lymph node

Examples of lymph node in the following topics:

• Lymph Nodes

  • Each lymph node has an afferent lymph vessel that directs lymph into the node, and an efferent lymph vessel called the hilum that directs lymph out of the node at the concave side of the node.
  • The hilum also contains the blood supply of the lymph node.
  • These antigens may be taken by cells into the lymph nodes.
  • The lymph nodes also filter the lymph fluid.
  • This is usually caused by increased lymph flow into the nodes.

• Lymph Transport

  • Lymph circulates to the lymph node via afferent lymphatic vessels and drains into the lymph node in the subcapsular sinus.
  • The collecting vessels typically transport lymph fluid either into lymph nodes or lymph trunks.
  • Lymph circulates to the lymph node via afferent lymphatic vessels.
  • The sinuses converge at the hilum of the node, where lymph then leaves the node via an efferent lymphatic vessel toward either a more central lymph node or a lymph duct for drainage into one of the subclavian veins.
  • The lymph flows from the afferent vessels into the sinuses of the lymph node, and then out of the node through the efferent vessels.

• Distribution of Lymphatic Vessels

  • Large lymphatic vessels can be broadly characterized into two categories based on lymph node distribution.
  • Afferent lymphatic vessels flow into a lymph node and carry unfiltered lymph fluid.
  • Efferent lymphatic vessels flow out of a lymph node and carry filtered lymph fluid.
  • There are few lymph nodes at the ends of the limbs.
  • Lymph nodes found closer to the heart filter lymph fluid before it is returned to venous circulation through one of the two lymph ducts.

• Structure of the Lymphatic System

  • The larger lymph vessels contain valves that prevent the backflow of lymph.
  • The lymphatic vessels make their way to the lymph nodes, and from there the vessels form into trunks.
  • Lymphoid tissue is found in many organs including the lymph nodes, as well as in the lymphoid follicles in the pharynx such as the tonsils.
  • Lymph nodes are found primarily in the armpits, groin, chest, neck, and abdomen.
  • This diagram shows the network of lymph nodes and connecting lymphatic vessels in the human body.

• Lymphoid Tissue

  • It is found mainly in the lymph nodes, but also in the lymphoid follicles in tonsils, Peyer's patches, spleen, adenoids, skin, and other areas associated with the mucosa-associated lymphoid tissue (MALT).
  • The lymphatic endothelial cells proliferate into sacs that eventually become lymph nodes, with afferent and efferent vessels that flow out from the lymph nodes.
  • This process begins with he lymph nodes closest to the thoracic and right lymph ducts, which arises from immature subclavian-jugular vein junction.
  • The lymph nodes organized around other lymph trunks, such as those in the abdomen and intestine, develop afterwards from nearby veins.
  • The thymus and bone marrow are primary lymphoid tissue, while the lymph nodes, tonsils, and spleen are secondary lymphoid tissue.

• Metastasis Through Lymphatic Vessels

  • The tumor cells are then transported to regional lymph nodes and ultimately, to other parts of the body.
  • Lymphatic spread: Invasion into the lymphatic system allows the transport of tumor cells to regional and distant lymph nodes and, ultimately, to other parts of the body.
  • Micrograph showing a lymph node invaded by ductal breast carcinoma and with extranodal extension of tumour.
  • The dark purple (center) is lymphocytes (part of a normal lymph node).
  • Micrograph of a colorectal adenocarcinoma metastasis to a lymph node, also lymph node metastasis.

• Lymphatic Tissue Development

  • The first lymph sacs to appear are the paired jugular lymph sacs at the junction of the internal jugular and subclavian veins.
  • The next lymph sac to appear is the unpaired retroperitoneal lymph sac at the root of the mesentery of the intestine.
  • The last of the lymph sacs, the paired posterior lymph sacs, develop from the iliac 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 .
  • A lymph node showing afferent and efferent lymphatic vessels, capsule, sinus, efferent lymphatic vessel, backflow valve, nodule, cortex, and hilum.

• Lymph Trunks and Ducts

  • The lymph trunks drain into the lymph ducts, which in turn return lymph to the blood by emptying into the respective subclavian veins.
  • After filtration by the lymph nodes, efferent lymphatic vessels take lymph to the end of the lymphatic system.
  • Jugular lymph trunks, located in the neck, drain lymph fluid from the cervical lymph nodes of the neck.
  • Subclavian lymph trunks, located beneath the clavicle, drain lymph fluid from the apical lymph nodes around the armpit, which carry lymph from the arms.
  • Two lymph ducts receive lymph from the lymph trunks.

• Spleen

  • The spleen, similar to a large lymph node, acts primarily as a blood filter in the mononuclear phagocyte system of the immune system.
  • Similar in structure to a large lymph node, it acts primarily as a blood filter.
  • It is similar to an enlarged lymph node but is a bit more complex.
  • Unlike lymph nodes, the spleen possesses only efferent lymphatic vessels, because it only filters blood instead of lymph fluid.
  • This stimulates the same type of adaptive immune response that occurs in the lymph nodes.

• Functions of the Lymphatic System

  • They are then transported to thicker collecting lymphatics, which are embedded with multiple lymph nodes, and are eventually returned to the blood circulation through the left and right subclavian veins and into the vena cava.
  • Lymph nodes located at junctions between the lymph vessels also filter the lymph fluid to remove pathogens and other abnormalities.
  • Most notably, highly-specialized white blood cells called lymphocytes and antigen-presenting cells are transported to regional lymph nodes, where the immune system encounters pathogens, microbes, and other immune elicitors that are filtered from the lymph fluid.
  • Much of the adaptive immune system response, which is mediated by dendritic cells, takes place in the lymph nodes.
  • This allows antigens to enter lymph nodes, where dendritic cells can present them to lymphocytes to trigger an adaptive immune response.