Lymphatic system - wikipedia Lymphatic system `` Lymphatic drainage '' redirects here. For the massage technique, see Manual lymphatic drainage. Lymphatic System Human lymphatic system Details Identifiers Latin systema lymphoideum TA A13. 0.00. 000 FMA 74594 Anatomical terminology ( edit on Wikidata ) The Lymphatic system is part of the circulatory system and a vital part of the immune system, comprising a network of lymphatic vessels that carry a clear fluid called lymph ( from Latin, lympha meaning `` water '' ) directionally towards the heart. The lymphatic system was first described in the seventeenth century independently by Olaus Rudbeck and Thomas Bartholin. Unlike the circulatory system, the lymphatic system is not a closed system. The human circulatory system processes an average of 20 liters of blood per day through capillary filtration, which removes plasma while leaving the blood cells. Roughly 17 litres of the filtered plasma are reabsorbed directly into the blood vessels, while the remaining three litres remain in the interstitial fluid. One of the main functions of the lymph system is to provide an accessory return route to the blood for the surplus three litres. The other main function is that of defense in the immune system. Lymph is very similar to blood plasma : it contains lymphocytes. It also contains waste products and cellular debris together with bacteria and proteins. Associated organs composed of lymphoid tissue are the sites of lymphocyte production. Lymphocytes are concentrated in the lymph nodes. The spleen and the thymus are also lymphoid organs of the immune system. The tonsils are lymphoid organs that are also associated with the digestive system. Lymphoid tissues contain lymphocytes, and also contain other types of cells for support. The system also includes all the structures dedicated to the circulation and production of lymphocytes ( the primary cellular component of lymph ), which also includes the bone marrow, and the lymphoid tissue associated with the digestive system. The blood does not come into direct contact with the parenchymal cells and tissues in the body ( except in case of an injury causing rupture of one or more blood vessels ), but constituents of the blood first exit the microvascular exchange blood vessels to become interstitial fluid, which comes into contact with the parenchymal cells of the body. Lymph is the fluid that is formed when interstitial fluid enters the initial lymphatic vessels of the lymphatic system. The lymph is then moved along the lymphatic vessel network by either intrinsic contractions of the lymphatic passages or by extrinsic compression of the lymphatic vessels via external tissue forces ( e.g., the contractions of skeletal muscles ), or by lymph hearts in some animals. The organization of lymph nodes and drainage follows the organization of the body into external and internal regions ; therefore, the lymphatic drainage of the head, limbs, and body cavity walls follows an external route, and the lymphatic drainage of the thorax, abdomen, and pelvic cavities follows an internal route. Eventually, the lymph vessels empty into the lymphatic ducts, which drain into one of the two subclavian veins, near their junction with the internal jugular veins. Play media Introduction to the lymphatic system Contents 1 Structure 1.1 Lymphoid tissue 1.1. 1 Thymus 1.1. 2 Spleen 1.1. 3 Lymph nodes 1.2 Other lymphoid tissue 1.3 Lymphatic vessels 1.4 Development 2 Function 2.1 Function of the fatty acid transport system 2.2 Immune function 3 Clinical significance 3.1 Lymphadenopathy 3.2 Lymphedema 3.3 Cancer 3.4 Other 4 History 4.1 Etymology 5 See also 6 References 7 External links Structure Lymphatic system The lymphatic system consists of lymphatic organs, a conducting network of lymphatic vessels, and the circulating lymph. The primary or central lymphoid organs generate lymphocytes from immature progenitor cells. The thymus and the bone marrow constitute the primary lymphoid organs involved in the production and early clonal selection of lymphocyte tissues. Bone marrow is responsible for both the creation of T cells and the production and maturation of B cells. From the bone marrow, B cells immediately join the circulatory system and travel to secondary lymphoid organs in search of pathogens. T cells, on the other hand, travel from the bone marrow to the thymus, where they develop further. Mature T cells join B cells in search of pathogens. The other 95 % of T cells begin a process of apoptosis, a form of programmed