPE?
Most stains won’t penetrate the wax as they are water-soluble.
What stains can be used on FFPE tissue?
Haematoxylin and Eosin (H&E) can be used. Haematoxylin is a blue-purple basic dye that binds to acidic cell structures like DNA, while Eosin binds to the cytoplasm.
What is the function of dark field microscopes?
Dark field microscopes are good for looking at the surfaces of cells.
What is phase contrast microscopy used for?
Phase contrast microscopy can be used to see transparent and colourless specimens without using stains.
How does fluorescence microscopy work?
Fluorescence microscopy uses a high intensity light source that excites a fluorescent molecule called a fluorophore, added via a stain or antibodies.
What is confocal microscopy?
Confocal microscopy is a specialised form of fluorescence microscopy that uses a pinhole to block out-of-focus light to create high resolution images of thick specimens.
What is immunohistochemistry?
Immunohistochemistry utilises labelled antibodies which bind to antigens. They can have a fluorophore label or an enzyme.
How are tissues prepared for electron microscopy?
In electron microscopy, tissues are fixed with glutaraldehyde and embedded in epoxy resin. They are stained with electron-dense chemicals.
What is the limit of resolution in microscopy?
The limit of resolution is determined by the wavelength used; a smaller limit of resolution indicates greater resolving power.
