unit 5. microscopy & cytology
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Unit 5. Microscopy & Cytology. Microscopy: Introduction. The unaided eye can distinguish objects more than 0.1 mm in diameter. Since most cells are between 0.1-0.01 mm in diameter, scientists use microscopes to view very small objects such as cells. - PowerPoint PPT PresentationTRANSCRIPT
The unaided eye can distinguish objects more than 0.1 mm in diameter. Since most cells are between 0.1-0.01 mm in diameter, scientists use microscopes to view very small objects such as cells.
Light microscopes bend visible light using optical devices such as lenses and prisms to magnify the apparent image size.
We will discuss the compound light microscope , you should learn all the parts and their functions, and know the proper care and use of one.
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Head
Arm
Coarse knob
Fine knob
On/off switch
Base
Ocular lens
Nose piece
Objectives
Stage
Mechanical stage
Condenser
Light source
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Ocular
Objectives
diaphragm
Stage control
knobs
Condenser
Light source 4
1. MagnificationOcular (10x) x objective (40x) = 400x
2. Parfocal and parcentral imagingParfocal: image remains in focus when
switching lenses.Parcentral: image remains in the center of field
of view when lenses are changed.
Field of view
40x 5
3. Depth of focusIs the vertical distance between the lens and
the object. Thickness of the specimen decreases as magnification increases.
400x
A 3-colored thread slide was focused. Note that one thread is in focus and the others are not. The clearly focused thread lies on top of the mount.
Top
Middle Bottom
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4. Image orientation The image seen will be
real, inverted, and magnified by the objective.
Notice the letter “e” is upside down in the slide.
When viewed through the microscope, it is right side up.
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5. Resolving power: the degree at which two adjacent points on a specimen are seen as separate detailed images.Difference between blurry and sharp images.
6. Contrast: how well the details of a specimen stand out against a background. Stains and lighting are used to increase contrast to see detail.
Protista Volvox seen through the microscope
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In Greek the term for “cell” is “cyto” ; therefore, cytology is the study of cells and how they function.
Types of cells There are two fundamental kinds of cells: prokaryotic and
eukaryotic. Prokaryotes: means “before the nucleus”. Lacks nuclear
membrane.Example: bacteria
This is a Bacillus type bacteria Eukaryotes: “eu” means “real” or “true nucleus”.
Eukaryotes can be uni- or multicellular organisms.Example: plans, animals, protists, fungi.
This picture is a dinoflagelate, of the group Protista. 9
Elodea wet mount Identify: cell wall, chloroplast, plasma membrane,
cytoplasm
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cell wall
plasma membrane
chloroplast
cytoplasm 11
This is the membrane between the thick layers of the onion.
Identify: plasma membrane, cell wall, nucleus, nucleolus, cytoplasm.
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cytoplasm cell wall
plasma membrane
nucleolus
nucleus
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Human cheek cells wet mount Identify: plasma membrane, cytoplasm, nucleus.
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plasma membrane
nucleus
cytoplasm
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