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Lymphatic system


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Typed-up notes taken during the PowerPoint in class.

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Lymphatic system

  1. 1. Lymphatic System
  2. 2. Purpose <ul><li>Transports excess fluids into blood stream </li></ul><ul><li>Absorbs fats in the small intestine </li></ul><ul><li>Helps defend body against diseases and their causing agents </li></ul>
  3. 3. Lymphatic Capillaries <ul><li>System begins as capillaries </li></ul><ul><ul><li>End in the subclavian veins of the thorax </li></ul></ul><ul><li>Closed-ended tubules </li></ul><ul><li>Extend into interstitial spaces </li></ul><ul><ul><li>Spaces/fluid spaces between tissues and cells </li></ul></ul><ul><li>Lymph is the fluid which has entered the lymph capillaries </li></ul>
  4. 4. Lymphatic Vessels <ul><li>Walls are thinner than veins </li></ul><ul><li>Contain semilunar valves to prevent backflow </li></ul><ul><li>Leads to specialized organs called lymph nodes </li></ul>
  5. 5. Collecting Ducts <ul><li>Lymphatic vessels drain into lymphatic trunks which drain into one of two collecting ducts </li></ul><ul><li>Thoracic duct </li></ul><ul><ul><li>Larger and longer of the two </li></ul></ul><ul><ul><li>Begins in abdomen </li></ul></ul><ul><ul><li>Empties into left subclavian vein </li></ul></ul><ul><li>Right lymphatic duct </li></ul><ul><ul><li>Empties into right subclavian vein </li></ul></ul>
  6. 6. Lymph
  7. 7. Lymph Formation <ul><li>Capillary blood pressure filters water and small molecules from the plasma </li></ul><ul><li>Interstitial hydrostatic pressure increases the forces the fluid into the lymphatic capillaries </li></ul><ul><li>Lymph formation prevents edema (build up of excess tissue fluid) </li></ul>
  8. 8. Lymph Function <ul><li>Returns small molecules and fluids to the blood stream </li></ul><ul><li>Transports foreign particles to the lymph nodes, including: </li></ul><ul><ul><li>Bacteria </li></ul></ul><ul><ul><li>Viruses </li></ul></ul>
  9. 9. Lymph Flow <ul><li>Movement of lymph is caused by </li></ul><ul><ul><li>Contracting skeletal muscles </li></ul></ul><ul><ul><li>Deep breathing </li></ul></ul><ul><li>Lymph flow peaks during physical exercise </li></ul><ul><li>Removal of lymphatic tissue can cause edema </li></ul><ul><ul><li>However, it prevents the spread of cancer cells </li></ul></ul>
  10. 10. Lymph Nodes
  11. 11. Lymph Nodes <ul><li>Located along lymphatic pathways </li></ul><ul><li>Contain large numbers of lymphocytes and macrophages </li></ul><ul><ul><li>They fight invasions of foreign and harmful particles </li></ul></ul>
  12. 12. Lymph Node Structure <ul><li>Bean shapred </li></ul><ul><li>Less than an inch long - ~2.5 cm </li></ul><ul><li>Hilum – the indented region of the node </li></ul><ul><li>Vessels lead to: </li></ul><ul><ul><li>Afferent vessels lead to the node </li></ul></ul><ul><ul><li>Efferent vessel leaves at the hilum </li></ul></ul><ul><li>Capsule divides into modules </li></ul><ul><ul><li>Contains masses of lymphocytes and macrophages </li></ul></ul><ul><ul><li>Spaces where the lymph can flow through the node </li></ul></ul>
  13. 13. Lymph Node Location and Function <ul><li>Grouped in chains along the larger lymphatic system/vessels </li></ul><ul><li>Absent in the central nervous system </li></ul><ul><li>Two primary functions </li></ul><ul><ul><li>Filter potentially harmful particles from the lump before returning it to the blood </li></ul></ul><ul><ul><li>Centers of lymphocyte production </li></ul></ul><ul><li>Macrophages in the lymph nodes engulf foreign particles </li></ul>
