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Questions and Answers
What is the main purpose of infiltration/impregnation in tissue processing?
Which method is considered the best for applying the infiltrating agent?
What characteristic must an infiltrating medium possess regarding its density?
Which of the following is considered the simplest and most commonly used infiltrating agent?
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What is the effect of not performing impregnation on tissue before microtomy?
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Which property is essential for an infiltrating medium regarding its interaction with other reagents?
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What is a potential consequence of using an infiltrating agent that contributes opacity to the tissue?
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Which condition should NOT be true for the formulation of an infiltrating medium?
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What happens to tissue juice during the dehydration process?
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Why is paraffin wax favored as an infiltrating agent?
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Which method of processing is known to be cost-effective and independent of machine use?
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What is the recommended temperature range for setting paraffin?
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Which of the following effects can heat have on tissue components during processing?
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Which infiltration medium is best suited for embedding dyes?
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What is a disadvantage of manual processing for tissue infiltration?
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What is an advantage of using automatic tissue processors?
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What characterizes the consistency of paraffin when it hardens?
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What is the melting point range for Ester wax?
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Which alternative to paraffin is described as more elastic and easier to mold?
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Which tissue component is best infiltrated using Celloidin?
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What is a characteristic of resins used for embedding tissues?
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Which infiltration method is not suitable for fatty tissues?
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Which of the following describes paraffin in routine histopathology?
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Which resin is recognized for performing both clearing and infiltration simultaneously?
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What is the main drawback of using agar as an infiltration medium?
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What is a significant drawback of acrylic plastics compared to other resins?
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Which embedding agent is generally used for frozen sections and delicate specimens?
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Under which condition is wet celloidin primarily used?
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What is the role of plasticizers like castor oil in low viscosity nitrocellulose?
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Which factor is crucial for successful infiltration during the embedding process?
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Carbowax is characterized by which of the following properties?
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Which clearing agent is used with cellosolve or xylene during the infiltration process?
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What is a common application for agar in the embedding process?
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What is a significant characteristic of epoxy plastics used in embedding?
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Which type of wax requires the ambient temperature to dictate its melting point?
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Which resin is not considered an embedding plastic?
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In the context of embedding, what is a critical step to remove the clearing agent?
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Which of the following statements is true regarding dry celloidin?
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Study Notes
Infiltration and Impregnation
- Infiltration involves replacing the clearing agent within a tissue with a supporting agent, typically wax or resin. This process facilitates microtomy.
- Impregnation is the process of embedding tissue in a supporting medium, usually wax, to provide structural rigidity and ease of cutting.
- Manual processing is cost-effective but prone to human error, while automatic processing eliminates these errors but is more expensive.
- Vacuum infiltration is the most efficient method for removing air pockets and allowing the infiltrating agent to penetrate.
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Properties of infiltrating media:
- Miscible with the clearing agent
- Non-polar
- Not too dense
- Cheap and reliable
- Compatible with reagents used in preceding procedures
- Supports tissue structure
- Transparent
- Paraffin is the most commonly used infiltrating medium due to its affordability, reproducibility, and compatibility with routine histopathology.
- Embedding media provide structural support for tissue during sectioning.
- Paraffin is the simplest and most common embedding medium, with a melting point of 60°C. It is recommended for routine histopathology.
- Paraplast is a more elastic and resilient alternative to paraffin, ideal for dense tissues like bones and brains.
- Embeddol is a synthetic wax substitute with a similar consistency to Paraplast.
- Ester wax is harder than paraffin and has a lower melting point. It is soluble in organic solvents.
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Alternative infiltration media are used when:
- Heat damages cellular components
- Thin sections are required
- Existing media cannot support the tissue
- Resins are used for special procedures, providing exceptional support and allowing thinner sections.
- Water-soluble waxes are used when dehydration and clearing are not desired.
- Celloidin is a suitable alternative for paraffin, particularly for large, hollow cavities, dense tissues, and delicate specimens.
- Agar is a last resort for embedding small, friable tissues.
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Important considerations
- Homogenous agent is crucial to avoid crystallization and proper embedding
- Temperature monitoring is vital to ensure proper melting and hardening of the embedding medium
- Use of fresh filtered wax minimizes impurities in paraffin
- Use of the same material for both infiltration and embedding
- Double embedding involves embedding tissue in two different media, typically paraffin followed by gelatin, for added structural support.
Considerations during Impregnation
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Temperature monitoring
- Temperature should be checked every 5 minutes.
- Ensure adequate heating of the infiltrating agent - at least 2-5℃ above its melting point.
- Multiple changes required to ensure complete replacement of the clearing agent.
- Optimal duration of infiltration is minimal for best results.
- Homogenous agent ensures uniform embedding without crystallization.
Paraffin Wax
- Melting point of 56℃ is commonly used in routine histopathology.
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Ambient temperature dictates the appropriate melting point of the wax for optimal results:
- Room temperature of 20-24°C: Wax with a melting point of 54-58°C
- Room temperature of 15-18°C: Wax with a melting point of 50-54°C
- Fresh wax must be filtered before use to remove impurities.
- Wiremesh is used for filtering.
- Pure paraffin is used in routine histopathology.
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Description
This quiz covers the processes of infiltration and impregnation in histology, particularly focusing on the materials and methods used for embedding tissues. It distinguishes between manual and automatic processing, highlights the benefits of vacuum infiltration, and describes the properties of ideal infiltrating media, especially paraffin. Test your understanding of these vital histological techniques!