cell death. Secondary or peripheral lymphoid organs, which include lymph nodes and the spleen, maintain mature naive lymphocytes and initiate an adaptive immune response. The peripheral lymphoid organs are the sites of lymphocyte activation by antigens. Activation leads to clonal expansion and affinity maturation. Mature lymphocytes recirculate between the blood and the peripheral lymphoid organs until they encounter their specific antigen. Secondary lymphoid tissue provides the environment for the foreign or altered native molecules ( antigens ) to interact with the lymphocytes. It is exemplified by the lymph nodes, and the lymphoid follicles in tonsils, Peyer 's patches, spleen, adenoids, skin, etc. that are associated with the mucosa - associated lymphoid tissue ( MALT ). In the gastrointestinal wall the appendix has mucosa resembling that of the colon, but here it is heavily infiltrated with lymphocytes. The tertiary lymphoid tissue typically contains far fewer lymphocytes, and assumes an immune role only when challenged with antigens that result in inflammation. It achieves this by importing the lymphocytes from blood and lymph. ) Lymphoid tissue Thymus Main article : Thymus The thymus is a primary lymphoid organ and the site of maturation for T cells, the lymphocytes of the adaptive immune system. The thymus increases in size from birth in response to postnatal antigen stimulation, then to puberty and regresses thereafter. The loss or lack of the thymus results in severe immunodeficiency and subsequent high susceptibility to infection. In most species, the thymus consists of lobules divided by septa which are made up of epithelium and is therefore an epithelial organ. T cells mature from thymocytes, proliferate and undergo selection process in the thymic cortex before entering the medulla to interact with epithelial cells. The thymus provides an inductive environment for development of T cells from hematopoietic progenitor cells. In addition, thymic stromal cells allow for the selection of a functional and self - tolerant T cell repertoire. Therefore, one of the most important roles of the thymus is the induction of central tolerance. The thymus is largest and most active during the neonatal and pre-adolescent periods. By the early teens, the thymus begins to atrophy and thymic stroma is mostly replaced by adipose tissue. Nevertheless, residual T lymphopoiesis continues throughout adult life. Spleen Main article : Spleen The main functions of the spleen are : to produce immune cells to fight antigens to remove particulate matter and aged blood cells, mainly erythrocytes to produce blood cells during fetal life The spleen synthesizes antibodies in its white pulp and removes antibody - coated bacteria and antibody - coated blood cells by way of blood and lymph node circulation. A study published in 2009 using mice found that the spleen contains, in its reserve, half of the body 's monocytes within the red pulp. These monocytes, upon moving to injured tissue ( such as the heart ), turn into dendritic cells and macrophages while promoting tissue healing. The spleen is a center of activity of the mononuclear phagocyte system and can be considered analogous to a large lymph node, as its absence causes a predisposition to certain infections. Like the thymus, the spleen has only efferent lymphatic vessels. Both the short gastric arteries and the splenic artery supply it with blood. The germinal centers are supplied by arterioles called penicilliary radicles. Up to the fifth month of prenatal development the spleen creates red blood cells. After birth the bone marrow is solely responsible for hematopoiesis. As a major lymphoid organ and a central player in the reticuloendothelial system, the spleen retains the ability to produce lymphocytes. The spleen stores red blood cells and lymphocytes. It can store enough blood cells to help in an emergency. Up to 25 % of lymphocytes can be stored at any one time. Lymph nodes Main article : Lymph node A lymph node showing afferent and efferent lymphatic vessels A lymph node is an organized collection of lymphoid tissue, through which the lymph passes on its way back to the blood. Lymph nodes are located at intervals along the lymphatic system. Several afferent lymph vessels bring in lymph, which percolates through the substance of the lymph node, and is then drained out by an efferent lymph vessel. There are between five and six hundred lymph nodes in the human body, many of which are grouped in clusters in different regions as in the underarm