Lymphatic system


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Lymphatic system

  1. 1. LECTURER: Lorraine Veraces-Pilapil, OTRP, OTR
  2. 3. <ul><li>Fluid balance </li></ul><ul><li>Fat absorption </li></ul><ul><li>Defense </li></ul>
  3. 4. FLUID BALANCE <ul><li>30 L of fluid  blood capillaries to interstitial spaces each day </li></ul><ul><li>27 L of fluid  interstitial spaces into blood </li></ul><ul><li>3 L of fluid  enters the lymphatic capillaries (lymph) and passes through the lymphatic vessels to return to the blood. </li></ul><ul><li>Lymph contains solutes derived from two sources: </li></ul><ul><ul><li>Substances in plasma, such as ions, nutrients, gases, and some proteins </li></ul></ul><ul><ul><li>Substances such as hormones, enzymes, and waste products derived from cells within the tissues. </li></ul></ul>
  4. 5. FAT ABSORPTION <ul><li>From the digestive tract </li></ul><ul><li>Lacteals (special lymphatic vessels) located in the lining of the small intestine  fat enters  lymphatic vessels  venous circulation </li></ul><ul><ul><li>Chyle  is lymph that is milky in appearance due to the fat content. </li></ul></ul>
  5. 6. DEFENSE <ul><li>Microorganisms and other foreign substances filtered from lymph by lymph nodes and from blood by the spleen. </li></ul>
  6. 7. <ul><li>Lymphatic system does not circulate blood to and from tissues. </li></ul><ul><li>Carries fluid in one direction from tissues to the circulatory system. </li></ul>
  7. 8. LYMPHATIC CAPILLARIES <ul><li>Tiny closed-ended vessels consisting of simple squamous epithelium. </li></ul><ul><li>More permeable than blood capillaries because they lack a basement membrane, and fluid moves easily into the lymphatic capillaries </li></ul><ul><li>Overlapping squamous cells of the lymphatic capillary walls act as valves that prevent the back-flow of fluid. </li></ul><ul><li>Are located in most tissues of the body except the CNS, bone marrow, and tissues without blood vessels such as epidermis and cartilages </li></ul><ul><li>Superficial group  drains the dermis and hypodermis </li></ul><ul><li>Deep group  drains muscles, viscera, and other deep structures </li></ul>
  8. 11. LYMPHATIC VESSELS <ul><li>Resemble small veins </li></ul><ul><li>Beaded appearance because of one way valves </li></ul><ul><li>Three factors that cause compression of the lymphatic vessels: </li></ul><ul><ul><li>Contraction of surrounding skeletal muscle during activity </li></ul></ul><ul><ul><li>Periodic contraction of smooth muscle in the lymphatic vessel wall </li></ul></ul><ul><ul><li>Pressure changes in the thorax during respiration </li></ul></ul><ul><li>Lymphatic vessels converge and eventually empty into: </li></ul><ul><ul><li>Right lymphatic duct  upper right limb and the right half of the head, neck, and chest and empties into the right subclavian vein. </li></ul></ul><ul><ul><li>Thoracic duct  rest of the body and empties into the left subclavian vein. </li></ul></ul>
  9. 13. <ul><li>Tonsils </li></ul><ul><li>Lymph Nodes </li></ul><ul><li>Spleen </li></ul><ul><li>Thymus Gland </li></ul>
  10. 14. LYMPHATIC TISSUES <ul><li>Consists of many lymphocytes and macrophages </li></ul><ul><li>Found within lymphatic organs </li></ul><ul><li>Originate from the red bone marrow and are carried by the blood to lymphatic organs </li></ul><ul><li>They divide and increase in number when the body is exposed to microorganisms or foreign substances </li></ul><ul><li>Has very fine reticular fibers that form an interlaced network that holds the lymphocytes and other cells in place as well as traps microorganisms and other items in the lymph. </li></ul>
  11. 15. TONSILS <ul><li>They form a protective ring of lymphatic tissue around the openings between the nasal and oral cavities and the pharynx. </li></ul><ul><li>Provide protection against pathogens and other potentially harmful material entering from the nose and mouth. </li></ul><ul><li>In adults, the tonsils decrease in size and may eventually disappear. </li></ul>
  12. 16. Three group of tonsils: <ul><li>Palatine tonsils (“ the tonsils ”) – located on each side of the posterior opening of the oral cavity. </li></ul><ul><li>Pharyngeal tonsils – located near the internal opening of the nasal cavity and when enlarged is commonly referred as “ adenoid ” </li></ul><ul><li>Lingual tonsils – posterior surface of the tongue. </li></ul>
