The Lymphatic System

1. The Lymphatic System Anatomy & Physiology

2. Lymphatic System-General • 2 Main Parts • Lymphatic vessels • Lymphoid tissues/organs • FUNCTIONS: • Drain excess fluid (edema) and returns it to blood • Plays essential roles in body defense and resistance to disease

3. Lymphatic System-General • Lymph—excess tissue fluid • Properties of lymphatic vessels • One way system toward the heart • No pump • Lymph moves toward the heart • Transported through milking action of skeletal muscle • Rhythmic contraction of smooth muscle in vessel walls helps pump the lymph through the system

4. Relationship of Lymphatic Vessels to Blood Vessels

5. Lymphatic Vessels • Lymph capillaries • Walls overlap to form flap-like minivalves to allow entrance for lymph • Fluid leaks into lymph capillaries • Lymph Capillaries are anchored to connective tissue by filaments • Higher pressure on the inside of the capillary closes minivalves • Fluid is forced along the vessel for examination • Examined by cells of immune system for any potential threats

7. Lymphatic Vessels • Lymphatic collecting vessels • Collect lymph from lymph capillaries • Carry lymph to and away from lymph nodes • Return fluid to circulatory veins near the heart • Right lymphatic duct • Drains lymph to right arm/head/thorax • Thoracic duct • Drains rest of body that R.Lymphduct doesn’t

8. Lymph • Harmful materials that enter lymph vessels • Bacteria • Viruses • Cancer cells • Cell debris

9. Lymph Nodes • Filter lymph before it is returned to the blood • Areas of high concentration? • Inguinal, axillary, and cervical regions • Defense cells within lymph nodes • Macrophages—engulf and destroy foreign substances • Lymphocytes—provide immune response to antigens • Nodes swell when fighting infection because nodes have engulfed the foreign substance to prevent it from spreading

10. Lymph Node Structure • Most are kidney-shaped and less than 1 inch long • Cortex • Outer part • Contains follicles—collections of lymphocytes • Medulla • Inner part • Contains phagocytic macrophages

11. Other Lymphoid Organs • Several other organs contribute to lymphatic function • Spleen • Thymus • Tonsils • Peyer’s patches

12. Spleen • Blood filled organ which filters blood • Location: Left side of abdomen above diaphragm • Functions: • Filters/cleanses blood of foreign substances • Destroy worn-out blood cells • Recycles components of worn out blood cells (i.e. hemoglobin) • Stores platelets • Protect body during hemorrhage

13. Thymus Gland • Lymphoid mass found in throat • Function: Programs lymphocytes with the help of thymosin (hormone)

14. Tonsils • Small, lymphoid tissue in back of throat • Function: Capture and remove any foreign pathogens(substances) • Reason they become swollen during colds/viruses

15. Peyer’s Patches • Location: Wall of small intestine • Function: Capture and destroy bacteria • Prevent foreign pathogens from penetrating intestinal wall

16. Body Defenses • The body is constantly in contact with bacteria, fungi, and viruses • The body has two defense systems for foreign materials • Innate (nonspecific) defense system • Attacks ANY foreign pathogen • Adaptive (specific) defense system • Attacks SPECIFIC substances • Immunity—specific resistance to disease • -Immun=free

17. Immune System

18. Innate Body Defenses • AKA “non-specific defense system” • Innate body defenses are mechanical barriers to pathogens such as • Body surface coverings • Intact skin • Mucous membranes • Line all body cavities that are exposed (i.e. digestive, respiratory, urinary, and reproductive tracts) • Specialized human cells • Chemicals produced by the body

19. Surface Membrane Barriers:First Line of Defense • Skin and mucous membranes • Physical barrier to foreign materials • Also provide protective secretions • pH of the skin is acidic to inhibit bacterial growth • Sebum is toxic to bacteria • Stomach releases hydrochloric acid to kill pathogens • Saliva and lacrimal fluid contain lysozymes which kill bacteria • Mucus traps microorganisms and prevent them from entering the digestive or respiratory tract

20. Cells and Chemicals:Second Line of Defense • Phagocytes • I.e. macrophage or neutrophil • Swallows foreign pathogen • Natural killer cells • Kill cancer and virus cells • Fight off these pathogens by detecting sugar molecules on pathogen’s surface

21. Cells and Chemicals:Second Line of Defense Cont’d • Inflammatory response • Happens when tissue is injured • 4 signs: Redness, heat, inflammation, swelling pain • Histamine & Kinins causes: • Vessels to dilate causing inflammation • Activate pain receptors to alert body of problem • Attract WBCs and phagocytes to clean cellular debris from tissue damage

22. Cells and Chemicals:Second Line of Defense Cont’d • Antimicrobial proteins • Help fight pathogens by attacking them or inhibiting their progress through the use of? • Complement proteins • Bind to sugar receptors on pathogen’s cell and causes holes which allow water to enter the cell and cause it to burst • Interferon: • Bind to viruses’ cells and cause proliferation of interferon molecules which hinder the viruses’ cell replication

23. Cells and Chemicals:Second Line of Defense Cont’d • Fever • Effects of fever include: • Prohibiting iron or zinc availability which bacteria require to multiply • Increases metabolic rate which in turn increases the repair process • HIGH fevers can denature proteins and enzymes causing breakdowns within the body

24. Adaptive Defense System: Third Line of Defense • Immune response is the immune system’s response to a threat • Provides protection by the use of antigens through specificity • Immunology is the study of immunity • Antibodies are proteins that protect from pathogens

25. Third Line of Defense • When the body is exposed to a pathogen it builds “antibodies” • Less likely the body will acquire that same pathogen again • Immune response becomes stronger when faced with this invading pathogen in the future • 3 steps involved in immune response: • 1. Antigen specific: It attacks particular pathogens/foreign substances • 2. Systemic: Immunity is not confined to only the “initial infection site.” Can work through the circulatory system • 3. Memory: Has stronger attacks against previously fought pathogens

