microscopic technique Flashcards
what does an optical microscope do
utilises light (photons) for image formation
what do electron microscopes do
utilises electrons for image formation
what do scanning probe microscopes do
utilises physical probe for the formation of surface images
what is a simple optical microscope
single convex lens or single set of lenses
what are compound light microscopes
contains two sets of lenses
one near the sample (objective)
one near the eye (eyepiece)
what are the optical parts of a light microscope
source of light, condenser, objective lenses and eye piece
what are the non optical parts of a microscope
arm, coarse and fine adjustment
nosepiece
stage
microscopic tube
base
what is magnification
ability to make small objects seem larger
what is resolution
ability to distinguish two objects from each other
what is the total magnification equation
objective lens power x eyepiece lens power
what is the stages in preparing a histological slide
1) taking samples
2) fixation
3) dehydration
4) clearing
5) embedding
6) sectioning
7) deparaffining
8) staining
9) mounting
how can tissue samples be collected
- cadavers
- forensics
- surgical procedures
- experimental animals
what is fixation
collected specimens are preserved to retain their biological structure without significant distortion or decomposition
- done with 4% sol. of formaldehyde
what are other fixation agents
- glutaraldehyde
- mercuric chloride
- osmium tetroxide
- freezing
what is microtome
instrument used for thin sectioning of tissue
paraffin block is fitted on microtome and cut into think sections and these are transferred to glass slides
how thin are sections sliced inn histology
0.5cm then to 5-7 micrometers
what is staining required for
- tissue contrast
- highlight particular features of interest
what are the 3 basic staining methods
- Hematoxylin and Eosin (H&E)
- Masson’s trichrome
- Weigert’s elastic stain
what are the special staining techniques
- Silver impregnation for reticular fibers in the liver or nervous tissue
- Mucin carmine for mucus secreting tissues like nasal cavities and the gastrointestinal
tract (GIT)
what times of tissue sectioning can be done
- longitudinal
- oblique
- transverse
what does H&E stain stand for
hematoxylin and eosin
what happens to eosinophilic cytoplasm when H&E stain is added
cytosol stained with acidic eosin
eosinophilia of entire cytoplasm is enhanced in high mitochondria content
appears pink
what happens to basophilic cytoplasm when H&E stain is added
rER ribosomes stain and those containing ribonucleic acids
appear purple
what is hematoxylin
naturally occurring chemical from logwood tree
what is eosin
synthetic organic dye
what causes large spaces in tissue
slight cracks in sections
what causes artificial spaces between cells or other tissues
fixative, heat needed for paraffin embedding, loss of lipids of low molecular weight substances
what causes unknown linear structures in tissues
small wrinkles in sections
what causes extra cellular structures eg. cytoplasmic granules
precipitations from the stain
