Lymph node 82342 225744957 2008-07-15T05:16:12Z KC Panchal 3449833 Reverted edits by [[Special:Contributions/76.65.4.171|76.65.4.171]] ([[User talk:76.65.4.171|talk]]) to last version by KC Panchal [[Image:Illu lymph node structure.png|thumb|350px|right|A lymph node showing [[Afferent lymph vessel| afferent]] and [[Efferent lymph vessel| efferent]] [[lymphatic vessel]]s]] A '''Lymph node''' ({{IPA2| lɪmf noʊdz, lɪmf nəʊdz}}) is an organ consisting of many types of cells, and is a part of the [[lymphatic system]]. Lymph nodes are found throughout the body, and act as filters or traps for foreign particles and contain white blood cells. Thus they are important in the proper functioning of the [[immune system]]. Lymph nodes have clinical significance, too. They get inflamed or enlarged in various conditions, which may range from as trivial as [[Pharyngitis| throat infection]] to life-threatening conditions as [[cancer]]s. In the latter, the condition of lymph nodes is so significant that it is used for [[cancer staging]], which decides the treatment modalities to be employed, and for determining the [[prognosis]] (the outcome of disease). Lymph nodes can be also used for diagnosis by [[biopsy]] whenever they are inflamed. Certain diseases affect lymph nodes with characteristic [[Wiktionary:consistency|consistency]] (feel) and location. ==Function== Nodes act as filters, with an internal honeycomb of [[reticular connective tissue]] filled with [[lymphocyte]]s that collect and destroy bacteria and viruses. When the body is fighting an infection, lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes. Lymphatic fluid in the tissues, before it has gone into a lymph node, is called interstitial fluid. == Structure == [[Image:Schematic of lymph node showing lymph sinuses.png|thumb|300px|left|Schematic diagram of lymph node showing the flow of lymph through the lymph sinuses. Note: Outflowing lymph has more lymphocytes]] The lymph node is surrounded by a fibrous [[capsule]], and inside the lymph node the fibrous [[capsule]] extends to form [[trabeculae]]. The substance of the lymph node is divided into the outer [[Wiktionary:cortex|cortex]] and the inner [[Wiktionary:medulla|medulla]] surrounded by the former all around except for at the hilum, where the medulla comes in direct contact with the surface.<ref name=grays>{{cite book |last= Warwick|first= Roger|coauthors= Peter L. Williams|editor= |others= illustrated by Richard E. M. Moore|title= Gray's anatomy|origyear= 1858|accessdate= 2008-06-30|edition= Thirty-fifth Edition||year= 1973|publisher= Longman|location= London|pages= 588&mdash;785|chapter= Angiology (Chapter 6)}}</ref> Thin reticular fibers, [[elastin]] and [[reticular fiber]]s form a supporting meshwork called ''reticular network'' (RN) inside the node, within which the [[white blood cell]]s (WBCs), most prominently, lymphocytes are tightly packed as follicles in the cortex. Elsewhere, there are only occasional WBCs. The RN provides not just the structural support, but also provide surface for adhesion of the [[dendritic cell]]s, [[macrophage]]s and lymphocytes. It allows for exchange of material with blood through the [[high endothelial venules]] and provides the growth and regulatory factors necessary for activation and maturation of immune cells.<ref name=kaldjian>{{cite journal|last=Kaldjian|first=Eric P.|coauthors=J. Elizabeth Gretz, Arthur O. Anderson, Yinghui Shi and Stephen Shaw|title=Spatial and molecular organization of lymph node T cell cortex: a labyrinthine cavity bounded by an epithelium-like monolayer of fibroblastic reticular cells anchored to basement membrane-like extracellular matrix|journal= International Immunology|volume=13|issue=10|pages=1243&mdash;1253|year=2001|month=October|url=http://intimm.oxfordjournals.org/cgi/content/full/13/10/1243|publisher=Oxford Journals|accessdate=2008-07-11}}</ref> The number and composition of follicles can change especially when challenged by an [[antigen]], when they develop a germinal center.<ref name=grays/> A ''lymph sinus'' is a channel within the lymph node lined by the endothelial cells along with fibroblastic reticular cells and allows for smooth flow of lymph through them. Thus, subcapsular sinus is a sinus immediately deep to the capsule, and its endothelium is continuous with that of the afferent lymph vessel. It is also continuous with similar sinuses flanking the trabeculae and within the cortex (cortical sinuses). The cortical sinuses and that flanking the trabeculae drain into the ''medullary sinuses'', from where the lymph flows into the efferent lymph vessel.