Lymphatic System and Non-Specific DefenseThe Lymphatic SystemParts of the Lymphatic SystemLymphatic VesselsSlide 5Lymph FluidLymph Nodes: Where Are They?Lymph Nodes: Function, Structure, & FlowOther Lymphoid OrgansCells of the Lymph: LymphocytesOther Lymphoid CellsLymphatic System and Non-Specific DefenseThe Lymphatic System•Anatomy of the Lymphatic System•Lymphatic Vessels and Flow•Lymph Nodes•Other Lymphoid OrgansThe Lymphatic SystemConsists of two semi-independent parts•Lymphatic vessels•Lymphoid tissues and organsLymphatic system functions•Transport fluids back to the blood•Play essential roles in body defense and resistance to diseaseParts of the Lymphatic SystemLymphatic vessel or duct• One way system toward the heart• No pump• One-way valves restrict flow• Made of overlapping endothelial cells; very permeable• Lymph moves toward the heart through milking action of skeletal muscle and rhythmic contraction of smooth muscle in vessel wallsLymphatic VesselsLymph Capillaries•Walls overlap to form flap-like mini-valves•Fluid leaks into lymph capillaries•Capillaries are anchored to connective tissue by filaments•Higher pressure on the inside closes mini-valvesLymphatic VesselsLymphatic collecting vessels•Collects lymph from lymph capillaries•Carries lymph to and away from lymph nodes•Returns fluid to circulatory veins near the heart•Thinner walls ,more valvesLymphatic ductsReturn to venous circulation•Right lymphatic duct•Thoracic ductLymph FluidMaterials returned to the blood•Water•Blood cells•Proteins Harmful materials that enter lymph vessels•Bacteria•Viruses•Cancer cells•Cell debrisLymph Nodes: Where Are They?Figure 12.3Lymph Nodes: Function, Structure, & FlowFiltering of lymph before it is returned to the bloodStructure•Mostly kidney shaped, < 1 inch long•Outer Cortex contains follicles – collections of lymphocytes that respond to antigens, intense B cell reproduction centers•Inner Medulla contains phagocytic macrophages that engulf and destroy foreign substancesLymph Flow•Lymph enters the convex side through afferent lymphatic vessels•Lymph flows through a number of sinuses inside the node•Lymph exits through efferent lymphatic vessels•Fewer efferent than afferent vessels causes flow to be slowedOther Lymphoid OrgansSpleen: Filtering and removal of old red blood cells; blood reservoir. Site of lymphocyte proliferation and immune surveillance and response.Thymus: Hormone production (thymosin) and maturation and "education" of T lymphocytes. Tonsils: Trap and remove bacteria and particulate matter; tonsilitis is bacterial inflammation (Part of MALT)Peyer’s patches: Capture and destroy bacteria in intestine, preventing them from breaching the intestinal wall (Part of MALT). Generates “memory” lymphocytes Figure 12.5* MALT: Mucosa-Associated Lymphatic TissueCells of the Lymph: LymphocytesTypes of Lymphocytes•T cells (cell-mediated and cytotoxic immunity)oManage the immune responseoAttack and destroy foreign cells•B cells (blood based or humoral immunity)oProduce plasma cells, which secrete antibodiesFunctions of Lymphocytes•T cells and B cells protect against antigensoAnything the body perceives as foreignBacteria and their toxins; virusesMismatched RBCs or cancer cellsOther Lymphoid CellsMacrophages phagocytize foreign substances and help activate T cellsDendritic cells capture antigens and deliver them to lymph nodesReticular cells produce stroma that supports other cells in lymphoid
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