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Instrumentation for Microtomy: Knives

Regardless of the type of microtome, the instrument cannot cut tissue without the use of a knife or a blade. Microtomes and knives were created to work together in order to produce super-thin tissue sections. Initially, microtomes used straight-edged razors to cut tissue, then heavy steel wedge knives were introduced specifically for microtomes. One of the main skills a histotechnologist had to possess was good knife sharpening skills! Knife sharpening was tremendously labor intensive and it was done by hand with natural stones or glass, leather or linen. The knife edge had to be inspected microscopically for the condition of the cutting edge. This process had to be repeated any time the knife became dull or had nicks in it after tissue cutting. Although knives still linger in some histology laboratory drawers, I have yet to see one used on a daily basis for routine sectioning.
With increased work volume, steel knives have slowly been replaced with disposable stainless steel blades. These blades come in two different profiles: high profile (most often used for dense tissue) and low profile (or feathers). Either blade can be used for paraffin-embedded tissue or frozen tissue sectioning. Blades are as individual as the histotechnologist using them. Preferences for high or low profile blades and the various blade tip angles are based on an individual's experiences and successes.
  • Pros of disposable blades: No time-consuming sharpening required and a sharp blade is available instantly.
  • Cons of disposable blades: Expensive and easily damaged, so they must be replaced frequently when tissue dulls or nicks the blade.