and abdominal areas. Lymph node clusters are commonly found at the base of limbs ( groin, armpits ) and in the neck, where lymph is collected from regions of the body likely to sustain pathogen contamination from injuries. The substance of a lymph node consists of lymphoid follicles in an outer portion called the cortex. The inner portion of the node is called the medulla, which is surrounded by the cortex on all sides except for a portion known as the hilum. The hilum presents as a depression on the surface of the lymph node, causing the otherwise spherical lymph node to be bean - shaped or ovoid. The efferent lymph vessel directly emerges from the lymph node at the hilum. The arteries and veins supplying the lymph node with blood enter and exit through the hilum. The region of the lymph node called the paracortex immediately surrounds the medulla. Unlike the cortex, which has mostly immature T cells, or thymocytes, the paracortex has a mixture of immature and mature T cells. Lymphocytes enter the lymph nodes through specialised high endothelial venules found in the paracortex. A lymph follicle is a dense collection of lymphocytes, the number, size and configuration of which change in accordance with the functional state of the lymph node. For example, the follicles expand significantly when encountering a foreign antigen. The selection of B cells, or B lymphocytes, occurs in the germinal center of the lymph nodes. Lymph nodes are particularly numerous in the mediastinum in the chest, neck, pelvis, axilla, inguinal region, and in association with the blood vessels of the intestines. Other lymphoid tissue Regional lymph nodes Lymphoid tissue associated with the lymphatic system is concerned with immune functions in defending the body against infections and the spread of tumors. It consists of connective tissue formed of reticular fibers, with various types of leukocytes, ( white blood cells ), mostly lymphocytes enmeshed in it, through which the lymph passes. Regions of the lymphoid tissue that are densely packed with lymphocytes are known as lymphoid follicles. Lymphoid tissue can either be structurally well organized as lymph nodes or may consist of loosely organized lymphoid follicles known as the mucosa - associated lymphoid tissue. The central nervous system also has lymphatic vessels, as discovered by University of Virginia Researchers. The search for T - cell gateways into and out of the meninges uncovered functional lymphatic vessels lining the dural sinuses, anatomically integrated into the membrane surrounding the brain. See Meningeal lymphatic vessels. Lymphatic vessels Main article : Lymphatic vessel Lymph capillaries in the tissue spaces The lymphatic vessels, also called lymph vessels, conduct lymph between different parts of the body. They include the tubular vessels of the lymph capillaries, and the larger collecting vessels -- the right lymphatic duct and the thoracic duct ( the left lymphatic duct ). The lymph capillaries are mainly responsible for the absorption of interstitial fluid from the tissues, while lymph vessels propel the absorbed fluid forward into the larger collecting ducts, where it ultimately returns to the bloodstream via one of the subclavian veins. These vessels are also called the lymphatic channels or simply lymphatics. The lymphatics are responsible for maintaining the balance of the body fluids. Its network of capillaries and collecting lymphatic vessels work to efficiently drain and transport extravasated fluid, along with proteins and antigens, back to the circulatory system. Numerous intraluminal valves in the vessels ensure a unidirectional flow of lymph without reflux. Two valve systems are used to achieve this one directional flow -- a primary and a secondary valve system. The capillaries are blind - ended, and the valves at the ends of capillaries use specialised junctions together with anchoring filaments to allow a unidirectional flow to the primary vessels. The collecting lymphatics, however, act to propel the lymph by the combined actions of the intraluminal valves and lymphatic muscle cells. Development Lymphatic tissues begin to develop by the end of the fifth week of embryonic development. Lymphatic vessels develop from lymph sacs that arise from developing veins, which are derived from mesoderm. The first lymph sacs to appear are the paired jugular lymph sacs at the junction of the internal jugular and subclavian veins. From the jugular lymph sacs, lymphatic capillary plexuses spread to the thorax, upper limbs, neck and