Ch 14

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					      Ch 14

The Lymphatic System
(The Immune System)
                      Ch 14
   4 types of common invaders that cause infection
    and disease:
   1) viruses
   2) bacteria
   3) fungi
   4) parasites (certain protists)

   They are called PATHOGENS
                    Ch 14

   Viruses are technically non-living because
    they lack cellular structure and exist only
    within a host cell. They consist only of
    nucleic acid and protein.
   The lymphatic system works after the
    barriers of the integumentary system have
    been compromised.
                    Ch 14
   4 components of the Lymphatic System:
    1) Vessels
    2) Fluid (lymph)
    3) Lymphocytes (specialized cells for
    defense)
    4) Lymphoid tissues (lymphoid nodules)
    and organs (tissue example: tonsils; organ
    examples: lymph nodes, spleen, thymus)
                    Ch 14
   3 functions of LS:
   1) production, maintenance, and
    distribution of lymphocytes
   2) the return of fluid and solutes from
    peripheral tissues to the blood
   3) the distribution of hormones, nutrients,
    and waste products from their tissues of
    origin to the general circulation
                      Ch 14
   LYMPHATIC VESSELS (lymphatics):
   -they carry lymph from the peripheral tissue to
    the venous system
   The smallest vessels are called Lymphatic
    Capillaries. From there, lymph flows into larger
    vessels that lead towards the trunk. (These walls
    of these vessels are similar to veins; they also
    have valves)
   They empty into 2 large Lymphatic ducts.
                      Ch 14
   Lymphatic Ducts:
   The Thoracic Duct collects lymph from the lower
    abdomen, pelvis, and lower limbs, and from the
    left half of the head, neck, and chest.
   The smaller Right Lymphatic Duct delivers lymph
    from the right side of the body above the
    diaphragm. It empties into the right subclavial
    vein.
                     Ch 14
   LYMPHOCYTES: account for about 25% of
    the circulating white blood cell population.
    (Most lymphocytes are non-circulating=
    found within lymphoid organs and tissues)
   3 classes of lymphocytes:
   1) T cells
   2) B cells
   3) NK cells
                       Ch 14
   T Cells: (80% of circulating lymphocytes)
   Cytoxic T cells directly attack foreign cells or
    body cells infected by viruses
   Helper T cells stimulate the activity of both T
    cells and B cells
   Suppressor T cells inhibit both T cells and B cells
   (Helper and Suppressor T cells are called
    REGULATORY T CELLS)
                     Ch 14
   B Cells: (derived from bone marrow;
    make up 10-15% of circulating
    lymphocytes)
   B cells can differentiate into PLASMA
    CELLS, which produce and secrete
    antibodies (immunoglobins)
   Antibodies bind to specific targets called
    antigens, which are usually pathogens.
                     Ch 14

   NK Cells: (“natural killer cells”; remaining
    5-10% of circulating lymphocytes)
   They attack foreign cells, normal cells
    infected with viruses, and cancer cells that
    appear in normal tissues.
                    Ch 14
 Lymphocyte production and development is
  called lymphopoiesis (occurs in the bone marrow
  and thymus).
 During development in the bone marrow,
  lymphoid stem cells are produced to carry on
  one of two roles:
 1) one group remains in the marrow to generate
  B cells and NK cells
 2) the other group migrates to the thymus to
  produce T cells (thymosins control this)
               Ch 14- Part 2

   Lymphoid Nodules- masses of lymphoid
    tissue not surrounded by a fibrous
    capsule; found beneath the epithelia lining
    of various organs of the respiratory,
    digestive, and urinary systems.
   The lymphocytes in a lymphoid nodule are
    not always able to destroy bacterial or
    viral invaders. (tonsillitis, appendicitis…)
                  Ch 14

   Lymphoid Organs- separated from
    surrounding tissues by a fibrous
    connective-tissue capsule
    1) Lymph nodes
    2) Thymus
    3) Spleen
                    Ch 14

   Lymph nodes- they filter and purify the
    lymph before it reaches the venous
    system; they are small, oval organs that
    can be up to 1 inch thick in diameter.
   Thymus- pink gland that lies posterior to
    the sternum; site of T cell production
    (thymosins control this process)
                        Ch 14
   Spleen- adult spleen contains the largest
    collection of lymphoid tissue in the body.
   It is about 5 in. long and is located to the left of
    the stomach. (deep red in color)
   It function is similar to that of the lymph nodes,
    but instead of filtering lymph, it filters blood. It
    removes abnormal blood cells, and initiates the
    responses of the T and B cells. It also stores iron
    from recycled RBCs.
                       Ch 14
   LS has 2 roles: non-specific defenses and
    specific defenses
   Non-Specific D: present at birth; responses are
    the same regardless of the type of invading
    agent; include physical barriers, immunological
    surveillance, inflammation, and fever (NK cells)
   Specific D: protect against particular threats;
    develop after birth (T and B cells)
                         Ch 14
   2 types of immunity:
   1) Innate Immunity- genetically determined; born with
    this (ex. Humans do not get sick with the same diseases
    as goldfish)
   2) Acquired Immunity- arises by active or passive means
    after birth.
   Active vs. Passive: active appears after exposure to an
    antigen, resulting in an immune response (vaccine);
    passive is produced by the transfer of antibodies to an
    individual from another source. (rabies shot)
                      Ch 14
   4 General Properties of Immunity:
   1) specificity
   2) versatility
   3) memory
   4) tolerance

   In an Immune Response, T cells are usually
    activated before B cells
                  Ch 14

 T cells divide into the following:
 Cytoxic T cells, Helper T cells, Memory T
  cells, Suppressor T cells
 (memory cells come from Helper T cells)

B cells also produce memory cells
                    Ch 14

   5 classes of antibodies (Immunoglobins):
   IgG, IgM, IgA, IgE, IgD

   IgG is the largest and most diverse class
    of antibodies (resist many viruses,
    bacteria, and bacterial toxins)
                    Ch 14

   Primary response if the initial response to
    an antigen exposure.
   Secondary response reflects the presence
    of large numbers of memory cells that are
    already primed for the arrival of the
    antigen.
                       Ch 14
   Key hormones of the IS:
   Interleukins (IL), Interferons, Tumor Necrosis
    Factors (TNFs)
   IL- most diverse and important messengers of
    the IS; increase lymphocyte activity and
    antibody production
   Interferons- released by infected cells to make
    neighbors more resistant; attract NK cells; can
    help some cancers
   TNFs- slow tumor growth and kill tumor cells
                      Ch 14
   Immune Disorders:
   Autoimmune Disorders- immune response
    mistakenly targets normal body cells and tissues
    (rheumatoid arthritis)
   Immunodeficiency Diseases- the immune
    response gets blocked some way (AIDS- helper
    T cells are targeted for destruction)
   Allergies- inappropriate or excessive immune
    responses to antigens
                    Ch 14

   Aging and the IS:
   T cells become less responsive to antigens
   Number of helper T cells is reduced
   B cells are less responsive
   Immunological surveillance declines
    (results in more cancers)
   More viruses and bacterial infections

				
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posted:4/19/2013
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