Methods In Light Microscopy Flashcards
What are the four classifications of tissues?
Epithelial tissue, connective tissue, nervous tissue, muscle tissue.
What is a tissue?
A collection of cells specialised to perform a particular function
What is the value of histology in diagnosis?
Can give a definitive diagnosis for conditions like cancer and Crohn’s disease (ulcerative colitis)
Can inform therapies by giving specific information on the type of disease and tissues involved.
What is the relationship between milli, micro and nano meters?
1mm=10^-3m
1um=10^-6m
1nm=10^-9m
What is the average diameter of a human cell?
10-20um
What is the diameter of an oocyte?
100um
What is the diameter of a red blood cell?
7.2um.
What is a biopsy?
The removal of a small piece of tissue from an organ or part of the body for microscopic examination.
What would a smear biopsy be used for?
Cervix or buccal cavity
What would a curretage biopsy be used for?
Endometrium.
What would a transvascular biopsy be used for?
Heart, liver
What would a needle biopsy be used for?
Brain, breast, liver, kidney, muscle
What tissues would be biopsied using direct incision?
Skin, mouth, larynx.
What tissues would be biopsied using endoscopy?
Lung, intestine, bladder.
What is used to cut thin slices of a specimen embedded in wax?
Microtome and steel blade.
Why do tissues need to be fixed?
It cross links macromolecules which preserves cellular structure, prevents autolysis and putrefaction.
What two fixatives can be used?
Glutaraldehyde, formaldehyde.
What is the process by which a fixed biopsy is embedded in and impregnated with wax?
Dehydration - ethanol replaces water
Clearing - xylene or toluene replace ethanol
Embed in wax at 56 degrees Celsius.
Describe the process by which a specimen embedded in wax becomes a stained histological slide
Section it. Rehydrate it (xylene->ethanol->water) Stain it (most stains water soluble) Dehydrate it (water->ethanol->xylene) Mount it
What does haematoxylin stain and what colour?
Acidic components of cells purple (nucleolus, chromatin)
What does eosin stain and what colour?
Basic components of cells pink (cytoplasm, extracellular fibres)
What does the Periodic Acid-Schiff method stain, and what colour?
Carbohydrates and glycoproteins magenta (for example mucous)
What stains elastic fibres?
Weigert’s elastin.
What does Elastic Van Gieson stain, and what colour?
Muscle yellow
Collagen pink/red
Elastin blue/black
What are three possible sections?
Oblique, transverse, longitudinal.
What is the advantage of phase contrast microscopy?
Can see detail in living cells
What can dark field microscopy be used for?
Diagnosis of syphilis and malaria
What is fluorescence microscopy?
Use antibodies to fluorescently stain particular components of the cell.
When is confocal microscopy used, and what does it eliminate?
What can it be used for, why?
Used to image tissues that have been labelled with fluorescent probes.
Eliminates out of focus flare.
Can section tissue in non invasive way, image living specimens.