<ref name=grays/> Multiple [[afferent lymph vessel]]s that branch and network extensively within the capsule bring lymph into the lymph node. This lymph enters the subcapsular sinus. The innermost lining of the afferent lymph vessels is continuous with the cells lining the lymph sinuses.<ref name=grays/> The lymph gets slowly filtered through the substance of the lymph node and ultimately reaches the medulla. In its course it encounters the lymphocytes and may lead to their activation as a part of [[adaptive immune system|adaptive immune response]]. The concave side of the lymph node is called the [[hilum]]. The [[Efferent lymphatic vessel| efferent]] attaches to the hilum by a relatively dense reticulum present ther, and carries the lymph out of the lymph node. ===Cortex=== In the cortex, the [[subcapsular sinus]] drains to ''cortical sinuses''. The outer cortex consists mainly of the [[B cell]]s arranged as follicles, which may develop a germinal center when challenged with an antigen, and the the deeper cortex mainly consisting of the [[T cell]]s. There a zone known as the ''cortical ridge'' that lies between the B- and the T-cell zones, composed mainly of the dendritic cells, and where the RN is dense.<ref name=katakai>{{cite journal|last=Katakai|first=Tomoya|coauthors=Takahiro Hara, Hiroyuki Gonda1, Manabu Sugai and Akira Shimizu|title=A novel reticular stromal structure in lymph node cortex: an immuno-platform for interactions among dendritic cells, T cells and B cells|journal=International Immunology|volume=16|issue=8|pages=1133&mdash;1142|year=2004-07-05|url=http://intimm.oxfordjournals.org/cgi/content/full/16/8/1133|accessdate=2008-07-11}}</ref> ===Medulla=== There are two named structures in the medulla: * The ''medullary cords'' are cords of lymphatic tissue, and include [[plasma cell]]s and [[T cell]]s * The ''medullary sinuses'' (or ''sinusoids'') are vessel-like spaces separating the medullary cords. The Lymph flows into the medullary sinuses from cortical sinuses, and into [[efferent lymphatic vessels]]. Medullary sinuses contain [[histiocyte]]s (immobile macrophages) and [[reticular cell]]s. ===Shape and size=== Human lymph nodes are bean-shaped and range in size from a few millimeters to about 1-2 cm in their normal state.<ref name=grays/> They may become enlarged due to a tumor or infection. [[White blood cells]] are located within honeycomb structures of the lymph nodes. Lymph nodes are enlarged when the body is infected due to enhanced production of some cells and division of activated T and B cells. In some cases they may feel enlarged due to past infections; although one may be healthy, one may still feel them residually enlarged. == Lymphatic circulation == [[Lymph]] circulates to the lymph node via ''[[afferent lymphatic vessels]]'' and drains into the node just beneath the capsule in a space called the ''[[subcapsular sinus]]''. The subcapsular sinus drains into trabecular sinuses and finally into medullary sinuses. The sinus space is criss-crossed by the [[pseudopod]]s of [[macrophage]]s which act to trap foreign particles and filter the lymph. The medullary sinuses converge at the hilum and lymph then leaves the lymph node via the ''[[efferent lymphatic vessel]]'' towards either a more central lymph node or ultimately for drainage into a central [[Subclavian_vein|venous subclavian blood vessel]], most via [[Virchow%27s_node|Virchow's node]] and [[Thoracic Duct|Ductus Thoracicus]]. Valves on the [[afferent lymphatic vessels|afferent side]] prevent backflow. [[Lymphocytes]], both [[B cell]]s and [[T cell]]s, constantly circulate through the lymph nodes. They enter the lymph node via the postcapillary [[venule]]s, and cross its wall by the process of [[diapedesis]]. * The B cells migrate to the nodular cortex and medulla. * The T cells migrate to the deep cortex ("paracortex"). When a lymphocyte recognizes an [[antigen]], B cells become activated and migrate to [[germinal center]]s (by definition, a "secondary nodule" has a germinal center, while a "primary nodule" does not). When antibody-producing plasma cells are formed, they migrate to the medullary cords. Stimulation of the lymphocytes by antigens can accelerate the migration process to about 10 times normal, resulting in characteristic swelling of the lymph nodes. The [[spleen]] and [[tonsil]]s are large