1 Chapter 20 ly mphatic System and Immunity

2 Introduction Network of vessels - Transport body fluids Network of vessels - Transport body fluids Lymphatic vessels Lymphatic vessels Collect excess fluid Collect excess fluid Carry excess fluid from spaces between cells Carry excess fluid from spaces between cells Special vessels called lacteals – transport fats to circulatory system Special vessels called lacteals – transport fats to circulatory system Organs of lymphatic system – defend against disease. Organs of lymphatic system – defend against disease.

3 Lymphatic system

4 Lymphatic pathways Start as lymphatic capillaries – merge to form larger vessels. Start as lymphatic capillaries – merge to form larger vessels. Empty into circulatory system. Empty into circulatory system. Tiny closed ended tubes that extend into interstitial spaces Tiny closed ended tubes that extend into interstitial spaces Receive tissue fluid through thin walls Receive tissue fluid through thin walls Once fluid is inside, called Lymph. Once fluid is inside, called Lymph. Vessels – thinner than veins, but have 3 layers and valves Vessels – thinner than veins, but have 3 layers and valves Larger vessels pass through lymph nodes and merge to form trunks. Larger vessels pass through lymph nodes and merge to form trunks. Trunks and ducts Trunks and ducts Drain lymph from body Drain lymph from body Named for regions they drain Named for regions they drain Join thoracic duct or right lymphatic duct. Join thoracic duct or right lymphatic duct. Dump into subclavian veins Dump into subclavian veins

5 Tissue fluid and Formation of Lymph Tissue fluid becomes lymph when it enters lymphatic capillary Tissue fluid becomes lymph when it enters lymphatic capillary Lymph formation depends on tissue fluid formation Lymph formation depends on tissue fluid formation Tissue fluid formation Tissue fluid formation Tissue fluid – water + dissolved substances Tissue fluid – water + dissolved substances During filtration, some fluid is forced into lymphatic capillaries During filtration, some fluid is forced into lymphatic capillaries

6 Lymph Movement Skeletal muscle contraction, breathingt etc force lymph through vessels Skeletal muscle contraction, breathingt etc force lymph through vessels Edema – condition that interferes with lymph flow Edema – condition that interferes with lymph flow Surgery may result in removal of lymphatic vessels Surgery may result in removal of lymphatic vessels

Lymph nodes Contains lymphocytes and macrophages Contains lymphocytes and macrophages Located along lymphatic pathways Located along lymphatic pathways Structure – bean shaped Structure – bean shaped Hilum – indented area where blood vessels enter Hilum – indented area where blood vessels enter Connecive tissue covering Connecive tissue covering Occur in chains along lymph vessels Occur in chains along lymph vessels Function – filter lymph, remove bacteria and cellular debris Function – filter lymph, remove bacteria and cellular debris Centers of lymphocyte production Centers of lymphocyte production

8 Lymph Node Locations

9 Lymph node

10 Thymus Soft, bi-lobed organ behind sternum Soft, bi-lobed organ behind sternum Shrinks during lifetime Shrinks during lifetime Surrounded by Connective tissue capsule Surrounded by Connective tissue capsule Lobules contain lymphocytes Lobules contain lymphocytes Some mature into T lymphocytes which provide immunity Some mature into T lymphocytes which provide immunity Secretes thymosin-hormone that influences t lymphocyte maturation Secretes thymosin-hormone that influences t lymphocyte maturation

11 Spleen Located in upper left abdominal cavity Located in upper left abdominal cavity Largest lymphatic organ Largest lymphatic organ Looks like lymph node, but contains blood Looks like lymph node, but contains blood Contains white and red pulp Contains white and red pulp Filters blood and removes damaged blood cells and bacteria Filters blood and removes damaged blood cells and bacteria

12 Flu attack

13 Body Defenses against Infection Pathogens – disease causing agents – produce infections Pathogens – disease causing agents – produce infections 2 Lines of defense 2 Lines of defense Non specific – guards against any pathogen Non specific – guards against any pathogen Specific (immunity) – mounts response against very specific target Specific (immunity) – mounts response against very specific target Carried out by lymphocytes that recognize invader Carried out by lymphocytes that recognize invader

