In mammals including humans, the lymphatic vessels (or lymphatics) are a network of thin tubes that branch, like blood vessels, into tissues throughout the body. Lymphatic vessels carry lymph, a colorless, watery fluid originating from interstitial fluid (fluid in the tissues). The lymphatic system transports infection-fighting cells called lymphocytes, is involved in the removal of foreign matter and cell debris by phagocytes and is part of the body's immune system. It also transports fats from the small intestine to the blood. Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals characterized by the presence of mammary glands... Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu (extinct) Homo sapiens sapiens Human beings define themselves in biological, social, and spiritual terms. ... The arterial system The blood vessels are part of the circulatory system and function to transport blood throughout the body. ... Interstitial fluid is one of the two components of extracellular fluid besides plasma. ... A lymphocyte is a type of white blood cell involved in the human bodys immune system. ... A phagocyte is a cell that ingests (and destroys) foreign matter, such as microorganisms or debris via a process known as phagocytosis, in which these cells ingest and kill offending cells by cellular digestion. ... The immune system is the organ system that protects an organism from outside biological influences. ... Fat is one of the three main classes of food and, at approximately 38 kJ (9 kilocalories) per gram, as compared to sugar with 17 kJ (4 kcal) per gram or ethanol with 29 kJ (7 kcal) per gram, the most concentrated form of metabolic energy available to humans. ... Diagram showing the poop shoot In biology the small intestine is the part of the gastrointestinal tract between the stomach and the large intestine (colon). ... Red blood cells (erythrocytes) are present in the blood and help carry oxygen to the rest of the cells in the body Blood is a circulating tissue composed of fluid plasma and cells (red blood cells, white blood cells, platelets). ...

Composition of lymph

Lymph vessels are usually associated with the circulatory system vessels. Larger lymph vessels are like veins. Lymph originates as blood plasma lost from the capillary beds of the circulatory system, which leaks out into the surrounding tissues. Although capillaries lose only about 1% of the volume of the fluid that passes through them, so much blood circulates that the cumulative fluid loss in the average human body is about 3L per day. The lymphatic system collects this fluid by diffusion into lymph capillaries, and returns it to the circulatory system. Once within the lymphatic system the fluid is called lymph, and has almost the same composition as the original interstitial fluid. Blood plasma is the liquid component of blood, in which the blood cells are suspended. ... Capillaries are the smallest of a bodys blood vessels, measuring 5-10 μm. ... The circulatory system or cardiovascular system is the organ system which circulates blood around the body of most animals. ...

Lymphatic circulation

Unlike the circulatory system, the lymphatic system is not closed and has no central pump; the lymph moves slowly and under low pressure. Like veins, lymph vessels have one-way valves and depend mainly on the movement of skeletal muscles to squeeze fluid through them. Rhythmic contraction of the vessel walls may also help draw fluid into the lymphatic capillaries. This fluid is then transported to progressively larger lymphatic vessels culminating in the right lymphatic duct (for lymph from the right upper body) and the thoracic duct (for the rest of the body); these ducts drain into the circulatory system at the right and left subclavian veins (sub = underneath, ,clavian = collar bones i.e. they run along the underside of the collar bones). The circulatory system or cardiovascular system is the organ system which circulates blood around the body of most animals. ... In biology, a vein is a blood vessel which returns blood from the microvasculature to the heart. ... A top-down view of skeletal muscle Muscle is a contractile form of tissue. ... In human anatomy, the thoracic duct is an important part of the lymphatic system — it is the largest lymphatic vessel in the body. ... The subclavian vein is a continuation of the axillary vein and runs from the outer border of the first rib to the medial border of scalenus anterior. ...

Major lymphatic vessels in humans

Lymph vessels are present in the lining of the gastrointestinal tract. Whilst 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 are passed on to the lymphatic system, to be transported to the blood circulation via the thoracic duct. 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. Diagram of the lymphatic system from public domain source at www. ... The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and expels the remaining waste. ... Diagram showing the poop shoot In biology the small intestine is the part of the gastrointestinal tract between the stomach and the large intestine (colon). ... The portal vein is a major vein in the human body draining blood from the digestive system and its associated glands. ... The liver is an organ in vertebrates, including humans. ... Fat is one of the three main classes of food and, at approximately 38 kJ (9 kilocalories) per gram, as compared to sugar with 17 kJ (4 kcal) per gram or ethanol with 29 kJ (7 kcal) per gram, the most concentrated form of metabolic energy available to humans. ... Chyle is a milky fluid (bodily fluid) consisting of lymph and emulsified fats. ... The liver is an organ in vertebrates, including humans. ...

Primary lymphoid organs

The thymus and bone marrow are the primary lymphatic organs. Lymphocytes are produced by stem cells in the bone marrow and then migrate to either the thymus or bone marrow where they mature. T-lymphocytes undergo maturation in the thymus (hence their name), and B-lymphocytes undergo maturation in the bone marrow. After maturation, both B- and T-lymphocytes circulate in the lymph and accumulate in secondary lymphoid organs, where they await recognition of antigens. In human anatomy, the thymus is a ductless gland located in the upper anterior portion of the chest cavity. ... Bone marrow is the tissue comprising the center of large bones. ... An antigen is a molecule that stimulates the production of antibodies. ...

