TISSUE

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					                   Histology
                   the study of
                     TISSUE
A groups of cells with similar structure that function
                  together as a unit
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             Types of Cell to Cell Junctions
     • Tight junctions provide seals to prevent leaking
       across the free epithelial surface.
          – Ex. epithelia in the digestive tract that prevents attack of
            the wall by acids and enzymes.
     • Adhesion junctions (AKA Desmosomes) are like
       "spot welds" that cement cells together and prevents
       them from pulling apart so that they function as a
       unit. Ex. Skin
     • Gap junctions contain hollow cylinders (connexons)
       that allow chemical cell to cell communication
       Ex. heart cells and embryonic cells
                      Before we start:

  Interstitial fluid (ISF):
  • The fluid found in the spaces between cells
  • Composed of water, amino acids, sugars, fatty
    acids, coenzymes, hormones, salts and cellular
    products.
  • It bathes and surrounds the cells of the body,
    and provides a means of delivering materials

To be discussed further when we discuss
the lymphatic system.
           1. Epithelial Tissue
• AKA: Epithelium (epi- upon)
  Functions
  – Protection, secretion, absorption, excretion
  – Mitosis is frequent to replace damaged cells
           Epithelial Tissue
Characteristics
– Closely packed flat cells
   (little intercellular material)
– Avascular (lacking blood vessels)
   needs are meet through diffusion from
   neighboring cells
                      Epithelial
Location
   • Coverings or linings of organs
      •   Upper surface of the epithelium is exposed to the
          outside of the body OR to an internal cavity
        1. Classifying Epithelium
A. Cell shape
• Squamous (squashed): cells are flat, nucleus
  near surface of cell, looks like “fried egg”
        1. Classifying Epithelium
cell shape
• Cuboidal (cube): cells square shaped with a
  central nucleus
         1. Classifying Epithelium
cell shape
• Columnar (column): enlongated cell, nucleus
  near the bottom, some have microvilli (finger-
  like projections that increase surface area),
  some have cilia (tiny “hair-like” structures that
  help move materials along)
         1. Classifying Epithelium
cell shape
• Transitional: flat and/or tall, can extend and
  compress
         1. Classifying Epithelium
B. Number of cell layers
• Simple: single layer
• Statified: (strat- layer) multiple layers
• Psuedostratified: (pseudo- false) seems to
  appear as if it is layered, however, it is one
  layer of cells that are differing in size
         Other terms to know:
• Apical surface: surface of epithelial tissue
  that is exposed to open space or the outside
  of the body
• Basal surface: surface of the epithelial tissue
  that is the furthest from the apical surface
• Basement membrane: extracellular substance
  secreted by epithelial cells, found on the basal
  surface of tissue
                          Practice Looks
•   Epithelia Page
•   1. Simple Squamous
    2. Simple Squamous
    3. Simple Cuboidal
    4. Simple Cuboidal
    5. Simple Columnar
    6. Simple Columnar
    7. Pseudostratified Columnnar
    8. Pseudostratified Columnnar (Ciliated)
    9. Transitional
    10. Transitional
    11. Stratified Squamous
    12. Stratified Squamous
    13. Stratified Squamous
    14. Stratified Squamous (Keratinized)
    15. Stratified Squamous (Keratinized
    16. Stratified (High) Cuboidal
    17. Stratified Cuboidal

				
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