14 Non Specific Species Resistance – resistant to diseases that affect other species – unique chemical environment/temperature Species Resistance – resistant to diseases that affect other species – unique chemical environment/temperature Mechanical barriers – unbroken skin/mucous membranes prevent entry Mechanical barriers – unbroken skin/mucous membranes prevent entry First line of defense First line of defense Chemical barriers – high acidity or caustic environment provided by gastric juice, or lysozyme in tears. Chemical barriers – high acidity or caustic environment provided by gastric juice, or lysozyme in tears. Interferons – antiviral – produced by infected cells to protect others Interferons – antiviral – produced by infected cells to protect others Fever – interferes with favorable conditions that promote bacterial growth Fever – interferes with favorable conditions that promote bacterial growth Iron is reduced, fewer nutrients Iron is reduced, fewer nutrients Phagocytic cells increase vigor of attack Phagocytic cells increase vigor of attack Inflammation – redness, swelling, heat, pain Inflammation – redness, swelling, heat, pain Increase of blood volume, dilation of blood vessels, invasion of white blood cells, fibroblast sac production Increase of blood volume, dilation of blood vessels, invasion of white blood cells, fibroblast sac production Phagocytosis by macrophage remove invaders Phagocytosis by macrophage remove invaders

15 Macrophage

16 Specific (immunity) 2 nd line of defense 2 nd line of defense Attack against specific recognized foreign molecule Attack against specific recognized foreign molecule Antigens Antigens Self inventory taken before birth Self inventory taken before birth Antigens - non self - produce immune response Antigens - non self - produce immune response

17 Antigens Self inventory before birth Self inventory before birth Body responds to non-self substances Body responds to non-self substances Antigens elicit immune response Antigens elicit immune response

Lymphocyte origins Fetal development – red bone marrow releases lymphocytes Fetal development – red bone marrow releases lymphocytes Most become t cells, remainder become b cells Most become t cells, remainder become b cells B and t cells stay in lymphatic organs. B and t cells stay in lymphatic organs. 18

19 Lymphocyte Functions T cells T cells Cell-mediated immunity - Attack foreign cells such as bacteria Cell-mediated immunity - Attack foreign cells such as bacteria Attack foreign particles by cell to cell contact Attack foreign particles by cell to cell contact Secrete cytokines Secrete cytokines Enhance cellular response to antigens Enhance cellular response to antigens Secrete toxins that kill target cells or inhibit growth Secrete toxins that kill target cells or inhibit growth B cells B cells Become plasma cells which produce antibodies - antibody mediated immunity Become plasma cells which produce antibodies - antibody mediated immunity

20 T cells and cellular immune response Requires presence of antigen-presenting cell that has already encountered antigen. Requires presence of antigen-presenting cell that has already encountered antigen. Encounters macrophage displaying antigen. If antigen fits helper t cells antigen receptor, it is activated Encounters macrophage displaying antigen. If antigen fits helper t cells antigen receptor, it is activated Cytotoxic t cells - eliminate tumor and virus infected cells by releasing perforin Cytotoxic t cells - eliminate tumor and virus infected cells by releasing perforin Memory t cells - future response to antigen Memory t cells - future response to antigen

21 Killer cells

22 B cells and Humoral Immune response B cell activated B cell activated Produces clone Produces clone Normally requires presence of helper t cells Normally requires presence of helper t cells T cell releases cytokines that activate it so it can form a clone T cell releases cytokines that activate it so it can form a clone Plasma cells produce and secrete antibodies Plasma cells produce and secrete antibodies

23 Macrophages, b-cells

24 Types of antibodies Antibodies - immunoglobulin Antibodies - immunoglobulin IgG IgG Defends again bacteria, viruses and toxins Defends again bacteria, viruses and toxins IgA IgA in exocrine gland secretions in exocrine gland secretions IgM IgM In plasma - activates complement In plasma - activates complement Reacts with blood cells in transfusions Reacts with blood cells in transfusions IgD IgD B cell activation B cell activation IgE IgE Promotes allergic reactions Promotes allergic reactions

25 Classification of immunity Natural active - occurs after exposure to pathogen Natural active - occurs after exposure to pathogen Artificially acquired active – through vaccines Artificially acquired active – through vaccines Artificially acquired passive – injection of antibiotics Artificially acquired passive – injection of antibiotics Naturally acquired passive – antibodies passed to fetus Naturally acquired passive – antibodies passed to fetus

26 Allergic reactions Excessive immune responses - may lead to tissue damage Excessive immune responses - may lead to tissue damage Delayed reaction - repeated exposure Delayed reaction - repeated exposure Immediate reaction - inherited Immediate reaction - inherited Histamine Anaphylactic shock Histamine Anaphylactic shock

27 Transplantation and tissue rejection Immune system reacts with foreign antigens Immune system reacts with foreign antigens Tissue rejection Tissue rejection Donor match reduce change of rejection Donor match reduce change of rejection

28 Autoimmunity Antibodies produced against own antigens Antibodies produced against own antigens Autoimmune disorders – may result from virus, t cell development, reaction to nonself antigen that bears close resemblance to self antigen. Autoimmune disorders – may result from virus, t cell development, reaction to nonself antigen that bears close resemblance to self antigen.