Microtomy and section cutting

MICROTOMY BASICS

1. What is microtomy?

   • A technique used in histology and pathology to prepare thin sections of biological tissues for microscopic examination.

2. Why is microtomy important in histopathology?

   • It ensures accurate diagnosis and research by producing high-quality tissue sections.

3. What is the process of microtomy?

   • Processed tissue, usually paraffin-embedded, is trimmed and cut into uniformly thin slices for microscopic study.

PARTS OF THE MICROTOME

4. What is the function of the microtome base or body?

   • It serves as the foundation, supporting the entire instrument and housing internal mechanisms.

5. What is the role of the block holder?

   • It holds the tissue in position during sectioning and aligns it properly for even slicing.

6. What is the knife carrier used for?

   • It holds the knife for the actual cutting of tissue sections.

7. What is the function of the hand wheel?

   • It rotates and advances the tissue block for sectioning.

8. What does the waste tray do?

   • It collects excess tissue and debris to keep the workspace clean.

KINDS OF MICROTOME

9. What is a rocking microtome used for?

   • Cutting serial sections of large paraffin-embedded tissue blocks.

10. What type of microtome is commonly used for paraffin-embedded sections?

• Rotary microtome.

11. Which microtome is used for celloidin-embedded sections?

• Sliding microtome.

12. Which microtome is used for frozen sections?

• Freezing microtome.

13. Which microtome is known as a ‘cold microtome’?

• Cryostat.

14. Which microtome is used for electron microscopy?

• Ultrathin microtome.

ROCKING (CAMBRIDGE) MICROTOME

15. Who invented the rocking microtome and when?

• Paldwell Trefall in 1881.

16. What are the key advantages of a rocking microtome?

• Simple, mechanically stable, and provides uniform tissue sections.

17. What is a major limitation of the rocking microtome?

• It is manually operated and considered outdated compared to modern microtomes.

ROTARY MICROTOME

18. Who invented the rotary microtome?

• Minot in 1885-1886.

19. Why is the rotary microtome widely used?

• It offers precision, ease of use, and produces consistent sections.

20. What is a disadvantage of the rotary microtome?

• It is limited to paraffin sections and requires frequent blade replacements.

SLIDING MICROTOME

21. Who developed the sliding microtome and when?

• Adams in 1789.

22. What kind of specimens is the sliding microtome best for?

• Large or hard specimens like the brain, spinal cord, and mineralized tissues.

FREEZING MICROTOME

23. Who invented the freezing microtome and when?

• Queckett in 1848.

24. What is the main advantage of the freezing microtome?

• It allows rapid sectioning without chemical fixation, preserving tissue components.

25. What is a disadvantage of the freezing microtome?

• Thicker sections compared to paraffin microtomes, making it less detailed.

CRYOSTAT

26. What is the purpose of a cryostat?

• It is a refrigerated microtome used for freezing tissues and sectioning them at low temperatures.

27. At what temperature does a cryostat operate?

• Between -5°C to -30°C (average -20°C).

28. Why is the cryostat essential for immunohistochemistry?

• It preserves protein antigenicity for antibody staining.

ULTRATHIN MICROTOME

29. What type of sections does an ultrathin microtome produce?

• Extremely thin sections (60-100 nanometers) for electron microscopy.

30. What type of knife does an ultrathin microtome use?

• Glass or industrial-grade diamond knives.

CARE OF THE MICROTOME

31. What should be done after sectioning to maintain the microtome?

• Brush away accumulated paraffin and tissue debris.

32. Why should the microtome be placed on a stable bench?

• To avoid vibrations and air drafts that interfere with sectioning.

33. How often should the microtome be inspected by a technician?

• At least once a year.

MICROTOME KNIVES

34. What are the three types of microtome knives?

• Plane-concave, biconcave, and plane-wedge.

35. Which knife is used for cutting paraffin sections?

• Biconcave knife.

36. Which knife is best for frozen sections and hard specimens?

• Plane-wedge knife.

KNIFE MAINTENANCE

37. What is the typical bevel angle of a microtome knife?

• 27° to 32°.

38. Why should a knife blade be sharper than the section being cut?

• To prevent uneven or alternating thick and thin sections.

39. What is honing?

• The process of sharpening a knife by removing nicks and dull edges.

40. What are the three types of hones used for sharpening microtome knives?

• Belgium Yellow, Arkansas, and Fine Carborundum.

41. What is stropping?

• The process of polishing and refining the knife edge after honing.

SAFETY MEASURES

42. Why should forceps or a brush be used instead of fingers when handling sections?

• To prevent injuries from sharp blades.

43. What safety measure should be taken when the microtome is unattended?

• The knife or blade should be removed.

44. Why should used blades be disposed of in a sharps container?

• To prevent injuries and contamination.

EMERGING TECHNOLOGIES IN MICROTOMY

45. What are magnetic knives used for?

• They attach to specific blade holders and are compatible with cryostats.

46. What is the advantage of disposable knives?

• They are cost-effective and eliminate the need for sharpening.

GLASS AND DIAMOND KNIVES IN ELECTRON MICROSCOPY

47. What are glass knives used for?

• Trimming and semi-thin sectioning of tissue blocks.

48. What is a key advantage of diamond knives?

• They provide high-precision cutting for ultrathin sections.

49. Why should glass knives be stored in dust-free boxes?

• To maintain cleanliness and prevent contamination.

OTHER EQUIPMENT

50. What is the purpose of a water bath in microtomy?

• To float and flatten tissue sections before mounting.

51. Why should drying ovens be used for tissue sections?

• To dry tissue sections efficiently without damaging them.

52. What is the preferred slide thickness for routine work?

• 1.0-1.2 mm thick.