Introduction to Histology by dfhdhdhdhjr

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									Introduction to
  Histology
    Cell Structures

  Dr. Rebecca A. Code
 Summer Scholars 2007
     Histology – the study of cellular
          structures of the body
   Anatomy at the microscopic level
    (microanatomy)
   Cells---tissues---organs---organ systems
   1015 cells in the human body
   200+ cell types in the body



Observation – the key to identifying cell types
    Nucleus – present in almost all cells,
      stains well with hematoxylin.
•    Size
•    Shape
•    Location
•    Number
•    Nucleolus – site of rRNA synthesis
•    Density
      •   Euchromatic – light staining nucleus
          due to regions of chromosomes that
          are less coiled, indicating that the
          DNA is actively transcribing mRNA.
      •   Heterochromatic – dense, darkly
          staining nucleus due to tightly coiled
          chromatin, presumably not
          transcriptionally active.
    Cytoplasmic organelles – other clues
       to differentiate cell types and
                  function
   Ribosomes
   Mitochondria
   Golgi apparatus
   Endoplasmic reticulum
   Microfilaments
   Secretory vesicles
   Pigment granules
   Lipid droplets
              Cell Specializations
   Microvilli – found on many epithelial cells; 1-2 mm long
    extensions of cell membrane; increase surface area (15-
    20X) for absorption; lots of microvilli = brush border
   Cilia – 7-10 mm long; motile structures stabilized by
    microtubules; function to move fluid over cells; found
    in trachea, bronchi, oviducts, flagella of sperm.
   Stereocilia –very long microvilli, non-motile; for
    absorption; in epidydimus and on hair cells of inner ear.
Microvillus   Cilium
        Cell Adhesions/Junctions
   Nearly all cells are connected to neighboring cells by
    cell junctions
   Occluding junctions join cells together to form
    impermeable barrier
   Adhering junctions provide mechanical attachment
    between cells.
   Communicating junctions permit movement of ions or
    molecules between cells
Cell Junctions
   Occluding – the most apical
    junction
       Zonula occludens, tight junctions


   Adhering – 2 types:
       Zonula adherentes
       Macula adherens = desmosomes


   Communicating
       Gap junctions
    Histology = 2 dimensional image
   A section is a slice of tissue
   Orientation when sectioned affects what you
    see.
Section of Round Solid Object




               A
                    B
    B   A
Sections cut through a curved tube
      Light Microscope = tool of the
               histologist

   Oculars (eyepieces)
   Stage
   Objective Lens
   Condenser
   Light source
   Focus knobs
          Specimen Preparation
   Fixation, dehydration, embedding
   Sectioning
   Staining: most common is H&E
     Hematoxylin: cationic dye (+ charge) that binds to
      negatively charged (acidic) structures in the cell.
      Example: nucleus = blue
     Eosin: anionic dye (- charge) adheres to basic
      structures in the cell. Example: amine groups
      (NH3+) on proteins make cytoplasm pink.
Kidney cells
Heterochromatic and Euchromatic Nuclei
Golgi Apparatus in Nerve Cells
Mitochondria and Myofibrils
Microvilli of Intestinal Epithelial Cells
Cilia of Tracheal Epithelial Cells
False Intercellular Bridges (Desmosomes)

								
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