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Transcript
LYMPHATIC SYSTEM Lymphatic System - functions Returns excess interstitial fluid (lymph) to blood (including lost plasma proteins) Transports dietary lipids from digestive system to blood Carries out Immune responses including: - Production & Differentiation of Lymphocytes - Formation of Antibodies - Other specific responses against microbes or abnormal cells 24-2 Lymphatic System Components Lymph - fluid Lymphatic Vessels – transport lymph - capillaries, vessels, trunks & ducts Lymphatic Organs and Tissues - Primary: red bone marrow & thymus - Secondary: lymph nodes, spleen, lymphatic nodules Lymph Fluid, similar to plasma Lost from blood capillaries Enters lymphatic system at lymph capillaries About 3 liters of interstitial fluid drain into lymph vessels daily Returned to bloodstream by series of lymph vessels Lymph & Blood Capillaries Intertwine Lymph Vessels/Lymphatics Transport Lymph (one-way) to Blood (Subclavian Veins) Under low pressure Lymph flow assisted by: Muscular compression One-way valves to prevent backflow Respiratory pump Rhythmically contracting smooth muscle in walls of largest lymphatics Lymphatic Ducts Two main channels drain lymph into veins: Thoracic Duct Begins as Cisterna Chyli - receives fatty lymph (chyle) from Digestive Organs Drains Lower Body + Upper Lt. Half into Lt. Subclavian Vein Right Lymphatic Duct Drains Upper Rt. Half into Rt. Subclavian Vein 10 Lymphatic Organs/Tissues Primary Site of lymphocyte development (from stem cells) Red bone marrow - Mature B cells - Immature T cells Thymus - T cells mature & differentiate - Site of T-Cell maturation (immunocompetence); able to mount immune response Thymus (Primary Lymphatic Organ) Mediastinum, between sternum & aorta Atrophies after puberty Populates secondary lymphatic organs & tissues with T-cells Lymphatic Organs/Tissues Secondary Sites where most immune responses occur - Lymph nodes - Spleen - Lymphatic Nodules *M.A.L.T. *Tonsils Lymph Nodes Secondary Lymphatic Organs Located along lymph vessels Often in clusters, receiving lymph from specific regions Filter Lymph; lymph enters through afferent vessels, exits through efferent vessels Site of proliferation of B cells & T cells Spleen Secondary Lymphatic Organ Blood filtered Macrophages phagocytize pathogens; lymphocytes perform immune functions Recycles RBCs & Stores Iron Stores blood & platelets Lymphatic Nodules Secondary Lymphatic Tissues Mucosa-associated lymphatic tissue (M.A.L.T.) Nodules in mucosa of G.I., urinary, reproductive tracts & respiratory airways - Tonsils in pharynx (protect against inhaled/ingested foreign substances) - Peyer’s patches (Lymph nodules) in small intestine Immune System Functions Antigens are substances capable of triggering an immune response. The Immune System: Patrols for antigens Recognizes, responds to, and eliminates foreign antigens Scavenges dead or dying cells Three Immune Strategies 1. Physical, chemical, & mechanical barriers to prevent entry Then to identify, and remove or neutralize invader: 2. General (non-specific) Immune Defense 3. Specific Immune Responses Physical Barriers Intact skin Nasal hairs Mucous membranes Sphincters to inhibit bacterial migration Chemical Barriers Low pH of stomach Urine Vaginal secretions Sebum on skin Lysozyme in tears Prostatic secretions Mechanical Barriers Cell turn over Trapping action of mucus Cilia Flushing action of tears, saliva, urine, defecation General Non-Specific Defenses Phagocytes – Neutrophils, Macrophages Natural Killer Cells – lymphocytes that lyse/kill abnormal cells (cancerous & virus-infected cells) Proteins – complement & interferon Inflammation – vasodilation & increased capillary permeability (redness, heat, swelling, pain) Fever Specific Immune Responses Antigen-specific (relies on recognition of foreign antigens) Systemic (body-wide) Forms Memory (stronger future immune response) 2 types of Immune Response: - Humoral (Antibody-Mediated) - Cellular (Cell-Mediated) Humoral Immunity B-Cells (B-Lymphocytes) - Mature in Bone Marrow - Divide to form: *Plasma Cells (Produce Antibodies) *Memory B Cells - Antibodies disable Bacteria & Viruses before they enter cells Cellular Immunity T-Cells (T-lymphocytes) - Mature in thymus - Form memory T cells - Directly attack Bacteria & Viruses - Attack virus-infected cells & cancerous cells - Influence B Cell Activity Major Types of T-Cells Helper T-cells - Activate B & T-cells specific immunity - Trigger B & T-cell proliferation Cytotoxic/Killer T-cells - Attack & kill other cells (e.g. virus-infected cells, cancer cells, donor cells, cells with bacteria or other intracellular parasites) Regulatory T-cells - Inhibit (dampen) the immune response