| 释义 |
surfactant
sur·fac·tant S0913700 (sər-făk′tənt, sûr′făk′-)n.1. A surface-active substance.2. A substance composed of lipoprotein that is secreted by the alveolar cells of the lung and serves to maintain the stability of pulmonary tissue by reducing the surface tension of fluids that coat the lung.
[surf(ace)-act(ive) + a(ge)nt.]surfactant (sɜːˈfæktənt) n (Chemistry) Also called: surface-active agent a substance, such as a detergent, that can reduce the surface tension of a liquid and thus allow it to foam or penetrate solids; a wetting agentadj (Chemistry) having the properties of a surfactant[C20: surf(ace)-act(ive) a(ge)nt]sur•fac•tant (sərˈfæk tənt)
n. any surface-active substance, as a detergent or a natural or artificial substance that coats the lungs and prevents them from collapsing. [1945–50; surf(ace)-act(ive)a(ge)nt] sur·fac·tant (sər-făk′tənt)1. A substance, such as detergent, that is added to a liquid to increase its ability to spread.2. A substance produced by the tiny air-filled sacs of the lung that reduces the surface tension of the fluids coating the lung. Surfactant helps keep the tiny air sacs from collapsing during normal breathing.surfactant(surface active agent) A substance (for example a detergent) added to a liquid which can alter its spreading or wetting characteristics by lowering its surface tension.Thesaurus| Noun | 1. | surfactant - a chemical agent capable of reducing the surface tension of a liquid in which it is dissolvedsurface-active agent, wetter, wetting agentemulsifier - a surface-active agent that promotes the formation of an emulsionchemical agent - an agent that produces chemical reactionsdetergent - a surface-active chemical widely used in industry and laundering |
Translationssurfactant
surfactant[sər′fek·tənt] (materials) surface-active agent surfactantA chemical wetting agent; added to water to improve its penetration into a material; often useful in reducing the amount of water required in removing a material from the surface on which it has been applied.surfactant
Surfactant DefinitionSurfactant is a complex naturally occurring substance made of six lipids (fats) and four proteins that is produced in the lungs. It can also be manufactured synthetically.PurposeSurfactant reduces the surface tension of fluid in the lungs and helps make the small air sacs in the lungs (alveoli) more stable. This keeps them from collapsing when an individual exhales. In preparation for breathing air, fetuses begin making surfactant while still in the womb. Babies that are born very prematurely often lack adequate surfactant and must receive surfactant replacement therapy immediately after birth in order to breathe.PrecautionsBabies are considered premature if they are born before 37 weeks gestation. Fetuses begin to produce surfactant between weeks 24 and 28. By about 35 weeks, most babies have enough naturally produced surfactant to keep the alveoli from collapsing. Babies born before 35 weeks, especially those born very prematurely (before 30 weeks), are likely to need surfactant replacement therapy. Over half the babies born before 28 weeks gestation need this treatment, while about one-third born between 32 and 36 weeks need supplemental surfactant. Some very premature infants may also need to be placed on a mechanical ventilator.DescriptionThe lungs consist of spongy tissue filled with air spaces called alveoli. In the alveoli, oxygen is taken up by the blood and carbon dioxide, a waste product of cellular metabolism, is released and exhaled. For efficient oxygen-carbon dioxide exchange to occur, the surface area of the alveoli must be as large as possible. Under normal conditions, when a person exhales, the alveoli would collapse into each other and form larger air sacs with less surface area. Surfactant prevents this collapse by reducing the surface tension of the fluids that line the lungs and helping to equalize the pressures between large and small air spaces.Surface tension is a measure of the attraction molecules of a fluid have for each other. The attractive force pulls fluids into a shape with the smallest surface area. This is why a drop of water on a flat surface is rounded rather than flat. If the surface tension is lowered, the attraction among molecules of the fluid is decreased and the surface area of the fluid increases. For example, if a drop of detergent is added to a drop of water, the detergent reduces the surface tension and the drop of water flattens out.In the lungs, surfactant reduces the surface tension and helps to maximize the surface area available for gas exchange. Without adequate surfactant, a baby works much harder to breathe, becomes exhausted, and does not get enough oxygen. Babies that do not have enough surfactant to breathe normally at birth are said to have infant respiratory distress syndrome (RDS) or hyaline membrane disease (HMD).Babies with RDS are given replacement surfactant as soon as possible within the first six hours after birth. Manufactured surfactant is a white powder that is mixed with sterile water. It is given through a breathing tube (endotracheal tube) that is inserted in the baby's lungs. Multiple doses are usually required.Surfactant replacement therapy continues until the baby's lungs have matured enough to make surfactant on their own. Some very premature babies are also put on mechanical respirators to help them breathe. Surfactant replacement therapy has reduced deaths due to respiratory distress by 50% since the early 