VIEWS: 6 PAGES: 14 POSTED ON: 5/28/2012
The Lymphatic System Organization Lymph Vessels Begin at peripheral tissue venous system Small valves prevent backflow Lymph Fluid Like plasma but w/less proteins Lymphocytes Cells defend body Lymph Tissue Loose connective tissue Tonsils Lymph Organs Lymph nodes Spleen Thymus Functions Production, maintenance, and distribution of lymphocytes Return fluid from peripheral tissues to blood Distribute hormones, nutrients, and waste to general circulation Lymph Vessels Lead towards trunk of body and empty into 2 ducts Thoracic duct – lower abdomen, pelvis, lower limbs, left head, neck, and chest Right lymphatic duct – right side of body, above diaphragm Lymphodema (edema) – blockage of lymph drain Lymphocytes 25% of circulating wbc T cells – thymus dependent (80% circulating lymphocytes) Cytotoxic T cells – attack foreign cells or body cells infected w/ virus Helper T cells – stimulate T cells and B cells Suppressor T cells – inhibit T cells and B cells B cells-bone marrow derived (10-15% circ. Lymphocytes) Plasma cells – secrete antibodies (immunoglobulins) Antibodies bind to antigens NK cells natural killer cells (5-10% circulating lymphocytes) Attack foreign cells, viral infected cells, and cancer cells Lymphopoeisis Lymphopoesis – lymphocyte production and development 80% last 4 years…some last 20 years or more! Hemocytoblasts (bone marrow) B cells and NK stem cells remain in bone marrow T cell stem cells migrate to thymus Enter blood stream and retain ability to divide and produce daughter cells of same type Lymphoid Nodules Size can increase or decrease depending on number of lymphocytes Tonsils, Appendix, Peyers patches (wall small intestines) If unable to destroy bacteria/viral invaders… becomes infected Lymphoid Organs Lymph Nodes Filter and purify lymph before enters venous system Detects and removes antigens Stimulates T cells and B cells initiating immune response Lymphomas – cancer arising from lymphocytes Thymus Decrease in size after puberty T cell production and maturation Spleen 5” long on left side, deep red Filters blood, removes abnormal blood cells and initiates B cell and T cell responses to antigens Macrophages identify and engulf damaged or infected cells Non-Specific Defenses Physical Barriers Epithelium, hair, secretions, acid, enzymes Phagocytes 1st line of cellular defense – removes debris and pathogens Microphages leave blood stream and enter peripheral tissues (neutrophils and eosinophils) Macrophages – sensitive to chems in surrounding fluids can be free or fixed Interferons Slow spread of viral infections Stimulate macrophages and NK cells Inflammation Initiated by mast cells releasing histamines and heparin Local swelling, heat, redness, and pain Slows spread of pathogens Incr. blood flow aids in tissue repair Necrosis – tissue destruction via lysosomes Pus – accumulation of dead cells and debris (abscess – accumulation of pus) Fever (>98oF) Pyrogens – proteins reset body's “thermostat” Incr. rate of metabolism Over 104oF damages CNS, nausea, hallucination, and convulsions Specific Defenses Immunity – respond to the presence of specific antigens Antigens – “non-self” substance that excites the immune system and stimulates a response Genes determine specificity T cells – cell mediated immunity Defend against abnormal cells Pathogens inside of cells B cells – antibody-mediated immunity Defend against antigens and pathogens in body fluids Antibodies (immunoglobulins) – bind to specific antigen, Y shape with 2 antigen binding sites Immune Response (antibody mediated) B cell binds w/antigen…becomes activated and produces clones B cell clones Plasma cells – secrete antibodies (2,000 per sec!)… reaches peak 10 days Memory B cells – continue to circulate, and can speed process to 2-3 days if recognizes an “old enemy” Immune Response (cell mediated) T cells cannot bind to “free” antigen Macrophages and B cells must present antigen to T cells Once T cell binds to “presented” antigen Killer (cytotoxic) T cells • Binds to target cell and inserts a toxic chem… target cell ruptures Helper T cells • Recruit other cells to fight invaders • Stimulates B cells to increase production of antibodies • Simulates Killer T cells to multiply Suppressor T cells • Release chems to suppress B and T cell activity • Most T cells enlisted to fight die w/in a few days • Some remain as memory cells to respond quickly to subsequent invasions Properties of Immunity Specificity T cells and B cells target one specific antigen Versatility Millions different lymphocytes w/diff antigen receptors Memory 1st exposure – lymphocytes divide to create “attack” cells and memory cells Response to 2o exposure to antigen is stronger than 1st Tolerance Doesn’t respond to normal “self” tissues or antigens Types of Immunity Innate – genetically determined Acquired – arises during life Active – appears after exposure to antigen • Naturally- continually induced as encounter “new” pathogens or antigens • Induced – stimulated under controlled conditions • Vaccine: dead/inactive pathogen that induces an immune response Passive – transfer of antibodies from another source • Naturally – mother to baby • Gestation – via placenta • Infancy – via breast milk • Induced – antibodies administered to fight infection or prevent disease after exposure
"The Lymphatic System"