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Transcript
Lecture Outline The Lymphatic System and Body Defenses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lymphatic System o o • • • • • Three main functions Fluid balance Fat absorption Defense Lymphatic vessels Form a one-way system Begins with lymphatic capillaries • Vessels merge and then enter one of two ducts: • • Tiny, closed-ended vessels Take up excess tissue fluid (lymph) Thoracic duct Right lymphatic duct Vessels have valves and movement of lymph depends on skeletal muscle contraction Edema is localized swelling caused by the accumulation of lymph Organs, Tissues, and Cells of the Immune System o • Primary Lymphatic Organs Lymphocytes originate and/or mature in these organs Red Bone Marrow • Site of stem cells that produce blood cells In an adult, red bone marrow is found in: Sternum Vertebrae Ribs Skull Part of the pelvic girdle Proximal heads of the humerus and femur Lymphocytes differentiate into B and T lymphocytes B lymphocytes mature in the red bone marrow T lymphocytes mature in the thymus Organs, Tissues, and Cells of the Immune System • Thymus Gland In the thoracic cavity Largest in children and shrinks as a person ages Lobules are filled with lymphocytes Produces thymic hormones Aids in maturation of T lymphocytes May have other functions in immunity Critical to immunity Organs, Tissues, and Cells of the Immune System o Secondary Lymphatic Organs • Places where lymphocytes encounter and bind with antigens Spleen • Largest lymphatic organ Consists of two types of tissue: White pulp – has a concentration of lymphocytes Red pulp – surrounds venous sinuses and is involved in filtering blood Blood entering the spleen is filtered through venous sinuses Lymphocytes and macrophages react to pathogens Macrophages engulf debris and remove old red blood cells Organs, Tissues, and Cells of the Immune System • Lymph nodes Small structures occurring along lymphatic vessels Connective tissue • Forms a capsule Divides node into compartments Contains nodules packed with B lymphocytes Sinus that contains T lymphocytes Lymph passing through the sinus is filtered by macrophages T lymphocytes fight infection and attack cancer cells Lymphatic nodules Concentrations of lymphatic tissue not surrounded by a capsule Tonsils Peyer patches Appendix Nonspecific and Specific Defenses o Nonspecific Defenses • Barriers to entry Physical Intact skin Mucous membranes Chemical Sebaceous gland secretions Lysozyme in perspiration, saliva, and tears Urine pH of the stomach Normal flora Nonspecific and Specific Defenses • Inflammatory reaction Four signs: Redness Heat Swelling Pain Nonspecific and Specific Defenses • Inflammatory reaction 5 steps 1. Chemical mediators cause capillaries to dilate and become more permeable - Excess blood causes redness and increased temperature 2. Increased permeability causes fluids and proteins to escape the capillaries and cause swelling 3. Edema and clot formation “wall off” the area 4. 5. Migration of phagocytes Monocytes become macrophages that devour pathogens and debris Nonspecific and Specific Defenses • Natural killer cells Kill virus-infected cells and tumor cells Large, granular lymphocytes No specificity and no memory • Protective proteins Complement Composed of blood plasma proteins Activated when pathogens enter the body Amplify the inflammatory response Bind to the surface of pathogens, ensuring that they will be phagocytized Form a membrane attack complex that punches holes in the walls and membranes of bacteria Interferon Produced by virus-infected cells Produce substances that interfere with viral replication Nonspecific and Specific Defenses o Specific Defenses • • Respond to antigens Lymphocytes have antigen receptors B lymphocytes Mature in the bone marrow Give rise to plasma cells that produce antibodies T lymphocytes Mature in the thymus gland Directly attack cells that have nonself proteins or regulate the immune response Nonspecific and Specific Defenses o Clonal Selection • When B cells encounter an antigen they are activated to divide many times Plasma cells – mature B cell that produces antibodies Clones • Most mature to form plasma cells Some become memory cells Make long-term immunity possible A second exposure to the same antigen produces a stronger, faster immune response Plasma