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The Lymphatic System by linzhengnd


									Honors Anatomy & Physiology
             Dawn McMahon
A.    Lymph
 1.       Defined as: a specialized fluid formed
          in the tissue spaces that returns excess
          fluid and protein molecules to the
     a.    The circulatory system functions to bring
           nutrients to and remove wastes from cells
     b.    This occurs in capillary beds
     c.    Lymph is made up of the substances that
           cannot pass through the capillary wall and
           need another route back to the blood
     d.    It is transported through lymphatic vessels
2.    Lymph is formed through a specialized
      process in the interstitial fluid
 a.         Blood plasma filters out of the capillaries
            into the spaces between the tissue cells
            because of the pressure generated by the
            pumping action of the heart
      i.     Here, the fluid is known as interstitial
      ii.    AKA tissue fluid
 b.         Much of this fluid goes back into the blood
            via capillary membranes
 c.         What is left over is called the lymph
3.    The newly formed lymph enters into
      tiny vessels in the tissue spaces called
      lymphatic capillaries
 a.         These capillaries allow the excess tissue
            fluid and other materials to leave the tissue
      i.     This process is to help keep fluids moving
             through the body
      ii.    This helps to maintain homeostasis by helping
             to move the ‘good things’ in and the ‘bad
             things’ out of the cells
b.        Lymphatic capillaries vs. blood capillaries
     i.   They are both made of simple squamous
          epithelium known as endothelium
     ii. The endothelium in blood capillaries is too
          tightly packed together, keeping excess fluid
          and protein molecules out
     iii. The endothelium in lymph capillaries is more
          loosely packed, allowing these materials to
          pass through
     iv. Blood capillaries also move in a circular
          motion while lymphatic capillaries go only
          one way
4.    Like the circulatory system, lymphatic
      capillaries flow into larger vessels
 a.         They first drain into lymphatic venules
 b.         From here lymph travels to lymphatic veins
 c.         The veins drain into two terminal vessels:
      i.     Right lymphatic duct – receives lymph from
             upper right quadrant and empties into right
             subclavian vein
      ii.    Thoracic duct – drains lymph from other ¾ of
             body into left subclavian vein; largest
             lymphatic vessel in the body
B.        Lymph Nodes
     1.        Lymph passes through these filtering clusters
               as it moves toward the thoracic or right
               lymphatic duct
          a.    The lymph is emptied of bacteria, cancer cells
                and damaged tissue cells
          b.    This prevents these harmful cells from returning
                to the blood
     2.        Lymph enters nodes through four afferent
               lymph vessels and leaves, filtered, through
               one efferent lymph vessel
3.        A common problem with lymph nodes
          involves their location
     a.    A large cluster of lymph nodes is found in the
           armpit, near the breast
     b.    In some cases, women with breast cancer will find
           that their cancer has spread to the lymph nodes,
           which then results in the cancer spreading
           throughout the lymph vessels in that area
     c.    This transport of cancer cells is dangerous and
           oftentimes fatal
A.    Thymus
 1.       Defined as: a small endocrine gland
          located in the mediastinum
     a.    It extends upward in the midline of the
     b.    It is composed of lymphocytes in an
           epithelial framework
     c.    At its largest, during puberty, the thymus
           weighs only 35 – 40 grams
2.    The thymus is highly functional in
 a.         A source of lymphocytes before birth
 b.         Important in the development of
            specialized circulating lymphocytes called T
      i.     T cells develop under the influence of
             hormones from the thymus
      ii.    T cells are crucial in immunity and travel to
             the spleen, tonsils, lymph nodes, and other
             lymphatic tissue
3.    The thymus is most active early in
 a.    It is then replaced largely by fat and
       connective tissue, with only a bit of
       functional tissue remaining
 b.    This process is called involution
B.    Tonsils
 1.       Defined as: masses of lymphoid tissue
          serving as the first line of defense
          from the exterior
     a.    They are located in a protective ring
           under the mucus membranes in the mouth
           and back of the throat
     b.    They help to protect against invading
           bacteria in and around the openings of the
           nasal and oral cavities
     c.    Because of their location, tonsils are
           subject to chronic infection and may be
           removed if necessary; tonsillectomy
2.    Three pairs of tonsils:
 a.    Palatine – on each side of the throat
 b.    Pharyngeal (adenoids) – near the posterior
       opening of the nasal cavity
 c.    Lingual – near the base of the tongue
C.    Spleen
 1.       Defined as: the largest lymphoid organ
          in the body
     a.    Located high in the upper left quadrant of
           the abdomen, lateral to the stomach
     b.    May contain more than 1 pint (500 mL) of
           blood at any time
 2.       Has many immunological functions
     a.    Uses filtration and phagocytosis to remove
           bacteria and foreign substances
     b.    Destroys worn out red blood cells
 c.    Salvages iron found in hemoglobin for
       future use
 d.    Serves as a reservoir for blood that can be
       returned to the circulatory system when
3.    It is susceptible to injury and life
 a.    Although protected by the ribs, the spleen
       can be injured through abdominal trauma
 b.    When ill, the spleen may be enlarge and
       thus, a larger target
 c.    If damaged and bleeding, a splenectomy
       may be necessary to stop the loss of blood
A.    The Immune System
     1. Defined as: the body’s defense system
        against disease
     2. Helps us to become immune to
        (possess the ability to resist) enemy
      a.   Protects us from disease-causing
           microorganisms that invade our bodies
      b.   Protects us from foreign tissue cells that
           may have been transplanted into our bodies
      c.   Protects us from our own cells when they
           have turned malignant or cancerous
B.    Nonspecific Immunity
     1.    Defined as: the protective mechanisms
           that provide immediate, generic
           protection against any bacteria, toxin,
           or other injurious particle
      a.    We are born with these nonspecific defenses
      b.    AKA innate immunity
     2.    Is maintained by mechanisms that
           attack any irritant or abnormal
           substance that threatens the internal
 3.    There are many types of nonspecific
       immune defenses in the body:
  a.    Skin and mucous membranes – external
        border from harmful substances
  b.    Tears – rinse harmful substances from the
  c.    Mucous – traps foreign material that may
        enter through the respiratory tract
  d.    Phagocytosis of bacteria by white blood
  e.    Inflammatory Response – results in redness,
        pain, heat, and swelling and promotes
        movement of WBCs to affected area
                      Bacteria enter tissue