  14. 14. Other Lymphatic Organs <ul><li>Thymus </li></ul><ul><ul><li>Larger during infancy and early childhood </li></ul></ul><ul><ul><ul><li>Shrinks during puberty </li></ul></ul></ul><ul><ul><li>Contains thymocytes developed in the red bone marrow </li></ul></ul><ul><ul><li>Some mature into T-lymphocytes </li></ul></ul><ul><ul><ul><ul><li>These leave the thymus and provide immunity </li></ul></ul></ul></ul><ul><li>Spleen </li></ul><ul><ul><li>Largest of the lymphatic organs </li></ul></ul><ul><ul><li>Resembles an overlarge lymph node </li></ul></ul>
  15. 15. Defense Against Infections
  16. 16. Defense System Against Infections <ul><li>Pathogen – a disease causing agent (infection) </li></ul><ul><ul><li>Bacteria </li></ul></ul><ul><ul><li>Fungi </li></ul></ul><ul><ul><li>Virus </li></ul></ul><ul><ul><ul><li>Not “living”, as it cannot procreate on its own and has to infect another cell in order to reproduce </li></ul></ul></ul><ul><li>Innate Defenses – nonspecific defenses </li></ul><ul><li>Adaptive Defenses – specific defenses </li></ul><ul><ul><li>Immunity </li></ul></ul>
  17. 17. Innate Defenses (Nonspecific) <ul><li>Specific Resistance – diseases are unique to a species </li></ul><ul><ul><li>(i.e. measles, mumps, gonorrhea, syphilis) </li></ul></ul><ul><li>Mechanical barriers – first line of defenses </li></ul><ul><ul><li>Skin </li></ul></ul><ul><ul><li>Mucous membranes in respiratory, digestive, urinary, and reproductive passageways </li></ul></ul><ul><li>Chemical barriers, including: </li></ul><ul><ul><li>Enzymes (gastric juices, tears, ect) </li></ul></ul><ul><ul><li>Salts in perspiration </li></ul></ul><ul><li>Fever – raises brain’s set point to a higher temperature </li></ul><ul><li>Natural Killer (NK) cells – a type of lymphocyte </li></ul><ul><ul><li>Protect body from viruses and cancer </li></ul></ul><ul><ul><li>Secret perforins which disintegrate cells </li></ul></ul><ul><li>Inflammation – white blood cells accumulate at site of infection/invasion </li></ul><ul><li>Phagocytosis – removal of foreign particles </li></ul><ul><ul><li>Neutrophils, monocytes become macrophages </li></ul></ul>
  18. 18. Adaptive Defenses – Immunity (Specific) <ul><li>Immune response distinguishes between “self” and “not-self” </li></ul><ul><li>Antigens = molecules that trigger immune response </li></ul><ul><li>Carried out by lymphocytes and macrophages </li></ul><ul><li>Before birth your cells inventory proteins and other large molecules of the body as “self” </li></ul><ul><li>Receptors on lymphocytes enable cells to recognize foreign antigens </li></ul>
  19. 19. Lymphocytes
  20. 20. Lymphocyte Origins <ul><li>T-Lymphocytes </li></ul><ul><li>Leave bone marrow as undifferentiated lymphocytes </li></ul><ul><li>70-80% of circulating lymphocytes </li></ul><ul><li>Reside in: </li></ul><ul><ul><li>Lymph nodes </li></ul></ul><ul><ul><li>Thoracic duct </li></ul></ul><ul><ul><li>White pulp of the spleen </li></ul></ul><ul><li>B-Lymphocytes </li></ul><ul><li>Thought to reside in the bone marrow until differentiation </li></ul><ul><li>20-30% of circulating lymphocytes </li></ul><ul><li>Reside in: </li></ul><ul><ul><li>Lymph nodes </li></ul></ul><ul><ul><li>Spleen </li></ul></ul><ul><ul><li>Bone marrow </li></ul></ul><ul><ul><li>Intestinal lining </li></ul></ul>
