The other circulatory system

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The Lymphatic System and Immunity

• The other circulatory system

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Summary

• Lymphatic system
• Fluid
• Vessels
• Nodes and Nodules
• Organs
• Immune system
• Nonspecific
• Specific
• Cells
• Mechanisms

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Lymphatic System

• Function responsible for returning tissue fluid
  to the blood and for protecting the body against
  foreign material.
• Lymph is a specialized fluid which is formed in
  the tissue spaces interstitial fluid. Contains
  excess fluid and protein molecules that cannot
  enter or return through the capillary walls.

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Lymphatic System

• Lymphatic vessels
• Lymph capillaries blind ended vessels that are
  very permeable collect tissue fluids and
  proteins in the tissues.

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Lymphatic System

• Vessels contd
• Lymph venules then veins collect fluid from the
  capillaries.
• Ducts large vessels that drain the lymph into
  the blood in veins (subclavian) in the neck area.
• Right lymphatic duct
• Thoracic duct

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Lymphatic System

• Vessels
• Cisterna chyli enlarged pouch-like structure
  formed by the union of the lower body lymphatic
  vessels. Lower portion of the thoracic duct in
  the abdomen serves as a storage area for lymph
  that is moving toward its point of entry into the
  venous system.

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Lymphatic System

• Fluid is moving under low pressure and against
  gravity How?
• Smooth muscle in the walls of the larger vessels
  contracts and moves fluid upward.
• Skeletal muscle pump
• Pressures in thoracic cavity

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Lymphatic System

• Lymph Nodes
• Clusters of small encapsulated masses of
  lymphatic tissue located at strategic spots in
  the lymph system. They may be the size of a pin
  head or a lima bean.
• Lymph enters the node through afferent vessels
  (usually more than one) and leaves through a
  single efferent vessel.

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Lymphatic System

• Lymph Nodes
• Serve to filter and trap bacteria, cancer cells
  and other foreign material picked up by the
  lymphatic vessels. Fixed macrophages in the
  nodes phagocytize (eat) these particles.
• Fixed plasma cells produce antibodies in response
  to foreign material and these antibodies then
  circulate in the blood stream.
• Also produce lymphocytes and monocytes.

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Lymphatic System

• Lymph Nodes
• Significant groups cervical, axillary and
  inguinal.
• Clinical significance

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Lymphatic System

• Lymph Nodules
• Smaller masses of lymphatic tissue (not
  encapsulated) found just beneath the epithelium
  of all mucous membranes.
• Mucous membranes are located at openings to the
  environment respiratory, digestive, urinary and
  reproductive systems. Why is this a good spot
  for lymph tissue?

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Lymphatic System

• Special Lymph Nodules
• Peyers patches located in the small intestine.
• Tonsils located in the pharynx form a
  protective ring under the mucous membranes in the
  mouth and back of throat.
• Palatine
• Pharyngeal
• Lingual

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Lymphatic System

• Organs
• Thymus located inferiorly to the thyroid gland
  in the mediastinum. Produces T-lymphocytes
  (T-cells) and secretes thymosin and other
  hormones that stimulate their development.
• The thymus is critical to immunity in the fetus
  and infant.
• The thymus shrinks with age but is still active.

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Lymphatic System

• Spleen
• Largest lymphoid organ in the body located in the
  upper left quadrant of the abdomen, lateral to
  the stomach, just below the diaphragm.
• Functions

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Lymphatic System

• Spleen
• Functions
• Fixed macrophages, reticuloendothelial cells,
  phagocytize pathogens in the blood. Also
  phagocytize and destroy old RBCs producing
  bilirubin.
• Stores about 1 pint of blood hemorrhage
• Splenectomy?
• Liver and red bone marrow will compensate to
  remove old RBCs and lymph nodes and nodules will
  produce lymphocytes and monocytes, etc.

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Immune System

• Immunity the bodys ability to destroy
  pathogens or other foreign material and prevent
  further cases of certain infectious diseases.
• Types of Immunity

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Immunity

• Non-specific (innate) immunity - maintained by
  mechanisms that attack any abnormal substance
  that threatens the body general protection.
• Barriers Skin, mucous membranes (and mucus),
  cilia.
• Lysozymes in tears and saliva.
• SQ and areolar connective tissue WBC phagocytize
  bacteria.