lymphoid organs that serve similar functions to lymph nodes, though the spleen filters blood cells rather than lymph. ==Distribution== [[Image:Lymph_node_regions.jpg|thumb|Regional lymph tissue]] Humans have approximately 500-600 lymph nodes distributed throughout the body, with clusters found in the underarms, groin, neck, chest, and abdomen. ===Lymph nodes of the human head and neck=== * [[Cervical lymph nodes]] **Anterior cervical: These nodes, both superficial and deep, lie above and beneath the [[sternocleidomastoid]] muscles. They drain the internal structures of the [[throat]] as well as part of the posterior [[pharynx]], [[tonsil]]s, and [[thyroid gland]]. ** Posterior cervical: These nodes extend in a line posterior to the sternocleidomastoids but in front of the [[trapezius]], from the level of the [[Mastoid portion of the temporal bone]] to the [[clavicle]]. They are frequently enlarged during upper [[respiratory infection]]s. * Tonsillar: (sub mandibular) These nodes are located just below the angle of the [[mandible]]. They drain the tonsillar and posterior pharyngeal regions. * Sub-mandibular: These nodes run along the underside of the jaw on either side. They drain the structures in the floor of the mouth. * Sub-mental: These nodes are just below the chin. They drain the teeth and intra-oral cavity. * [[Supraclavicular lymph nodes]]: These nodes are in the hollow above the [[clavicle]], just lateral to where it joins the [[sternum]]. They drain a part of the [[thoracic cavity]] and abdomen. [[Virchow's node]] is a left supraclavicular lymph node which receives the lymph drainage from most of the body (especially the abdomen) via the [[thoracic duct]] and is thus an early site of [[metastasis]] for various malignancies. ===Lymph nodes of the arm=== These drain the whole of the arm, and are divided into two groups, superficial and deep. The superficial nodes are supplied by lymphatics which are present throughout the arm, but are particularly rich on the palm and flexor aspects of the digits. * Superficial lymph glands of the arm: ** supratrochlear glands: Situated above the medial epicondyle of the [[humerus]], medial to the [[basilic vein]], they drain the C7 and C8 [[Dermatomic area|dermatome]]s. ** deltoideopectoral glands: Situated between the [[pectoralis major]] and [[deltoid]] [[muscle]]s inferior to the [[clavicle]]. * Deep lymph glands of the arm: These comprise the [[axillary glands]], which are 20-30 individual glands and can be subdivided into: ** lateral glands ** anterior or pectoral glands ** posterior or subscapular glands ** central or intermediate glands ** medial or subclavicular glands ===Lower limbs=== * [[Superficial inguinal lymph nodes]] * [[Deep inguinal lymph nodes]] ==Pathology== {{See|Lymphadenopathy}} Lymphadenopathy is a term meaning "disease of the lymph nodes." It is, however, almost synonymously used with "swollen/enlarged lymph nodes". In this case, the lymph nodes are palpable, and is a sign of various infections and diseases. ==Additional images== <gallery> Image:Illu lymphatic system.jpg|Lymphatic system Image:Lymphatic system.png|The human lymphatic system Image:Gray597.png|Section of small lymph node of rabbit. X 100. Image:Gray606.png|Lymphatics of the arm Image:Gray607.png|Lymphatics of the axillary region Image:Gray1074.png|Transverse section of human vermiform process. X 20. Image:Gray1082.png|Section of mucous membrane of human rectum. X 60. </gallery> == References == {{Reflist}} ==See also== *[[Adenitis]] *[[Lymphadenectomy]] *[[Lymphoma]] *[[Hematological_malignancy#List_of_Diseases|List of hæmatological diseases and malignancies]] ==External links== *[http://bioweb.wku.edu/courses/biol328/Lecture4.html Immunology Lecture 4, Biology 328] at [[Western Kentucky University]] *[http://www.thelymphnodes.com Lymph Nodes] {{Template:Lymphatic flow}} * {{BUHistology|07101loa}} {{lymphatic_system}} [[Category:Lymphatic system]] [[ar:عقدة لمفاوية]] [[ca:Gangli limfàtic]] [[da:Lymfeknude]] [[de:Lymphknoten]] [[el:Λεμφαδένας]] [[es:Ganglio linfático]] [[eo:Limfaj ganglioj]] [[fr:Ganglion lymphatique]] [[ko:림프절]] [[hr:Limfni čvorovi]] [[id:Nodus limfa]] [[ia:Glandula lymphatic]] [[is:Eitill]] [[it:Linfonodo]] [[la:Nodi lymphatici]] [[lt:Limfmazgis]] [[hu:Nyirokcsomó]] [[nl:Lymfeklier]] [[ja:リンパ節]] [[no:Lymfeknute]] [[pl:Węzeł chłonny]] [[pt:Linfonodo]] [[ru:Лимфатический узел]] [[fi:Imusolmuke]] [[sv:Lymfknuta]] [[uk:Лімфатичні вузли]] [[ur:سیالہ عقدہ]] [[zh:淋巴結]]