Chapter 14 Lymphatic System and Immunity

1. 1 Chapter 14 Lymphatic System and Immunity

2. 2 BellworkMarch 21, 2011 What are the organs & general functions of the lymphatic system?

3. 3 14.1 Introduction The lymphatic system is comprised of a network of vessels that transport body fluids, cells and chemicals in those vessels and organs and glands that produce them. Lymphatic vessels collect and carry away excess fluid from interstitial spaces and special vessels called lacteals transport fats to circulatory system. The organs of lymphatic system help defend against disease.

4. 4 14.2 Lymphatic Pathways Lymphatic pathways start as lymphatic capillaries that merge to form larger vessels that empty into circulatory system. Lymphatic capillaries are tiny, closed-ended tubes that extend into interstitial spaces. They receive tissue fluid through their thin walls; once inside, tissue fluid is called lymph.

5. 5 Lymphatic Vessels The walls of lymphatic vessels are thinner than those of veins but are constructed with same three layers with semilunar valves on inside. Larger lymphatic vessels pass through lymph nodes and merge to form lymphatic trunks.

6. 6 Lymphatic Trunks and Collecting Ducts Lymphatic trunks drain lymph from body and are named for regions they drain. These trunks join one of two collecting ducts--either thoracic duct or right lymphatic duct. Thoracic duct drains into left subclavian vein, while right lymphatic duct drains into right subclavian vein.

7. 7 BellworkMarch 22, 2011 Trace the general pathway of lymph from the interstitial spaces to the bloodstream.

8. 8 14.3 Tissue Fluid and Lymph - Tissue fluid becomes lymph once it has entered a lymphatic capillary; lymph formation depends on tissue fluid formation.

9. 9 Tissue Fluid Formation Tissue fluid is made up of water and dissolved substances that leave blood capillaries by filtration and diffusion. During filtration, some smaller proteins leak from capillaries into tissues and are not returned to bloodstream, thus increasing osmotic pressure within tissues.

10. 10 Lymph Formation and Function Rising osmotic pressure in tissues interferes with the return of fluids to bloodstream. Increasing interstitial pressure forces some of the fluid into lymphatic capillaries.

11. 11 14.4 Lymph Movement Hydrostatic pressure of tissue fluid drives entry of lymph into lymphatic capillaries. Forces that move blood in veins (skeletal muscle contraction, breathing movements, and contraction of smooth muscle in walls of lymphatic trunks) are forces that propel lymph through lymphatic vessels.

12. 12 Edema A condition that interferes with flow in lymph will result in edema. During surgery, lymphatic vessels or tissues may be removed or disturbed, resulting in edema.

13. 13 BellworkMarch 24, 2011 What are two functions of lymph?

14. 14 14.5 Lymph Nodes

15. 15 Location & Function of Lymph Nodes

16. 16 14.6 Thymus and Spleen

17. 17 Spleen

18. 18 BellworkMarch 25, 2011 What is the location & function of the thymus? Of the spleen?

19. 19 14.7 Body Defenses Against Infection Pathogens: disease-causing agents Can produce infections within the body. Body has two lines of defense against pathogens: Nonspecific defenses - guard against any pathogen Specific defenses (immunity) that mount a response against a specific target. Carried out by lymphocytes that recognize a specific invader.

20. 20 14.8 Nonspecific Defenses - Species Resistance: A species is resistant to diseases that affect other species because it has a unique chemical environment or temperature that fails to provide conditions required by pathogens of another species.

21. 21 Mechanical Barriers Mechanical Barriers: Unbroken skin and mucous membranes of body create Prevent entry of certain pathogens Body’s first line of defense

22. 22 Chemical Barriers Chemical barriers: highly acidic and caustic environment provided by gastric juice, or lyzozyme in tears, kill many pathogens. Interferons: hormone-like peptides that serve as antiviral substances Produced by cells when infected with viruses and induce nearby cells to produce antiviral enzymes that protect them from infection.

23. 23 Fever Offers powerful protection against infection by interfering with proper conditions that promote bacterial growth. During fever, amount of iron in blood is reduced, and fewer nutrients are available to support growth of pathogens. Phagocytic cells attack with greater vigor when temperature rises.

24. 24 Inflammation Inflammation: tissue response to a pathogen Signs: redness, swelling, heat, and pain. Major actions that occur during an inflammatory response include: dilation of blood vessels; increase of blood volume in affected areas invasion of white blood cells into affected area appearance of fibroblasts and their production of a sac around the area.

25. 25 Phagocytosis Most active phagocytes are neutrophils and monocytes; these leave bloodstream at areas of injury by diapedesis. Neutrophils engulf smaller particles; monocytes attack larger ones. Monocytes give rise to macrophages, which become fixed in various tissues. Monocytes, macrophages, and neutrophils constitute mononuclear phagocytic system. Removes foreign particles from the lymph.

