Y khoa, dược - The lymphatic and immune systems

28The Lymphatic and Immune Systems28-2Learning Outcomes28.1 List the pathways and organs of the lymphatic system and give their locations.28.2 Define lymph and tell how it is circulated in the body.28.3 Define the terms infection, pathogen, and antigen. 28.4 List and describe the nonspecific body defense mechanisms.28.5 Explain the signs and causes of inflammation. 28-3Learning Outcomes (cont.)28.6 Explain what is meant by body defenses.28.7 Define B cells and T cells and describe their locations and functions.28.8 Explain the importance of MHC proteins.28.9 List the different types of T cells and describe their functions.28.10 Explain how antibodies fight infection.28-4Learning Outcomes (cont.)28.11 List the different types of antibodies and tell how they differ.28.12 Define complement proteins and give their function.28.13 Explain the difference between the primary immune response and secondary immune response.28.14 Explain the four different types of acquired immunities.28.15 Describe the function of a vaccine.28-5Learning Outcomes (cont.)28.16 Define the terms cancer and carcinogen.28.17 Describe how cancers are diagnosed and treated.28.18 Explain how cancers are classified.28.19 Describe how allergies develop.28.20 Describe the causes, signs and symptoms, and treatments of other common immune disorders.28-6Introduction Immune system Protects the body againstBacteria Viruses Fungi Toxins Parasites CancerLymphatic systemWorks with immune system to remove disease-causing agentsOrgansThymusSpleenLymph nodes28-7The Lymphatic SystemNetwork of connecting vessels Collects fluid (lymph) between cells and returns it to bloodstreamPicks up lipids from digestive organs and transports them to bloodstreamFunctions to defend the body against pathogens28-8Lymphatic PathwaysLymphatic capillariesExtend into interstitial spacesPermeable, thin walls pick up fluid, now lymphDelivers lymph to lymphatic vesselsLymphatic vessels Deliver lymph to lymph nodesCells in nodes can remove pathogens from lymph and start an immune responseLeaves nodes through efferent lymphatic vesselsLymph System28-9Lymphatic Pathways (cont.)Lymphatic trunksReceive lymph from efferent lymphatic vessels Deliver it to Lymphatic collecting ductsThoracic ductLeft side of head and neck, left arm, left side of thorax, entire abdominopelvic area, and both legsRight lymphatic duct Right side of head and neck, right arm, and right side of chestLymph System28-10Tissue Fluid and LymphInterstitial fluidFluid in spaces between cells that has leaked from blood capillaries and has not been picked up by body cellsHigh in nutrients, oxygen, and small proteinsBecomes lymphPushed through lymphatic vessels by squeezing action of neighboring skeletal muscles and breathing movement28-11Back28-12Lymph NodesSmall, glandular structuresLocated along paths of larger lymphatic vesselsAfferent lymphatic vessels – Lymph to nodeEfferent lymphatic vessels – Lymph from node28-13Lymph Nodes (cont.)More lymph enters than can leave at one timeCells in nodesMacrophages – digest unwanted pathogensLymphocytes – start an immune response against pathogenNodes can generate some lymphocytes28-14The Thymus and SpleenThymus Soft, bi-lobed organLocated just above the heart in the mediastinumLarge in children, shrinks as we ageFunctions Same as lymph nodesAlso produces lymphocytesProduces thymosin – stimulates production of lymphocytes28-15The Thymus and Spleen (cont.)SpleenLargest lymphatic organLocated in the upper left quadrant of abdominal cavityFunctionsFilters blood similarly to lymph nodesRemoves worn-out red cellsIf removed (splenectomy), liver takes over most of its function28-16Apply Your KnowledgeWhat are the lymphatic collecting ducts and what area do they drain?ANSWER: The collecting ducts are: Thoracic duct, which drains the left side of the head and neck, left arm, left side of thorax, entire abdominopelvic area, and both legs; and the right lymphatic duct, which drains the right side of the head and neck, right arm, and right side of the chest.Correct!28-17Defenses Against DiseaseInfection The presence of a pathogen in or on the bodyPathogen A disease-causing agentInnate immunityNonspecific defenses to protect against pathogensNonspecific defensesSpecies resistanceMechanical barriersChemical barriersPhagocytosisFeverInflammation 28-18Specific Defenses Against DiseaseImmunities Protect against very specific pathogensAntigens Foreign substances in the bodyHaptensForeign substances too small to start an immune response by themselvesOther substancesProteins – antibodies and complementsWBCs – lymphocytes and macrophagesLymph systemCytokines – assist in immune response regulationMonokines – increase B cell production and stimulate WBC production28-19Defenses Against Disease (cont.)Two major types of lymphocytesB Cells and T CellsRecognize antigens in the bodyT Cells Cell-mediated response Bind to antigens on cells  and attack them directly Secrete lymphokines that  increase T cell production and directly kill cells with antigensB cells Respond to antigens by becoming plasma cells Plasma cells make antibodies Memory B cells produce stronger response with next exposure to antigenDiagram28-20Back28-21Defenses Against Disease (cont.)T cell activation Begins when macrophage ingests and digests pathogen with antigen