Transcript Document
Chapter 20 lymphatic System and Immunity 1 Introduction Network of vessels - Transport body fluids Lymphatic vessels Collect excess fluid Carry excess fluid from spaces between cells Special vessels called lacteals – transport fats to circulatory system Organs of lymphatic system – defend against disease. 2 Lymphatic system QuickTime™ and a decompressor are needed to see this picture. 3 Lymphatic pathways Start as lymphatic capillaries – merge to form larger vessels. Empty into circulatory system. Tiny closed ended tubes that extend into interstitial spaces Receive tissue fluid through thin walls Vessels – thinner than veins, but have 3 layers and valves Once fluid is inside, called Lymph. Larger vessels pass through lymph nodes and merge to form trunks. Trunks and ducts Drain lymph from body Named for regions they drain Join thoracic duct or right lymphatic duct. Dump into subclavian veins 4 Tissue fluid and Formation of Lymph Tissue fluid becomes lymph when it enters lymphatic capillary Lymph formation depends on tissue fluid formation Tissue fluid formation Tissue fluid – water + dissolved substances During filtration, some fluid is forced into lymphatic capillaries 5 Lymph Movement Skeletal muscle contraction, breathingt etc force lymph through vessels Edema – condition that interferes with lymph flow Surgery may result in removal of lymphatic vessels 6 Lymph nodes Contains lymphocytes and macrophages Located along lymphatic pathways Structure – bean shaped Hilum – indented area where blood vessels enter Connecive tissue covering Occur in chains along lymph vessels Function – filter lymph, remove bacteria and cellular debris Centers of lymphocyte production Lymph Node Locations 8 Lymph node 9 Thymus Soft, bi-lobed organ behind sternum Shrinks during lifetime Surrounded by Connective tissue capsule Lobules contain lymphocytes Some mature into T lymphocytes which provide immunity Secretes thymosin-hormone that influences t lymphocyte maturation 10 Spleen Located in upper left abdominal cavity Largest lymphatic organ Looks like lymph node, but contains blood Contains white and red pulp Filters blood and removes damaged blood cells and bacteria 11 Flu attack QuickTime™ and a decompressor are needed to see this picture. 12 Body Defenses against Infection – disease causing agents – produce infections 2 Lines of defense Pathogens specific – guards against any pathogen Specific (immunity) – mounts response against very specific target Non Carried out by lymphocytes that recognize invader 13 Non Specific Species Resistance – resistant to diseases that affect other species – unique chemical environment/temperature Mechanical barriers – unbroken skin/mucous membranes prevent entry Chemical barriers – high acidity or caustic environment provided by gastric juice, or lysozyme in tears. Iron is reduced, fewer nutrients Phagocytic cells increase vigor of attack Inflammation – redness, swelling, heat, pain Interferons – antiviral – produced by infected cells to protect others Fever – interferes with favorable conditions that promote bacterial growth First line of defense Increase of blood volume, dilation of blood vessels, invasion of white blood cells, fibroblast sac production Phagocytosis by macrophage remove invaders 14 Macrophage QuickTime™ and a decompressor are needed to see this picture. 15 Specific (immunity) 2nd line of defense Attack against specific recognized foreign molecule Antigens Self inventory taken before birth Antigens - non self - produce immune response 16 Antigens Self inventory before birth Body responds to non-self substances Antigens elicit immune response 17 Lymphocyte origins Fetal development – red bone marrow releases lymphocytes Most become t cells, remainder become b cells B and t cells stay in lymphatic organs. 18 Lymphocyte Functions T cells Cell-mediated immunity - Attack foreign cells such as bacteria Secrete cytokines Attack foreign particles by cell to cell contact Enhance cellular response to antigens Secrete toxins that kill target cells or inhibit growth B cells Become plasma cells which produce antibodies antibody mediated immunity 19 T cells and cellular immune response 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 Cytotoxic t cells - eliminate tumor and virus infected cells by releasing perforin Memory t cells - future response to antigen 20 Killer cells QuickTime™ and a decompressor are needed to see this picture. 21 B cells and Humoral Immune response B cell activated Produces clone Normally requires presence of helper t cells T cell releases cytokines that activate it so it can form a clone Plasma cells produce and secrete antibodies 22 Macrophages, b-cells QuickTime™ and a decompressor are needed to see this picture. 23 Types of antibodies Antibodies - immunoglobulin IgG Defends again bacteria, viruses and toxins IgA in exocrine gland secretions IgM IgD In plasma - activates complement Reacts with blood cells in transfusions B cell activation IgE Promotes allergic reactions 24 Classification of immunity Natural active - occurs after exposure to pathogen Artificially acquired active – through vaccines Artificially acquired passive – injection of antibiotics Naturally acquired passive – antibodies passed to fetus 25 Allergic reactions Excessive immune responses - may lead to tissue damage Delayed reaction - repeated exposure Immediate reaction - inherited Histamine Anaphylactic shock 26 Transplantation and tissue rejection Immune system reacts with foreign antigens Tissue rejection Donor match reduce change of rejection 27 Autoimmunity 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. 28