Tissue fixation, processing and staining, H and E, special stains, frozen sections, Pap test classification and specimen handling.
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- What is the primary purpose of tissue fixation in histology?
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To preserve tissue structure and prevent autolysis/putrefaction by stabilizing proteins.- How does formalin fix tissue at the molecular level?
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It cross-links proteins via methylene bridges between amino acids.- What is the most commonly used fixative in routine histology?
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10% neutral buffered formalin (NBF).- What is the recommended ratio of fixative volume to tissue volume?
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10 to 1 (ten parts fixative to one part tissue).- What is the correct order of the major tissue processing steps after fixation?
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Dehydration, clearing, infiltration, and embedding.- What reagent is used to dehydrate tissue during processing?
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A graded series of increasing ethanol concentrations.- What is the purpose of the clearing step in tissue processing?
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It removes the dehydrating agent and makes the tissue miscible with paraffin, usually using xylene.- What medium is tissue embedded in for routine paraffin sectioning?
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Paraffin wax.- What instrument is used to cut thin tissue sections from a paraffin block?
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A microtome.- What is the standard thickness of a routine paraffin tissue section?
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4 to 5 micrometers.- What cellular structure does hematoxylin primarily stain?
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The nucleus, a basophilic structure, staining it blue to purple.- What does eosin primarily stain in H and E staining?
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The cytoplasm, an eosinophilic structure, staining it pink.- What type of compound is required to bind hematoxylin to tissue?
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A mordant, typically an aluminum salt (alum).- What does the Periodic Acid-Schiff (PAS) stain detect?
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Glycogen, mucins, fungal cell walls, and basement membranes.- What tissue component does Masson trichrome stain highlight in blue or green?
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Collagen fibers, used to assess fibrosis.
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