                     Tissue damage occurs

                     Mediators are released

                     Increased blood flow
   Attraction of                                      Increased
      WBCs                   Increased                 vascular
                             number of               permeability
                        mediators at site
                        of tissue damage

No bacteria remain   Bacteria are contained,     Bacteria remain
                        destroyed, and
                                               Additional mediators
  Tissue repair                                      activated
B.    Specific Immunity
     1.    Defined as: the protective mechanisms
           that provide specific protection against
           certain types of bacteria or toxins
      a.    Involves memory and the ability to
            recognize and respond to certain harmful
      b.    Possesses the ability to adapt to newly
            encountered enemies
      c.    AKA adaptive immunity
 2.    Specific immunity is very selective
  a.        When the body is first attacked by
            particular bacteria or viruses, disease
            symptoms are likely to occur as the body
            fights to destroy the invaders
  b.        If the body is exposed a second time to the
            same invading organism, no serious
            symptoms occur
       i.     The organism is destroyed quickly
       ii.    The person is now ‘immune’ to that organism
       iii.   Immunity to one type of organism does not provide
              immunity to any other organism
 3.    Specific immunity is categorized by
       how the body is exposed to the
       harmful agent
  a.    Natural (accidental) vs Artificial
  b.    Active (own immune system) vs. Passive
        (others immune system)
  c.        Natural Immunity – exposure to the
            causative agent is not intentional; happens
            naturally in course of living
       i.    Active: A child develops measles and acquires
             immunity to a subsequent infection
       ii.   Passive: A fetus receives protection from the
             mother through the placenta, or an infant receives
             protection via the mother’s milk
  d.        Artificial Immunity – exposure to the
            causative agent is deliberate
       i.    Active: injection of the causative agent, such as a
             vaccine against polio, provides immunity
       ii.   Passive: injection of protective material
             (antibodies) that was developed by another
             individual’s immune system provides immunity
A.    Antibody
     1.    Defined as: a substance produced by
           the body that destroys or inactivates a
           specific substance that has entered
           the body
      a.        They are protein molecules normally
                already present in the body
      b.        They are characterized by a unique shape:
           i.    Contain concave regions called combining sites on
                 the surface
           ii.   These allow them to combine with antigens
B.    Antigen
     1.    Defined as: a substance that, when
           introduced into the body, causes
           formation of antibodies against it
      a.        They are often protein molecules imbedded
                in the surface membranes of invading or
                diseased cells such as microorganisms or
                cancer cells.
      b.        They are characterized by a unique shape:
           i.    Contain small regions on their surfaces shaped
                 specifically to fit into the combining sites of a
                 specific antibody molecule
           ii.   Antibodies and antigens fit together like a key in a
C.    Complement Proteins
     1. Defined as: a group of protein enzymes
        normally present in an inactive state in
        the blood
     2. They are activated by exposure of
        complement binding sites on antibodies
        when they attach to antigens
      a.   This results in the formation of highly
           specialized protein molecules that target
           foreign cells for destruction
      b.   This initiates the complement cascade
 3.    Complement proteins also function to:
  a.    Attract immune cells to a site of infection
  b.    Activate immune cells
  c.    Mark foreign cells for destruction
  d.    Increase permeability of blood vessels
D.    Antigen-Antibody Complex
     1. Formed when an antibody attaches to
        an antigen invader
     2. They change the antigens so they
        cannot harm the body