  13. 18. LYMPH NODES <ul><li>Rounded structures that vary in size. </li></ul><ul><li>Distributed along the various lymphatic vessels and most lymph passes through at least one lymph node before entering the blood. </li></ul><ul><li>Three superficial aggregations: </li></ul><ul><ul><li>Inguinal nodes </li></ul></ul><ul><ul><li>Axillary nodes </li></ul></ul><ul><ul><li>Cervical nodes </li></ul></ul><ul><li>Capsule – dense connective tissue that surrounds each lymph node </li></ul><ul><li>Trabeculae – extensions of the capsule and subdivides lymph nodes into compartments containing lymphatic tissue and lymphatic sinuses. </li></ul>
  14. 19. LYMPH NODES <ul><li>Lymphatic nodules – are dense aggregations of lymphatic tissue containing lymphocytes and other cells </li></ul><ul><li>Lymphatic sinuses – spaces between lymphatic tissue which contain macrophages on a network of fibers. </li></ul><ul><li>Germinal centers – lymph nodules containing rapidly dividing lymphocytes </li></ul><ul><li>Lymph enters the lymph node through afferent vessels, passes through the lymphatic tissue and sinuses, and exits through efferent vessels. </li></ul><ul><li>2 functions: </li></ul><ul><ul><li>Activation of the immune system </li></ul></ul><ul><ul><li>Removal of microorganisms and foreign substances from the lymph by macrophages </li></ul></ul>
  15. 22. SPLEEN <ul><li>Roughly the size of a clenched fist located in the left, superior corner of the abdominal cavity. </li></ul><ul><li>Outer capsule – dense connective tissue and a small amount of smooth muscle </li></ul><ul><li>Trabeculae – divide the spleen into small, interconnected compartments containing two specialized types of lymphatic tissue: </li></ul><ul><ul><li>White pulp – lymphatic tissue surrounding the arteries within the spleen </li></ul></ul><ul><ul><li>Red pulp – associated with veins and consists of a fibrous network filled with macrophages and red blood cells, and enlarged capillaries that connect to the veins. </li></ul></ul>
  16. 24. SPLEEN <ul><li>Spleen filters blood instead of lymph. </li></ul><ul><li>Cells within the spleen detect and respond to foreign substances in the blood and destroy worn-out red blood cells. </li></ul><ul><li>Also function as a blood reservoir holding a small volume of blood. </li></ul>
  17. 26. THYMUS <ul><li>Bilobed gland roughly triangular in shape </li></ul><ul><li>Located in the superior mediastinum </li></ul><ul><li>The thymus increase in size until the first year of life, after which it remains approximately the same size even though the size of the individual increases </li></ul><ul><li>After 60 years of age, it decreases in size </li></ul><ul><li>By 40 years of age much of the thymus has been replaced with adipose tissue. </li></ul><ul><li>Capsule – thin connective tissue that surrounds each lobe of the thymus </li></ul><ul><li>Trabeculae – divide each lobe into lobules </li></ul>
  18. 27. THYMUS <ul><li>Cortex – an area near the capsule and trabeculae where lymphocytes are numerous and form a dark-staining area </li></ul><ul><li>Medulla – lighter staining central portion of the lobule and has fewer lymphocytes </li></ul><ul><li>Thymus functions as a site for production and maturation of lymphocytes </li></ul><ul><li>Large numbers of lymphocytes are produced in the thymus, but for unknown reasons, most degenerate. </li></ul><ul><li>While in the thymus, lymphocytes do not respond to foreign substances </li></ul><ul><li>Matured lymphocytes enter the blood and travel to other lymphatic tissues  help protect against microorganisms and other foreign substances </li></ul>
  19. 32. IMMUNITY <ul><li>Is the ability to resist damage from foreign substances, such as microorganisms, and harmful chemicals, such as toxins released by microorganisms </li></ul><ul><li>Innate immunity – body recognizes and destroys certain foreign substances, but the response to them is the same each time the body is exposed to them </li></ul><ul><li>Adaptive immunity – body recognizes and destroys foreign substances, but the response to them improves each time the foreign substance is encountered. </li></ul><ul><ul><li>Specificity and memory are characteristics of adaptive immunity which results in a faster, stronger and longer response. </li></ul></ul><ul><ul><li>Specificity – the ability of adaptive immunity to recognize a particular substance </li></ul></ul><ul><ul><li>Memory – the ability of adaptive immunity to “remember” previous encounters with a particular substance </li></ul></ul>
