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The Lymphatic System by ert554898

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									The Lymphatic
System
          Organization
   Lymph Vessels
       Begin at peripheral tissue
        venous system
       Small valves prevent backflow
   Lymph Fluid
       Like plasma but w/less proteins
   Lymphocytes
       Cells defend body
   Lymph Tissue
       Loose connective tissue
       Tonsils
   Lymph Organs
       Lymph nodes
       Spleen
       Thymus
         Functions

   Production, maintenance,
    and distribution of
    lymphocytes
   Return fluid from
    peripheral tissues to blood
   Distribute hormones,
    nutrients, and waste to
    general circulation
         Lymph Vessels
   Lead towards trunk of body
    and empty into 2 ducts

   Thoracic duct – lower
    abdomen, pelvis, lower limbs,
    left head, neck, and chest

   Right lymphatic duct – right
    side of body, above diaphragm

   Lymphodema (edema) –
    blockage of lymph drain
    Lymphocytes
   25% of circulating wbc
   T cells – thymus dependent (80% circulating
    lymphocytes)
      Cytotoxic T cells – attack foreign cells or body cells
       infected w/ virus
      Helper T cells – stimulate T cells and B cells
      Suppressor T cells – inhibit T cells and B cells
   B cells-bone marrow derived (10-15% circ. Lymphocytes)
      Plasma cells – secrete antibodies (immunoglobulins)
      Antibodies bind to antigens
   NK cells natural killer cells (5-10% circulating
    lymphocytes)
      Attack foreign cells, viral infected cells, and cancer cells
           Lymphopoeisis

   Lymphopoesis – lymphocyte
    production and development
   80% last 4 years…some last 20
    years or more!
   Hemocytoblasts (bone marrow)
       B cells and NK stem cells
        remain in bone marrow
       T cell stem cells migrate to
        thymus
   Enter blood stream and retain
    ability to divide and produce
    daughter cells of same type
    Lymphoid Nodules
 Size can increase or decrease
  depending on number of lymphocytes
 Tonsils, Appendix, Peyers patches
  (wall small intestines)
 If unable to destroy bacteria/viral
  invaders… becomes infected
           Lymphoid Organs
   Lymph Nodes
        Filter and purify lymph before enters
         venous system
        Detects and removes antigens
        Stimulates T cells and B cells initiating
         immune response
        Lymphomas – cancer arising from
         lymphocytes
   Thymus
        Decrease in size after puberty
        T cell production and maturation
   Spleen
        5” long on left side, deep red
        Filters blood, removes abnormal blood
         cells and initiates B cell and T cell
         responses to antigens
        Macrophages identify and engulf damaged
         or infected cells
Non-Specific Defenses
   Physical Barriers
        Epithelium, hair, secretions, acid, enzymes
   Phagocytes
        1st line of cellular defense – removes debris and pathogens
        Microphages leave blood stream and enter peripheral tissues (neutrophils
         and eosinophils)
        Macrophages – sensitive to chems in surrounding fluids can be free or fixed
   Interferons
        Slow spread of viral infections
        Stimulate macrophages and NK cells
   Inflammation
        Initiated by mast cells releasing histamines and heparin
        Local swelling, heat, redness, and pain
        Slows spread of pathogens
        Incr. blood flow aids in tissue repair
        Necrosis – tissue destruction via lysosomes
        Pus – accumulation of dead cells and debris (abscess – accumulation of pus)
   Fever (>98oF)
        Pyrogens – proteins reset body's “thermostat”
        Incr. rate of metabolism
        Over 104oF damages CNS, nausea, hallucination, and convulsions
        Specific Defenses
   Immunity – respond to the presence of specific antigens
   Antigens – “non-self” substance that excites the immune
    system and stimulates a response
   Genes determine specificity
   T cells – cell mediated immunity
      Defend against abnormal cells
      Pathogens inside of cells
   B cells – antibody-mediated immunity
      Defend against antigens and pathogens in body fluids
      Antibodies (immunoglobulins) – bind to specific antigen, Y
       shape with 2 antigen binding sites
     Immune Response
    (antibody mediated)
 B cell binds w/antigen…becomes
  activated and produces clones
 B cell clones

 Plasma cells – secrete antibodies (2,000
  per sec!)… reaches peak 10 days
 Memory B cells – continue to circulate,
  and can speed process to 2-3 days if
  recognizes an “old enemy”
          Immune Response (cell
          mediated)
   T cells cannot bind to “free” antigen
   Macrophages and B cells must present antigen to T cells
   Once T cell binds to “presented” antigen
      Killer (cytotoxic) T cells
         • Binds to target cell and inserts a toxic chem… target cell ruptures
       Helper T cells
         • Recruit other cells to fight invaders
         • Stimulates B cells to increase production of antibodies
         • Simulates Killer T cells to multiply
       Suppressor T cells
         • Release chems to suppress B and T cell activity
         • Most T cells enlisted to fight die w/in a few days
         • Some remain as memory cells to respond quickly to subsequent
           invasions
        Properties of Immunity
   Specificity
       T cells and B cells target one specific antigen
   Versatility
       Millions different lymphocytes w/diff antigen
        receptors
   Memory
       1st exposure – lymphocytes divide to create
        “attack” cells and memory cells
       Response to 2o exposure to antigen is stronger
        than 1st
   Tolerance
       Doesn’t respond to normal “self” tissues or
        antigens
         Types of Immunity
   Innate – genetically determined
   Acquired – arises during life
       Active – appears after exposure to antigen
         • Naturally- continually induced as encounter “new” pathogens
           or antigens
         • Induced – stimulated under controlled conditions
             • Vaccine: dead/inactive pathogen that induces an immune
               response
       Passive – transfer of antibodies from another source
         • Naturally – mother to baby
             • Gestation – via placenta
             • Infancy – via breast milk
         • Induced – antibodies administered to fight infection or prevent
           disease after exposure

								
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