Microscopy Flashcards
use of a microscope to magnify objects too small
to be visualized with the naked eye so that their
characteristics are readily observable
MICROSCOPY
APPLICATIONS OF MICROSCOPY
- Rapid preliminary organism identification
- Rapid final identification of certain organisms
- Detection of different organisms present in the same specimen
- Detection of organisms not easily cultivated in the laboratory
- Evaluation of patient specimens for the presence of cells indicative of inflammation or contamination
- Determination of an organism’s clinical significance
- Provide pre-culture information
- Determine which tests and methods should be used for identification and characterization of
cultivated organisms - Provide a method for investigating unusual or
unexpected laboratory test results
TYPES OF MICROSCOPY
BRIGHT-FIELD (LIGHT) MICROSCOPY
PHASE-CONTRAST MICROSCOPY
FLUORESCENT MICROSCOPY
DARK-FIELD MICROSCOPY
ELECTRON MICROSCOPY
visible light is passed through the specimen and then through a series of lenses that bend the light in a manner that results in magnification of the organisms present in
the specimen
PRINCIPLES BRIGHT-FIELD (LIGHT) MICROSCOPY
PRINCIPLES OF LIGHT MICROSCOPY
A. MAGNIFICATION
B. RESOLUTION
B.1 RESOLVING POWER
C. CONTRAST
→extent to which detail in the magnified object is maintained
RESOLUTION
→ability of the lenses to distinguish fine detail and structure
RESOLUTION
→determined by numerical aperture and wavelength of light
RESOLUTION
→closest distance between two objects that
when magnified still allows the two objects to be distinguished from each other
RESOLVING POWER
FACTORS AFFECTING RESOLVING POWER
IMMERSION OIL
(TRUE OF FALSE)
Shorter the wavelength of light used in the instrument, the greater the resolution
TRUE
specific optical and viscosity characteristics
designed for use in microscopy
IMMERSION OIL
→used to fill the space between the objective lens and the glass slide onto which the specimen has been affixed
IMMERSION OIL
→enhances resolution by preventing light rays from dispersing and changing wavelength after passing through the specimen
IMMERSION OIL
measure of the light-bending ability of
a medium
Refractive Index
required for optimal detection and
characterization of bacteria
1000× magnification
needed to make objects stand out from the background
CONTRAST
achieved by staining techniques that highlight organisms and
allow them to be differentiated from one another and from
background material and debris
CONTRAST
Kohler Illumination
designed to provide maximum illumination and resolution when observing images using a microscope
detailed examination of internal structures in living microorganisms
PHASE-CONTRAST MICROSCOPY
not necessary to fix or stain the
specimen
PHASE-CONTRAST MICROSCOPY
based on the wave nature of light ray
PRINCIPLE OF PHASE-CONTRAST MICROSCOPY
light rays can be in phase (their peaks and valleys
match) or out of phase
PRINCIPLE OF PHASE-CONTRAST MICROSCOPY
wave peak of light rays from one source coincides with the wave peak of
light rays from another source
Reinforcement (relative brightness)
wave peak from one light
source coincides with the wave trough from another light source
Interference (relative darkness)
Set of light rays
a. direct from light source
b. reflected or diffracted from a particular
structure in the specimen
scattering of light rays as they touch a
specimen’s edge
Diffraction
Two sets of light rays are brought together, form an image of the specimen on the ocular lens, containing areas that are relatively light and through shades of _______
gray, to black
PRINCIPLE OF FLUORESCENT MICROSCOPY
Fluors or Fluorochromes
→raised to a higher energy level after absorbing ultraviolet
(excitation) light
Fluors or Fluorochromes