head. Some of the plexuses enlarge and form lymphatic vessels in their respective regions. Each jugular lymph sac retains at least one connection with its jugular vein, the left one developing into the superior portion of the thoracic duct. The next lymph sac to appear is the unpaired retroperitoneal lymph sac at the root of the mesentery of the intestine. It develops from the primitive vena cava and mesonephric veins. Capillary plexuses and lymphatic vessels spread from the retroperitoneal lymph sac to the abdominal viscera and diaphragm. The sac establishes connections with the cisterna chyli but loses its connections with neighboring veins. The last of the lymph sacs, the paired posterior lymph sacs, develop from the iliac veins. The posterior lymph sacs produce capillary plexuses and lymphatic vessels of the abdominal wall, pelvic region, and lower limbs. The posterior lymph sacs join the cisterna chyli and lose their connections with adjacent veins. With the exception of the anterior part of the sac from which the cisterna chyli develops, all lymph sacs become invaded by mesenchymal cells and are converted into groups of lymph nodes. The spleen develops from mesenchymal cells between layers of the dorsal mesentery of the stomach. The thymus arises as an outgrowth of the third pharyngeal pouch. Function The lymphatic system has multiple interrelated functions : It is responsible for the removal of interstitial fluid from tissues It absorbs and transports fatty acids and fats as chyle from the digestive system It transports white blood cells to and from the lymph nodes into the bones The lymph transports antigen - presenting cells, such as dendritic cells, to the lymph nodes where an immune response is stimulated. Function of the fatty acid transport system Lymph vessels called lacteals are in the beginning of the gastrointestinal tract, predominantly in the small intestine. While most other nutrients absorbed by the small intestine are passed on to the portal venous system to drain via the portal vein into the liver for processing, fats ( lipids ) are passed on to the lymphatic system to be transported to the blood circulation via the thoracic duct. ( There are exceptions, for example medium - chain triglycerides are fatty acid esters of glycerol that passively diffuse from the GI tract to the portal system. ) The enriched lymph originating in the lymphatics of the small intestine is called chyle. The nutrients that are released to the circulatory system are processed by the liver, having passed through the systemic circulation. Immune function Further information : Immune system The lymphatic system plays a major role in body 's immune system, as the primary site for cells relating to adaptive immune system including T - cells and B - cells. Cells in the lymphatic system react to antigens presented or found by the cells directly or by other dendritic cells. When an antigen is recognized, an immunological cascade begins involving the activation and recruitment of more and more cells, the production of antibodies and cytokines and the recruitment of other immunological cells such as macrophages. Clinical significance Main article : Lymphatic disease The study of lymphatic drainage of various organs is important in the diagnosis, prognosis, and treatment of cancer. The lymphatic system, because of its closeness to many tissues of the body, is responsible for carrying cancerous cells between the various parts of the body in a process called metastasis. The intervening lymph nodes can trap the cancer cells. If they are not successful in destroying the cancer cells the nodes may become sites of secondary tumors. Lymphadenopathy Main article : Lymphadenopathy Lymphadenopathy refers to one or more enlarged lymph nodes. Small groups or individually enlarged lymph nodes are generally reactive in response to infection or inflammation. This is called local lymphadenopathy. When many lymph nodes in different areas of the body are involved, this is called generalised lymphadenopathy. Generalised lymphadenopathy may be caused by infections such as infectious mononucleosis, tuberculosis and HIV, connective tissue diseases such as SLE and rheumatoid arthritis, and cancers, including both cancers of tissue within lymph nodes, discussed below, and metastasis of cancerous cells from other parts of the body, that have arrived via the lymphatic system. Lymphedema Main article : Lymphedema Lymphedema is the swelling caused by the accumulation of lymph, which may occur if the lymphatic system is