Ch. 21 Lymphatic System & Immune PDF

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Chapter 21 Lymphatic System Lecture Notes...

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Lymphatic System & Immunity ○ Fx 1. Defense & assistance (immunity) a. physical/chemical barriers b. Specific & non specific responses 2. Absorb excess tissue fluid a. Lymphedema b. Elephantiasis - disease due to parasite infection i. Hot tropical areas usually

3. Absorb & transport dietary lipids a. Lacteal - in SI b. Chyle i. Fat soluble Vitamins 4. Produce, Maintain & Distribute a. Lymphocytes b. Macrophages 5. Defend Against Pathogens a. Search & destroy

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Lymph ○ Plasma from blood enters intercellular spaces of tissue ○ Recovered fluid ■ 72% of Total blood leaves, 30 Liters a day ■ But 3 Liters stay in interstitial fluid ○ This clear watery proteinaceous tissue fluid enters lymph structures ○ Plasma → interstitial fluid → lymph ■ Lymph - fluid in lymphatic vessels & nodes

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Lymph Pathway ○ Lymph capillaries ■ Overlapping endothelial cells ■ Valves prevent backflow ● Dead end - nestled among capillary bed ● Anchored in place ■ No basal membrane ● Easy diffusion of all

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Lymphatic Vessels ■ Resembles small veins ● 3 tunics ● Valves ■ Lymph movement dependent ● Smooth muscle in vessel wall contracting (SNS) ● Skeletal muscle contraction ● Pressure changes with breathing ■ No RBCs ■ @ times empty into lymph nodes Lymphatic Trunks ■ 6 ■ Larger vessels ■ Each drains a major body region ● Cisterna chyli

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Lymphatic Ducts ■ 2 ■ Return lymph to bloodstream ● Right - drains ¼ body ● Left (thoracic duct) origins @ cisterna chyli ■ Both empty at junction of internal jugular vein & subclavian vein

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Cisterna Chyli ○ Origin of thoracic duct ○ At L2 level ■ Collects from abdomen, pelvis, lower limbs ■ All dietary fat enters here ● Chyle after meals

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Lymphatic Sites ○ Sites where lymphocytes made / mature ■ Bone marrow, thymus ○ Sites where lymphocytes stored or work ■ Spleen, lymph nodes, lymphoid tissues ● Lymphatic nodules & MALT

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Red Bone Marrow - important suppliers of lymphocytes ○ B cells ○ Natural Killer Cells ■ Both B cell & T cell precursors originate here ● But only B cells / NK mature here ○ Hemocytoblast → lymphoid stem cell → ■ B lymphoblast → B cell ■ NK Precursor → NK cell ■ T lymphoblast → leaves

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Leukopoiesis in RBM ○ All WBC from hemocytoblast ○ Lymphocyte production stimulated by interleukins (ILs) & colony stimulating factors (CSFs)

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Natural Killer Cell ○ Widespread surveillance - “lookout” ○ Cytotoxic lymphocyte ■ Recognize / kill cells containing pathogens ■ Recognize / destroy tumor cells ○ Release small cytoplasmic granules of proteins (perforin & granzyme) → apoptosis of target cell ■ Perforin - make holes in membrane ■ Granzyme - enter ● Protein degrading enzyme

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Thymus ○ T cells made here ○ Bi lobed organ bet/ sternum & great vessels ○ Involuted @ puberty ■ Mitosis still persists ○ Mostly lymphocytes ○ Epithelial cells secrete hormones/signaling molecules to promote T cell development & action ■ Thymosin - makes more T cells ■ Interleukins ■ Interferon - cell infected w/ virus that produces protein

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Thymus Histology ○ Cortex of immature T cells ○ Junction of macrophages & dendritic cells bet/ cortex & inner medulla ○ Medulla of mature T cells ■ Blood thymic barrier in cortex ● Isolates developing T cells from antigen exposure ○ Antigens would simply attack immature T cells ● T cells in thymus do NOT partake in immune response ○ Mature T cells enter blood in medulla & leave Thymus

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Spleen ○ Largest mass of lymphoid tissue ○ Just below the diaphragm, LUQ ■ Reticular CT w/ capsule ■ No cortex/medulla ■ Red & white pulp ○ RBC Graveyard

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Spleen histology ○ White pulp ■ Lymphocytes & macrophages surround arterial branches/arterioles ■ Monitors blood for antigens ● Can initiate response ○ Red pulp ■ Sinusoidal capillaries allow RBC to exit → sinuses engorged w/ blood (Concentrated RBCs) ■ Macrophages removed damaged RBC ■ Large reservoir of subcapsular monocytes ■ Fetal RBC production

