Anatomy- Lab 3
Describe the proper procedure for preparing a wet mount.
Place the specimen on the slide with a medicine dropper or place a drop of water or saline on the slide. Mix specimen into drop using a toothpick. If staining, add a drop of stain and mix with a toothpick. Hold a coverslip with forceps so that the coverslip touches one side of the specimen drop, and then slowly and carefully lower the angled coverslip onto the specimen.
A blood smear is used to diagnose malaria. In patients with malaria, the protozoa can be found near and inside red blood cells. Explain why a microscope capable of high magnification and high resolution would be needed to diagnose malaria?
Since the malaria protozoa live inside the red blood cells, the diagnostician would need to be able to see objects in the field of view that are less than 10 microns (the average size of a human red blood cell). Therefore the high-power objective (100) would have to be used to obtain adequate resolution.
Say you are observing an object in the low-power field. When you switch to high power, it is no longer in your field of view. Why might this occur? What should you do initially to prevent this from happening?
The field of view decreases proportionally as the magnification increases. Therefore, if the object was not near the center of view it might now be outside the field diameter of the higher-power lens. Make sure the object you are viewing is at or near the center of the field of view before switching to the higher-power objective lens.
Only half of the field is illuminated:
The lens in not fully rotated into place.
The visible field does not change as the mechanical stage is moved:
The slide is not correctly positioned in the clamp and therefore does not move when the mechanical stage moves.
Your lab microscope is parfocal. What does this mean?
The slide should be almost in focus when changing to higher magnifications.
A student has the high-power lens in position and appears to be intently observing the specimen. The instructor, noting a working distance of about 1 cm, knows the student isn't actually seeing the specimen. How so?
The working distance of a high-power lens is closer to 1 mm than 1 cm.
Assume there is an object on the left side of the field that you want to bring to the center (that is, toward the apparent right). In what direction would you move your slide? .
To the left
Histopathology is the use of microscopes to view tissues to diagnose and track the progression of diseases. Why are thin slices of tissue ideal for this procedure?
With a light microscope, it is essential that light can pass through the sample. Ideally the sample would only be one cell layer thick to allow for proper identification of individual structures.
delivers a concentrated beam of light to the specimen
condenser
working distance with higher magnification
decreases
The area of the slide seen when looking through the microscope is the
field diameter
When focusing on high power, always use the ________ adjustment knob to focus.
fine
used for precise focusing once initial focusing has been done
fine adjustment knob
amount of light needed when moved to higher mag
increases
resolution as one moves to higher mag
increases (to a point)
used to adjust the amount of light passing through the specimen
iris diaphragm lever
The microscope should be stored with the________lens in position over the stage.
lowest power or scanning
controls the movement of the slide on the stage
mechanical stage
carries the objective lenses; rotates so that the different objective lenses can be brought into position over the specimen
nosepiece
If, after focusing in low power, you need to use only the fine adjustment to focus the specimen at the higher powers, the microscope is said to be ___
parfocal
When beginning to focus, use the___________lens
scanning objective
The microscope slide rests on the _____________ while being viewed.
stage
platform on which the slide rests for viewing
stage
The microscope lens may be cleaned
with grit-free lens paper
How do you clean the lenses of your microscope?
with special lens paper and cleaner
A coverslip should always be used
with wet mounts
The distance from the bottom of the objective lens to the surface of the slide is called the .
working distance
If the diameter of the low-power field is 1.5 mm, an object that occupies approximately a third of that field has an estimated diameter of _____ mm
0.5
You are using a 10× ocular and a 15× objective, and the field diameter is 1.5 mm. The approximate field size with a 30× objective is _____ mm.
0.75
If the ocular lens magnifies a specimen 103, and the objective lens used magnifies the specimen 353, what is the total magnification being used to observe the specimen?
350
If a microscope has a 10× ocular lens and the total magnification is 950×, the objective lens in use at that time is _____
95
resolution:
Ability to discriminate between two closely situated objects and perceive them as two separate entities and not fused into one.
depth of field with higher mag
Decreases
You should always begin observation of specimens with the oil immersion lens.
False
Explain the proper technique for transporting the microscope.
Hold the microscope in an upright position with one hand on its arm and the other supporting its base.
Why should the light be dimmed when looking at living (nearly transparent) cells?
Increases contrast
Total Magification
Is the combined power of magnification and is computed by multiplying the power of the eye piece by the power of the objective lens being used for viewing.
