They're also found along the lymphatic pathways in the chest, abdomen, and pelvis, where they filter the blood. When a person has an infection, germs collect in the lymph nodes.
If the throat is infected, for example, the lymph nodes in the neck may swell. That's why doctors check for swollen lymph nodes sometimes called swollen "glands" in the neck when someone has a sore throat.
This is called lymphadenopathy. Reviewed by: Larissa Hirsch, MD. Larger text size Large text size Regular text size. What Are the Spleen and Lymphatic System? These vessels carry a fluid called lymph away from body tissues and capillary beds to be filtered by nodes and organs, then returned to the bloodstream.
The lymph nodes and lymphatic organs provide the key functional sites of the lymphatic system. The lymphatic organs, including the thymus and spleen, and diffuse tissues contain lymphocytes and other defense cells produced by the bone marrow.
The lymph nodes are interspersed along the vessel network and filter lymph. Node lymphocytes can enter the lymph vessels in order to eliminate pathogens. Lymph derives from interstitial fluid that surrounds the cells of body tissues. This interstitial fluid comes from the bloodstream, as capillaries exchange substances with tissue cells and fluid leaves the capillaries. Much of the fluid reenters the capillaries directly.
The rest moves into lymphatic capillaries and vessels as lymph. Lymph is clear and colorless and contains white blood cells. From developing new therapies that treat and prevent disease to helping people in need, we are committed to improving health and well-being around the world. The Manual was first published in as a service to the community. Learn more about our commitment to Global Medical Knowledge. This site complies with the HONcode standard for trustworthy health information: verify here.
Common Health Topics. Disorders of the lymphatic system. Lymphatic Disorders. Test your knowledge. An aortic dissection occurs when the inner layer lining of the aortic wall tears and separates from the middle layer of the wall. Aortic dissection is frequently fatal. Among which of the following groups is aortic dissection most common?
More Content. Click here for the Professional Version. Thin-walled lymphatic vessels. Lymph transport refers to the transport of lymph fluid from the interstitial space inside the tissues of the body, through the lymph nodes, and into lymph ducts that return the fluid to venous circulation. Lymphatic capillaries are the site of lymph fluid collection from the tissues. The fluid accumulates in the interstitial space inside tissues after leaking out through the cardiovascular capillaries. The fluid enters the lymphatic capillaries by leaking through the minivalves located in the junctions of the endothelium.
Under ordinary conditions these minivalves prevent the lymph from flowing back into the tissues. In addition to interstitial fluid, pathogens, proteins, and tumor cells may also leak into the lymph capillaries and be transported through lymph. The lymph capillaries feed into larger lymph vessels. The lymph vessels that receive lymph fluid from many capillaries are called collecting vessels.
Semilunar valves work together with smooth muscle contractions and skeletal muscle pressure to slowly push the lymph fluid forward while the valves prevent backflow. 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 lymph fluid drains into the node just beneath the capsule of the node into its various sinus spaces. These spaces are loosely separated by walls, so lymph fluid flows around them throughout the lymph node.
The sinus space is filled with macrophages that engulf foreign particles and pathogens and filter the lymph. 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 nodes contain a large number of B and T lymphocytes, which are transported throughout the node during many components of the adaptive immune response.
When a lymphocyte is presented with an antigen such as by an activated helper T cell , B cells become activated and migrate to the germinal centers of the node, where they proliferate and differentiate to be specific to that antigen. When antibody-producing B cells are formed, they migrate to the medullary central cords of the node. Stimulation of the lymphocytes by antigens can accelerate the migration process to about ten times normal, resulting in the characteristic swelling of the lymph nodes that is a common symptom of many infections.
The lymphocytes are transported through lymph fluid and leave the node through the efferent vessels to travel to other parts of the body to perform adaptive immune response functions. Flow of Lymph : The lymph flows from the afferent vessels into the sinuses of the lymph node, and then out of the node through the efferent vessels.
After leaving the lymph node through efferent vessels, lymph travels either to another node further into the body or to a lymph trunk, the larger vessel where many efferent vessels converge. Four pairs of lymph trunks are distributed laterally around the center of the body, along with an unpaired intestinal trunk.
The lymph trunks then converge into the two lymph ducts, the right lymph duct and the thoracic duct. These ducts take the lymph into the right and left subclavian veins, which flow into the vena cava. This is where lymph fluid reaches the end of its journey from the interstitial space of tissues back into blood circulation. Lymph capillaries are tiny, thin-walled vessels, closed at one end and located in the spaces between cells throughout the body.
Describe the location, structure, and role of lymphatic capillaries in maintaining the pressure of the interstitial fluid. Lymphatic circulation begins in the smallest type of lymph vessels, the lymph capillaries.
These regulate the pressure of interstitial fluid by draining lymph from the tissues. Lymph or lymphatic capillaries are tiny thin-walled vessels, closed at one end and located in the spaces between cells throughout the body. These are particularly dense within connective tissue. Lymphatic capillaries are primarily made out of an endothelium layer that sits on a permeable basement membrane. The flap-like minivalves, located at gap-like junctions in the endothelium, are formed from the overlap of endothelial cells and are normally closed.
Attached to the outer opening of the minivalves are anchoring filaments containing elastic fibers. They extend out from the lymphatic capillary, attaching the endothelium to fibroblast cells in the connective tissue. Unlike larger lymphatic vessels, lymphatic capillaries do not contain smooth muscle nor do they have a well developed adventitia, only small elastic filaments that perform a similar function.
Lymphatic capillaries collect lymph fluid from the tissues, which allows them to regulate the pressure of interstitial fluid. This fluid is essentially plasma that leaks out of cardiovascular capillaries into the tissues due to the forces of hydrostatic or oncotic pressure. When pressure is greater in the interstitial fluid than in lymph due to accumulation of interstitial fluid, the minivalves separate slightly like the opening of a one-way swinging door so that fluid can enter the lymphatic capillary.
When pressure is greater inside the lymphatic capillary, the cells adhere more closely to each other to prevent lymph backflow. The anchoring filaments are also pulled when the tissues are swollen. This opens the lymph capillaries more, increasing their volume and reducing their pressure to further facilitate fluid flow into the capillaries. Lymph capillaries have a greater oncotic pressure a pulling pressure exerted by proteins in solution than blood plasma due to the greater concentration of plasma proteins in lymph.
0コメント