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Histology Tissue Preparation
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Histology Tissue Preparation

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Questions and Answers

What is the primary purpose of a cytologist examining cells obtained from body tissue or fluid?

  • To study the function of cells in terms of chemistry
  • To identify the type of stain used in cytology
  • To look for cancerous changes to cells (correct)
  • To examine the structure of cells

    • What type of cytology specimen is obtained from the respiratory, urinary, or gastro-intestinal systems?

  • Non-gynaecological (correct)
  • Gynaecological
  • Fine needle aspirations
  • Cervical smears

    • What is the name of the staining technique that involves five dyes in three solutions?

  • Romanowsky-type stain
  • Giemsa stain
  • Papanicolaou stain (correct)
  • Hematoxylin and Eosin stain

    • What is the purpose of using Harris' hematoxylin in the Papanicolaou staining technique?

    <p>To stain cell nuclei blue</p> Signup and view all the answers

    What is the name of the type of cytology specimen that includes any site from which a clinician can obtain a specimen using a fine needle?

    <p>Fine needle aspirations</p> Signup and view all the answers

    What is the name of the stain used to differentiate cells for microscopic examination in pathological studies?

    <p>Romanowsky-type stain</p> Signup and view all the answers

    What is the name of the collection device used to collect cervical smears?

    <p>Rover Cervex Brush</p> Signup and view all the answers

    What is the minimum number of years that slides must be kept in cytology?

    <p>5 years</p> Signup and view all the answers

    What is the term for the study of cells in terms of structure, function, and chemistry?

    <p>Cytology</p> Signup and view all the answers

    What is the purpose of increasing the temperature of fixation?

    <p>To increase the rate of diffusion of the fixative into the tissue</p> Signup and view all the answers

    What is the recommended minimum time for fixation of a 4 mm piece of tissue?

    <p>8 hours</p> Signup and view all the answers

    Which of the following fixatives is commonly used for electron microscopy?

    <p>Glutaraldehyde</p> Signup and view all the answers

    What is the primary purpose of the gross description in histology?

    <p>To create a written record of the examiner's findings</p> Signup and view all the answers

    What is the purpose of the cassette labeler in histology?

    <p>To etch the numbers on the cassette</p> Signup and view all the answers

    What is the purpose of the dehydration step in tissue processing?

    <p>To remove water from the tissue and replace it with alcohol</p> Signup and view all the answers

    What is the purpose of the clearing step in tissue processing?

    <p>To remove ethanol from the tissue and replace it with xylene</p> Signup and view all the answers

    What is the typical temperature at which paraffin wax is infiltrated into tissue?

    <p>60°C</p> Signup and view all the answers

    What is the purpose of adding additives to paraffin wax?

    <p>To improve the consistency of paraffin wax</p> Signup and view all the answers

    What is the primary function of the histology department?

    <p>To prepare slides of tissue from various sources for pathologist examination</p> Signup and view all the answers

    What is the purpose of fixation in histology?

    <p>To preserve tissue and prevent structural change</p> Signup and view all the answers

    What is the common brand name of the paraffin wax used in the embedding process?

    <p>Paraplast</p> Signup and view all the answers

    What is the temperature of the embedding oven in the wax infiltration step?

    <p>60-degree C</p> Signup and view all the answers

    What is the most common fixative used in histology?

    <p>10% formalin</p> Signup and view all the answers

    What is the advantage of using 10% N.B. formalin as a fixative?

    <p>It penetrates tissue rapidly and preserves the natural state</p> Signup and view all the answers

    What is the purpose of adding an external base to the tissue during the embedding process?

    <p>To make the tissue more stable</p> Signup and view all the answers

    How is 10% formalin prepared?

    <p>By mixing 40% formaldehyde with 100ml of water</p> Signup and view all the answers

    What is the thickness of the sections cut on a microtome?

    <p>3-5 um</p> Signup and view all the answers

    What is the purpose of the hot water bath in the staining process?

    <p>To flatten and remove wrinkles from the sections</p> Signup and view all the answers

    What is the difference between formaldehyde and formalin?

    <p>Formaldehyde is a mixture of formaldehyde gas and water, while formalin is the addition of methyl alcohol to formaldehyde</p> Signup and view all the answers

    What is the solvent used to remove wax from the sections during the staining process?

    <p>Xylene</p> Signup and view all the answers

    Why is it necessary to add a buffer to formalin?

    <p>To neutralize the pH of the solution</p> Signup and view all the answers

    What is the purpose of the dehydration step in the permanent mounting process?

    <p>To prepare the sections for mounting</p> Signup and view all the answers

    What is the ideal ratio of fixative to specimen volume?

    <p>15-20:1</p> Signup and view all the answers

    What is the advantage of using frozen sections over paraffin wax embedding?

    <p>Faster processing time</p> Signup and view all the answers

    What is the order of steps in preparing histological sections?

    <p>Fixation, embedding, sectioning, staining</p> Signup and view all the answers

    What should you do with small amounts of ethyol alcohol?