26. 26 BellworkMarch 28, 2011 Defense mechanisms that prevent the entry of many types of pathogens and destroy them if they enter provide ___________ defense. Mechanisms that are very precise,targeting specific pathogens provide _____________ defense.

27. 27 14.9 Adaptive (Specific) Defenses or Immunity - The body’s third line of defense, immunity refers to the response mounted by body against specific, recognized foreign molecules.

28. 28 Antigens Before birth, body makes an inventory of “self” proteins and other large molecules. Antigens are generally larger molecules that elicit an immune response. Sometimes small molecules called haptens combine with larger molecules and become antigenic.

29. 29 Lymphocyte Origins During fetal development, red bone marrow releases lymphocytes into circulation 70-80% become T lymphocytes (T cells) and the rest become B lymphocytes (B cells). Undifferentiated lymphocytes that reach thymus become T cells; B cells are thought to mature in bone marrow. Both B and T cells reside in lymphatic organs.

30. 30 T Cells T cells attack foreign, antigen-bearing cells, such as bacteria, by direct cell-to-cell contact, providing cell-mediated immunity. T cells also secrete cytokines (lymphokines) that enhance cellular response to antigens. T cells may also secrete toxins that kill target cells, or produce growth-inhibiting factors or interferon to interfere with viruses and tumor cells.

31. 31 B Cells B cells attack pathogens by differentiating into plasma cells that secrete antibodies (immunoglobulins). Body fluids attack and destroy specific antigens or antigen-bearing particles through antibody-mediated immunity also called humoral immune response.

32. 32 T Cells and Cellular Immune Response T cell activation requires the presence of an antigen-presenting cell, such as a B cell or macrophage, that has already encountered antigen. In order for a helper T cell to become activated, it must first encounter a macrophage displaying antigen on its major histocompatibility complex (MHC) proteins; if antigen fits helper T cell’s antigen receptor, it becomes activated and stimulates B cells to produce antibodies

33. 33 T Cells and Cellular Immune Response Cytotoxic T cells continually monitor body's cells, recognizing and eliminating tumor cells and virus-infected cells by release of proteins Cytotoxic T cells become activated when antigen binds to its receptors. Memory T cells provide a no-delay response to any future exposure to the same antigen.

34. 34 BellworkMarch 29, 2011 What are the functions of T Cells and B Cells?

35. 35 B Cells and Humoral Immune Response B cell may become activated and produce a clone of cells when its antigen receptor encounters its matching antigen, but most B cells need helper T cells for activation. When a helper T cell encounters a B cell that has itself encountered an antigen, helper T cell releases cytokines that activate the B cell so that it can divide and form a clone.

36. 36 B Cells and Humoral Immune Response Some of the B cells become plasma cells, producing and secreting antibodies. Like T cells, some of the B cells become memory cells to respond to future encounters with the antigen.

37. 37 5 Major Types of Antibodies IgG - tissue fluid and plasma and defends against bacterial cells, viruses, and toxins and activates complement. 2. Inga is in exocrine gland secretions (breast milk, saliva, tears) and defends against bacteria and viruses. 3. IgM is found in plasma & activates complement and reacts with blood cells during transfusions. 4. IgD is found on the surface of most B lymphocytes and functions in B cell activation. 5. IgE is found in exocrine gland secretions and promotes allergic reactions

38. 38 Immune Response - When B or T cells become activated first time, their actions constitute a primary immune response, after which some cells remain as memory cells. - If same antigen is encountered again, more numerous memory cells can mount a more rapid response, known as the secondary immune response.

39. 39 Classification of Immunity Naturally acquired active immunity occurs after exposure to antigen itself. Artificially acquired active immunity occurs through use of vaccines, without person becoming ill from disease. Naturally acquired passive immunity occurs as antibodies are passed from mother to fetus and is short-lived.

40. 40 Allergic Reactions Allergic reactions to allergens are excessive immune responses that may lead to tissue damage. A delayed-reaction allergy results from repeated exposure to substances that cause inflammatory reactions in skin. An immediate-reaction allergy is an inherited ability to overproduce IgE. During allergic reactions, mast cells release histamine and leukotrienes, producing a variety of effects. Allergy mediators sometimes flood body, resulting in anaphylactic shock, a severe form of immediate- reaction allergy.

41. 41 Transplantation and Tissue Rejection A transplant recipient’s immune system may react with foreign antigens on the surface of transplanted tissue, causing a tissue rejection reaction. Close matching of donor and recipient tissues can reduce chances of tissue rejection, and use of immunosuppressive drugs may reduce rejection, although individual may be more susceptible to infection.

42. 42 Autoimmunity (Autoimmune Disorders) Immune system manufactures antibodies against some of its own antigens. Autoimmune disorders may result from viral infection, faulty T cell development, or reaction to a nonself antigen that bears close resemblance to a self antigen.

43. How the Immune System Works Video