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Lymphatic System: Structures & Immune Response Honors Anatomy & Physiology Wbc engulfs bacteria: http://www.youtube.com/watch?v=Jn lULOjUhSQ
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Lymph Vessels Lymphatic vessels – drainage of excess interstitial fluid (lymph) that is returned to blood vessels Lymphatic capillaries weave between tissue cells and blood capillaries in areolar tissue Very permeable ◦Lacteals – specialized capillaries found in villi of intestinal mucosa to help absorb fats Flows to collectively larger vessels
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Lymphatic Vessel Drainage Right lymphatic duct Right arm, side of head and upper thorax Empties into the right subclavian vien Thoracic duct Much larger Rest of the body Empties into junction of left subclavian vein & jugular vein About 3L enters blood every 24 hours
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What is elephantiasis? Lymphatic ducts get clogged with parasitic roundworms Swelling of lower limbs and scrotum due to edema
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Lymph Nodes Filters lymph fluid ◦Macrophages destroy microorganisms Help activate the immune system ◦Lymphocytes monitor & attack antigens 100’s of these small organs Bean shaped <1inch long Cortex (outer region) ◦Dividing B cells ◦Circulating T cells Medulla (inner region) ◦Plasma cells ◦macrophages Fewer efferent lymph vessels than afferent vessels
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Lymph Organs Spleen – monitors blood ◦Red pulp -extracts aged & defective blood cells ◦Stores hemoglobin & platelets (recycled) ◦White Pulp -contains lymphocytes & macrophages Thymus – T cells become immunocompetent (specific) ◦Atrophy after puberty (replaced by adipose tissue) ◦Does not directly fight pathogens Tonsils – invaginations trap pathogens ◦Contains lymphocytes & macrophages Palatine tonsils Lingual tonsils Pharyngeal tonsil Tubal tonsils
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Lymphatic Tissues MALT: Mucosa Associated Lymphatic Tissue Protects passages open to exterior Produces memory cells against invaders Includes: ◦Peyers Patches Clusters of lymph tissue on small intestine ◦Appendix Off shoot of large intestine Destroys any bacteria may leave intestine
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Innate (Non Specific) Defenses 1 st line defense- Surface Barriers: ◦Skin & Mucous Membranes Physical barrier Acidity of skin secretions (ph 3-5) Sebum – toxic to bacteria HCl of stomach Saliva & lacrimal fluid contain lysozyme ◦ Enzyme destroys bacteria Mucus traps microorganisms
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Innate (Non Specific) Defenses (2 0 Defense) Cells ◦Phagocytes – engulfs & digests Macrophages from WBC monocytes ◦ Free (mobile) or fixed (liver, brain) Neutrophils (WBC) ◦ Become phagocytic after encounters pathogen ◦ Destroy self in process Eosinophils (WBC) ◦ defend against parasitic worms ◦Natural Killer (NK) Cells “police” blood & lymph Detect lack of “self” antigens Direct contact induces target cell to undergo apoptosis Lyse & kill cancer cells & viral infected cells
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Innate (Non Specific) Defenses Chemicals ◦Inflammation -Prevents spreading of pathogen & disposes pathogens & cell debris Redness & heat ◦ Mast cells release histamines causing vasodilatation Swelling & pain ◦ Increased permeability of capillaries ◦ Clotting factors, antibodies & fluid leak into tissues ◦Antimicrobial proteins Interferons (IFNs) ◦ Secreted by viral infected cells to prevent other cells from becoming infected ◦ Stimulate synthesis of proteins that interfere w/viral protein synthesis (not specific) ◦Fever Response to widespread infection Macrophages and WBC release pyrogens ◦ Chem that resets thermostat in Hypothalmus ◦ Increases metabolism
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Adaptive Defenses (Specific) Must be primed by initial exposure before it can defend against it 3 important features: Specific against a particular pathogen Systemic – not restricted to infection site ◦Humoral Immunity – circulating antibodies in body fluids ◦Cell Mediated Immunity – lymphocytes attack pathogens Memory – recognizes and mounts strong attacks against previously encountered pathogens
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Antigens Antigens – Foreign substances that provoke an immune response ◦Non-self - not normally found in the body ◦Cause proliferation of lymphocytes & antibodies Self-Antigens ◦MHC (major histocompatibility complex) proteins on surface of “self” cells ◦Variety - genetically determined
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Antibodies AKA immunoglobulin (Igs) Secreted by B cells or plasma cells Structure: ◦‘Y’ shaped; 4 polypeptide chains (2 Heavy, 2 Light) ◦Variable region – 2 binding sites that responds to specific antigens ◦Constant region – determines Ig class Antigen-antibody complex: ◦Neutralizes - no longer harmful ◦Agglutination – cross linked causing clumping Inactivates pathogens and tags for destruction
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Humoral Immune Response Antigen binding to receptor on specific B lymphocyte stimulates proliferation forming clones that differentiate into: Plasma cells – secrete 2,000 antibodies per second (for about 5 days then dies)!!! Memory cells – will respond to subsequent exposures to same antigen
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How do Vaccines work? Contain dead or attenuated (weakened) pathogens or their components Spares us symptoms of disease that would normally occur during a primary response Memory cells are formed against antigen (humoral only)
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Cell Mediated Response T cells mature in Thymus Targets infected cells, cancer cells, foreign tissues Helper T cells (CD4) ◦Stimulates production of cytotoxic T cells and B cells, activates macrophages, and releases cytokines (chemicals that trigger proliferation and inflammation) Cytotoxic T cells (CD8) ◦Binds to infected cells and inserts chemicals causing apoptosis Regulatory T cells ◦Suppresses immune activity Memory T cells ◦Responds quickly to subsequent infections (last years) Double recognition on an antigen presenting cell: ◦Non self antigen ◦MHC proteins indicating “self” cell
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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
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Select your Task… Create a comic strip depicting the specific response of lymphatic system (combating a pathogen of your choice) Write a script for a mini-play describing specific response of lymphatic system May work in pairs Either choice should include: B cells, plasma cells, antibodies, helper T cells, cytotoxic T cells, memory cells, suppressor (regulator) T cells, and macrophages
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