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Immune System

• Specific immunity
• Includes protective mechanisms that confer very
  specific protection against certain types of
  invading materials.
• Involves memory when the body is attacked the
  first time a disease develops the next time no
  disease signs/symptoms develop i.e. the body is
  immune.

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Immune System

• Specific Immunity - Inherited
• Genetic, inborn immunity is the result of our
  genetic make-up, i.e. we do not get distemper and
  dogs dont get measles (species immunity).
• This type does not involve antibodies and the
  efficiency does not increase with subsequent
  exposures.

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Immune System

• Specific Immunity - Acquired
• Natural exposure to the causative agent is not
  deliberate.
• Active
• Passive

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Immune System

• Specific Immunity Acquired
• Artificial exposure to the causative agent is
  deliberate.
• Active - injection of the agent (vaccine) results
  in production of your own antibodies and memory
  cells.
• Passive injection of protective material
  (antibodies) that was developed by another
  individuals immune system (gamma globulins or
  immune globulins).

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Immune System - Cells

• Phagocytes neutrophils, monocytes and
  macrophages, derived from bone marrow, carry out
  ingestion and digestion of foreign cells or
  particles.
• Monocytes develop into macrophages.
• Macrophages some wander and some are fixed
  example Kupffers cells in the spaces between
  liver cells.

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Immune System - Cells

• Lymphocytes most numerous cells of the immune
  system responsible for antibody production
• T-cells produced in the bone marrow and thymus
  of the embryo. They mature in the thymus and
  migrate to the spleen, lymph nodes and nodules.

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Immune System - Cells

• Lymphocytes
• B-cells produced in the bone marrow
• When activated by an antigen, they become plasma
  cells that produce antibodies.
• They also can become memory cells that remain in
  reserve until a stimulus by the same antigen is
  repeated and then produce antibodies.

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Immune System Cells

• Lymphocytes
• Natural Killer Cells (Killer T-cells) smaller
  in number but can attack many types of pathogens
  and tumor cells. Formed from activated T-cells.
  Mechanism disrupt cell membranes of foreign
  cells.

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Immune System - Cells

• Review Definitions
• Antigen chemical markers that identify cells.
  Each cells has its own set of markers.
• Antibodies (immune or gamma globulins)
• Proteins produced by plasma cells in response to
  foreign antigens each one is specific for a
  certain antigen.
• Mechanism When bound to an antigen they cause
  agglutination (clumping) of the material.
• Also the mechanism for allergic responses.

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Mechanisms of Immunity

• Recognition of an antigen as foreign
  accomplished by macrophages and helper T-cells.
• Foreign antigen is phagocytized by a macrophage.
• Macrophage presents antigen material on its cell
  membrane.
• Helper T-cell is exposed to this part of the
  macrophage membrane and becomes sensitized.

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Mechanisms of Immunity

• Once an antigen has been recognized, the
  activated helper T cells initiate one or both
  immune mechanisms.
• Cell Mediated Immunity
• Humoral Immunity

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Mechanisms of Immunity

• Cell- mediated Immunity no antibody produced
• T-cells activated by foreign material form memory
  T-cells and killer (cytotoxic) T-cells.
• Memory cells will remember the specific antigen
  and become active if it enters body again.
• Killer T-cells chemically destroy foreign
  antigens (disrupt cell membranes).

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Mechanisms of Immunity

• Cell-mediated immunity
• T-cells contd
• Killer T-cells also produce cytokines chemicals
  that attract macrophages to an area to promote
  phagocytosis.
• Suppressor T-cells stop the immune response once
  the antigen has been destroyed.

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Mechanisms of Immunity

• Humoral Immunity involves production of
  antibodies.
• Recognition of foreign antigen by macrophages and
  activation of helper T-cells.
• Sensitized helper T-cell presents antigen to
  B-cells
• B-cells activate the memory B cells and plasma
  cells. The plasma cells then produce antibodies.

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Mechanisms of Immunity

• Humoral Immunity
• Antibodies bind to antigens forming an
  antigen-antibody complex.
• Complex is labeled for phagocytosis by
  macrophages opsonization.
• Complement fixation complement binds to complex
  and is destroyed by lysis.

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