HTL Laboratory Instrumentation & Equipment 2 — Questions and Answers
Question 1: Which type of microtome is most commonly used for cutting frozen sections in a cryostat?
- Rotary microtome (Correct answer)
- Sledge microtome
- Vibratome
- Ultramicrotome
Correct answer: Rotary microtome
The cryostat houses a rotary microtome inside a refrigerated cabinet to cut frozen tissue sections.
Question 2: What is the purpose of the knife angle (clearance angle) on a microtome knife?
- To prevent the knife heel from dragging on the tissue block (Correct answer)
- To increase section thickness
- To cool the blade during cutting
- To align the block face parallel to the knife edge
Correct answer: To prevent the knife heel from dragging on the tissue block
The clearance angle prevents the back (heel) of the blade from contacting the block face after the cutting edge passes through.
Question 3: A tissue processor that uses a closed system with vapor-phase infiltration is best described as:
- Microwave processor
- Vacuum infiltration processor (Correct answer)
- Carousel processor
- Capillary action processor
Correct answer: Vacuum infiltration processor
Vacuum infiltration processors use reduced pressure and vapor-phase reagents to enhance penetration, reducing processing time and fume exposure.
Question 4: Which component of a brightfield microscope controls the angle and diameter of the illuminating cone of light?
- Ocular lens
- Substage condenser (Correct answer)
- Objective nosepiece
- Field diaphragm
Correct answer: Substage condenser
The substage condenser focuses and shapes the cone of light directed onto the specimen to optimize resolution and contrast.
Question 5: When a water bath used for section flotation is contaminated with mold, the FIRST corrective action should be:
- Add bleach directly to the water while sections are floating
- Drain, clean with dilute bleach solution, and refill with distilled water (Correct answer)
- Increase water temperature to 60°C
- Add ethanol to inhibit mold growth
Correct answer: Drain, clean with dilute bleach solution, and refill with distilled water
The bath must be drained and decontaminated with dilute bleach before refilling to eliminate contamination without damaging sections.
Question 6: A microtome chuck that does not hold the tissue block firmly most likely indicates:
- Dull knife edge
- Worn or damaged chuck jaws (Correct answer)
- Incorrect section thickness setting
- Improper embedding orientation
Correct answer: Worn or damaged chuck jaws
Worn or damaged chuck jaws lose their clamping ability, causing the block to shift during sectioning and producing uneven sections.
Question 7: Which safety feature is essential when operating a cryostat to protect against infectious tissue?
- UV light decontamination cycle (Correct answer)
- Positive-pressure airflow inside the chamber
- Carbon dioxide fire suppression
- Automatic blade retraction only
Correct answer: UV light decontamination cycle
UV light decontamination cycles are used between cases to inactivate pathogens on interior cryostat surfaces and the blade.
HTL Laboratory Instrumentation & Equipment 2
Which type of microtome is most commonly used for cutting frozen sections in a cryostat?