    <p>Pour it down the drain</p> Signup and view all the answers

    What is the primary purpose of the cytocentrifuge?

    <p>To transfer biological cells from liquid suspension onto a microscope slide</p> Signup and view all the answers

    What is the purpose of the ThinPrep 2000 processor?

    <p>To prepare cervical smears for cytology</p> Signup and view all the answers

    What is the role of a Medical Laboratory Assistant (MLA) in histology?

    <p>To perform routine tissue processor maintenance and reagent changes</p> Signup and view all the answers

    What is the purpose of Histogel in cell block preparation?

    <p>To harden the specimen block in the centrifuge tube</p> Signup and view all the answers

    What is the purpose of the supernatant removal in cell block preparation?

    <p>To remove remaining specimen for cell block preparation</p> Signup and view all the answers

    What is the role of a Medical Laboratory Assistant (MLA) in cytology?

    <p>To prepare specimens for cytology</p> Signup and view all the answers

    What is the purpose of securely tightening the cap on the vial?

    <p>To ensure the specimen is safely transported to the lab</p> Signup and view all the answers

    What is the purpose of the Cytology fixed spray?

    <p>To fix the slide for cytology</p> Signup and view all the answers

    What is the purpose of placing the specimen block on tissue paper?

    <p>To wrap the specimen block for processing</p> Signup and view all the answers

    Study Notes

    Histology and Cytology

    Purpose of Histology Department

    • Prepare slides of tissue from various sources for pathologist examination

    Preparation of Histological Sections

    • Steps:
    • Preserve tissue (fixation)
    • Embed tissue in supporting medium
    • Sectioning
    • Staining

    Fixation

    • Purpose: preserve tissue, prevent structural change
    • Fixative: 10% Neutral Buffered (N.B.) Formalin
    • Characteristics of Formalin:
    • Cheap
    • Rapidly penetrates tissue
    • Preserves natural state
    • Made by mixing 40% Formaldehyde with 100ml water
    • To get 10% Formalin, mix 10ml of 100% Formalin with 90ml water

    Factors Affecting Fixation

    • Temperature: increases rate of fixation
    • Time: longer time generally better
    • Penetration rate: depends on fixative
    • Specimen dimensions: 1-4 mm thickness

    Other Fixatives

    • Bouin's solution: picric acid
    • Zenker's fixative: mercuric chloride
    • Glutaraldehyde: electron microscopy
    • Alcohols: good for cytology

    Tissue Processing

    • Steps:
    • Dehydration (removal of water using ascending series of alcohols)
    • Clearing (using xylene to displace ethanol)
    • Wax infiltration (paraffin wax)
    • Can be done manually or by machine (HistoCore PELORIS 3 Premium Tissue Processing System)

    Embedding

    • Purpose: stabilize tissue with external base
    • Process: place tissue in mold, add hot wax, and cool to form a wax block

    Microtomy

    • Process: cut sections of tissue embedded in wax block using a microtome
    • Thickness: 3-5 um

    Staining

    • Most common stain: Hematoxylin and Eosin (H&E)
    • Steps:
    • Remove wax using xylene
    • Hydrate sections using descending alcohols and water
    • Stain with Hematoxylin and Eosin

    Permanent Mounting

    • Steps:
    • Dehydrate sections using ascending alcohols
    • Clear using xylene
    • Mount with a mountant (e.g. Permount) and glass coverslip

    Cytology

    • Definition: study of cells in terms of structure, function, and chemistry
    • Objectives:
    • Different types of cytology specimens
    • Procedures used in cytology
    • Common stains used in cytology
    • Papanicolaou stain

    Types of Cytology Specimens

    • Gynaecological (cervical cancer)
    • Non-gynaecological (respiratory, urinary, gastro-intestinal systems)
    • Fine needle aspirations (breast, lung, salivary glands, etc.)

    Stains Used in Cytology

    • Papanicolaou stain (for nuclear details)
    • Romanowsky-type stain (for acid-fast bacteria)

    Papanicolaou Stain

    • Five dyes in three solutions:
    • Hematoxylin (nuclear stain)
    • Orange Green 6 (acidic counterstain)
    • Eosin Azure (counterstain)
    • Eosin Y (cytoplasmic stain)
    • Light green SF (cytoplasmic stain)

    Specimen Preparation

    • Various methods:
    • Cytocentrifugation preparation (Cytospin)
    • ThinPrep preparation (mainly for cervical smears)
    • Cell block preparation (captures remaining specimen in centrifuge tube)

    Role of a MLA in Histology/Cytology

    • Prepares specimens for histology
    • Labels tissue cassettes
    • Performs routine tissue processor maintenance and reagent changes
    • Files and retrieves stained slides and paraffin blocks
    • Performs routine staining procedures
    • Mounts slides
    • Assists in the cutting room
    • Prepares specimens for cytology
    • Stains and mounts pap slides

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    Description

    Learn about the process of preparing histological sections, including fixation, embedding, sectioning, and staining, in a histology department.

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