Microtome in Microscopy

Microtome

• A device used to cut extremely thin slices of material, known as sections, for observation under transmitted light or electron radiation.
• Uses steel, glass, or diamond blades depending on the specimen being sliced and the desired thickness of the sections.

Types of Blades

• Steel blades: used for preparing sections of animal or plant tissues for light microscopy histology.
• Glass knives: used for slicing sections for light microscopy and for slicing very thin sections for electron microscopy.
• Diamond knives: used for slicing hard materials such as bone, teeth, and plant matter for both light and electron microscopy.

Microtomy

• Used to prepare thin sections for materials such as bones, minerals, and teeth.
• Can produce sections thin enough to section a human hair across its breadth, with section thickness between 50 nm and 100 μm.

History of Microtomy

• Earliest form of microtomy was the freehand sectioning of fresh or fixed material using a sharp razor.
• With practice, sections could be made quite thin and translucent.

Types of Microtomes

• Based on the mechanism:
  • Rocking microtome
  • Rotary rocking microtome
  • Sledge microtome
  • Rotary microtome
  • Cryomicrotome
  • Ultramicrotome
  • Vibrating microtome
  • Saw microtome
  • Laser microtome

Main Types of Microtomes

• Sledge microtome:
  • Typical applications: preparation of large samples, such as those embedded in paraffin for biological preparations.
  • Typical cut thickness: 1-60 μm.
• Rotary microtome:
  • Typical cut thickness: 1-60 μm.
  • Can be adapted for cutting hard materials, such as samples embedded in a synthetic resin, with a thickness of as low as 0.5 μm.
• Cryomicrotome:
  • For cutting frozen samples.
  • Allows the preparation of semi-thin samples with a thickness of as low as 0.5 μm.
  • Requires controlled sample and knife temperature.
• Ultramicrotome:
  • Allows the preparation of extremely thin sections.
  • Typical thickness: 40-100 nm for transmission electron microscopy.
  • Uses diamond knives (preferably) and glass knives.
• Vibrating microtome:
  • Operates by cutting using a vibrating blade, allowing for less pressure and easier cutting.
  • Typically used for difficult biological samples.
  • Cut thickness: 30-500 μm for live tissue and 10-500 μm for fixed tissue.
• Saw microtome:
  • Especially for hard materials such as teeth or bones.
  • Has a recessed rotating saw that slices through the sample.
  • Minimal cut thickness: approximately 30 μm.
• Laser microtome:
  • Contact-free slicing.
  • No prior preparation of sample required.
  • Can be used for very hard materials, such as bones or teeth, as well as some ceramics.
  • Thickness: 10-100 μm.