damaged or has malformations. It usually affects limbs, though the face, neck and abdomen may also be affected. In an extreme state, called elephantiasis, the edema progresses to the extent that the skin becomes thick with an appearance similar to the skin on elephant limbs. Causes are unknown in most cases, but sometimes there is a previous history of severe infection, usually caused by a parasitic disease, such as lymphatic filariasis. Lymphangiomatosis is a disease involving multiple cysts or lesions formed from lymphatic vessels. Lymphedema can also occur after surgical removal of lymph nodes in the armpit ( causing the arm to swell due to poor lymphatic drainage ) or groin ( causing swelling of the leg ). Treatment is by massage, and is not permanent. Cancer Reed -- Sternberg cells. Main article : Lymphoma Cancer of the lymphatic system can be primary or secondary. Lymphoma refers to cancer that arises from lymphatic tissue. Lymphoid leukemias and lymphomas are now considered to be tumors of the same type of cell lineage. They are called `` leukemia '' when in the blood or marrow and `` lymphoma '' when in lymphatic tissue. They are grouped together under the name `` lymphoid malignancy ''. Lymphoma is generally considered as either Hodgkin lymphoma or non-Hodgkin lymphoma. Hodgkin lymphoma is characterised by a particular type of cell, called a Reed -- Sternberg cell, visible under microscope. It is associated with past infection with the Epstein - Barr Virus, and generally causes a painless `` rubbery '' lymphadenopathy. It is staged, using Ann Arbor staging. Chemotherapy generally involves the ABVD and may also involve radiotherapy. Non-Hodgkin lymphoma is a cancer characterised by increased proliferation of B - cells or T - cells, generally occurs in an older age group than Hodgkin lymphoma. It is treated according to whether it is high - grade or low - grade, and carries a poorer prognosis than Hodgkin lymphoma. Lymphangiosarcoma is a malignant soft tissue tumor, whereas lymphangioma is a benign tumor occurring frequently in association with Turner syndrome. Lymphangioleiomyomatosis is a benign tumor of the smooth muscles of the lymphatics that occurs in the lungs. Lymphoid leukemia is another form of cancer where the host is devoid of different lymphatic cells. Other Lymphangitis Kikuchi disease Chylothorax Castleman 's disease Kawasaki disease Lymphatic filariasis Solitary lymphatic nodule History Hippocrates, in 5th century BC, was one of the first people to mention the lymphatic system. In his work On Joints, he briefly mentioned the lymph nodes in one sentence. Rufus of Ephesus, a Roman physician, identified the axillary, inguinal and mesenteric lymph nodes as well as the thymus during the 1st to 2nd century AD. The first mention of lymphatic vessels was in 3rd century BC by Herophilos, a Greek anatomist living in Alexandria, who incorrectly concluded that the `` absorptive veins of the lymphatics, '' by which he meant the lacteals ( lymph vessels of the intestines ), drained into the hepatic portal veins, and thus into the liver. The findings of Ruphus and Herophilos were further propagated by the Greek physician Galen, who described the lacteals and mesenteric lymph nodes which he observed in his dissection of apes and pigs in the 2nd century AD. In the mid 16th century, Gabriele Falloppio ( discoverer of the fallopian tubes ), described what are now known as the lacteals as `` coursing over the intestines full of yellow matter. '' In about 1563 Bartolomeo Eustachi, a professor of anatomy, described the thoracic duct in horses as vena alba thoracis. The next breakthrough came when in 1622 a physician, Gaspare Aselli, identified lymphatic vessels of the intestines in dogs and termed them venae alba et lacteae, which is now known as simply the lacteals. The lacteals were termed the fourth kind of vessels ( the other three being the artery, vein and nerve, which was then believed to be a type of vessel ), and disproved Galen 's assertion that chyle was carried by the veins. But, he still believed that the lacteals carried the chyle to the liver ( as taught by Galen ). He also identified the thoracic duct but failed to notice its connection with the lacteals. This connection was established by Jean Pecquet in 1651, who found a white fluid mixing with blood in a dog 's heart. He suspected that fluid to be chyle as its flow increased when abdominal pressure was applied. He traced this fluid to the thoracic duct, which he then followed to a chyle - filled sac he called