microscopy practical notes
descriptions of different types of microscopes and their techniques - stereoscopic microscopes, brightfield, darkfield, phase contrast
annotated diagrams of microscopes
- Low power microscopes.
- Always binocular – Have two ocular lenses.
- Have built-in light sources that illuminate from top and/or from underneath. Fiber optic cold
light sources can be added.
Uses:
- Used for observations at low magnifications.
- Can examine whole specimens or specimens in containers due to large working distance
between optic lens and stage.
- Also known as a dissecting microscope – Used for dissection as the image is viewed right side up.
- In biomed labs, used for gross examination of tissue samples prior to histological preparation.
Practical process:
- Looked at mystery specimen under stereoscopic microscope.
- Appeared to be some sort of worm.
- Almost cylindrical shape, skinny, had no appendages, looked smooth, no hairs or openings.
Question: Which Phylum of animals does the specimen belong to?
Answer: Species is a Parasitic Nematode which belongs to the phylum Nematoda (round worm).
, Question: What is the species and which disease does it cause?
Answer: The species is Ascaris Lumbricoides, and it causes a disease called Ascariasis – Ingestion of these
round worms causing blockages in the intestines.
Brightfield Microscopy:
Structure:
Condenser disc:
A - bright field
DF – dark field
Ph1/Ph2 – phase contrast
Sub stage condenser:
Focuses light on the object.
Uses:
- Most commonly used microscopy technique.
- Provides a dark image against a bright background.
- Used for the viewing of high-contrast specimens or stained organisms. E.G. blood stains, tissue
sections, vitally stained organisms.
- Not suitable for unstained biological specimens with low contrast. E.G. live cells.
Practical process:
- Studied a human blood smear.
- Blood smear was pre-stained with Eosin and Methylene Blue. The Eosin stained the cytoplasm of
the cells pink, and the Methylene Blue interacted with the nucleic acids off the Nucleus, staining
it blue so it’s visible.
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