  20. 33. <ul><li>Mechanical mechanism </li></ul><ul><li>Chemical mediators </li></ul><ul><li>Cells </li></ul><ul><li>Inflammatory response </li></ul>
  21. 34. MECHANICAL MECHANISMS <ul><li>Prevent the entry of microorganisms and chemicals in 2 ways: </li></ul><ul><ul><li>Skin and mucous membranes form barriers that prevent their entry </li></ul></ul><ul><ul><li>Tears, saliva, and urine act to wash them from the surfaces of the body </li></ul></ul>
  22. 35. CHEMICAL MEDIATORS <ul><li>Molecules responsible for many aspects of innate immunity. </li></ul><ul><li>Lysozyme in tears and saliva are surface chemicals that kill microorganisms or prevent their entry. </li></ul><ul><li>Histamine, complement, prostaglandins, leukotrines, promote inflammation by causing vasodilation, increasing vascular permeability, and stimulating phagocytosis </li></ul><ul><li>Interferons protect cells against viral infections. </li></ul>
  23. 36. A. Complement <ul><li>A group of approximately 20 proteins found in plasma </li></ul><ul><li>Normally circulate in blood in an inactive form  activated by combining with foreign substances or by combining with antibodies  each complement protein activates the next  promote inflammation and phagocytosis and directly lyse bacterial cells </li></ul>
  24. 37. B. Interferons <ul><li>Proteins that protect the body against viral infections </li></ul><ul><li>Viruses stimulate infected cells to produce interferons  bind to the surface of neighboring cells and stimulate them to produce antiviral proteins  inhibit viral reproduction by preventing the production of new viral nucleic acids and proteins. </li></ul><ul><li>Some play a role in the activation of immune cells such as macrophages and natural killer cells </li></ul>
  25. 38. CELLS <ul><li>White blood cells are the most important cellular components of immunity </li></ul><ul><li>WBC are produces in the bone marrow and lymphatic tissue. </li></ul><ul><li>Chemotaxis – is the movement of WBC toward chemicals (complement, leukotrines, kinins, and histamine). </li></ul>
  26. 39. A. Phagocytic Cells <ul><li>Phagocytes – most important are neutrophils, and macrophages </li></ul><ul><li>Phagocytosis – is the ingestion and destruction of particles by phagocytes </li></ul><ul><li>Neutrophils </li></ul><ul><ul><li>Small phagocytic cells that are usually the first to enter infected tissues </li></ul></ul><ul><ul><li>Often die after phagocytizing a single microorganism </li></ul></ul><ul><ul><li>Pus – is an accumulation of fluid, dead neutrophils, and other cells at site of infection. </li></ul></ul>
  27. 40. A. Phagocytic Cells <ul><li>Macrophages </li></ul><ul><ul><li>Monocytes that enlarge fivefold after entering the tissues. </li></ul></ul><ul><ul><li>Form the mononuclear phagocytic system because they are phagocytes with a single, unlobed nucleus. </li></ul></ul><ul><ul><li>Kupffer cells – liver </li></ul></ul><ul><ul><li>Microglia – CNS </li></ul></ul><ul><ul><li>Ingest more and larger items than neutrophils and they appear in the later stages of infection </li></ul></ul><ul><ul><li>Found in uninfected tissues </li></ul></ul>
  28. 41. B. Cells of Inflammation <ul><li>Basophils – derived from red bone marrow are motile WBC that can leave the blood and enter infected tissues. </li></ul><ul><li>Mast cells </li></ul><ul><ul><li>Derived from red bone marrow are nonmotile cells in connective tissues near capillaries </li></ul></ul><ul><ul><li>Located at potential points of entry for microorganisms such as the skin, lungs, GI tract, urogenital tract. </li></ul></ul><ul><li>Basophils and mast cells can be activated in innate and adaptive immunity. They release chemicals such as histamine and leukotrines that produce an inflammatory response or activate other mechanisms such as smooth muscle contraction in the lungs. </li></ul>
