Histology (the basics) Flashcards
1
Q
What is histology?
A
- The microscopic study of tissue
- maintains the tissue architecture and can encompass multiple cell types
2
Q
What are the uses of histology?
A
- Biopsy - representative sample of tissue
- Thin sectioning - to avoid unclear stack of cells
- Dyes - to allow cell types/proteins to be visible under microscope
3
Q
What is cytology?
A
- The study of cells
- tends to focus on single cell type away from tissue (lavage, aspiration, skin scrape)
4
Q
Histology can tell you about the function of a cell based on what?
A
- shape
- polarisation
- intracellular contents
- location compared to other cells/structures
- if a cells are failing in a function
5
Q
What are the stages to produce sections of tissue for light microscopy?
A
- fixation
- processed
- sectioned
- stained
6
Q
Without processing tissue for microscopy what would happen?
A
- it is not permanent so tissue decays
- its difficult to cut thin sections to allow light to pass through
- it lacks colour
7
Q
Fixative for the preservation of tissue is chosen depending on what?
A
- the size of the tissue
8
Q
Describe fixation (1)
A
- fixed in formon (24hrs)
- stored in 70% alcohol
- original sample = trimmed, transferred into plastic cassette then into a stainless steel carrier
9
Q
Describe Processing (2)
A
- to remove water the tissue samples go through increasing strengths of alcohol sol.
- water in tissue is replaced with molten paraffin wax
- tissue dehydrated gradually to avoid shrinkage
- tissue exposed to clearing agent to make it translucent
10
Q
Describe embedding (part of processing tissue)
A
- specimen immersed in paraffin wax (1hr)
- tissue removed and put in metal mould filled with molten wax - more wax added on top
- placed on cold plate and solidifies, them removed from mould.
11
Q
Describe sectioning
A
- sections cut using a rotary microtome
- tissue clamped into microtome, knife inserted and clamped in holder
- stage is locked and dial set at required thickness
- the sections of wax and tissue form a ribbon that can be lifted off Kinfe and laid down in strips
- sections collected onto slide and dried in oven 40.C
- dewaxing and rehydrating is next to make slides ready to stain
12
Q
Describe staining
A
- Haematoxylin and eosin (H&E)
- haematoxylin stains nuclei a blue-black colour
- eosin stains cytoplasm and intercellular components pink
- the blue dye is removed by 1% hydrochloric acid solution until the nuclei can be seen clearly (differentiation)
- then placed in weak ammonium to produce deep blue colour
- slide then stained with eosin, cytoplasm and intercellular contents = red, pink
- once staining is complete it looks purple and pink
13
Q
Describe how sections are made permanent after staining
A
- dehydrated in alcohol and cleared in clearing agent to make it translucent
- PIX is a mounting medium and adheres the cover slip to the section
- left in oven to dry overnight
14
Q
What type of microscope does histology use
A
- light microscope
15
Q
what is a longitudinal section?
A
- A section that is cut along the long axis of a structure