cells undergo apoptosis when an infection has passed Nonspecific and Specific Defenses o Structure of Antibodies • Basic unit is a Y-shaped protein molecule with two arms • • • • • o “heavy” polypeptide chain “light” polypeptide chain Chains have constant regions at the trunk of the Y The class of antibody is determined by the structure of the constant region Monomers – single Y-shaped molecules Dimers – paired Y-shaped molecules Pentamers – clusters of 5 Y-shaped molecules linked together Function of Antibodies • • Neutralization Forming immune complexes Nonspecific and Specific Defenses Nonspecific and Specific Defenses o T Cells and Cell-Mediated Immunity • Antigen must be presented to T cells by an antigen-presenting cell Major histocompatability (MHC) proteins • • T cell compares the antigen and the self protein • Called HLA (human leukocyte antigens) Are self proteins Activated T cell and all daughter cells can recognize “foreign” from “self” Will destroy cells carrying foreign antigens Activated T cells produce cytokines that stimulate various immune cells to perform their functions Nonspecific and Specific Defenses o Types of T Cells • Cytotoxic T cells • Destruction of virus-infected or cancer cells Have storage vacuoles containing Perforin molecules Responsible for cell-mediated immunity Helper T cells regulate immunity by secreting cytokines Nonspecific and Specific Defenses o Cytokines in Cancer Chemotherapy • • Used as immunotherapeutic drugs Interferon and interleukins are also used as immunotherapeutic drugs Creating and Immune Response o Active Immunity • • Often develops naturally Immunization • • Involves the use of vaccines After the first exposure, a primary response occurs A second exposure (“booster”) produces a secondary response Depends on the presence of memory cells Usually long-lasting Creating and Immune Response o Passive Immunity • • • Occurs when an individual is given prepared antibodies (immunoglobulins) Is temporary Can be used in the event of an unexpected exposure to an infectious disease Creating and Immune Response o Monoclonal Antibodies • • • • • Every plasma cell derived from the same B cell Secretes antibodies against one antigen Can be produced in vitro Are being used for quick and certain diagnosis of various conditions Used to carry radioactive isotopes or toxic drugs to tumors Creating and Immune Response o Hypersensitivity Reactions • Allergies Response to substances that are harmless to the body (allergens) IgE-Mediated Allergic Response Immediate allergic response Caused by IgE antibodies When an allergen attaches to the IgE antibodies, histamine is released Anaphylactic shock occurs when the allergen has entered the blood stream T-Cell Mediated Allergic Response Initiated by memory T-cells at the site of allergen contact Regulated by cytokines Creating and Immune Response • Tissue Rejection Transplanted tissue is recognized as not “self” Cytotoxic T cells cause disintegration of the transplanted tissue Can be controlled by: Selecting organs that have the same type of HLA antigens as those of the recipient Administering immunosuppressive drugs Creating and Immune Response • Autoimmune Diseases Cytotoxic T cells or antibodies attack the body’s own cells Cause is unknown Examples: Myasthenia gravis Multiple sclerosis Systemic lupus erythematosus Rheumatoid arthritis No cures, but can be managed with medications Creating and Immune Response • Immune Deficiency The immune system is unable to protect the body from disease Can be acquired or genetic Without treatment, common infections can be fatal Effects of Aging o o o o o Aging people become more susceptible to infections and disorders Thymus gland degenerates and number of T cells decreases B cells sometimes do not form clones Incidence of autoimmune diseases increases Response to vaccines is decreased Homeostasis o The lymphatic system helps the following: • • • o Nonspecific immune responses are dependent on: • • o o The digestive system by absorbing fat The cardiovascular system by absorbing lymph The immune system in protection against infectious diseases The skin Mucous membranes of the respiratory tract, the digestive tract, the reproductive and urinary systems Specific defenses are dependent on blood cells There is a strong connection between the immune, nervous, and endocrine systems