HT Histology Techniques & Technology 2 — Questions and Answers
Question 1: Which embedding medium is most commonly used for routine paraffin processing in histology?
- Optimal cutting temperature (OCT) compound
- Paraplast or similar paraffin wax blend (Correct answer)
- Epoxy resin
- Celloidin
Correct answer: Paraplast or similar paraffin wax blend
Paraplast and similar paraffin blends are the standard embedding media for routine formalin-fixed tissue in most histology laboratories.
Question 2: What is the primary purpose of the clearing step in tissue processing?
- To remove formalin fixative from the tissue
- To remove dehydrant and make tissue miscible with paraffin (Correct answer)
- To harden the tissue for easier sectioning
- To stain the tissue for visualization
Correct answer: To remove dehydrant and make tissue miscible with paraffin
Clearing agents (such as xylene) remove the dehydrating alcohol and render the tissue transparent and miscible with molten paraffin.
Question 3: A cryostat section is BEST suited for which of the following applications?
- Long-term archival storage of sections
- Intraoperative frozen section diagnosis (Correct answer)
- Demonstration of glycogen in tissue
- Routine H&E staining of fixed tissue
Correct answer: Intraoperative frozen section diagnosis
Cryostat sections are primarily used for intraoperative frozen sections because they can be prepared rapidly while the patient is still in surgery.
Question 4: Which instrument setting on a rotary microtome controls the thickness of each section?
- Coarse advance knob
- Section thickness micrometer (Correct answer)
- Block clamp tension
- Knife angle adjustment
Correct answer: Section thickness micrometer
The section thickness micrometer on a rotary microtome is the control that sets how many micrometers of tissue are advanced per revolution.
Question 5: What is the recommended knife angle (clearance angle) for paraffin sectioning with a steel knife on a rotary microtome?
- 0–2 degrees
- 5–8 degrees (Correct answer)
- 15–20 degrees
- 25–30 degrees
Correct answer: 5–8 degrees
A clearance angle of approximately 5–8 degrees is standard for paraffin sectioning and prevents the knife heel from dragging on the block face.
Question 6: Chatter artifact in paraffin sections most commonly results from which of the following?
- Incomplete dehydration of tissue
- Loose knife or block clamp causing vibration (Correct answer)
- Excessive decalcification
- Over-staining with hematoxylin
Correct answer: Loose knife or block clamp causing vibration
Chatter produces regularly spaced lines across a section and is caused by vibration from a loose knife holder, dull knife, or loose tissue clamp.
Question 7: Which of the following correctly describes the tissue orientation used when embedding a hollow tubular organ such as the intestine?
- Lay flat so the lumen is parallel to the block face
- Stand on end so the lumen is perpendicular to the block face (Correct answer)
- Embed at a 45-degree angle
- No specific orientation is required
Correct answer: Stand on end so the lumen is perpendicular to the block face
Standing the intestine on end allows the microtome to cut cross-sections through all layers (mucosa, submucosa, muscularis, serosa) simultaneously.
HT Histology Techniques & Technology 2
Which embedding medium is most commonly used for routine paraffin processing in histology?