Histotechnology Fixation and Dehydration
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Questions and Answers

What is the ideal location for fixation of a specimen after dissection?

  • At the site of removal (correct)
  • In a transport container
  • In a storage facility
  • In a laboratory setting

    • What should be done with specimens after dissection to ensure their integrity?

  • They should be fixed as soon as possible (correct)
  • They should be left out for observation
  • They can be stored at room temperature
  • They must be handled carelessly to avoid damage

    • What is a critical step after specimen dissection?

  • Transporting the specimen to a distant location
  • Fixation of the specimen should be delayed
  • Handling the specimen with care (correct)
  • Immediate disposal of the specimen

    • Why is it important to fix specimens promptly?

    <p>To ensure accurate analysis and preservation</p> Signup and view all the answers

    What can occur if fixation is not properly handled after dissection?

    <p>Damage to the specimen may occur</p> Signup and view all the answers

    What is a crucial requirement for reagents used in fixation?

    <p>They must retain some chemical reactivity</p> Signup and view all the answers

    What is the primary purpose of using a liquid fixing agent like formaldehyde solution?

    <p>To harden and preserve the tissue</p> Signup and view all the answers

    Why is it important for tissue components to retain chemical reactivity during fixation?

    <p>To allow for specific staining techniques to be applied</p> Signup and view all the answers

    Which of the following best describes how formaldehyde solution interacts with tissue?

    <p>It penetrates slowly, causing chemical and physical changes</p> Signup and view all the answers

    Which of the following can be considered unsuitable for fixation due to its properties?

    <p>A reagent that alters tissue structure significantly</p> Signup and view all the answers

    What is a characteristic that fixation reagents must possess?

    <p>They must be chemically reactive</p> Signup and view all the answers

    What happens to tissue after it is treated with a liquid fixing agent?

    <p>It is permanently altered and preserved</p> Signup and view all the answers

    Which property of fixation reagents can directly impact staining results?

    <p>Their retention of chemical reactivity</p> Signup and view all the answers

    Which step occurs immediately after applying a fixative like formaldehyde to tissue?

    <p>Chemical and physical changes begin to occur</p> Signup and view all the answers

    Why is it important for a fixative to protect tissue during subsequent processing steps?

    <p>To maintain the original form and structure of the tissue</p> Signup and view all the answers

    What is the primary purpose of using formalin in tissue preservation?

    <p>To fix and preserve tissues for processing</p> Signup and view all the answers

    In what form is formalin typically used for tissue fixation?

    <p>As a phosphate-buffered solution</p> Signup and view all the answers

    How long should specimens ideally remain in fixative?

    <p>Long enough to ensure complete fixation</p> Signup and view all the answers

    What is one key characteristic of tissues that have been fixed in formalin?

    <p>They remain structurally intact</p> Signup and view all the answers

    What should not be expected from specimens submerged in formalin?

    <p>Immediate susceptibility to decay</p> Signup and view all the answers

    What is the primary purpose of substituting water with alcohol in the dehydration process?

    <p>To preserve the structure of the specimen</p> Signup and view all the answers

    What is the correct concentration of ethanol used in the first step of the dehydration sequence for specimens up to 4mm thick?

    <p>70%</p> Signup and view all the answers

    How long should a specimen be immersed in 100% ethanol during the dehydration process according to the typical sequence?

    <p>15 minutes</p> Signup and view all the answers

    What is the order of the ethanol concentrations in the dehydration sequence for specimens not more than 4mm thick?

    <p>70%, 90%, 100%, 100%</p> Signup and view all the answers

    Which concentration of ethanol is used for the second step in the dehydration process?

    <p>90%</p> Signup and view all the answers

    What is the outcome after using ethanol for 45 minutes at 100% concentration?

    <p>A tiny residue of tightly bound water is left.</p> Signup and view all the answers

    How long should ethanol be applied to effectively remove tightly bound water?

    <p>45 minutes</p> Signup and view all the answers

    What concentration of ethanol was used for the removal of tightly bound molecular water?

    <p>100%</p> Signup and view all the answers

    After using ethanol for 30 minutes, what state is the remaining water in the specimen?

    <p>A mixture of bound and free water remains.</p> Signup and view all the answers

    What should be expected after treating a specimen with ethanol for a prolonged period?

    <p>Reduction of free water but tightly bound water remains.</p> Signup and view all the answers

    Study Notes

    Histotechnology: Fixation and Dehydration

    • Specimen Acquisition: Fresh tissue specimens originate from various sources. They can be easily damaged during removal, so careful handling and prompt fixation are crucial. Ideal fixation occurs at the site of removal (e.g., operating theater) or immediately following.

    Fixation

    • Purpose: Tissue specimens are placed in a liquid fixing agent (fixative) like formalin to cause chemical and physical changes hardening and preserving the tissue, protecting it from subsequent processing.

    • Fixative Selection: Only a limited number of reagents can be used for fixation, because the fixative must possess specific properties to be suitable. These properties ensure tissue preservation and chemical reactivity for subsequent staining procedures.

    • Formalin: Formalin (a phosphate-buffered solution) is the most commonly used fixative for paraffin sections.

    • Fixation Time: Specimens typically require between 6 to 24 hours of fixation to allow the fixative to penetrate all tissue components, and the chemical reactions to reach equilibrium.

    Dehydration

    • Purpose: Melted paraffin wax is hydrophobic (water-resistant), so any water present must be removed from the specimen before infiltration with wax.

    • Method: Dehydration is commonly achieved by immersing the specimen in a series of increasing concentrations of ethanol (alcohol) solutions until pure, water-free alcohol is reached.

    • Ethanol's Properties: Ethanol is miscible with water. This ensures the water in the specimen is replaced progressively by the alcohol.

    • Dehydration Sequence: A common dehydration sequence for specimens not exceeding 4mm thick involves specific ethanol concentrations and time durations (e.g., 15 minutes in 70% ethanol, 90%, and later stages at 100% with increasing durations). This process aims to remove almost all of the water from the specimen.

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    Related Documents

    Fixation and Dehydration (Histology) 2024 PDF

    Description

    This quiz explores the essential processes of fixation and dehydration in histotechnology. It covers specimen acquisition, the purpose of fixation, suitable fixatives, and the importance of formalin. Enhance your understanding of tissue preservation techniques used in laboratory settings.

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