Microtome
A microtome is a specialized instrument designed for producing exceptionally thin slices, or sections, of samples, which can be either organic or inorganic. These sections are primarily prepared for examination under optical or electron microscopes and play a crucial role in the scientific fields of microtomy and histology, particularly within biology and medicine. The microtome's design includes various components that control the angle and orientation of its cutting blade, which can be made from materials like steel, glass, or diamond, depending on the type of sample being processed.
There are several types of mechanical microtomes, including rotary, sliding, saw, and vibrating microtomes. Rotary microtomes are the most commonly used, capable of creating sections as thin as 0.5 micrometers. Sliding microtomes have a unique design that allows for maintenance advantages while producing sections ranging from 1 to 60 micrometers. Saw microtomes, often equipped with diamond blades, are suited for cutting hard samples, and vibrating microtomes minimize pressure to preserve delicate tissues. For more advanced applications, laser microtomes employ precision lasers for contact-free cutting, while ultramicrotomes can create ultra-thin sections for transmission electron microscopy. Overall, microtomes are essential tools in specimen preparation, enabling detailed study and analysis of biological materials.
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Microtome
A microtome is a specialized machine used to create extremely thin precision-cut samples or specimens. When a sample or specimen is cut with a microtome, it is known as a “section.” These sections can consist of either organic or inorganic materials. Sections are typically prepared for study under optical or electron microscopes.
The scientific discipline of using microtomes to obtain organic or tissue specimens is known as microtomy and the study of such organic tissue specimens is called histology. Most practical uses of microtomy and histology apply to the fields of biology and medicine.
Overview
Mechanical microtomes primarily consist of block-shaped housings, sample holders, and components for controlling the angle and orientation of the microtome’s blade and the direction of the sample feed. The blades used in mechanical microtomes can be made of steel, glass, or diamond. Steel blades are primarily used for applications involving the preparation of soft tissue sections drawn from plants or animals. Glass blades facilitate the precision cutting of extremely thin sections, while diamond blades are mostly used in industrial settings and for tasks that require the cutting of highly resistant solid materials such as hardwood, teeth, or bones.
The four main types of mechanical microtomes include rotary, sliding, saw, and vibrating microtomes. Rotary microtomes are the most common type of mechanical microtome. They create sections ranging in size from approximately 0.5–60 micrometers and typically consist of a handwheel, sample holder, and an assembly housing containing the cutting components. Most rotary microtomes use motorized controls that automatically create sections conforming to user inputs.
Sliding microtomes are similar to rotary microtomes in design and function but feature a slide-mounted blade that moves while the sample or specimen is held in a fixed position. They offer maintenance advantages and typically create sections in a size range of 1–60 micrometers.
Saw microtomes are the most likely type of mechanical microtome to use a diamond blade for creating sections from particularly hard samples or specimens. They have spinning blades, which are placed at recessed positions within the housing block. Samples or specimens are placed in direct contact with the blade, and the blades of saw microtomes are cooled by lightly pressurized streams of water that prevent excessive heat buildup. Saw microtomes create relatively thick sections starting in the range of 30 micrometers.
Vibrating microtomes allow users to create sections using minimal pressure, which protects the integrity of soft samples or specimens such as spinal cord, nerve, or brain tissue. The sections created with vibrating microtomes typically start at 10–30 micrometers in size.
Users often pretreat the samples and specimens cut with mechanical microtomes by freezing them or placing them in celloidin or paraffin to harden them. However, these techniques can alter the morphology of the samples or specimens on a cellular level. When this is undesirable, contact-free laser microtomes can be used. Laser microtomes use precision lasers rather than physical blades to cut sections. Another specialized type of microtome, known as an ultramicrotome, facilitates the production of minute samples smaller than 150 nanometers in size for study under transmission electron microscopes.
Bibliography
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