The Lymphatic System and Immunity

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The Lymphatic System and Immunity Powered By Docstoc
					The Lymphatic System
and Immunity




11/23/2011   Bio 111-73   1
Functions of LS
  Absorption of excess tissue
  fluid
  Absorption of fat from
  intestines
  Defense of body from infection
  and disease



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Structures of the LS
I. Lymphatic vessels
II. Lymph Nodes
III. Lymphoid organs




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I. Lymphatic Vessels
     Carry Lymph




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I. Lymphatic Vessels
     Similar to veins
        Contain valves
        From tissues
         lymphatic
         capillaries take
         fluid back toward
         Vena Cava


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Lymph
  Interstitial fluid (tissue fluid)
  forced out of capillaries
  Resembles plasma but with
  less proteins




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Lymph nodes
  Also sometimes referred to as lymph glands, lymph
  nodes are small rounded or bean-shaped masses of
  lymphatic tissue surrounded by a capsule of connective
  tissue.
  Lymph nodes filter the lymphatic fluid and store special
  cells that can trap cancer cells or bacteria that are
  traveling through the body in the lymph fluid.
  The lymph nodes are critical for the body’s immune
  response and are principal sites where many immune
  reactions are initiated.
  During a physical examination, doctors often look for
  swollen lymph nodes in areas where lymph nodes are
  abundant, including the neck, around the collarbone, the
  armpit (axilla), and the groin.
             http://www.medterms.com/script/main/art.asp?articlekey=4213
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Lymphoid organs
  Have a surrounding fibrous
  capsule
     Separates it from surrounding
      tissue
     Filters lymph fluid

   Examples
     Lymph nodes
     Thymus

     spleen
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III. Lymphoid Tissues
    Made of Connective tissue and
    lymphocytes
    2 types
     A. Lymphoid Nodules
     B. Lymphoid organs




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Lymphoid nodule
  Filters surrounding tissue fluid
  not lymph
  Examples
       Tonsils
          Pharyngeal
          Palatine
          lingual


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Thymus
    T Cell Maturation
    Produces hormones
       Thymosins




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Spleen
  Located near stomach
  Removes abnormal blood cells
  Stores iron from recycled RBCs
  Monitors and responds to
  pathogens and foreign antigens
  in body


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Lymphocytes
   Make up 25% of WBCs in blood
   Most found outside of BVs
   3 main types
     T cells (T for thymus)
     B cells (B for Bone marrow)

     NK cells (natural killers cells)




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Lymphocytes




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T cells
  Originate in Bone Marrow
  Mature in Thymus
  Make up 75% of lymphocytes
  Several different types of
T cells with different functions


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B cells
  Originate in BM
  Mature in BM
  Make up 12.5% of lymphocytes
  Mature into plasma cells which
  secrete soluble proteins, called
  antibodies or immunoglobulins


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NK cells
  Originate in BM
  Make up 12.5% of lymphocytes
  Readily attack foreign cells,
  infected cells and abnormal cells
  Responsible for immunological
  surveillance


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Defense Mechanisms
   Specific
   Non-specific (general)




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Non-specific Defense
  Present at birth
  Do not discriminate between
  one threat or another
  Deny entrance or limit the
  spread of microorganisms or
  other environmental hazards

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Non-specific Defense
   Physical barriers
   Phagocytic cells
   Immunological surveillance
   Interferon
   Complement
   Inflammation
   Fever

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Physical barriers
   Skin
   Hair
   Tears
   Sweat and sebaceous galnds
   Mucus
   Stomach acid
   Urine
   Reproductive secretions
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Phagocytic cells
   Engulf other cells
   2 classes
     Microphages: neutrophils and
      eosinophils
     Macrophages:monocytes




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Immunological Surveillance
  NK cells are sensitive to
  changes in cell membranes,
  usually associated with
     Cancer cells
     Viral infections




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Immunologically Important
Proteins
    Interferon
    Complement




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Interferon
  Released by activated
  lymphocytes and Ms or by
  viral infected cells
  Causes cells to make proteins
  that interfere with viral
  reproduction

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Complement
  Supplements the actions of
  Abs
  Enhances phagocytic action
  Destroys cell membranes
  Promotes Inflammation


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Inflammation
  Localized tissue response to
  injury
  Symptoms:
     Swelling
     Redness

     Heat

     pain




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Inflammation
  Produced by any stimulus that
  damages cells or connective tissue
  Mast cells found in CT releases
  histamine and heparin to initiate
  inflammation
  Stops pathogens from leaving “scene
  of the crime”
  Promotes their removal and repair of
  damage

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Fever
   Continued body temp > 99oC
   Body temp controlled hormonally
   Harmful
       Too high may damage
        tissues/organs
   Beneficial
       promotes activity of immune cells


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Specific Defense
  Provides protection from
  threats on individual basis
  Also called IMMUNITY




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Specific Defense (immunity)
  Resistance to injuries/disease
  caused by specific antigens or
  chemicals (toxins)
  2 types
       Innate
          Inherited or inborn immunity
       Acquired
          Passive
          Active
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Passive Acquired Immunity
  Short term
  Receipt of antibodies
  produced by someone else
     Injected
     Fetal development or breast

      feeding

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Active Acquired Immunity
   Long term
   Results from exposure to Ag
   2 origins
     Accidental/natural
     Artificial/vaccination




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Immune response
  GOAL: to destroy or inactivate
  pathogens, abnormal cells or
  foreign molecules (toxins)
  RESULT: immunity
  Types of response:
     Cell-mediated
     Ab-mediated (humoral)




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T cell Immunity
  Once activated, cells divide
  and differentiate into 4 types:
  Cytotoxic T cells
  Memory T cells
  Suppressor T cells
  Helper T cells

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B cell Immunity
  Activated by exposure to Ag or
  chemicals released by Helper T
  cells (Interleukins)
  Cells divide and differentiate into
  2 types of cells:
     Plasma Cells
     Memory B cells




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      Primary vs Secondary
        Immune response
   Primary
     Results from initial exposure to
      Ag
     Takes 7-10 days for response

     Response (abs, cells, etc) peaks

      after several weeks


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      Primary vs Secondary
        Immune response
   Secondary
     Respnse that results from 2nd
      exposure to same Ag
     Tales 1-3 days for response to
      peak
     Stronger and longer response




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             Primary vs Secondary




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