Chapter 1 Flashcards
Why do we preserve specimens?
To enable them to be cut into sections to observe under microscope.
To enable them to be treated with a variety of different stains to distinguish between different types of cells.
Function of the eyepiece on a microscope?
Magnifies specimen
Function of the barrel on a microscope?
Passes light from objective lens to eyepiece
Function of turret on microscope?
Holdd objective lenses
Rotates to enable selection of objective lens
Function of objective lens on microscope?
Magnifies and resolves specimen.
Function of stage on microscope?
Supports slide in correct position at 90 degrees to illumination source.
Enables light to pass through specimen
Function of iris diaphragm on microscope?
Controls amount of light reaching specimen
Best definition achieved with lower light intensity.
Function of substage illumination?
Source of illumination
Blue light bulb can be used to use light of shorter wavelength to improve resolution.
Advantages of the method of preparing a temporary slide?
Rapid and simple procedure - No complex apparatus or skill required.
Can mount specimen in glycerine to prolong examination period.
What does fixation do for a permanent slide?
Preserves specimen in lifelike condition.
Minimises distortion.
What does dehydration do for a permanent slide?
Removes traces of water from fixed material.
Achieved by placing specimen in increasing conc of alcohol.
What does clearing do for a permanent slide?
Addition on xylol removes dehydrating alcohol.
Ensures material is made transparent.
What does embedding do for a permanent slide?
Supports material so itβs firm enough for sectioning.
Can be resin, plastic or wax.
What does sectioning do for a permanent slide?
Use a microtome to cut fine slices so light can pass through specimen.
What does differential staining do for a permanent slide?
Improves contrast between different tissues and/or structures.
What does mounting do for a permanent slide?
Embeds and protects material.
Ensures material can be observed over a long period of time.
Advantages of using differential stains?
Most biological specimens are colourless so staining makes it easier to observe tissues and distinguish between different types of cells,eg.
Advantages of using a light microscope?
Low skill set needed by user.
Can be transported to use in field work
Can observe living microorganisms
Relatively inexpensive so available for schools and colleges.
Disadvantages of using a light microscope?
Low resolution
Limited magnification
Many internal cellular structures canβt be seen, eg, ribosomes, cristae.