M16-17

• Lymphatic System


  • Carries fluid in one direction, from tissues to circulatory system; it does not circulate to or from tissues; includes lymph, lymphocytes, lymphatic vessels, lymph nodes, tonsils, spleen, and thymus
• Lymph

  The clear, nearly colorless, alkaline fluid that occupies the space between all cells of the body; 95% water; seeps in and out through the walls of very small vessels called capillaries
• Lymph flow


  Fluid that moves from blood capillaries into tissue spaces (most of fluid returns to blood) moves from tissue spaces into lymphatic capillaries
• Lymphatic Capillaries

  • Tiny, closed-ended vessels; more permeable than blood capillaries & fluid moves easily into; contain valves from overlapping squamous cells in the walls that prevent the backflow of fluid; Superficial group collects excess interstitial fluids from dermis & subcutaneous tissues; Deep group collects from muscle, the viscera, & other deep structures; CNS, bone marrow, & tissues lacking blood vessels (epidermis & cartilage) do not have lymphatic capillaries
• Lymphatic Vessels


  • Where lymphatic capillaries join; resemble small veins that have a beaded appearance; valves prevent backward & cause forward movement through vessels when compressed, caused by: 1. Contraction of skeletal muscle due to activity, 2. Periodic contraction of smooth muscle, 3. Pressure changes in the thorax during breathing
• Right Lymphatic Duct


  • Formed by vessels from the right upper limb and right half of head, neck, chest; empties into right subclavian vein

  
• Thoracic Duct


  • Where the rest of the body enters which empties into the left subclavian vein
• Lymphatic Tissue


  • Characterized by housing many lymphocytes & other defense cells (macrophages); has very fine reticular fibers that trap microorganisms & other items in fluid

  
• Tonsils


  • Form a protective ring of lymphatic tissue around openings between nasal & oral cavities and pharynx; protect against pathogens entering from nose & mouth; includes Palatine Tonsils, Pharyngeal Tonsil, and Lingual Tonsil
• Lymph Nodes


  • Rounded structures distributed along lymphatic vessels & has 3 superficial aggregations on each side of body: inguinal nodes in groin, axillary nodes in armpit, & cervical nodes in neck;
• Spleen


  • Located in left, superior corner of abdominal cavity; filters blood instead of lymph & serves as blood reservoir; has two specialized types of lymphatic tissue: White Pulp surrounding the arteries, and Red Pulp associated with veins and filled with macrophages

  
• Thymus


  • Bilobed gland roughly triangular in shape; site for the maturation of T cell lymphocytes; located in superior mediastinum that contains Cortex (dark-staining areas formed by numerous lymphocytes) and Medulla (lighter-staining, central portion of lobules that has fewer lymphocytes)

  
• Immunity


  Ability to resist damage from pathogens, harmful chemicals, & internal threats, making a person immune in second exposure before any symptoms develop; categorized into innate immunity & adaptive immunity
• Innate Immunity / Nonspecific Resistance


  • Present at birth; the body recognizes & destroys certain pathogens, but the response is the same each time the body is exposed; mechanisms include Physical Barriers, Chemical Mediators, White Blood Cells, and Inflammatory Response
• Adaptive Immunity / Specific Immunity


  • Body recognized & destroys pathogens, but the response improves each time the pathogen is encountered
• Chemicals that damage cell membranes

  Cause cell lysis
• Inflammatory Response


  1. Stimulates release of chemical mediators

  2. Amount of mediators & phagocytes increase until the cause of inflammation is destroyed

  3. Mediators produce effects: vasodilation, phagocytes leave blood & enter tissue, increased vascular permeability
• Local Inflammation


  Inflammatory response confined to a specific area of body; produces redness, heat, swelling, pain, & loss of function
• Systemic Inflammation


  Response that is generally distributed throughout the body; produces local symptoms & three additional features: increased neutrophils, fever (presence of pyrogens), & decreased blood volume (shock)
• Adaptive Immunity / Specific Immunity


  • Body recognizes & destroys pathogens, but the response improves each time the pathogen is encountered due to specificity & memory
• Lymphocyte Development


  1. Pre-T cells migrate through blood to thymus to divide & processed into T cells

  2. Pre-B cells processed in red bone marrow into B cells
• Antigen Recognition


  1. B & T cells have antigen receptors on surfaces, clones are lymphocytes with the same antigen receptor, each receptor binds with only specific antigen that activates lymphocytes & adaptive immunity begins

  2. Major Histocompatibility Complex (MHC) Molecules function as "serving tray" that hold & present a processed antigen on outer surface of cell membrane
• Antibody-Mediated Immunity


  Involves a group of B cell lymphocytes & proteins called antibodies; effective against extracellular antigens (bacteria, viruses, & toxins) & in certain allergic reactions
• Antibodies


  Produced by plasma cells and bind to the antigen; Y-shaped molecules with variable region for antigen-binding & constant region to activate complement or bind to other immune cells
• Gamma Globulins


  Other term of antibody since they are found mostly in gamma globulin part of plasma
• Immunoglobulin (Ig)


  Another term for antibody since they are globulin proteins involved in immunity
• Effects of Antibodies

  • Inactivate antigen
  • Bind antigens together
  • Active complement cascades
  • Initiate release of inflammatory chemicals
  • Facilitate phagocytosis
• Primary Response


  Results from 1st exposure of B cell to an antigen; person usually develops disease symptoms because the antigen has time to cause tissue damage
• Secondary Response / Memory Response


  Initiated by memory B cells to quickly form plasma cells; responsible for formation of new memory cells
• Cell-Mediated Immunity


  Involves the actions of T cells; most effective against microorganisms that live inside body cells; also functions in allergic reactions, control of tumors, & graft rejections
• Types of T Cells

  • Cytotoxic T Cells
  • Helper T Cells
  • Memory T Cells
• Cytotoxic T Cells


  Responsible for immediate immune response; release cytokines that activate additional components of immune system & also activate additional cytotoxic T cells; bind to antigen on surfaces of these cells (viral antigen, tumor antigen, & foreign antigen) & kill them
• Helper T Cells


  Promote or inhibit the activities of both adaptive immunities; promote production of cytotoxic T cells & activate macrophages
• Memory T Cells


  Provide a secondary response & long-lasting immunity
• Immunotherapy


  Treats disease by altering immune system function or by directly attacking harmful cells; can be done through administering cytokines, vaccination, or monoclonal antibodies
• Multiple Sclerosis is an autoimmune disease in which immune system treats self-antigens as foreign, destroying the myelin that covers axons
• Systemic Lupus Erythematosus (SLE) is a disease in which tissues & cells are damaged by immune system; no cure
• Lymphedema


  Swelling due to build-up of lymph fluid in the body; lymph nodes act like a drain, if the drain is clogged, the fluid cannot drain
• Lymphoma


  Two types of cancer that begin in the lymphatic system when abnormal white blood cells grow
• The lymphatic system plays an important role in the development or spread of cancer