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  <head>
    <title>083-01 Microscopy, tissue preparation, epithelial organisation, glands, and surface specialisations</title>
    <ownerName>Integrated Medical Foundations</ownerName>
  </head>
  <body>
    <outline text="Microscopy, epithelium, glands, and surface specialisations">
      <outline text="Reading a section">
        <outline text="Thin processed sample, not the tissue itself"/>
        <outline text="Identify artefacts and orientation first"/>
        <outline text="Relate cells, matrix, lumina, vessels, stroma"/>
        <outline text="Combine pattern with mechanism"/>
      </outline>
      <outline text="Tissue preparation">
        <outline text="Formaldehyde fixation cross-links proteins"/>
        <outline text="Dehydrate, embed in paraffin, section, stain"/>
        <outline text="Frozen sections made rapidly during surgery">
          <outline text="Preserve lipids and enzyme activity"/>
          <outline text="Morphology usually less crisp"/>
        </outline>
        <outline text="Decalcification allows mineralised tissue">
          <outline text="May alter cellular and matrix detail"/>
        </outline>
      </outline>
      <outline text="Stains and imaging">
        <outline text="Haematoxylin colours acidic structures blue-purple">
          <outline text="Basophilia reflects abundant nucleic acid"/>
        </outline>
        <outline text="Eosin colours proteins pink">
          <outline text="Eosinophilia reflects protein-rich cytoplasm or matrix"/>
        </outline>
        <outline text="Intensity is not an absolute measurement"/>
        <outline text="Special stains: periodic acid–Schiff, trichrome, silver"/>
        <outline text="Immunohistochemistry localises proteins"/>
        <outline text="In situ hybridisation localises nucleic acids"/>
        <outline text="Transmission microscopy: membranes, organelles, junctions"/>
        <outline text="Scanning microscopy shows surface topography"/>
        <outline text="Digital pathology: sampling and interpretation stay human"/>
      </outline>
      <outline text="Resolution and sectioning">
        <outline text="Magnification enlarges, resolution separates points">
          <outline text="Numerical aperture and wavelength set resolution"/>
          <outline text="Excess magnification only enlarges blur"/>
        </outline>
        <outline text="Low, intermediate, and high power for different levels"/>
        <outline text="Three-dimensional structures become flat profiles">
          <outline text="Tube: circle, oval, or elongated by plane"/>
          <outline text="Gland looks solid if lumen missed"/>
        </outline>
        <outline text="Artefacts mimic pathology">
          <outline text="Shrinkage spaces, folds, hyperchromatic crushed cells"/>
          <outline text="Consistent relationships separate biology from artefact"/>
        </outline>
      </outline>
      <outline text="Epithelial organisation">
        <outline text="Closely apposed cells with little matrix"/>
        <outline text="Avascular, nourished by diffusion"/>
        <outline text="Apical-basal polarity and basement membrane"/>
        <outline text="Classified by layers and surface cell shape">
          <outline text="Pseudostratified: every cell touches basement membrane"/>
        </outline>
        <outline text="Simple squamous minimises diffusion distance">
          <outline text="Endothelium is an active regulatory organ"/>
          <outline text="Mesothelium lines serous cavities"/>
        </outline>
        <outline text="Simple cuboidal: small ducts, tubules, thyroid follicles"/>
        <outline text="Simple columnar: gut and gallbladder"/>
        <outline text="Airway: cilia move trapped mucus to pharynx"/>
        <outline text="Stratified squamous protects against abrasion">
          <outline text="Keratinised: limits water loss, resists injury"/>
          <outline text="Non-keratinised lines moist surfaces"/>
        </outline>
        <outline text="Urothelium: distensible yet impermeable">
          <outline text="Umbrella cells, membrane plaques, tight junctions"/>
        </outline>
      </outline>
      <outline text="Surface specialisations">
        <outline text="Microvilli: actin projections enlarge surface area">
          <outline text="Brush border in intestine and proximal tubule"/>
        </outline>
        <outline text="Stereocilia: long actin projections"/>
        <outline text="Motile cilia: microtubules move fluid"/>
        <outline text="Goblet cells: unicellular mucous glands">
          <outline text="Excess obstructs airways, deficiency weakens defence"/>
        </outline>
      </outline>
      <outline text="Glands and secretion">
        <outline text="Arise by epithelial downgrowth"/>
        <outline text="Exocrine keep ducts, endocrine release to blood"/>
        <outline text="Simple or compound, tubular or acinar"/>
        <outline text="Serous watery, mucous viscous, mixed both"/>
        <outline text="Merocrine, apocrine, holocrine: release mechanism"/>
        <outline text="Protein cells: basal basophilia, Golgi, granules"/>
        <outline text="Steroid cells: smooth reticulum, lipid, tubular cristae"/>
        <outline text="Ion transport: basolateral folds, mitochondria"/>
        <outline text="Myoepithelial cells expel secretion"/>
        <outline text="Ducts modify ions and water"/>
      </outline>
      <outline text="Basement membrane, renewal, and reading">
        <outline text="Basement membrane anchors, filters, polarises">
          <outline text="Breach marks invasive malignancy"/>
        </outline>
        <outline text="Stem cells in protected niches renew epithelium"/>
        <outline text="Metaplasia swaps programme under stress">
          <outline text="May not perform the original function"/>
        </outline>
        <outline text="Read surface, layers, basal contact, apex, ducts">
          <outline text="Predict function and vulnerabilities"/>
        </outline>
      </outline>
    </outline>
  </body>
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