on itAntigens are placed on cell membrane of macrophage T cell recognizes and binds to antigen and the major histocompatibility complex (MHC) on the surface of the macrophageNow can divide to form other types of T cells28-22Defenses Against Disease (cont.)Types Cytotoxic T cellsProtect body against viruses and cancer cellsHelper T cellsIncrease antibody formation, memory cell formation, B cell formation, and phagocytosisMemory T cellsRemember the pathogen that activated original T cellLater exposures trigger an immune response more effective than initial response28-23Defenses Against Disease (cont.)Natural killer (NK) cellsType of lymphocytePrimarily target cancer cellsKill on contactDo not recognize a specific antigen28-24Apply Your KnowledgeIdentify whether each item refers to T cells, B cells, or NK cells:___ Primarily target cancer cells___ Respond to antigens by becoming plasma cells___ Must be activated to respond to an antigen___ Bind to antigens on cells and attack them directly___ Kill on contact___ Need macrophages and MHC for activation___ Make antibodies against specific antigenBNKTTTBNKANSWER:Right on Target!28-25AntibodiesAlso called immunoglobulins IgA Prevents pathogens from entering bodyIgD Found on B cell membranesThought to control B cell activityIgE Found with IgAInvolved in triggering allergic reactions28-26Antibodies (cont.)IgGRecognizes bacteria, viruses, and toxinsActivates complementsIgM Large and binds to antigens on food, bacteria, or incompatible blood cellsActivates compliments28-27Antibodies (cont.)Actions that occur when antibodies bind to antigensAllow phagocytes to recognize and destroy antigensCause antigens to clump together, causing them to be destroyed by macrophages Cover the toxic portions of antigens, making them harmlessActivate complement Group of proteins in serum that attack pathogens by forming holes in themAttract macrophages to pathogens and can stimulate inflammation28-28Apply Your KnowledgeWhat are the possible actions that occur when antibodies bind to antigens?ANSWER: Possible actions include: They allow phagocytes to recognize and destroy  antigens. They make antigens clump together, causing them to be  destroyed by macrophages. They cover the toxic portions of antigens to make them harmless. They activate complements. Very Good!28-29Immune Responses and Acquired ImmunityPrimary immune response occurs with first exposure to antigenSlow processMemory cells are formedSecondary immune response with next exposure to same antigenQuick and carried out by memory cellsUsually prevents person from developing disease from the antigen28-30Immune Responses and Acquired Immunity (cont.)Naturally acquired active immunityNatural exposure to antigen – having an illnessMakes antibodies and memory cellsLong-lastingArtificially acquired active immunityInjected with pathogen – immunizations or vaccinesMakes antibodies and memory cellsLong-lasting28-31Immune Responses and Acquired Immunity (cont.)Naturally acquired passive immunityAcquired from motherBreast milkPlacentaShort-livedArtificially acquired passive immunityInjected with antibodies (such as antivenom)Short-lived28-32Apply Your KnowledgeANSWER: Immunization is an artificially acquired immunity because a person develops this immunity by being injected with a pathogen and then making antibodies and memory cells against the pathogen. After you give an immunization to a 2-year-old, her mother asks you why this will work to prevent her from getting a disease.Good Answer!28-33Major Immune System DisordersCancerUncontrolled growth of abnormal cells form malignant tumorsFactors known to cause cancer are called carcinogensTreatment based on stage0 – very early; cancer cells localizedI – spread to deeper layers or some in surrounding tissuesII – spread to surrounding tissues but contained in primary siteIII – spread beyond primary site into nearby areasIV – spread to other organsRecurrent – reappeared after treatment28-34Major Immune System Disorders (cont.)AllergiesImmune response to an allergenIgE antibodies bind to allergens and stimulate mast cells to release histamine and heparin, triggering allergic responseAllergy shotsSmall amounts of allergen stimulates production of IgG to prevent IgE from binding to antigen IgG antibodies do not stimulate mast cells, so immune response is not generated28-35Major Immune System Disorders (cont.)Allergy signs/symptomsInhaled allergens – runny nose, sneezing, coughing, wheezingIngested allergens – nausea, vomiting, diarrheaSkin allergens – rashesAllergens in blood – most life-threatening; can affect many organsTreatmentAntihistamines, decongestants – OTC or prescriptionEpinephrine for anaphylaxis – vasoconstriction, increasing BPAnaphylaxis – life-threatening response28-36Common Immune System Disorders Autoimmune diseaseBody attacks its own antigensExamples SclerodermaRheumatoid arthritisMultiple sclerosisGlomerulonephritisCrohn’s diseaseDiabetes mellitus, type I28-37Common Immune System Disorders (cont.)DisorderDescription AIDSDevelopment of severe signs and symptoms caused by HIV as it destroys lymphocytes; leaves immune system weakened and susceptible to other diseasesChronic fatigue syndrome (CFS)Condition of severe tiredness not relieved by rest and not related to other illnessesLymphedemaBlockage of lymphatic vessels results in tissue swelling that