the chyli receptaculum, which is now known as the cisternae chyli ; further investigations led him to find that lacteals ' contents enter the venous system via the thoracic duct. Thus, it was proven convincingly that the lacteals did not terminate in the liver, thus disproving Galen 's second idea : that the chyle flowed to the liver. Johann Veslingius drew the earliest sketches of the lacteals in humans in 1647. The idea that blood recirculates through the body rather than being produced anew by the liver and the heart was first accepted as a result of works of William Harvey -- a work he published in 1628. In 1652, Olaus Rudbeck ( 1630 -- 1702 ), a Swede, discovered certain transparent vessels in the liver that contained clear fluid ( and not white ), and thus named them hepatico - aqueous vessels. He also learned that they emptied into the thoracic duct, and that they had valves. He announced his findings in the court of Queen Christina of Sweden, but did not publish his findings for a year, and in the interim similar findings were published by Thomas Bartholin, who additionally published that such vessels are present everywhere in the body, not just in the liver. He is also the one to have named them `` lymphatic vessels. '' This had resulted in a bitter dispute between one of Bartholin 's pupils, Martin Bogdan, and Rudbeck, whom he accused of plagiarism. Galen 's ideas prevailed in medicine until the 17th century. It was thought that blood was produced by the liver from chyle contaminated with ailments by the intestine and stomach, to which various spirits were added by other organs, and that this blood was consumed by all the organs of the body. This theory required that the blood be consumed and produced many times over. Even in the 17th century, his ideas were defended by some physicians. Alexander Monro, of the University of Edinburgh Medical School, was the first to describe the function of the lymphatic system in detail. `` Claude Galien ''. Lithograph by Pierre Roche Vigneron. ( Paris : Lith de Gregoire et Deneux, ca. 1865 ) Gabriele Falloppio Portrait of Eustachius Olaus Rudbeck in 1696. Thomas Bartholin Etymology Lymph originates in the Classical Latin word lympha `` water '', which is also the source of the English word limpid. The spelling with y and ph was influenced by folk etymology with Greek νύμφη ( nýmphē ) `` nymph ''. The adjective used for the lymph - transporting system is lymphatic. The adjective used for the tissues where lymphocytes are formed is lymphoid. Lymphatic comes from the Latin word lymphaticus, meaning `` connected to water. '' See also List of lymphatic vessels of the human body American Society of Lymphology Glymphatic system and Meningeal lymphatic vessels - equivalent for the central nervous system Lymphangiogenesis Lymphangion Manual lymphatic drainage Mononuclear phagocyte system Waldemar Olszewski -- discovered fundamental processes in human tissues connected with function of the lymphatic system ru : Чепеленко, Геннадий Владимирович -- author of the lymphatic system segmental theory Trogocytosis References Jump up ^ `` Lymph - Definition and More from the Free Merriam - Webster Dictionary ''. www.merriam-webster.com. Retrieved 2010 - 05 - 29. Jump up ^ Human Physiology : From Cells to Systems, by Lauralee Sherwood Jump up ^ Tak W. Mak ; Mary E. Saunders ( Ph. D. ) ; Mary E. Saunders ( 2008 ). Primer to the immune response. Academic Press. pp. 28 --. ISBN 978 - 0 - 12 - 374163 - 9. Retrieved 12 November 2010. ^ Jump up to : Warwick, Roger ; Peter L. Williams. `` Angiology ( Chapter 6 ) ''. Gray 's anatomy. illustrated by Richard E.M. Moore ( Thirty - fifth ed. ). London : Longman. pp. 588 -- 785. access - date = requires url = ( help ) Jump up ^ Wisco, Jonathan. `` Lymphatic System ''. AnatomyOne. Amirsys, Inc. Retrieved 26 October 2012. Jump up ^ Goldsby, Richard ; Kindt, TJ ; Osborne, BA ; Janis Kuby ( 2003 ) ( 1992 ). `` Cells and Organs of the Immune System ( Chapter 2 ) ''. Immunology ( Fifth ed. ). New York : W.H. Freeman and Company. pp. 24 -- 56. ISBN 0 - 7167 - 4947 - 5. ^ Jump up to : Miller, J.F. ( 2002 ). `` The discovery of thymus function and of thymus - derived lymphocytes ''. Immunol Rev. 185 ( 1 ) : 7 -- 14. PMID 12190917. doi : 10.1034 / j. 1600 - 065X. 2002.18502. x. ^ Jump up to : Swirski, FK ; Nahrendorf, M ; Etzrodt, M ; Wildgruber, M ; Cortez - Retamozo, V ; Panizzi, P ; Figueiredo, JL ; Kohler, RH ; Chudnovskiy, A ; Waterman, P ; Aikawa, E ; Mempel, TR ; Libby, P ; Weissleder, R ; Pittet, MJ ( 2009 ). `` Identification of splenic reservoir monocytes and their deployment to inflammatory sites ''. Science. 