Histology Techniques Flashcards
What is histology?
Microscopic anatomy
What factors can affect resolution?
-Wavelength of light
- Numerical apeture (the ability of a lens to gather light + resolve a point at a fixed distance from the lens)
-Reflective index of mounting media (slower speed of light= better resolution)
What is the goal of fixation?
-To imobilize components to maintain structura relationships
-Prevent autolysis
-Firm up structures to allow sectioning
What five factors can affect fixation?
- Time until tissue is placed in fixative
- Fixative volume (min of 10 parts formalin)
- Fixation time
4.Tissue thickness - Tissue type
What do you need to do if the sample contains calcification?
You must decalcify it after it has been fixed. For this we would use a strong acid
Define basophilia
blue color resulting from basic dye binding to negative charge
Define eosinophilia
Pink color resulting from acidic dye binding to positive charges
How would something look if stained with H&E?
Hematoxylin (H): Imparts blue color to acidic components like DNA and RNA and some cellular secretions
Eosin (E): Imparts pink to red color to basic components like the cytoplasm and extracellular products
What is a romanovsky stain? How does it differ from H&E? Examples?
It is a combination of eosin and methylene blue
It differs from H&E because methylene blue stains deeper blue and can result in metachromasia
Define metachromasia
characterized by a shift in the normal color of the dye (blue) to a metachromatic color in the presence of highly acidic (polyanionic) substances
- highly basophilic stains can exhibit this phenomena (toluidine blue and methylene blue)
Describe Periodic Acid-Schiff (PAS), what does it stain for?
A histochemical procedure used to identify intra- and extra- cellular carbohydrates, that particularly contain adjacent glycol linkages
Step 1: tx with periodic acid
Step 2: Stain aldehyde groups w/ schiff stain (will appear magenta)
Describe silver impregnation methods
Used to demonstrate different structures, target structures stain black.
Describe elastic fiber stains
Used to highlight elastic fibers in connective tissues. Stain black
Describe trichrome stain
Used to enhance connective tissue elements
Describe acid fast stain
Used to identify different types of organisms
Describe different artifacts and processing errors
-artifacts resulting from antemortem procedures
-change in cell volume due to fixation and/or dehydration
- inactivation of most enzymes and some antigenic molecules
-no fats/lipids after processing leaving vacules
-air bubbles under tissues
-dull blade
-wrinkling of tissue
-knife chatter
-plane of section
What is immunohistochemistry?
“staining” with antibody against a specific molecule used to label that molecule in a tissue section
What is Electron Microscopy? And what is its benefits over other types of staining?
“stained” with heavy metals. Accelerated electrons are the source of illumination, and provides better magnification + resolution. Able to visualize cellular organelles+ macromolecules
What two cellular organelles are basophilic?
The nucleus and ribosomes
What two cellular organelles are basophilic?
The nucleus and ribosomes
What two cellular organelles are eosinophilic?
Mitochondria and the Smooth ER
Define Heterochromatin
Highly condensed chromatin in which genes are NOT expressed. Found consistently in marginal chromatin, nucleolar associated, karyosomes ( discrete clumps of chromatin)
Define euchromatin
Uncoiled chromatin w active DNA. Properties of these chromatic vary between cell types and their metabolic activity
How can you determine if a cell is more metabolically active?
There is more euchromatic vs heterochromatin
Define static cell type
No longer capable of division
Define stable cell type
Will undergo periodic division to maintain normal function
Define continuously dividing cell type
Constant dividing i.e skin, intestinal, and bone marrow
What are the two types of cell death?
Necrosis: “cell murder” the cell bursts and causes an inflammatory reaction
Apoptosis: programmed cell death. Cell shrinks, blebs into fragments. NO inflammatory reaction associated with it.
