Introduction Flashcards
What is tissue biology/histology?
Study of the morphological features of normal tissues and the relationship to tissue function
What is morphology?
The form and structure of organisms
Why must we fix tissue?
Because unfixed tissue will degrade by autolysis
What is autolysis?
Self digestion - the destruction of a cell through the action of its own enzymes
Give two examples of fixatives?
Alcohol based of formalin
How does an alcohol based fixative work?
By denaturing the proteins
How does formalin work and what is the active agent?
The active agent is formaldehyde (37%) - it works by cross-linking proteins
Why are tissue blocks passed through graded alcohols in the tissue fixation process?
To dehydrate the tissue
What are the tissues embedded into?
Paraffin wax
What type of block is the tissue embedded into?
A paraffin blox
What machine cuts sections from the paraffin block?
A microtome
What size are the tissues cut into from the paraffin block?
0.004mm
After the sectioning procedure what is done?
The tissue sections are mounted onto a glass slide
When the tissue sections are on the glass sides what is done next?
The glass slide sections are stained
What does the processing and embedding stage of the preparation process provide you with?
It leaves you with tissues embedded into molten wax
If you could describe the preparation of a tissue on a glass side in five stages what would they be?
Processing and embedding Embedding tissue into paraffin block Sectioning Mounted onto a glass slide Section stained
Give an example of a basic dye
Haematoxylin
Give an example of an acidic dye
Eosin
What are the two main dyes used in tissue fixation?
Haematoxylin and eosin
What charge do basic dyes have?
positive
What charge do acidic dyes have
negative
What charge do basic dyes bind to and why?
Basic dyes are positively charged so they bind to negatively charged tissue components
What charge do acidic dyes bind to and why?
Acidic dyes are negatively charged so they bind to positively charged tissue components
What is basophilia?
Binding of a basic due to a tissue component
What colour does haematoxylin stain?
Blue
What components would the basic dye haematoxylin bind to?
Nuclear chromatin, cytoplasmic rna and certain extracellular matrix proteins such as cartilage
What is acidophilia?
The binding of an acidic dye with tissue
What colour does eosin stain?
pink
What components would the acidic dye eosin bind to?
Cytoplasmic proteins including cytoskeleton, intracellular membranes, most extracellular protein fibers, e.g. collagen
How many times does a light microscope magnify?
1000x
How many times does an electron microscope magnify?
100,000x
How does fluorescence microscopy work?
Antibodies or probes with a fluorescent tag introduced
