Lecture 1 Flashcards
What is medical hisology?
identifying tissues and cells
what is dynamic histology?
is an extension of medical histology where we not only identify the tissues, but we examine functions of the cells and molecules that make up that tissue
what are the different types of sections you can have?
cross section, oblique section, and longitudinal section
1 nm = __ A (Angstrom units)
10
Thickness of a section - ___
Diameter of cell - ____
Diameter of a lysosome ___
Thickness of PM - ____
Thickness of a section - 5um
Diameter of cell - 10 um
Diameter of a lysosome 200nm
Thickness of PM - 75A (7.5 nm)
What are the steps to make a histology slide for a light microscope?
- fixation
- dehydration
- clearing
- infiltration
- embedding
- sectioning
- mounting
- removal of paraffin
- rehydration
- staining
what are the steps to make a histology slide for electron microscopy?
- fixation
- dehydration
- clearing
- infiltration
- embedding
- sectioning
- mounting
- staining
what is the fixation process for light and electron microscopy?
light: through perfusion or emersion using Bouin’s Fluid (Acetic Acid, Picric Acid, Formalin (formaldehyde), Water)
EM: through perfusion using Glutaraldehyde (2.5% - 5%)
what is the difference between perfusion and immersion fixation?
in perfusion, you inject the fixative in the animal, whereas in immersion you take the organ out and you soak in the fixative.
what do you have to do to the fixed tissue in order to section it?
- dehydrate it by soaking it in a water and ethanol solution while gradually increasing the ethanol concentration (from 50% to 100%) – need this for the next step since doesn’t mix with water
- clearing: soak it in xylene
- infiltration: soak in a half xylene/paraffin solution, allowing all the crevasses to be filled with the wax
- embedding: put in 100% parafinn solution
all this is for light microscopy, same principle for EM, but instead of xylene, it is propylene glycol and it is plastic instead of wax
what is used for the sectioning of tissues?
microtome for light microscopy and ultramicrotome for EM
what needs to be done to the sections before being able to stain them?
- mounting: for light, is put on a glass slide, and for EM on a metal grid.
(then for EM can be stained directly) - Paraffin is removed by adding xylene
- rehydration: stain is water-based so have to gradually add water by dipping in a ethanol and water solution, gradually increasing the water concentration from 50% to 100%
what is used to stain tissue? (don’t explain them)
for light microscopy: H&E stain
for EM: lead citrate
what is the H&E stain and how does it work?
1) basic dye hematoxylin - stains basophilic structures with blue-purple hue
stains cell nucleus and other acidic structures
2) acidic dye eosin - which colors eosinophilic structures bright pink.
stains cytoplasm and collagen
what basophilic and eosinophilic mean?
baso: Basophilic structures are usually the ones containing nucleic acids, such as the ribosomes and the chromatin-rich cell nucleus, and the cytoplasmatic regions rich in RNA (stained with hemotoxylin)
acid: Eosinophilic structures are generally composed of intracellular or extracellular protein. Most of the cytoplasm is eosinophilic
(based on affinity of dyes NOT whether they are acid or basic)