1990s. This therapy is expensive, but it is normally covered by insurance.PreparationThe administration of surfactant is often a neonatal emergency. The only way to prevent the need for surfactant replacement therapy is to prevent a premature birth. Mothers who are at known high risk to deliver prematurely are given drugs called corticosteroids toward the end of the pregnancy that stimulate the lungs of the fetus to mature and begin producing surfactant sooner. This helps reduce the need for surfactant replacement therapy. Although babies of all races may be born prematurely, prematurity is more common if the mother is diabetic, is carrying multiple fetuses, or has delivered a previous premature baby. The decision to use surfactant replacement therapy is based on the condition of the baby, its blood oxygen level, and degree of respiratory distress.AftercareBabies receiving surfactant therapy are normally cared for by a neonatologist, a pediatrician that specializes in newborn care. Premature newborns often have other health problems in addition to RDS. Aftercare varies depending on their other health risks.RisksDelivery of surfactant requires inserting a breathing tube into the baby's lungs. Complications of this therapy include air leaking into the area between the chest wall and the lungs and air leaking into the sac around the heart. Some infants also develop chronic lung disease.Normal resultsNormally surfactant replacement therapy keeps the infant alive until the lungs start producing their own surfactant.Abnormal resultsSurfactant replacement therapy is very effective if begun within six hours after birth. When it fails, death may result.ResourcesOtherDoctors Lounge, The. "Chronically Ventilated Premature Infants Need Continued Surfactant," 15 November 2004 [cited 16 February 2005]. http://www.thedoctorslounge.net/pedlounge/articles/surfactant.Hyaline Membrane Disease/Respiratory Distress Syndrome. Lucile Packard Children's Hospital at Stanford. 2001–2005 [cited 16 February 2005]. http://www.lpch.org/DiseaseHealthInfo/HealthLibrary/hrnewborn/hmd.html.Pramanik, Arun. Respiratory Distress Syndrome, 2 July 2002 [cited 16 February 2005]. http://www.emedicine.com/ped/topic1993.htm.Surfactant. Johns Hopkins School of Medicine. 1995 [cited 16 February 2005]. 〈http://oac.med.jhmi.edu/res_phys/Encyclopedia/Surfactant/Surfactant.HTMLgt;Key termsAlveolus (plural alveoli) — The terminal air sacs of the lungs where gas exchange occurs.Hyaline membrane — A thin layer of cells that line the lung.Surface tension — The attraction of molecules in a fluid for each other.surfactant [sur-fak´tant] 1. surface-active agent.2. In pulmonary physiology, a mixture of phospholipids (chiefly lecithin and sphingomyelin) secreted by the great alveolar (type II) cells into the alveoli and respiratory air passages, which reduces the surface tension of pulmonary fluids and thus contributes to the elastic properties of pulmonary tissue. A synthetic surfactant is commercially available for use in the treatment of respiratory distress syndrome of the newborn. See also acute respiratory distress syndrome.sur·fac·tant (sŭr-fak'tănt), 1. A surface-active agent, including substances commonly referred to as wetting agents, surface tension depressants, detergents, dispersing agents, emulsifiers, and quaternary ammonium antiseptics. 2. Those surface-active agents forming a monomolecular layer over pulmonary alveolar surfaces; lipoproteins, lecithins, and sphingomyelins that stabilize alveolar volume by reducing surface tension and altering the relationship between surface tension and surface area. [surface active agent] surfactant Physiology A mixture of phospholipids and proteins lining the alveoli that allows optimal gas–CO2, O2 exchange, by minimizing surface tension; surfactant is produced by type II pneumocytes and secreted as lamellar bodies into the amniotic fluid; fetal surfactant production begins by the 20th wk of gestation; it effectively prevents respiratory distress syndrome after wk 35. See L/S ratio, Respiratory distress syndrome, SP-A, SP-B, SP-C, Surfactant replacement therapy. sur·fac·tant (sŭr-fak'tănt) 1. A surface-active agent, including substances commonly referred to as wetting agents, surface tension depressants, detergents, dispersing agents, and emulsifiers. 2. Those surface-active agents forming a monomolecular layer over pulmonary alveolar surfaces; lipoproteins that include lecithins and sphingomyelins that stabilize alveolar volume by reducing surface tension and altering the relationship between surface tension and surface area. surfactant An agent that reduces the surface tension of oil or solid-water interfaces and therefore has cleaning properties. Note: the term is an acronym made from the following italic letters; surface active agent. Example: poloxamine, which is used in multipurpose solutions for soft contact lenses. See contact lens deposits; disinfection; enzyme; wetting solution.sur·fac·tant (sŭr-fak'tănt) A surface-active agent, including substances commonly referred to as wetting agents, surface tension depressants, detergents, dispersing agents, and emulsifiers. surfactant
Related to surfactant: emulsifier, Pulmonary surfactantSynonyms for surfactantnoun a chemical agent capable of reducing the surface tension of a liquid in which it is dissolvedSynonyms- surface-active agent
- wetter
- wetting agent
Related Words- emulsifier
- chemical agent
- detergent
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