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					Lymphatic System
I. Lymphatic Network
      A. Functions
        1. Fluid Balance - Transport lost fluid (lymph) back to
      the circulatory system.

       2. Defend the body against pathogens.

       3. Fat absorption.
B. Lymphatic Capillaries
       1. Microscopic dead end tubes found between cells.
               (Not found in the brain, spinal cord, bone,
       2. Similar to blood capillaries.

       3. Loosely Joined endothelial cells

C. Lymphatic Vessels
       1. Same three layers

D. Lymph Nodes
E. Lymphatic Trunks & Collecting
   1. Trunks – merging vessels.

  2. Collecting Ducts – One duct
  before returning back to the
       a. Thoracic Duct – left side
       of the head, neck, thorax,
       left arm, entire lower
               1. Empties into left

              2. Originates from
              Cysterna Chyli.

      b. Right Lymphatic
      Duct – Right side of
      the head, neck, right arm

              1. Empties into
              right subclavin
F. Lymph Movement
   1. Formation – Interstitial fluid formed by movement of
   blood plasma out of the capillary bed.

       a. Increased interstitial fluid, increase pressure forces
       lymph pores open – fluid flows in.

  2. Movement

       a. Force of interstitial fluid entering vessel

       b. Similar to veins:

              1. Valves
              2. Skeletal movement.
II. Lymphatic Organs
    A. True organs
         1. Lymhpoid tissue containing lymphocytes (white blood

  B. Lymph Node
       1. Cervical – neck
       2. Axillary – armpit
       3. Inguinal – groin
       4. Deep with in

  C. Structure
       1. Afferent Lymphatic Vessels – Towards.
       2. Hilus- Concave margin
       3. Efferent Lymphatic Vessels – Away.
       4. Fibrous Capsule
       5. Cortex - Outer
       6. Medulla – Inner
       7. Trabeculae -Extensions
       8. Lymph Nodules – Main structure of lymph nodes, gathering of
D. Node Function
     1. Filter

E. Spleen
      1.Largest lymphatic organ
      2. Fibrous Capsule – outer,
      3. Red Pulp – Large number of red
      blood cells.
      4. White Pulp – Large number of
      white blood cells.

F. Thymus
      1. Only active during immune
      2. T cell production
      3. Capsule
      4. Cortex
      5. Medulla

G. Tonsils
     1. Two Palatine – Back of palate
     2. Two Pharyngeal –Upper throat
     3. Two Lingual – Base of tongue

H. Peyer’s Patches
     1. Clusters located along the small
III. Defense Mechanisms
  A. Immune system has ability to recognize foreign
  particles (pathogens &/or toxins).

  B. Major Histocompatibility Complex (MHC) –
  markers that can distinguish between self & non

  C. Two types of defense.
      1. Non Specific (innate)
      2. Specific (adaptive)

  D. Type of responses
      1. Antibodies
E. Innate or Non Specific Mechanisms – Defends against all
types of pathogens & has the same response.
     1. Mechanical barriers
            a. Skin
            b. Mucus membranes

    2. Phagocytosis – Cellular Eating
           a. Monocytes
           b. Neutrophils
           c. Macrophages
           d. Natural Killer Cells
                  Punches holes
                  in cells.
           e. Swelling
                  Mast cells
3. Chemical Mediators
    a. Complement
         1. 20 proteins
         2. Helps enhance phagocytes

   b. Interferons
         1. Secreted by infected cells to
         stimulate neighboring cells to
         produce antibodies.
4. Inflammation
      a. Edema
           - vasodilation
            - chemical attraction
            of phagocytes

      b. Local inflammation
      c. Systematic inflammation
F. Specific Mechanisms – Adaptive Response
   1. Ability to recognize a specific antigen or toxin.
        a. Antigen recognition
        b. Proliferation

  2. Components of Immunity

       a. Antigen – any substance that causes an immune

       b. Antibody (Ab) (gamma globulins or
       immunoglobulins)– protein molecule that is produced
       in response to a specific antigen.
               - 2 heavy chains
               - 2 light chains

       c. AB + Antigen = Antigen-Ab complex
d. Five Classes of Ab
             1. IgG – Most common - small
             2. IgA – protection on body surfaces
             3. IgM – First to be produced – large
             4. IgD – Antigen-antibody receptors
             5. IgE – Allergies (bind to mast cells)

e. Variable region – made for specific antigens
f. constant region – same between all antibodies
Specific Defense
e. Lymphocytes – come bone marrow
        1. B-cells – develop in bone marrow
                  a. Memory
                  b. Plasma – AB

        2. T-cell – develop in thymus
                  a. Killer T cells – destroy’s infected cell
                  b. Helper T cells – stimulates immune system
                  c. Suppressor T cells – stops the body’s response
                  d. Memory T cells – remembers for future infections
3. Cell Mediated – T cell

  a. Kills invaded & infected

  b. Macrophage identified an
  antigen, phagocytized it, &
  processed it.

  c. Process antigen is placed
  on macrophage surface & is
  presented to the T-cells.

  d. Activates the T-cells.
Cell Mediated Response
4. Humoral Immunity – Ab Response
    a. Macrophage identified an antigen,
    phagotized it, & processed it.

   b. Process antigen is placed on
   macrophage surface & is presented
   to the B-cells.

   c. Activates the B-cells with the help
   of Helper T-cells.

   d. Grows & multiple into memory B
   cells (immunization) & Plasma cells

   e. AB production takes 3-5 days,
   peaks in 3 weeks.

   f. AB binds to antigen surface
   forming the antigen-Ab complex

   g. Labeled for destruction for natural
   killer cells.
Humoral Response
 Effect of
Specific response review
G. Allergic Response – Type of humoral resposne.
   1. IgE Ab is released into blood in response to the allergen.

  2. Comes into contact with the mast cell (concentrated in
  skin & mucus layer).

  3.Mast cell stores histamines.

  4. IgE + Mast cell = release of histamine (causes

       Ex. Hives & asthma
           Systemic anaphylaxis

5. Immediate hypersensitivities – hay fever, asthma
6. Delayed hypersensitivities – poison ivy, soaps, cosmetics
H. Acquired Immunity
   1. Persons ability to mount a defense.
   2. Two Types

        1. Naturally acquired
                a. Active – develop after exposure.
                         ex- chicken pox, flu, measles.
                b. passive – passed from 1 person to another.
                         ex- Polio, rubella – mother to baby by
                         placenta or breast milk.

        2. Artifically Acquired - Vaccine
                 Killed or weaken virus that causes an
                 immune response with out the symptoms.

                a. Active – Lifelong
                         ex. polio, measles

                b. Passive – Short term
                        ex- rabies, hepatitis, tetanus, snake
IV. Homeostasis
    1. Recycling valuable fluids.
    2. Defense against diseases.
V. Immunodefiency
   1. WBC are reduced which reduces the body’s ability to defend
         a. Attacked by pathogens.
         b. Low level production.

               1. SCID – Severe Combined Immundeficiency
                       a. Born without the ability to produce active
                               B & T cells.
                       b. Treatment – bone marrow transplant.

               2. AIDS
                         a. Caused by HIV virus
                         b. Destroy’s the helper T cells – body never
                         knows it is getting invaded by other
                         c. ID in US – 1981

               3. Hodgkins – Cancer
                      a. large multinucleated cell in affected
                      lymphoid tissue
                      b. 15-38 & over 50 yrs old.

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