Secondary lymphoid organs

The spleen, lymph nodes, and accessory lymphoid tissue (including the tonsils and appendix) are the secondary lymphoid organs. These organs contain a scaffolding that support circulating B- and T-lymphocytes and other immune cells like macrophages and dendritic cells. When microorganisms invade the body or the body encounters other antigens (such as pollen), the antigens are transported from the tissue to the lymph. The lymph is carried in the lymph vessels to regional lymph nodes. In the lymph nodes, the macrophages and dendritic cells phagocytose the antigens, process them, and present the antigens to lymphocytes, which can then start producing antibodies or serve as memory cells to recognize the antigens again in the future. The spleen is a ductless, vertebrate gland that is not necessary for life but is closely associated with the circulatory system, where it functions in the destruction of old red blood cells and removal of other debris from the bloodstream, and also in holding a reservoir of blood. ... Lymph nodes are components of the lymphatic system. ... The Palatine tonsils. ... In human anatomy, the vermiform appendix (or appendix) is a blind ended tube connected to the cecum. ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... Dendritic cells (DC) are immune cells and form part of the mammal immune system. ... Phagocytosis (literally, cell eating) is a form of endocytosis where large particles are enveloped by the cell membrane of a (usually larger) cell and internalized to form a phagosome, or food vacuole. ... Schematic of antibody binding to an antigen An antibody is a protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ...

The spleen contains lymphocytes that filter the blood stream rather than the lymphatics. Thus, the spleen has importance in fighting infections that have invaded the blood.

Accessory lymphoid tissues act as barriers along points of entry for infections, such as the lung, the reproductive system, and the gut. (See separate section below)

Lymph nodes

See also: lymph node.

Along this network of vessels are small organs called lymph nodes. Clusters of lymph nodes are found in the underarms, groin, neck, chest, and abdomen. Lymph nodes act as filters, with an internal honeycomb of connective tissue filled with lymphocytes that collect and destroy bacteria and viruses. When the body is fighting an infection, these lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes. Approximately 25 billion different lymphocytes migrate through each lymph node every day. Structure of the lymph node. ... Structure of the lymph node. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Three types of viruses: a bacterial virus, otherwise called a bacteriophage (left center); an animal virus (top right); and a retrovirus (bottom right). ...

Accessory lymphoid tissue

Accessory lymphoid tissue consists of unorganized patches of lymphoid tissue found diffusely in various sites of the body. They are similar in function to the lymph nodes but are anatomically different and are sometimes termed extra-nodal lymphoid tissue. Tonsils and the vermiform appendix are examples of accessory lymphoid tissue. The Palatine tonsils. ... In human anatomy, the vermiform appendix (or appendix) is a blind ended tube connected to the cecum. ...

Mucosa-associated lymphoid tissue (MALT) is the diffuse system of small concentrations of lymphoid tissue found in various sites of the body such as the gastrointestinal tract, thyroid, breast, lung, salivary glands, eye, and skin. The components of MALT are sometimes subdivided into GALT (gut or GI-associated lymphoid tissue), BALT (bronchial-associated lymphoid tissue), NALT (nose-associated lymphoid tissue), and SALT (skin-associated lymphoid tissue). A newly recognized entity is vascular-associated lymphoid tissue (VALT) that exists inside arteries; its role in the immune response is unknown.

Peyer's patches are a component of GALT found in the lining of the small intestines. Diagram showing the poop shoot In biology the small intestine is the part of the gastrointestinal tract between the stomach and the large intestine (colon). ...

See also: MALT lymphoma.

Disorders of the lymphatic system

Whenever the lymphatic system cannot drain interstitial fluid from tissues faster than they accumulate, the resulting swelling is known as lymphedema. Accumulation of lymph fluid in the pleural cavities leads to chylothorax. Cancers that develop from lymphocytes are known as lymphomas. Lymphedema is a condition of localized fluid retention caused by a compromised lymphatic system. ... In anatomy, the pleural cavity is the potential space between the lungs and the chest wall. ... A chylothorax is a condition that results from lymphatic fluid accumulating in the pleural cavity. ... For other uses, see Cancer (disambiguation). ... A lymphocyte is a type of white blood cell involved in the human bodys immune system. ... Lymphoma is a general term for localized malignancies that develop in the lymphatic or reticuloendothelial system. ...

External links

• The Lymphatic System (MedicalEngineer.co.uk)
• Lymphatic System Overview (innerbody.com)

See also

• Olaus Rudbeckius, one of the discoverers of the lymphatic system
  • History of anatomy in the 17th and 18th centuries

Olaus Rudbeckius, senior or (1630-1702), Swedish scientist and writer, professor of medicine at Uppsala University and for several periods rector magnificus (headmaster) of the same university. ... See also History of the French school of anatomy M. R. Columbus and Gabriele Falloppio were pupils of Vesalius, the 16th century anatomist, regarded by many as the founder of the science. ...