Microtome: A Device for Cutting Thin Slices

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.
• Sections can be made thin enough to section a human hair across its breadth, with section thickness between 50 nm and 100 μm.

History of Microtomy

• The earliest form of microtomy involved freehand sectioning of fresh or fixed material using a sharp razor.

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: used for preparing large samples, such as those embedded in paraffin for biological preparations, with a typical cut thickness of 1-60 μm.
• Rotary microtome: used for hard materials, with a typical cut thickness of 1-60 μm, and can achieve semi-thin sections with a thickness of as low as 0.5 μm.
• Cryomicrotome: used for cutting frozen samples, with a typical cut thickness of semi-thin samples, and requires controlled sample and knife temperatures.
• Ultramicrotome: used for preparing extremely thin sections, with a typical cut thickness of 40-100 nm for transmission electron microscopy, and uses diamond or glass knives.
• Vibrating microtome: uses a vibrating blade to cut with less pressure, and is used for difficult biological samples, with a typical cut thickness of 30-500 μm for live tissue and 10-500 μm for fixed tissue.
• Saw microtome: used for hard materials such as teeth or bones, with a recessed rotating saw, and a minimal cut thickness of approximately 30 μm.
• Laser microtome: uses contact-free slicing, prior preparation of the sample is not required, and can be used for very hard materials, with a typical cut thickness of 10-100 μm.