      a.    They can neutralize a toxic cell
      b.    They can agglutinate enemy cells
      c.    They can promote phagocytosis
     3.    This is called antibody-mediated
      a.    AKA humoral immunity
E.    Complement Cascade
     1.    Initiated when antigens bind to
           antibodies, changing their shape, and
           exposing previously hidden regions
      a.    These are called compliment-binding sites
      b.    This exposure activates previously inactive
            complement proteins
     2.    The end result is that doughnut shaped
           protein rings are formed and literally
           bore holes in the foreign cell
  a.   The newly formed holes allow sodium to
       quickly diffuse into the cell
  b.   Then water flows into the cell through the
       process of osmosis
  c.   As the pressure inside increases, the cell
A.    Phagocytes
 1. Defined as: white blood cells that
    engulf microbes and digest them
 2. Blood phagocytes migrate out of the
    blood and into the tissues in response
    to an infection
     a.         There are two types:
          i.     Neutrophils – functional, but short lived in the
          ii.    Monocytes – once in the tissue, develop into
3.    Macrophages
 a.         Macrophages have multiple functions:
      i.     Some ‘wander’ through the tissues to engulf
             bacteria wherever they find them
      ii.    Others become permanent residents of other
 b.         Specialized antibodies that bind to and coat
            certain foreign particles help macrophages
            function effectively
      i.     They serve as ‘flags’ that alert the macrophages
             to the presence of foreign material, infectious
             bacteria, or cellular debris
      ii.    They also help bind the phagocyte to the invader
             so it can be engulfed more effectively
B.    Lymphocytes
 1.       The most numerous immune system
     a.    Several million patrol the body
     b.    They densely populate the lymph nodes
     c.    They are also present in large
           concentrations in the spleen, thymus and
 2.       There are 2 major types:
     a.    B cells
     b.    T cells
3.    B Cells
 a.         Begin as primitive (stem) cells
      i.     Stem cells transform into immature B cells in the
             liver and bone marrow before birth and in the
             bone marrow only in adults
 b.         Each immature B cell carries antibodies
            specific to one type of invader
 c.         The immature cells eventually leave their
            original tissue, enter the blood, and are
            transported to their new location
      i.     They arrive in the lymph nodes where they act as
             seed cells
      ii.    Each cell undergoes mitosis and produces several
             clones, all bearing the same antibodies
d.          Following mitosis, immature B cells are
            changed into activated B cells
     i.      Not all immature B cells undergo this change
     ii.     They do so only if they come into contact with an
     iii.    The antigen binds to the immature B cell’s
             antibody and activates the cell
e.          Once activated, the B cell forms 2 clones
     i.      Plasma cells – secrete antibodies into the blood
     ii.     Memory cells – wait in lymph nodes until called
             upon by same antigen involved in their formation,
             then immediately become plasma cells
4.    T Cells
 a.          Also begin as stem cells
      i.      Stem cells from bone marrow migrate to thymus
      ii.     In the first few months before and after birth,
              stem cells develop into T cells in the thymus
      iii.    Mature T cells enter the blood and migrate to the
              lymph nodes
      iv.     If a T cell binds to the specific antigen that it
              ‘fits’ with, it develops into a sensitized T cell
b.         Produce cell-mediated immunity
     i.     This is a resistance to disease organisms that
            results from the actions of sensitized T cells
c.         Some sensitized T cells kill invading cells
     i.     When bound to antigens on an invading cell’s
            surface, they release a substance that acts as a
            specific and lethal poison against the bound cell
d.         Others act indirectly against invaders
     i.     They release compounds into the area of enemy
            cells that attract macrophages into the vicinity of
            the enemy cells
     ii.    The macrophages then destroy the cells through

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