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Lymph Node ○ Along lymph vessel pathway ■ Reticular CT ■ Filters lymph ■ Often in clusters ■ Antigens can stimulate immune response here ● Increase in cell # & node size ○ Contain lymphocytes & macrophages

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Lymph Node Microanatomy ○ afferent/effect lymph vessels ○ Outer CT capsule ■ Subcapsular sinus where lymph enters ● B cells ○ Cortex contains lymphoid (lymphatic) follicles ■ Outer edge - mostly T cells ■ Central area - mostly B cells ○ Medulla cells are unorganized ■ Lymphocytes ■ Macrophages ■ Plasma cells (activated B cells) ● T cells ○ Efferent - away CNS ○ Afferent - towards CNS

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Lymphoma 1. Non-Hodgkin’s a. Many cell types b. Variable: indolent → aggressive c. Many cures in childhood lymphoma! 2. Hodgkin Lymphoma a. Less common b. 85% curbale c. Peakes 19-25 & again 55+ d. Mono / EB virus association e. More often in males

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Diffuse Lymphatic Tissue & Nodules ● Lymphatic tissue = lymph node ● Lymphoid tissue = lymphatic nodule, lymphoid nodule, lymphoid follicle, lymphatic follicle, lymph follicle ○ Diffuse Lymphatic Tissue ■ Found in CT ■ Irregular dense scattering of dark cells ● Mostly T lymphocytes ■ Prevalent in areas open to exterior ● MALT ○ Nodules ■ Avoid collection of densely packed cells ● Lymphocyte & macrophages into dense nodules ○ Clusters = Peyer’s Patches ■ Outer mantle ● Darker stained ● Small lymphocytes (resting) ■ Inner germinal center ● Lighter stained ● “Reactive area” ○ Activated B cells ○ Macrophages ○ Lymphoblasts! ○ Reticular Cells (fibroblasts)

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MALT ○ Mucosa Associated Lymphoid Tissue ■ Generates immune response for pathogen on surface ● Respiratory tract ● Genital tract ● Digestive tract

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Tonsils (MALT) ○ First site to meet pathogens that enter via nose/mouth ○ Crypts traps material & facilitate immune reaction ■ Crypts - deep pits that trap & contain pathogens

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Terminology ○ Autophagy - self eating ■ Remove damaged cell componentes via lysosomal enzymes → replace w/ new ones ○ Cytokines ■ Secreted by immune cells ■ Small proteins important in cell signaling ■ Cannot cross lipid bilayer to enter cell ● Interferon, interleukins, growth factors, tumor necrosis factor, chemotactic factors ■ Different kind of chemicals

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Chemotaxis ■ Movement of cells/organisms ■ In response to chemical stimulus

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Immunity ○ Body’s ability to resist / combat disease

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In Sickness & In Health 1. Non specific (innate) a. Present since birth b. Immediate but general protection c. Wide range of pathogens d. Response doesn’t change over time i. 1st & 2nd Line of Defense 1. Local, nonspecific & lacks memory 2. Specific (acquired/adaptive) a. Develops in response to pathogen b. Specific for one pathogen c. Response enhanced over time (faster/stronger) → aforementioned memory i. For any one disease ii. 3rd Line of Defense

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First Line of Defense ○ Keep it Out ■ Barriers - skin & mucous membranes

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Nonspecific: Barriers to Entry ○ Physical Barriers ■ Skin, mucous membranes, cilia ○ Chemical barriers ■ Oil, sweat, saliva, urine, tears, secretions ○ Resident bacteria ■ Normal flora

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Second Line of Defense ○ Protection against Pathogens ○ Breaching external barriers ■ When 1st line fails

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Granulocytes in Tissue ○ Neutrophils wander in CT killing bacteria ■ Phagocytosis & lysosomal digestion of single cells ■ Degranulation → chemical killing zone kills many cells but also neutrophil ● Degranulation - discharge enzymes into tissue fluid ○

Eosinophils common in mucous membranes ■ Congregate @ site of allergen, parasite, inflammation ■ Degranulation → chemical killing zone ■ Degrabe ag-ab complex ● Antigen-antibody ■ Promote basophils. action but degrade / limit histamine action

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Basophils → mast cells ■ Secrete leukotrienes: activate/attract neutrophils & eosinophils ■ Secrete histamine → proinflammatory ● Increases blood flow & WBCs to area for immune response ■ Secrete heparin → inhibits coagulation cascade ● Blood clots impede leukocyte mobility...