Lymphatic System and Immunity:

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Lymphatic System and Immunity
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Lymphatic System

• Lymph
• Lymphatic vessels
• Lymphatic tissue
• Lymphatic nodules
• Lymph nodes
• Tonsils
• Spleen
• Thymus

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Functions of the Lymphatic System

• Fluid balance
• Excess interstitial fluid enters lymphatic
  capillaries and becomes lymph
• Fat absorption
• Absorption of fat and other substances from
  digestive tract
• Defense
• Microorganisms and other foreign substances are
  filtered from lymph by lymph nodes and from blood
  by spleen

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Lymphatic Vessels

• Carry lymph away from tissues
• Lymphatic capillaries
• More permeable than blood capillaries
• Epithelium functions as series of one-way valves

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Lymphatic Vessels

• Lymphatic capillaries join to form
• Lymphatic vessels
• Have valves that ensure one-way flow
• Lymph nodes Distributed along vessels and filter
  lymph
• Lymphatic trunks Jugular, subclavian,
  bronchomediastinal, intestinal, lumbar
• Lymphatic ducts Right and thoracic which connect
  to large veins

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Lymph Drainage Into Veins
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Lymphatic Tissue and Nodules

• Lymphatic tissue
• Consists mainly of lymphocytes
• Encapsulated or not
• Lymphatic nodules
• Numerous in loose connective tissue of digestive
  (Peyers patches), respiratory, urinary,
  reproductive systems

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Tonsils

• Large groups of lymphatic nodules in nasopharynx
  and oral cavity
• Provide protection against bacteria and other
  harmful material
• Groups
• Palatine
• Pharyngeal
• Lingual

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Lymph Nodes

• Organized in cortex and medulla
• Substances removed by phagocytosis or stimulate
  lymphocytes or both
• Only structures to filter lymph
• Afferent and efferent vessels

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Spleen

• Located in left superior side of abdomen
• Can be ruptured in traumatic abdominal injuries
  resulting in bleeding, shock, death
• Blood flows through at 3 different rates
• Fast (most), slow, intermediate
• Functions
• Destroys defective RBCs
• Detects and responds to foreign substances
• Limited reservoir for blood

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Spleen
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Thymus

• Located in superior mediastinum
• Divisions Cortex and medulla
• Site of maturation of T cells

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Immunity

• Ability to resist damage from foreign substances
  as microorganisms and harmful chemicals
• Categories
• Innate or nonspecific resistance
• Mechanical mechanisms Prevent entry or remove
  microbes
• Chemical mediators Promote phagocytosis and
  inflammation
• Cells Involved in phagocytosis and production of
  chemicals
• Adaptive or specific immunity
• Specificity Ability to recognize a particular
  substance
• Memory Ability to remember previous encounters
  with a particular substance and respond rapidly

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Innate Immunity Cells

• White blood cells
• Most important cellular components of immune
  system
• Methods
• Chemotaxis
• Phagocytosis
• Neutrophils
• Phagocytic and first cells to enter infected
  tissue

• Macrophages
• Monocytes that leave blood, enter tissues
• Large phagocytic cells
• Basophils and mast cells
• Promote inflammation
• Eosinophils
• Reduce inflammation
• Natural killer cells
• Lyse tumor and virus-infected cells

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Inflammatory Response
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Inflammatory Response

• Tissue injury regardless of type can cause
  inflammation
• Response initiated by chemical mediators that
  produce vasodilation, chemotactic attraction,
  increased vascular permeability
• Types
• Local Symptoms are redness, heat, swelling,
  pain, loss of function
• Systemic Symptoms are increase in neutrophil
  numbers, fever and shock

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Adaptive Immunity

• Involves the ability to recognize, respond to,
  and remember a particular substance
• Stimulants
• Antigens Large molecules
• Foreign Not produced by body, introduced from
  outside
• Self-antigens Produced by body
• Haptens Small molecules and capable of combining
• Types
• Humoral or Antibody-mediated B cells
• Cell-mediated T cells

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Origin and Developmentof Lymphocytes

• B and T cells
• Originate in red bone marrow
• Move to lymphatic tissue from processing sites
  and continually circulate
• Clones are small groups of identical lymphocytes

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Origin and Developmentof Lymphocytes

• Positive selection
• Ensures survival of lymphocytes that react
  against antigens
• Negative selection
• Eliminates lymphocytes that react against
  self-antigens
• Primary lymphatic organs (red bone marrow,
  thymus)
• Where lymphocytes mature into functional cells
• Secondary lymphatic organs
• Where lymphocytes produce an immune response

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Antigenic Determinants

• Antigenic determinants
• Specific regions of a given antigen recognized by
  a lymphocyte
• Antigenic receptors
• Surface of lymphocyte that combines with
  antigenic determinant

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Major Histocompatability Complex (MHC)

• Most lymphocyte activation involves glycoproteins
  of cell surfaces called MHC molecules
• Class I molecules display antigens on surface of
  nucleated cells, resulting in destruction of
  cells
• Class II molecules display antigens on surface of
  antigen-presenting cells, resulting in activation
  of immune cells

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Antigen Processing
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Costimulation
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Proliferation of Helper T Cells
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Proliferation of B Cells
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Lymphocyte Inhibition

• Tolerance To prevent the immune system from
  responding to self-antigens
• Provoked by
• Deletion of self-reactive lymphocytes
• Preventing activation of lymphocytes
• Activation of suppressor T cells

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Antibody-Mediated Immunity

• Antibodies or Immunoglobulins (Ig)
• Classes IgG, IgM, IgA, IgE, IgD
• Structure
• Variable region Part that combines with
  anitgenic determinant of antigen
• Constant region Responsible for activities

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Actions of Antibodies
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Antibody Production
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Cell-Mediated Immunity

• Antigen activates effector T cells and produces
  memory T cells
• Cytotoxic T cells lyse virus-infected cells,
  tumor cells, and tissue transplants
• Cytotoxic T cells produce cytokines, which
  promote phagocytosis and inflammation

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Interactions and Responses ofInnate and Adaptive
Immunity
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Acquired Immunity

• Active natural immunity
• Results from natural exposure to an antigen
• Active artificial immunity
• Results from deliberate exposure to an antigen
• Passive natural immunity
• Results from transfer of antibodies from a mother
  to her fetus or baby
• Passive artificial immunity
• Results from transfer of antibodies (or cells)
  from an immune animal to a nonimmune one

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Ways to Acquire Adaptive Immunity
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Effects of Aging

• Little effect on lymphatic system
• Decreased ability of helper T cells to
  proliferate in response to antigens
• Decreased primary and secondary antibody
  responses
• Decreased ability of cell-mediated immunity to
  resist intracellular pathogens

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Immune System Problems

• Hypersensitivity reactions
• Autoimmune disease
• Severe combined immunodeficiency disease (SCID)
• Transplantation
• Acute rejection
• Chronic rejection

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Blood
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