  29. 42. B. Cells of Inflammation <ul><li>Eosinophils </li></ul><ul><ul><li>Produces in red bone marrow </li></ul></ul><ul><ul><li>Enzymes break down chemicals released by basophils and mast cells that contain and reduce the inflammatory response </li></ul></ul><ul><li>Too much inflammation is harmful, resulting in unnecessary destruction of healthy tissues as well as the destruction of the microorganisms. </li></ul>
  30. 43. C. Natural Killer Cells <ul><li>Type of lymphocyte produced in the red bone marrow </li></ul><ul><li>15% of lymphocytes </li></ul><ul><li>Recognize classes of cells such as tumor cells or virus-infected cells in general  do not exhibit memory response </li></ul><ul><li>Release chemicals that damage cell membranes, causing the cell to lyse. </li></ul>
  31. 44. <ul><li>Most are very similar, although some details can vary depending on the intensity of the response and the type of injury. </li></ul><ul><li>Fibrinogen is converted to fibrin which isolates the infection by walling off the infected area. </li></ul>
  32. 46. A. Local Inflammation <ul><li>Confined to a specific area of the body </li></ul><ul><li>Symptoms – redness, heat, swelling, pain, and loss of function. </li></ul><ul><li>Redness, heat, swelling – result of increased blood flow and increased vascular permeability </li></ul><ul><li>Pain – caused by swelling and by chemical mediators acting on pain receptors </li></ul><ul><li>Loss of function – tissue destruction, swelling, and pain. </li></ul>
  33. 47. B. Systemic Inflammation <ul><li>Distributed throughout the body </li></ul><ul><li>Three features </li></ul><ul><ul><li>Red bone marrow produces and releases large numbers of neutrophils </li></ul></ul><ul><ul><li>Pyrogens released by microorganisms, neutrophils, and other cells stimulate fever production </li></ul></ul><ul><ul><ul><li>Affect the temperature-regulating mechanisms in the hypothalamus of the brain </li></ul></ul></ul><ul><ul><ul><li>Fever promotes the activities of the immune system, such as phagocytosis, and inhibits the growth of some microorganisms </li></ul></ul></ul><ul><li>In sever cases, vascular permeability can increase  can cause shock and death </li></ul>
  34. 49. ADAPTIVE IMMUNITY <ul><li>Exhibits specificity and memory </li></ul><ul><li>Antigens are substances that stimulate adaptive response. </li></ul><ul><li>Two groups of antigens: </li></ul><ul><ul><li>Foreign antigen </li></ul></ul><ul><ul><li>Self-antigens </li></ul></ul>
  35. 50. FOREIGN ANTIGENS <ul><li>Introduced from outside the body </li></ul><ul><li>Bacteria and viruses, components of microorganisms are examples of antigens </li></ul><ul><li>Pollen, animal hairs, foods, and drugs – allergic reactions </li></ul><ul><li>Transplanted tissues and organs contain foreign antigens </li></ul>
  36. 51. SELF-ANTIGENS <ul><li>Molecules produced by the person’s body that stimulate an immune system response. </li></ul><ul><li>Beneficial – recognition of tumor antigens can result in destruction of the tumor. </li></ul><ul><li>Harmful – autoimmune diseases </li></ul>
  37. 52. Divisions of Adaptive Immunity <ul><li>Humoral immunity or antibody-mediated immunity </li></ul><ul><li>Cell-mediated immunity </li></ul>
  38. 53. LYMPHOCYTES <ul><li>2 TYPES: </li></ul><ul><li>B cells </li></ul><ul><ul><li>Give rise to cells that produce proteins called antibodies which are found in the plasma. </li></ul></ul><ul><ul><li>Responsible for antibody-mediated immunity. </li></ul></ul><ul><li>T cells </li></ul><ul><ul><li>Responsible for cell-mediated immunity </li></ul></ul><ul><ul><li>Subpopulations </li></ul></ul><ul><ul><ul><li>Cytotoxic T cells produce the effects of cell-mediated immunity </li></ul></ul></ul><ul><ul><ul><li>Helper T cells can promote or inhibit the activities of both antibody-mediated immunity and cell-mediated immunity. </li></ul></ul></ul>
  39. 54. ORIGIN AND DEVELOPMENT OF LYMPHOCYTES <ul><li>There are about 5 T cells for every B cell in the blood. </li></ul><ul><li>Clones </li></ul><ul><ul><li>Are small groups of identical B or T cells formed during embryonic development. </li></ul></ul><ul><ul><li>Each clone is derived from a single, unique B or T cell </li></ul></ul><ul><ul><li>Each can respond only to a particular antigen. </li></ul></ul>
  40. 56. <ul><li>Antigen Recognition </li></ul><ul><li>Lymphocyte proliferation </li></ul>
