LYMPHATIC

• Lymphatic System


  System that helps maintain fluid balance, absorb fats, and provide defense against pathogens

  
• Functions of the Lymphatic System

  • Fluid balance
  • Fat Absorption
  • Defense

  
• Lymph


  • Fluid that enters lymphatic capillaries composed of water and some solutes

  
• Components of the Lymphatic System


  • Lymphocytes
  • Lymphatic vessels
  • Lymph nodes
  • Tonsils
  • Spleen
  • Thymus gland

  
• Lymphatic Capillaries


  • Carry fluid in one direction from tissues to circulatory system
  • Fluid moves from blood capillaries into tissue spaces
  • Tiny, closed-ended vessels
  • Fluid moves easily into capillaries
  • In most tissues
  • Join to form lymphatic vessels

  
• Lymphatic Vessels


  • Resemble small veins
  • Where lymphatic capillaries join
  • Have one-way valves
• Right Lymphatic Duct


  Where lymphatic vessels from right upper limb and right head, neck, chest empty, empties into right subclavian vein
• Thoracic Duct


  Collects lymph from the remaining lymphatic vessels which do not enter the right lymphatic duct, empties into left subclavian vein

  
• Lymph Formation and Movement


  1. Fluid moves from blood capillaries into tissue spaces

  2. Lymphatic capillaries absorb fluid

  3. Lymph flows through lymphatic vessels

  4. Lymph passes through lymph nodes

  5. Lymph enters blood circulation

  
• Tonsils


  • Palatine tonsils on each side of oral cavity
  • Pharyngeal tonsils near internal opening of nasal cavity (adenoid)
  • Lingual tonsils posterior surface of tongue
  • Form a protective ring of lymphatic tissue around nasal and oral cavities
• Lymph Nodes

  • Rounded structures that vary in size
  • Located near lymphatic vessels
  • Groin, armpit, neck
  • Lymph passes through lymph nodes before entering blood
  • Lymph moves through and immune system is activated (lymphocytes produced) if foreign substances are detected
  • Removes microbes by macrophages
• Spleen


  • Size of clenched fist
  • Located in abdomen
  • Filters blood
  • Detects and responds to foreign substances
  • Destroys old red blood cells
  • Serves as a blood reservoir
• Thymus Gland


  • Bilobed gland
  • Located in mediastinum behind the sternum
  • Stops growing at age 1
  • Decreases in size by age 60
  • Produces and matures lymphocytes
• Immunity is the ability to resist damage from foreign substances
• Innate Immunity


  Present at birth, defense against any pathogen, accomplished by physical barriers, chemical mediators, cells, inflammatory response
• Physical Barriers


  • Skin and mucous membranes act as barriers to pathogens and toxins
  • Tears, saliva, urine wash away pathogens and toxins
• Chemical Mediators


  • Lysozyme in tears and saliva kills bacteria
  • Mucous membranes prevent entry of microbes
  • Histamine promotes inflammation by causing vasodilation
  • Interferons protect against viral infections by stimulating surrounding cells to produce antiviral proteins
• Cells of the Immune System


  • Neutrophils
  • Eosinophils
  • Basophils
  • Macrophages
  • Mast cells
  • Natural Killer Cells
• Inflammatory Response


  1. Involves chemicals and cells produced due to injury

  2. Signaled by presence of foreign substance

  3. Stimulates release of chemical mediators
• Adaptive Immunity


  Defense that involves specific recognition to a specific antigen, acquired after birth, reacts when innate defenses don't work, slower than innate immunity, has memory, uses lymphocytes (B and T cells), includes antibody-mediated and cell-mediated immunity
• Antigen


  Substance that stimulates an immune response, e.g. bacteria, virus, pollen, food, drugs
• Self-Antigen


  Molecule produced by the person's body that stimulates an immune system response
• Antibody


  Proteins the body produces in response to an antigen
• Stem Cells


  • Live in red bone marrow
  • Give rise to all blood cells
  • Give rise to some pre-T cells and pre-B cells
• Lymphocytes


  Type of white blood cell involved in adaptive immunity, develop from stem cells, differentiate into specific lymphocytes such as B or T cells
• B Cells


  • Type of lymphocytes involved in antibody-mediated immunity
  • Originate from stem cells
  • Mature in red bone marrow
  • Move to lymphatic tissue after mature
  • Lead to production of antibodies
• T Cells

  • Type of lymphocytes involved in cell-mediated immunity
  • Originate from stem cells
  • Mature in thymus gland
  • Recognize and destroy infected or cancerous cells
• Stem cells


  • Live in red bone marrow
  • Give rise to all blood cells
  • Give rise to some pre-T cells and pre-B cells
• Lymphocytes


  • Type of white blood cell
  • Involved in adaptive immunity
  • Develop from stem cells
  • Differentiate into specific lymphocytes such as B or T cells
• B cells


  • Type of lymphocytes
  • Involved in antibody-mediated immunity
  • Originate from stem cells
  • Mature in red bone marrow
  • Move to lymphatic tissue after mature
  • Lead to production of antibodies
• T cells


  • Type of lymphocyte
  • Involved primarily in cell-mediated immunity but also participate in antibody-mediated immunity
  • Mature in thymus gland
  • Move to lymphatic tissue after mature
  • 4 types
• Origin and Processing of B Cells and T Cells


  1. Stem cells give rise to pre-T cells and pre-B cells

  2. Pre-T cells mature in thymus gland to become T cells

  3. Pre-B cells mature in red bone marrow to become B cells

  4. Mature B and T cells move to lymphatic tissue
• Antigen receptors


  • Lymphocytes have antigen receptors on their surface
  • B-cell receptors on B cells and T-cell receptors on T cells
  • Each receptor only binds with a specific antigen
  • When antigen receptors combine with the antigen, the lymphocyte is activated and adaptive immunity begins
• MHC molecule


  • Contains binding sites for antigens
  • Specific for certain antigens
  • Holds and presents a processed antigen on the surface of the cell membrane
  • Binds to antigen receptor on B or T cells and stimulates response
• Cytokines


  • Proteins secreted by a cell that regulates neighboring cells
  • Example—interleukin 1 released by macrophages stimulates helper T cells
• Lymphocytes give rise to 2 types of immune responses: antibody-mediated and cell-mediated
• Antigens can trigger both antibody-mediated and cell-mediated immune responses
• Both antibody-mediated and cell-mediated immune responses are able to recognize self versus non-self, use specificity, and have memory
• Antibody-mediated immunity


  • Effective against antigens in body fluids (blood and lymph)
  • Effective against bacteria, viruses, toxins
  • Uses B cells to produce antibodies
• Antibody structure


  • Y shape
  • Variable region (V of Y) binds to epitopes of antigen using antigen-binding site
  • Constant region (stem of Y) has same structure for each class of immunoglobulin