26. Third Line of Defense • Humoral Immunity/Antibody-mediated immunity • Antibodies fight off infection in the blood stream (humors/fluids) • Cellular Immunity/Cell-mediated immunity • Fights off viral cells, cancer cells, and foreign graft cells either directly or indirectly

27. Third Line of Defense • Antigen: • Any substance responsible for initiating an immune response • Examples of common antigens • Foreign proteins (strongest) • Nucleic acids • Large carbohydrates • Some lipids • Pollen grains • Microorganisms

28. Third Line of Defense • Self-antigens • Human cells have many surface proteins • Our immune cells do not attack our own proteins because they are recognizable in our bodies • Our cells in another person’s body can trigger an immune response because they are foreign • Restricts donors for transplants • Unless…medications are taken to suppress immune system • Hapten/Incomplete Antigen: • A small molecule antigen that cannot initiate the creation of antibodies • Instead, it binds with our proteins • The body doesn’t not recognize combination and attacks it • Examples: • Poison ivy, detergents, hair dyes, etc

29. Third Line of Defense-Cells • B lymphocytes/B-cells • Create antibodies and direct humoral immunity • T lymphocytes/T-cells • These cells do not produce antibodies • Mature T-cells are the most effective in fighting off foreign antigens

30. Third Line of Defense-Cells • Immunocompetent—cell becomes capable of responding to a specific antigen by binding to it • Cells of the adaptive defense system • Lymphocytes • Originate from hemocytoblasts in the red bone marrow • B lymphocytes become immunocompetent in the bone marrow (rememberBfor Bonemarrow) • T lymphocytes become immunocompetent in the thymus (rememberTforThymus)

31. Third Line of Defense-Cells • Cells of the adaptive defense system (continued) • Macrophages • Arise from monocytes found in bone marrow • Become widely distributed in lymphoid organs • Secrete cytokines (proteins important in the immune response) • Tend to remain fixed in the lymphoid organs • Unlike lymphocytes that circulate

32. Humoral (Antibody-Mediated) Immune Response • B lymphocytes with specific receptors bind to a specific antigen • The binding event activates the lymphocyte to undergo clonal selection • Lymphocyte grows and multiplies • Most B cells turn into plasma cells • The remaining B cells are stored as memory cells for future encounters with that antigen

33. Humoral (Antibody-Mediated) Immune Response • Secondary humoral responses • Memory cells are long-lived • A second exposure causes a rapid response • The secondary response is stronger and longer lasting

34. Active Immunity • Occurs when B cells encounter antigens and produce antibodies • Active immunity can be • Naturally acquired during bacterial and viral infections • Artificially acquired from vaccines

35. Passive Immunity • Occurs when antibodies are obtained from someone else • Acquired naturally from a mother to her fetus (naturally acquired) when passing through placenta • Conferred artificially from immune serum or gamma globulin (artificially acquired) • Shots given after exposure to certain pathogens • Immunological memory does not occur • Protection provided by “borrowed antibodies” • Lasts 2-3 weeks

36. Types of Acquired Immunity

37. Antibodies (Immunoglobulins or Igs) • Secreted by activated B cells • Respond to a specific antigen

38. Antibodies (Immunoglobulins or Igs) • Antibody classes • Antibodies of each class have slightly different roles • Five major immunoglobulin classes (MADGE) • IgM—can fix complement • IgA—found mainly in mucus • IgD—important in activation of B cell • IgG—can cross the placental barrier and fix complement • IgE—involved in allergies

39. Antibodies • Antibody function • Antibodies inactivate antigens in a number of ways • Complement fixation • Causes lysis of the cell • Neutralization • Bind to bacterial cells to block the release of that cell’s toxic chemicals • Agglutination • Clumping of foreign cells • Precipitation • When antigen-antibodies combine forming large complexes that settle out a solution that was agglutinated

40. Antibody Function

41. Cellular (Cell-Mediated) Immune Response • Antigens must be presented by macrophages to an immunocompetent T cell • T cells must recognize nonself and self (double recognition) • After antigen binding, clones form as with B cells, but different classes of cells are produced • Cytotoxic (killer T cells): Attack virus infected, cancer, or foreign graft cells • Helper T cells: Directors of immune system Recruit other cells to fight pathogens • Regulatory T cells: Stop the immune response once antigen is destroyed

42. Organ Transplants and Rejection • Major types of grafts • Autografts—tissue transplanted from one site to another on the same person • Isografts—tissue grafts from an identical person (identical twin) • Allografts—tissue taken from an unrelated person • Xenografts—tissue taken from a different animal species

43. Organ Transplants and Rejection • Autografts and isografts are ideal donors • Xenografts are never successful • Allografts are more successful with a closer tissue match

44. Disorders of Immunity: Allergies (Hypersensitivity) • Abnormal, vigorous immune responses • Types of allergies • Immediate hypersensitivity • Triggered by release of histamine from IgE binding to mast cells • Causes dilation of small blood vessels • Leads to: itchy, watery, runny nose/eyes • Reactions begin within seconds of contact with allergen • Anaphylactic shock—dangerous, systemic response • Throat closes in response to allergy, blocking airway

45. Disorders of Immunity: Immunodeficiencies • Production or function of immune cells or complement is abnormal • May be congenital or acquired • Includes AIDS (Acquired Immune Deficiency Syndrome) • Kills of Helper T-cells • Includes Severe Combined Immunodeficiency Disease (SCID) • Congenital condition • The immune system does not distinguish between self and nonself • The body produces antibodies and sensitized T lymphocytes that attack its own tissues