The Lymphatic SystemIntroductionSlide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Lymph CapillariesSlide 13Slide 14Slide 15Distribution of Lymphatic VesselsSlide 17Slide 18Slide 19Slide 20Lymph Collecting VesselsSlide 22Slide 23Slide 24Slide 25Slide 26Slide 27Lymph NodesSlide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Lymph TrunksLumbar TrunksIntestinal TrunkBrachiomediastinal TrunksSubclavian TrunksJugular TrunksLymph DuctsThoracic DuctSlide 50Right lymphatic DuctSlide 52Slide 53Lymphatic VesselsImmune SystemSlide 56LymphocytesSlide 58Slide 59Slide 60Lymphocyte ActivationSlide 62Slide 63Slide 64Slide 65Slide 66Slide 67Slide 68Slide 69Slide 70Slide 71Slide 72Lymph Nodes: ClinicalLymphoid TissueSlide 75Slide 76Slide 77Slide 78Slide 79Slide 80Slide 81Slide 82Slide 83Lymphoid OrgansSlide 85Slide 86Slide 87Slide 88Slide 89Slide 90SpleenSlide 92Slide 93Slide 94Slide 95Slide 96Slide 97Slide 98Slide 99Slide 100ThymusSlide 102Slide 103Slide 104Slide 105Slide 106Slide 107Slide 108Slide 109Slide 110The TonsilsSlide 112Slide 113Slide 114Slide 115Slide 116Slide 117Slide 118Slide 119Slide 120Slide 121Aggregates of Lymphoid FolliclesSlide 123Slide 124The AppendixSlide 126Slide 127The Lymphatic SystemChapter 20IntroductionThe lymphatic system supports the function of the cardiovascular and immune systems of the bodyThe lymphatic system consists of two semi-independent parts–A network of lymphatic vessels–Lymphoid organs scattered throughout the bodyIntroductionThe lymphatic vessels transport fluids that have escaped from the cardio-vascular systemThe main components of the immune system (lymphocytes, lymphoid tissue, and lymphoid organs) fight infections and confer immunity to diseaseThe Lymphatic SystemAn elaborate system of lymphatic vessels runs throughout the bodyThese vessels collect a fluid called lymph from the loose connective tissue around blood capillaries and carry this fluid to the great veins at the root of the neckThe Lymphatic SystemBecause lymph flows only toward the heart, the lymphatic vessels form a one-way system rather than a full circuitThe Lymphatic SystemThere are several orders of vessels–Lymph capillaries–Lymphatic collecting vessels–Lymph nodes–Lymph trunks–Lymph ductsThe Lymphatic SystemRecall that all blood capillaries are surrounded by a loose connective tissue that contains tissue fluid or interstitial fluidThe fluid arises from blood filtered through the capillary wallsThe Lymphatic SystemTissue fluid consists of small molecules of blood plasma, water, various ions, nutrient molecules, and respiratory gasesThe Lymphatic SystemTissue fluid is continuously leaving and re-entering the blood capillariesFor complex reasons slightly more fluid arises from the arteriole end than re-enters the venule endThis amounts to about 3 liters a dayThe Lymphatic SystemThe lymphatic vessels function to collect this excess fluid and return it to the bloodstreamAny blockage of the lymphatic vessels causes the affected body region to swell with excess tissue fluid resulting in edemaThe Lymphatic SystemThe lymphatic vessels also perform another related functionBlood proteins leak slowly from blood capillaries into the surrounding tissue fluidLymph vessels return leaked proteins to the bloodstreamThis is important because proteins in blood generate osmotic forces that are essential for keeping water in the bloodstreamLymph CapillariesLymph capillaries are permeable vessels that receive the tissue fluidThey are located near blood vessels in the loose connective tissueLike blood capillaries their walls consists of a single layer of endothelial cellsLymph CapillariesLymph capillaries are very permeableThe permeability results from the structure and arrangement of the endothelial cellsThey have few intercellular junctionsLymph CapillariesIn lymph capillaries the adjacent edges of cells overlap to form easily opened mini- valvesThese valves open to allow tissue fluid to enter the lymphatic capillaryCollagen filaments anchor the cells to the connective tissueLymph CapillariesThe minivalves work because the collagen filaments anchor portions of the cell wall to the surrounding connective tissueAny fluid pressure in the volume of the tissue fluid separates the minivalvesThis opens gaps in the wall of the capillary allowing fluid to enterOnce in the lymphatic capillary, it cannot leak out, because backflow pressure forces the minivalve flaps togetherDistribution of Lymphatic VesselsLymph capillaries are widespread, occurring almost everywhere blood capillaries occurLymph capillaries are absent from bone and teeth, bone marrow, and the entire central nervous systemLymph CapillariesOnce interstitial fluid enters the lymphatic ducts it is called lymph Although the high permeability of lymph capillaries allows the uptake of large quantities of tissue fluid and protein molecules it also allows bacteria, viruses, or cancer cells in the loose connective tissue to enter these capillaries with easeLymph CapillariesThese pathogenic agents can then travel throughout the body via the lymphatic vesselsHowever, most pathogenic agents are destroyed in the lymph nodes by various antibodies before reaching the general circulationCancer cells can be the most problematic and can actually use lymph nodes as a site to metastasize furtherLymph CapillariesLymph capillaries are widespread, occurring almost everywhere blood capillaries occurLymph CapillariesLymph capillaries are absent from bone and teeth, from bone marrow, and from the entire CNSIn the CNS excess fluid drains into the cerebrospinal fluid and then returns it to the blood at the superior sagittal sinusLymph Collecting VesselsFrom the lymph capillaries, lymph enters lymphatic collecting vessels which accompany blood vesselsLymph Collecting VesselsIn general, the superficial lymphatic collecting vessels in the skin travel with superficial veinsDeep lymphatic collecting vessels of the trunk and digestive viscera travel with the deep arteriesLymph Collecting VesselsLymphatic collecting vessels are narrow and delicate and are usually not seen in a laboratory dissectionThe vessels have the same tunics as blood vessels but their walls are always thinnerThe thinness reflects the fact that lymph flows under very low pressure and have