  21. 21. Lymphocyte Function <ul><li>T-Cells </li></ul><ul><li>Attach to antigen bearing cells  cellular immune response </li></ul><ul><li>Release cytokines (i.e. interleukins) which cause a cellular response to antigens </li></ul><ul><li>Release toxins which kill target cells </li></ul><ul><li>B-Cells </li></ul><ul><li>Differentiate into plasma cells and produce antibodies </li></ul><ul><li>Humoral reponse (fluids) </li></ul><ul><li>Up to 2000 antibodies per second </li></ul><ul><li>Antibodies travel through fluids to destroy antigens </li></ul><ul><li>T-Cells and B-Cells both: </li></ul><ul><li>Respond to recognized antigens and create clones of themselves </li></ul><ul><li>Have millions of varieties </li></ul><ul><ul><li>Each variety responds to a specific antigen </li></ul></ul>
  22. 22. T-Cells <ul><li>Activation requires an antigen presenting cell </li></ul><ul><ul><li>Macrophages, B-cells, ect </li></ul></ul><ul><li>Helper T-Cells </li></ul><ul><ul><li>Stimulate B-cells to produce antibodies </li></ul></ul><ul><ul><li>CD4 helper T-cells largest target of HIV </li></ul></ul><ul><li>Cytotoxic T-Cells </li></ul><ul><ul><li>Watch for cancerous and virally infected cells </li></ul></ul><ul><ul><li>When activated: </li></ul></ul><ul><ul><ul><li>proliferates and creates more clones </li></ul></ul></ul><ul><ul><ul><li>binds and releases more perforins to cut open antigen bearing cells </li></ul></ul></ul><ul><li>Memory T-Cells </li></ul><ul><ul><li>Responds to a second exposure of an antigen and immediately becomes a cytotoxic T-cell </li></ul></ul>
  23. 23. B-Cells <ul><li>Activated when it fits an antigen that fits its antigen receptors </li></ul><ul><ul><li>Immediately divides repeatedly </li></ul></ul><ul><ul><ul><li>Most need helper T-cell cytokines to stimulate clone proliferation </li></ul></ul></ul><ul><li>Some B-cells become memory B-cells, others become plasma cells that secrete antibodies </li></ul><ul><li>Different B-Cells respond to different antigens on a pathogen’s surface </li></ul>
  24. 24. Antibodies
  25. 25. Antibody Molecules <ul><li>Make up gamma-globulin part of plasma protein (aka immunoglobulins) </li></ul><ul><li>Each immunoglobulin contains 4 chains of amino-acids </li></ul><ul><li>Make a “Y” shape, where the legs, or “v”, of the “Y” is the binding site </li></ul><ul><li>Each binding site is specialized to react to a specific antigen molecule </li></ul>
  26. 26. Types of Immunoglobulins <ul><li>G, A, M, E, D </li></ul><ul><ul><li>E = least common immunoglobulin </li></ul></ul><ul><li>G, A, M (IgG, IgA, IgM) = most common immunoglobulins </li></ul><ul><li>IgG – found in tissue and plasma </li></ul><ul><ul><li>Effective against bacteria, viruses, and toxins </li></ul></ul><ul><ul><li>Activates complement </li></ul></ul><ul><li>IgA – found in breast milk, tears, nasal fluid, gastric juice, intestinal juice, bile, and urine </li></ul><ul><li>IgM – found in the plasma </li></ul><ul><ul><li>Contains anti-IgA and anti-IgB antibodies </li></ul></ul>
  27. 27. Antibody Actions <ul><li>Directly attack antigens </li></ul><ul><ul><li>Agglunation, precipitation, neutralization </li></ul></ul><ul><li>Activates enzymes (complements) that attack the antibodies </li></ul><ul><li>Stimulate local changes to prevent spread of infection (i.e. inflammation) </li></ul>
  28. 28. Complements <ul><li>Opsonization – cells more susceptible to phagocytosis </li></ul><ul><li>Chemotaxis – attracts macrophages and neutrophils </li></ul><ul><li>Agglutination – clumping together of antigen bearing cells </li></ul><ul><li>Lysis – causes osmotic rupture of foreign cell </li></ul><ul><li>Neutralization – altering molecular structure of viruses, making them harmless </li></ul>