Lymphatic system(redirected from lymphatic systems)
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Related to lymphatic systems: Respiratory systems, Digestive systems
The parts of a system can be referred to as its elements or components; the environment of the system is defined as all of the factors that affect the system and are affected by it. A living system is capable of taking in matter, energy, and information from its environment (input), processing them in some way, and returning matter, energy, and information to its environment as output.
An open system is one in which there is an exchange of matter, energy, and information with the environment; in a closed system there is no such exchange. A living system cannot survive without this exchange, but in order to survive it must maintain pattern and organization in the midst of constant change. Control of self-regulation of an open system is achieved by dynamic interactions among its elements or components. The result of self-regulation is referred to as the steady state; that is, a state of equilibrium. homeostasis is an assemblage of organic regulations that act to maintain steady states of a living organism.
A system can be divided hierarchically into subsystems, which can be further subdivided into sub-subsystems and components. A system and its environment could be considered as a unified whole for purposes of study, or a subsystem could be studied as a system. For example, the collection of glands in the endocrine system can be thought of as a system, each endocrine gland could be viewed as a system, or even specific cells of a single gland could be studied as a system. It is also possible to think of the human body as a living system and the endocrine system as a subsystem. The division of a system into a subsystem and its environment is dependent on the perspective chosen by the person studying a particular phenomenon.
The lymphatics begin with lymphatic capillaries, permeable endothelial vessels one-cell thick, which absorb interstitial tissue fluid, particles, microbes, debris, and, from the small intestines, fat. Lymphatic capillaries empty into larger lymph vessels that eventually empty their contents (lymph) into the venous circulation through lymphatic ducts.
Lymph nodes are interposed between lymph vessels at some of the junctions between vessels. As it percolates through a lymph node, lymph is modified: debris is filtered out, lymphocytes are activated, and antibodies and lymphocytes are added to the fluid. Other lymphoid tissues have similar functions: The spleen filters the circulating blood, to which it adds antibodies and lymphocytes. Tonsils, Peyer’s patches, and other unencapsulated lymphoid tissues line epithelia that are in contact with the outside environment; unencapsulated lymphoid tissues activate lymphocytes and manufacture antibodies against foreign antigens. Lymphoid tissues in the bone marrow are proliferation and activation centers for lymphocytes, and the thymus is a proliferation and maturation center for T lymphocytes, especially during the neonatal and early postnatal years.
lymphatic systema system of tubules in vertebrates that drains excess tissue fluid (LYMPH) from the tissue spaces to the blood system. Unlike blood CAPILLARIES, lymph capillaries are blind-ending in the tissue spaces, gradually joining up to larger and larger vessels with two major lymphatic ducts entering the venous system in the upper thoracic cavity. Lymph is not moved along by heart contractions but (as in veins) by the action of skeletal muscles. Lymph vessels contain one-way valves to prevent backflow of fluid to the tissues.
Mammals and some birds possess clumps of lymphatic tissue called LYMPH NODES that act as filters for the removal of pathogens and are also sites of LYMPHOCYTE formation. Nodes are especially prevalent in the neck, underarm and groin, becoming swollen when adjacent to an infection. Besides returning excess water and protein to the blood system and being active in combating infection, lymph (rather than blood) transports fats from the gut wall, the lymph vessels being called LACTEALS since their contents are milky white.
lymphatic systemtakes part in the movement of body fluids and in the immune system. Networks of lymph vessels (lymphatics) drain extracellular fluid as lymph from all body tissues (except the central nervous system), maintaining balance with fluid that enters the tissues from blood capillaries. After passage through regional lymph nodes interpolated in the system of vessels, lymph is returned to the circulating blood via veins in the thorax. The lymph nodes 'filter' the lymph of foreign material, including bacteria, and may become inflamed if draining an area with local infection. lymphocytes originate in the bone marrow and pass into the circulation, where they are one of the types of white blood cell (leucocytes); they also become widely distributed in organs and tissues, notably the spleen, tonsils and gut lining, as well as in the lymph glands. Lymphocytes are involved, by complex interactions between their different types (B- and T-lymphocytes) in the production of specific antibodies (immunoglobulins). An individual can have a total of up to 109 different antibodies carried in the blood, providing defence against specific antigens.
lymph system or
n a complex network of capillaries, thin vessels, valves, ducts, nodes, and organs that helps to protect and maintain the internal fluid environment of the entire body by producing, filtering, and conveying lymph and by producing various blood cells. See also vessels, afferent and vessels, efferent.