  41. 57. A NTIGEN RECOGNITION <ul><li>Lymphocytes have antigen receptors in their surface (B-cell receptors, T-cell receptors) </li></ul><ul><li>Each receptor binds with only a specific antigen </li></ul><ul><li>B and T cells typically recognize antigens after large molecules have been processed or broken down into smaller fragments </li></ul><ul><li>Major histocompatibility complex (MHC) molecules </li></ul><ul><ul><li>Glycoproteins that have binding sites for antigens </li></ul></ul><ul><ul><li>Specific </li></ul></ul><ul><ul><li>“ serving trays” that hold and present a processed antigen on the outer surface of the cell membrane. </li></ul></ul>
  42. 58. ANTIGEN RECOGNITION <ul><li>Costimulation is a second signal required to produce a response from a B or T cell. </li></ul><ul><ul><li>Achieved by cytokins (ex. Interleukin I) which are proteins or peptides secreted by one cell as a regulator of neighboring cells. </li></ul></ul><ul><li>CD4 of helper T cells and CD8 of cytotoxic T cells helps connect the T cells to the macrophage by binding to MHC molecules. </li></ul>
  43. 60. LYMPHOCYTE PROLIFERATION <ul><li>Helper T cells produce interleukin 2 receptors and interleukin 2. </li></ul><ul><li>Interleukin 2 binds to the receptors and stimulates the helper T cell to divide </li></ul>
  44. 64. <ul><li>Are proteins produced in response to an antigen </li></ul><ul><li>Y-shaped molecules consisting of four polypeptide chains: two identical heavy chains and two identical light chains. </li></ul><ul><li>Variable Region </li></ul><ul><ul><li>End of each arm of the antibody </li></ul></ul><ul><ul><li>Part of the antibody that combines with the antigen </li></ul></ul><ul><ul><li>Can only join a particular antigen </li></ul></ul><ul><li>Constant region </li></ul><ul><ul><li>Rest of the antibody </li></ul></ul><ul><ul><li>Several functions: activate complement, or attach the antibody to cells such as macrophages, basophils, and mast cells. </li></ul></ul>ANTIBODIES
  45. 66. ANTIBODIES <ul><li>Antibodies make up a large portion of the proteins in plasma </li></ul><ul><li>Most plasma proteins can b separated into albumin and alpha, beta, and gamma globulin portions. </li></ul><ul><li>Called gamma globulins because they are found mostly in the gamma globulin part of plasma </li></ul><ul><li>Called immunoglobulins ( Ig ) because they are globulin proteins involved in immunity. </li></ul><ul><li>Five general classes of immunoglobulins : IgG, IgM, IgA, IgE, and IgD </li></ul>
  46. 68. EFFECTS OF ANTIBODIES <ul><li>Directly or indirectly </li></ul>
  47. 70. ANTIBODY PRODUCTION <ul><li>Primary response results from the first exposure of a B cell to an antigen </li></ul><ul><ul><li>B cells divide and form memory cells and plasma cells. </li></ul></ul><ul><ul><li>Plasma cells – produce antibodies </li></ul></ul><ul><ul><li>Normally takes 3-14 days to produce enough antibodies to be effective against the antigen </li></ul></ul><ul><li>Secondary or memory response </li></ul><ul><ul><li>Memory B cells </li></ul></ul><ul><ul><li>Occurs when the immune system is exposed to an antigen against which it has already produced a primary response. </li></ul></ul><ul><ul><li>When exposed to the antigen, the B memory cells quickly divide to form plasma cells. </li></ul></ul>
  48. 71. ANTIBODY PRODUCTION <ul><li>Secondary or memory response </li></ul><ul><ul><li>Provides better protection than primary response for two reasons: </li></ul></ul><ul><ul><ul><li>The time required to produce antibodies is less </li></ul></ul></ul><ul><ul><ul><li>More plasma cells and antibodies are produced </li></ul></ul></ul><ul><ul><li>Also includes the formation of new memory cells, which provides protection against additional exposures to a specific antigen </li></ul></ul><ul><li>Plasma cells die after the destruction of antigen </li></ul><ul><li>Memory cells persists for many years </li></ul>
  49. 74. CELL-MEDIATED IMMUNITY <ul><li>Function of cytotoxic cells </li></ul><ul><li>Most effective against microorganisms that live inside the cells of the body </li></ul><ul><li>Involved with some allergic reactions, control of tumors, and graft rejections. </li></ul><ul><li>Essential for fighting viral infections. </li></ul>