increases over time28-38Common Immune System Disorders (cont.)DisorderDescription Mononucleosis“Mono”; highly contagious viral infection spread through saliva of infected personSystemic lupus erythematous (SLE)Autoimmune disorder; produces antibodies that target own cells and tissues; affects women more often than men28-39Apply Your KnowledgeMatching:___ Immune response to a substance A. CFS___ Blockage of lymphatic vessels B. SLE___ “Kissing disease” C. Cancer___ “Butterfly” rash on face D. Autoimmune disease___ Severe tiredness E. Lymphedema___ Uncontrolled growth of abnormal cells F. Mononucleosis___ Body attacks its own antigens G. AllergyGFEDCBAANSWER:Excellent!28-40In Summary28.1 The lymph system is composed of pathways known as lymph vessels. In addition to the lymph vessels, the organs of the lymphatic system include lymph nodes located throughout the body, the thymus in the mediastinum, and the spleen located in the LUQ.28.2 Lymph is the body fluid found between the body’s cells. It circulates through the body via lymphatic capillaries, lymphatic vessels, lymph nodes, lymphatic trunk, collecting ducts, and to the subclavian vein.28-41In Summary (cont.)28.3 Infection is the presence of a pathogen in or on the body. A pathogen is a disease-causing agent, and antigens are foreign substances within the body that may or may not cause disease. 28.4 The nonspecific body defenses include species resistance, mechanical and chemical barriers, phagocytosis, fever, and inflammation.28.5 Inflammation is the result of injury or infection. Signs are redness, heat, swelling, and pain.28-42In Summary (cont.)28.6 Specific defenses are immunities or defenses against very specific antigens.28.7 B and T cells come from the bone marrow, thymus, lymph nodes, spleen, and the lining of the digestive tract and are found circulating in the blood. B cells utilize memory and plasma cells in a process called humoral or antibody-mediated immunity, and T cells bind directly to cell antigens, attacking them directly, producing cell-mediated immunity.28-43In Summary (cont.)28.8 T cells cannot be activated to produce immunity without MHC proteins and macrophages.28.9 Activated T cells may form cytotoxic cells which protect the body against viruses and certain types of cancer. Other T cells may become helper T cells, which increase antibody and memory cell and B cell formation and phagocytosis. Still other T cells become memory cells.28.10 Antibodies may work in the following ways: phagocytosis, antigen clumping, covering (inactivating) toxic portions of antigens, and activating complements.28-44In Summary (cont.)28.11 Antibodies are also known as immunoglobulins. IgA prevents pathogens from entering the body; IgD controls B cell activity; IgE works with IgA in triggering allergic reactions; IgG recognizes bacteria, viruses and toxins and activates complements; and IgM binds to antigens on food, bacteria, or incompatible blood cells. IgM also activates complements.28-45In Summary (cont.)28.12 Complements are serum proteins that attack pathogens by forming holes in them. They also attract macrophages and can stimulate inflammation.28.13 A primary immune response occurs the first time a person is exposed to an antigen. The response is slow and takes several weeks to occur. A secondary immune response occurs at the next exposure. This response is very quick and may prevent the person from becoming ill. 28-46In Summary (cont.)28.14 The four types of immune response are natural active immunity, such as when someone becomes ill and develops immunity; artificial active immunity, as when an injection is given against a pathogen, preventing illness; natural passive immunity occurs when an infant has its mother’s immunity for a short while after birth and through breast-milk; and artificial passive immunity occurs after injection of antibodies such as with an antivenom.28-47In Summary (cont.)28.15 Vaccines are used to produce artificially acquired active immunity.28.16 Cancer is defined as the uncontrolled growth of abnormal cells. A carcinogen is an agent that is known to cause cancer.28.17 Cancer diagnoses can come about in many ways, but often a biopsy confirms the diagnosis. Treatments vary depending on the type and stage of the cancer, but treatment options include surgery, including bone marrow transplants, chemotherapy, and radiation therapy, as well as newer immune therapies. 28-48In Summary (cont.)28.18 Cancers are classified as Stages IIV and recurrent. Definitions of these stages may be found in Table 28-1.28.19 An allergic reaction is an immune response to a substance that is not normally considered harmful to the body. Allergic reactions can also be an excessive immune response. Allergens are substances that produce an allergic response.28-49In Summary (cont.)28.20 Diseases and disorders of the immune system include autoimmune diseases, where the body attacks its own antigens, as well as numerous other diseases, including some cancers, caused by pathogens, allergens, and other antigens. The signs, symptoms and treatments are as numerous and varied as the diseases. Some of the more common diseases and disorders are discussed in the Pathophysiology section at the end of this chapter.28-50End of Chapter 28Thought is an infection. In the case of certain thoughts, it becomes an epidemic. ~Wallace Stevens