Introduction to histology Flashcards
What are the 4 main tissue types?
Epithelial
Connective
Nervous
Muscle
What is histology?
The microscopic study of normal cells and tissues
What is pathology?
The microscopic study of diseased cells and tissues
What disease is caused by dysplastic squamous cells degrading the basement membrane?
Squamous cell carcinoma
What are 2 ways tissue samples are illuminated?
Light or electron microscope
What microscope reveals basic cellular structure?
Light microscope
What microscope can reveal ultrastructure?
Electron microscope
What are the 6 steps of acquiring a thin tissue sample?
- Specimen collection
- Fixation
- Dehydration
- Embedding
- Sectioning
- Staining
What are three examples of biopsies?
Incision biopsy (skin)
Needle biopsy (organs)
Endoscopic biopsy (tube with light inside body cavity)
What is the purpose of the fixation stage?
To preserve the structural arrangement between cells and prevents tissue decomposition by terminating all biochemical reactions
Give an example of a substance used in fixation.
Formaldehyde
Why is the dehydration stage necessary?
To remove water from tissue, as water is not soluble in paraffin embedding.
At what rate is water removed during dehydration and why?
Gradually to prevent distortion
How is water removed during dehydration?
Using series of graded alcohols
Why is embedding a necessary stage?
Tissue must be supported to allow very thin sections to be cut
What 2 materials are most commonly used in embedding?
Paraffin wax and resin
What 2 substances is paraffin incompatible with?
Water and alcohol
What is alcohol replaced with in order to be compatible with paraffin?
Xylene
What is used to section specimens during the sectioning stage?
A microtome
Most stains for light microscopy are ___1__ and are not compatible with ___2___
- Aqueous
2. Paraffin
What must take place in order for the tissue to be stained?
Reversal of dehydration to remove paraffin wax and replace with water
What is the most common stain?
Haematoxylin and Eosin (H&E)
What colour does Haematoxylin stain acidic structures? (nuclei)
Blue/purple
What colour does Eosin stain basic structures? (proteins)
Red/pink
What does PAS stain?
Complex carbohydrates magenta
What does Masson trichrome stain?
Connective tissues