Introduction To Histology- Staining And Sectioning Flashcards
What can occur depending on type of microscopy or method of preparation used
The same tissue can appear different depending on method of preparation
What is the method for tissue processing ?
Fixation -> embedding -> sectioning -> staining
What is the aim of fixation ?
Cross linking of macromolecules
Reduces or arrests biological activity
Cells more amendable to staining
How is fixation carried out ?
Freezing about -80 degrees
Using dry ice or liquid nitrogen
Chemical fixation - aldehyde based - binds to protein denaturing them
Preserves tissue
Why is embedding required
To facilitate the cutting of thin sections
By providing support for the tissue when sectioning
How is embedding carried out ?
Frozen samples - dehydrated
Tissue embedded in a hard medium such as paraffin wax or plastic resin
Why is sectioning used ?
Most tissues are too thick to be examined directly - cut into thin slices
Thinner the slice -> higher the resolution
How is sectioning carried out ?
Using microtome
Produces 2d representation of 3d object
Why is staining carried out ?
Most cells - colourless and transparent
Staining - colours tissue
Allows to see different structures
What has to occur before staining ?
Tissue is rehydrated to remove wax
What is the most common stain used ?
H&E
Haemotoxylin and Eosin
How does haematoxylin work ?
It is basic
Binds to acidic components
Due to oxidation -> hematein producing blue-purplish colour
What is an example of acidic substances that stain blue and are basophillic
DNA therefore nuclei stain blue
What does basophilic mean
Affinity for basic dye
How does Eosin work ?
Acidic dye
It is a counterstain to hematoxylin
Stains basic structures red or pink