325 ( 5940 ) : 612 -- 6. PMC 2803111. PMID 19644120. doi : 10.1126 / science. 1175202. Jump up ^ Jia, T ; Pamer, EG ( 2009 ). `` Immunology. Dispensable but not irrelevant ''. Science. 325 ( 5940 ) : 549 -- 50. PMC 2917045. PMID 19644100. doi : 10.1126 / science. 1178329. Jump up ^ Finally, the Spleen Gets Some Respect By NATALIE ANGIER, The New York Times, August 3, 2009 Jump up ^ Blackbourne, Lorne H ( 2008 - 04 - 01 ). Surgical recall. Lippincott Williams & Wilkins. p. 259. ISBN 978 - 0 - 7817 - 7076 - 7. Jump up ^ `` Penicilliary radicles ''. Medical-dictionary.thefreedictionary.com. Retrieved 2011 - 04 - 03. Jump up ^ `` Spleen : Information, Surgery and Functions ''. Childrens Hospital of Pittsburgh - Chp.edu. 2010 - 11 - 17. Retrieved 2011 - 04 - 03. Jump up ^ `` lymphoid tissue '' at Dorland 's Medical Dictionary Jump up ^ Louveau, Antoine ; Smirnov, Igor ; Keyes, Timothy J ; Eccles, Jacob D ; Rouhani, Sherin J ; Peske, J David ; Derecki, Noel C ; Castle, David ; Mandell, James W ; Lee, Kevin S ; Harris, Tajie H ; Kipnis, Jonathan ( 2015 ). `` Structural and functional features of central nervous system lymphatic vessels. ''. Nature. 523 ( 7560 ) : 337 -- 41. PMC 4506234. PMID 26030524. doi : 10.1038 / nature14432. Lay summary. we discovered functional lymphatic vessels lining the dural sinuses. These structures express all of the molecular hallmarks of lymphatic endothelial cells, are able to carry both fluid and immune cells from the cerebrospinal fluid, and are connected to the deep cervical lymph nodes. The unique location of these vessels may have impeded their discovery to date, thereby contributing to the long - held concept of the absence of lymphatic vasculature in the central nervous system. The discovery of the central nervous system lymphatic system may call for a reassessment of basic assumptions in neuroimmunology and sheds new light on the aetiology of neuroinflammatory and neurodegenerative diseases associated with immune system dysfunction. Jump up ^ https://www.nih.gov/news-events/news-releases/nih-researchers-uncover-drain-pipes-our-brains Jump up ^ `` Definition of lymphatics ''. Webster 's New World Medical Dictionary. medicineNet.com. Retrieved 2008 - 07 - 06. Jump up ^ Vittet, D. `` Lymphatic collecting vessel maturation and valve morphogenesis ''. Microvasc Res. 96 : 31 -- 7. PMID 25020266. doi : 10.1016 / j. mvr. 2014.07. 001. Jump up ^ Heppell C1, Richardson G ; Roose, T. `` A model for fluid drainage by the lymphatic system ''. Journal. 75 ( 1 ) : 49 -- 81. PMID 23161129. doi : 10.1007 / s11538 - 012 - 9793 - 2. Jump up ^ Bazigou, E ; Wilson, J ; Moore, JE ( 2014 ). `` Primary and secondary lymphatic valve development : Molecular, functional and mechanical insights ''. Microvasc Res. 96 : 38 -- 45. PMC 4490164. PMID 25086182. doi : 10.1016 / j. mvr. 2014.07. 008. Jump up ^ `` The functions of the Lymphatic System. ''. Retrieved Feb 25, 2011. Jump up ^ Britton, the editors Nicki R. Colledge, Brian R. Walker, Stuart H. Ralston ; illustrated by Robert ( 2010 ). Davidson 's principles and practice of medicine. ( 21st ed. ). Edinburgh : Churchill Livingstone / Elsevier. p. 1001. ISBN 978 - 0 - 7020 - 3085 - 7. Jump up ^ `` Lymphedema ''. Jump up ^ Anthony S. Fauci ; Eugene Braunwald ; Dennis Kasper ; Stephen Hauser ; Dan L. Longo ( 19 March 2009 ). Harrison 's Manual of Medicine. McGraw Hill Professional. pp. 352 --. ISBN 978 - 0 - 07 - 147743 - 7. Retrieved 12 November 2010. ^ Jump up to : Britton, the editors Nicki R. Colledge, Brian R. Walker, Stuart H. Ralston ; illustrated by Robert ( 2010 ). Davidson 's principles and practice of medicine. ( 21st ed. ). Edinburgh : Churchill Livingstone / Elsevier. pp. 1001, 1037 -- 1040. ISBN 978 - 0 - 7020 - 3085 - 7. ^ Jump up to : Ambrose, C. ( 2006 ). `` Immunology 's first priority dispute -- An account of the 17th - century Rudbeck -- Bartholin feud ''. Cellular Immunology. 242 ( 1 ) : 1 -- 8. PMID 17083923. doi : 10.1016 / j. cellimm. 2006.09. 004. ^ Jump up to : Fanous, Medhat YZ ; Anthony J Phillips ; John A Windsor ( 2007 ). `` Mesenteric Lymph : The Bridge to Future Management of Critical Illness ''. Journal of the Pancreas. Department of Internal Medicine and Gastroenterology ALMA MATER STUDIORUM - UNIVERSITY OF BOLOGNA. 