Microscopy Flashcards
eyepiece or ocular lens
moves to focus the image onto the eye
objective lens
provides image magnification and image resolution
lens
magnifies light from the objective lens
nosepiece
revolves to move the desired lens into position
diaphragm lever
controls the amount of light reaching the object
condenser
concentrates light on the tissue section, needs to be focused on the same plane as the tissue section
compound microscope
combination of two simple microscopes or magnifying lens systems
resolving power
the least distance between 2 objects that are still seen as two rather than one. Usually 0.2um minimum distance apart to be resolved
achromatic objectives
corrected for 2 colors, red and blue, most lab microscopes
apochromatic lens
corrected for 3 colors
parfocal
same plane of focus when switching between objectives to avoid refocusing
total magnification
multiply the ocular lens by the objective lens
x10 oculars and a x45 objective would give a total magnification of x450
substage
usually attached below the stage, consists of the condenser and the iris diaphragm
iris diaphragm
regulates the amount of illumination on the tissue section. Varies with different objectives
polarizing microscope
primarily used in histology to identify crystals such as talc, silica, or urate. Examines tissue for anisotropism and birefringence
anisotropism
having unlike properties in different directions, appears bright against a dark background when the optical paths of the polarizer and analyzer are crossed
birefringence (double refraction)
transmitting light unequally in different directions, appears bright against a dark background when the optical paths of the polarizer and analyzer are crossed
polarizer
positioned between the light source and the specimen
analyzer
positioned between the specimen and the eye
phase contrast microscope
used for the examination of unstained specimens, especially living cells
allows transparent objects to be seen clearly
not typically used in histology
darkfield microscope
objects appear self luminous on a dark background when hit by oblique light
objects appear much larger than they are and this makes it easier to see fine structures
typically used to study unstained microorganisms or silver grains in radioactive staining
rarely used in histopathology
fluorescence
an optical phenomenon in which light of one wavelength is absorbed by a substance and almost instantly reemitted as light of a longer wavelength
fluorescence microscopes
usually use mercury or halogen lamps
exciter
a filter placed between the light source and the specimen, obscures all visible light except for the desired wavelength
barrier
a filter placed in the eyepiece that absorbs all UV rays and allows only visible light rays to pass. Protects the eyes from damaging UV and reduces non-specific fluorescence so that the object is seen as a bright object against a dark background
autofluorescence
also known as natural fluorescence or primary fluorescence
ex collagen fluoresces naturally
some tissues autofluoresce the same as a fluorochrome, esp when using blue light
fluorochrome
a dye that fluoresces when excited by UV light
tend to be maximally excited in the blue range
immunofluorescence
labeling with a fluorescent dye such as fluorescein isothiocyanate (FITC)
direct immunofluorescence
labeled primary antibodies are applied directly to tissue sections to combine with antibodies or antigens in the tissue
indirect immunofluorescence
unlabeled primary antibody is applied then a secondary FITC labeled antibody is applied, which is conjugated against the species of the primary antibody
more sensitive than direct immunofluorescence
non-immunological fluorescence
acid-fast bacilli (bacteria) and amyloid
amyloid
an abnormal protein that is produced in your bone marrow and can be deposited in any tissue or organ
can be stained with thioflavin T
acid-fast bacilli
can be stained with auramine-rhodamine
Neurofibrillary plaques and tangles
can be stained with thioflavin-S
transmission electron microscopy
electrons pass through clear areas ans deflect off of dark areas. useful in the diagnosis of muscle and kidney disease and in tumor identification
scanning electron microscopy
renders a 3 dimensional image
greater depth of focus compared to transmission, but less resolving power
typically used in research settings
