Presentation on theme: "Chapter 20 The Lymphatic System"— Presentation transcript:
1 Chapter 20 The Lymphatic System Use the video clip: CH 20 - Lymph Node Anatomyfor a review of lymph node structureG.R. Pitts, J.R. Schiller, and James F. Thompson, Ph.D.
2 The Lymphatic System Basic organization Functions Lymph fluid in lymph vesselsStructures: organs with lymphatic tissue, red bone marrow, liver and spleenFunctionsreturn interstitial fluid and proteins to the bloodtransport dietary fats to adipose tissueprotect against cancer & infectionresistance - fight off diseasenonspecific resistance - general protection against diseaseimmunity - specific protectionsusceptibility - lack of resistance
3 Lymph FlowMore fluid moves out of the blood capillaries by filtration than returns by reabsorption - Starling’s Law≈ 3Ll day of lymph is generatedProteins escaped from the blood or secreted by tissues are transferred back to the blood by the lymphaticsLymph flow is facilitated by muscle pumps, the respiratory pump, valves, and smooth muscle (in the walls of the trunks & thoracic duct)Smaller vessels drain into larger vessels
4 Lymphatic Capillaries “Blind ended,” covered vessels between cells, larger than capillariesNot found in avascular tissues (CNS, cartilage) nor in the splenic pulp, and bone marrow
5 Lymphatic Capillaries Structure/Function regulates fluid flowAnchoring filaments - from lymphatic endothelium attach to surrounding tissuesEndothelial cells overlaphigh hydrostatic fluid pressure separates cells, fluid into capshydrostatic fluid pressure in cap prevents fluid movement outminivalve
6 Lymph Flow Follows Venous Circulation Lymph vessels have the same organization and routing as the vascular tree
7 Lymphatic Flow (cont.) Lymphatic vessels have no separate pump (heart) All lymph returns to the vena cava and to the right side of the heart
8 Lymphatic Flow (cont.) Lymph ducts Right lymphatic duct about ½ inch longdrains lymph from upper right side of body (arm & head)Thoracic (left) ductmain collecting duct of the lymphatic system38-45 cm longdrains 75% of bodybegins as a dilation known as the cisterna chyli located anterior to lumbar disk #2
9 Lymphatic Flow (cont.)Lymph returns to the venous drainage through right and left lymphatic ducts at the junction of the internal jugular and subclavian veins
10 Summary of Lymphatic Vessels Lymph Flow from smallest to largest:Capillaries vessels trunks ductsLymph vessels anastomose and supply and drain lymph nodes along their course
11 Two Main Types Of Lymphocytes B lymphocytes = B cellsattack microbes, especially bacteriadevelop into plasma cells to produce antibodies (Ab)bind to antigen to form antibody-antigen (Ag-Ab) complexescomplexes prevents Ag from interacting with other body cells or moleculesmemory B cells – dormant until future exposure to AgT lymphocytes = T cellsregulate many immune responsesattack viruses, fungi, transplants, cancer, some bacteria4 types of T cellscytotoxic (killer) T cells - destroy foreign invadershelper T cells - assist B cells and cytotoxic T cellssuppressor T cells – help bring immune response to an endmemory T cells - dormant until future exposure to Ag
12 Lymphocyte Development primary lymphatic organs - site of lymphocyte (B cell and T cell) productionbone marrow - produces B cells, immature T cellsT cells migrate to the thymus gland to mature or die if determined to be impropersecondary lymphatic organssites of activated immune responseslymphatic nodules (lymph follicles)lymph nodes, spleen, tonsils
13 Other Lymphoid Tissue Cells Macrophages & Dendritic cellsPhagocytize foreign substances and cellsTransport them to lymphatic tissuesProcess foreign things into individual antigensPresent Ags to T & B lymphocyte to help activate themReticular cellsSimilar to fibroblastsProduce reticular fibers (stroma) that provide the framing structure for other cells in lymphoid organs
14 Lymphatic Tissue - General Stroma of reticular connective tissue (except thymus)Parenchyma of macrophages, B and T lymphocytes, occasional other leukocytesMay or may not have a connective tissue capsule
15 Lymphatic Organs – Thymus Gland Two lobes between the sternum and the heartThymocytes produce hormonesAtrophies with age (starting ~20)Structure/FunctionOuter cortex – immature T cellsscreened for functional capacitystimulated to proliferationstimulated to maturationInner medulladefective T cells degeneratemature T cells move into blood
16 Lymphatic Organs – Lymph Nodes Anatomyoval, bean shaped small structures scattered throughout body along lymph vesselsmay be deep or superficialconcentrated along the respiratory tree and GI tract, in the mammary glands, axillae, and groinfilter lymph fluid to trap foreign organisms, cell debris, and tumor cells
17 Circulation in the Lymph Nodes Lymph enters via a number of afferent lymphatic vesselsIt then enters a large subcapsular sinus and travels into a number of smaller sinusesIt meanders through these sinuses and exits the node at the hilus via efferent vesselsThe node acts as a “settling tank,” because there are fewer efferent vessels, lymph stagnates somewhat in the nodeThis allows lymphocytes and macrophages time to carry out their protective functionsOnly lymph nodes filter lymph!
18 Cancer Metastasizes To Lymph Nodes Cancer cells from the tumor are first trapped in a lymph node
19 Lymphatic Organs - Spleen largest lymphoid organ in the bodyfibrous capsule with arteries, veins, and efferent lymph vesselslocated between stomach and diaphragm
20 Spleen Functions: White Pulp a site of immune surveillance and responsemacrophages phagocytize bacteria, worn-out RBC's, plateletshemoglobin is recycled and components transferred to livermacrophage antigen-presentation and lymphocyte activation and proliferationsome B cells mature into plasma cells
21 Spleen Functions: Red Pulp Site of fetal erythrocyte production (normally ceases after birth)Stores ~ 1 L of blood which can be released during an emergency (hemorrhage)
22 Unencapsulated Lymphatic Tissue Diffuse lymphatic tissueSmall scattered patchsIn nearly every organLymphoid follicles (nodules)More organized, more cellular clusterssmallbronchus
23 Mucosa-Associated Lymphatic Tissue (MALT) found in the lamina propria of mucous membranes of the GI tract, respiratory tract, urinary tract, and reproductive tractPeyer’s patchesin the intestines
24 Lymphatic Organs - Tonsils lymphoid tissue beneath the mucosaetonsilar crypts trap micro-organismsimmune cells destroy the micro-organismspalantine tonsils – largest and most frequently infected
25 LymphadenopathyEnlarged lymph nodes due to increased drainage from inflammatory lesions or infections.Associated with malignant and nonmalignant diseases.Lymphocyte leukemia with severe lymphadenopathy
26 Hodgkin’s Disease: one of the significant malignant lymphomas Cervicallymph nodes
27 Burkitt’s Lymphoma Commonly found in central Africa and New Guinea. Associated with Epstein-Barr virus which causes infectious mononucleiosis in North America and Europe.Rarer American type has extensive marrow replacement.Cancerous cell is a B lymphocyte.
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