8 ( 4 ) : 374 -- 399. PMID 17625290. Retrieved 2008 - 07 - 11. ^ Jump up to : Flourens, P. ( 1859 ). `` ASELLI, PECQUET, RUDBECK, BARTHOLIN ( Chapter 3 ) ''. A History of the Discovery of the Circulation of the Blood. Rickey, Mallory & company. pp. 67 -- 99. Retrieved 2008 - 07 - 11. ^ Jump up to : Eriksson, G. ( 2004 ). `` Olaus Rudbeck as scientist and professor of medicine ( Original article in Swedish ) ''. Svensk Medicinhistorisk Tidskrift ( in Swedish ). 8 ( 1 ) : 39 -- 44. PMID 16025602. Jump up ^ `` Disputatio anatomica, de circulatione sanguinis ''. Account of Rudbeck 's work on lymphatic system and dispute with Bartholin. The International League of Antiquarian Booksellers. Retrieved 2008 - 07 - 11. Jump up ^ Turner, A. Logan ( 1937 ). Story of a Great Hospital : The Royal Infirmary of Edinburgh 1729 - 1929. Oliver and Boyd. p. 360. Jump up ^ lympha. Charlton T. Lewis and Charles Short. A Latin Dictionary on Perseus Project. Jump up ^ `` lymph ''. Oxford English Dictionary ( 3rd ed. ). Oxford University Press. September 2005. ( Subscription or UK public library membership required. ) External links Wikimedia Commons has media related to Lymphatic system. The Wikibook Anatomy and Physiology of Animals has a page on the topic of : Lymphatic System Library resources about Lymphatic system Resources in your library Lymphatic System Lymphatic System Overview ( innerbody.com ) Organs of the lymphatic system Primary organs Bone marrow Hematopoietic stem cell Thymus Hassall 's corpuscles Secondary organs Spleen Structure Hilum Trabeculae Red pulp Cords of Billroth Marginal zone White pulp Periarteriolar lymphoid sheaths Germinal center Blood flow Trabecular arteries Trabecular veins Tonsils Palatine Lingual Pharyngeal Tubal Tonsillar crypts Waldeyer 's tonsillar ring Lymph nodes Lymphatic vessel T cells High endothelial venules B cells Germinal center Mantle zone Marginal zone MALT GALT Peyer 's patch Germinal center Lymphatic vessels Nodal Lymph capillary Lymphatic vessel Other Lymph trunk Lymph Lymphangion Anatomy of the lymphatic system Head and neck Head Back Occipital Mastoid / retroauricular Parotid Superficial Deep preauricular infra - auricular intraglandular Front Facial buccinator nasolabial Mandibular Submandibular Submental Cervical Superficial anterior lateral Deep Deep anterior cervical pretracheal paratracheal prelaryngeal thyroid Deep lateral cervical superior deep cervical inferior deep cervical retropharyngeal jugulodigastric jugulo - omohyoid Other Anterior cervical Lateral cervical Supraclavicular Virchow 's Vessels Jugular trunk Arm and axilla Nodes Axillary Brachial Pectoral Subscapular Central Apical Arm Supratrochlear Deltopectoral Vessels Subclavian lymph trunk Chest Nodes Parasternal Intercostal Superior diaphragmatic Trachea and bronchi superior inferior bronchopulmonary paratracheal intrapulmonary Vessels Thoracic duct Right lymphatic duct Bronchomediastinal lymph trunk Abdomen Nodes Paraaortic Retroaortic Lateral aortic Preaortic ( Celiac gastric hepatic splenic Superior mesenteric mesenteric ileocolic mesocolic Inferior mesenteric pararectal ) Other Iliac Common external internal Sacral Retroperitoneal lymph nodes Vessels Lumbar lymph trunk Intestinal trunk Cisterna chyli Leg Inguinal deep Cloquet 's node superficial Popliteal Biology portal Medicine portal Retrieved from `` https://en.wikipedia.org/w/index.php?title=Lymphatic_system&oldid=808365411 '' Categories : Lymphatic system Animal anatomy Angiology Hidden categories : Pages using citations with accessdate and no URL CS1 Swedish - language sources ( sv ) All articles with dead external links Articles with dead external links from September 2010 Wikipedia articles needing clarification from November 2016 Wikipedia articles that may have off - topic sections Articles containing Latin - language text Articles containing Ancient Greek - language text Talk Contents About Wikipedia Aragonés অসমীয়া Azərbaycanca Беларуская Беларуская ( тарашкевіца ) ‎ Български Bosanski Català Čeština Cymraeg Dansk Deutsch ދިވެހިބަސް Eesti Ελληνικά Español Euskara فارسی Français Gaeilge Galego 한국어 Հայերեն हिन्दी Bahasa Indonesia Interlingua Íslenska Italiano עברית Basa Jawa Қазақша Kurdî Кыргызча Latina Latviešu Lietuvių Magyar Македонски Bahasa Melayu Nederlands 日本 語 Norsk Oʻzbekcha / ўзбекча Polski Português Română Русский සිංහල Simple English Slovenčina کوردی Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska Tagalog తెలుగు ไทย Türkçe Українська اردو ئۇيغۇرچە / Uyghurche Tiếng Việt ייִדיש 中文 Edit links This page was last edited on 2 November 2017, at 12 : 49. 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Question: the primary gland of the lymph system is the
Answer: thymus