What is pulmonary surfactant

Pulmonary surfactant is a complex and highly surface active material composed of lipids and proteins which is found in the fluid lining the alveolar surface of the lungs.

Surfactant is an agent that decreases the surface tension between two media. The surface tension between gaseous-aqueous interphase in the lungs is decreased by the presence of a thin layer of fluid known as pulmonary surfactant. It is essential for efficient exchange of gases and for maintaining the structural integrity of alveoli. Surfactant is a secretory product, composed of lipids and proteins. The lipid and protein components are synthesized separately and are packaged into the lamellar bodies in the AT-II cells.

What is pulmonary surfactant

Pulmonary surfactant is a surface-active complex of phospholipids and proteins formed by type II alveolar cells. By adsorbing to the air-water interface of alveoli , with hydrophilic head groups in the water and the hydrophobic tails facing towards the air, the main lipid component of surfactant, dipalmitoylphosphatidylcholine DPPC , reduces surface tension. As a medication, pulmonary surfactant is on the WHO Model List of Essential Medicines , the most important medications needed in a basic health system. Alveoli can be compared to gas in water, as the alveoli are wet and surround a central air space. The surface tension acts at the air-water interface and tends to make the bubble smaller by decreasing the surface area of the interface. Compliance is the ability of lungs and thorax to expand. Lung compliance is defined as the volume change per unit of pressure change across the lung. This difference in inflation and deflation volumes at a given pressure is called hysteresis and is due to the air-water surface tension that occurs at the beginning of inflation. However, surfactant decreases the alveolar surface tension , as seen in cases of premature infants with infant respiratory distress syndrome. Pulmonary surfactant thus greatly reduces surface tension , increasing compliance allowing the lung to inflate much more easily, thereby reducing the work of breathing. It reduces the pressure difference needed to allow the lung to inflate. The lung's compliance, and ventilation decrease when lung tissue becomes diseased and fibrotic. As the alveoli increase in size, the surfactant becomes more spread out over the surface of the liquid. This increases surface tension effectively slowing the rate of expansion of the alveoli. This also helps all alveoli in the lungs expand at the same rate, as one that expands more quickly will experience a large rise in surface tension slowing its rate of expansion.

It also has a higher compaction capacity than the other phospholipids, because the apolar tail is less bent.

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Federal government websites often end in. Before sharing sensitive information, make sure you're on a federal government site. The site is secure. NCBI Bookshelf. Hina Khawar ; Komal Marwaha. Authors Hina Khawar ; Komal Marwaha 1. Pulmonary surfactant is a lipoprotein complex that lines the alveoli and decreases the surface tension to prevent lung atelectasis. Surfactant deficiency is a documented cause of neonatal respiratory distress syndrome NRDS , a significant cause of morbidity and mortality in premature infants.

What is pulmonary surfactant

Federal government websites often end in. The site is secure. Pulmonary surfactant is essential for life as it lines the alveoli to lower surface tension, thereby preventing atelectasis during breathing. The hydrophobic proteins, SP-B and SP-C, together with dipalmitoylphosphatidylcholine, confer surface tension—lowering properties to the material.

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Respiratory physiology-- the essentials. It reduces the pressure difference needed to allow the lung to inflate. Surfactant degradation or inactivation may contribute to enhanced susceptibility to lung inflammation and infection. Bibcode : PNAS Alveolar surfactant has a half-life of 5 to 10 hours once secreted. Meanwhile, during expiration the surface area decreases at a rate which is always in excess of the rate at which the surfactant molecules are driven from the interface into the water film. Protein : cell membrane proteins other than Cell surface receptor , enzymes , and cytoskeleton. Compliance is the ability of lungs and thorax to expand. Journal of Applied Physiology. The surface tension between gaseous-aqueous interphase in the lungs is decreased by the presence of a thin layer of fluid known as pulmonary surfactant. It also means the rate of shrinking is more regular as if one reduces in size more quickly the surface tension will reduce more, so other alveoli can contract more easily than it can. It also regulates inflammatory responses and interacts with the adaptive immune response. Alveoli can be compared to gas in water, as the alveoli are wet and surround a central air space. Surfactant production in humans begins in type II cells during the alveolar sac stage of lung development. Lamellar bodies appear in the cytoplasm at about 20 weeks gestation.

Lung surfactant is a complex with a unique phospholipid and protein composition.

Comparative Biochemistry and Physiology A. This also helps all alveoli in the lungs expand at the same rate, as one that expands more quickly will experience a large rise in surface tension slowing its rate of expansion. For some pulmonary conditions surfactant replacement therapy is on the horizon, but for the majority much more needs to be learnt about the pathophysiological role the observed surfactant abnormalities may have. Nevertheless, without the other substances of the pulmonary surfactant mixture, the DPPC's adsorption kinetics is very slow. Abstract Pulmonary surfactant is a complex and highly surface active material composed of lipids and proteins which is found in the fluid lining the alveolar surface of the lungs. The lung's compliance, and ventilation decrease when lung tissue becomes diseased and fibrotic. They also make weak bonds with the surfactant molecules at the interface and hold them longer there when the interface is compressed. Annual Review of Physiology. OCLC Tools Tools. Because during ventilation there is a variation of the lung surface area, the surfactant's interface concentration is not usually at the level of saturation. ISBN However, surfactant decreases the alveolar surface tension , as seen in cases of premature infants with infant respiratory distress syndrome. Biochemical surfactant abnormalities of varying degrees have been described in obstructive lung diseases asthma, bronchiolitis, chronic obstructive pulmonary disease, and following lung transplantation , infectious and suppurative lung diseases cystic fibrosis, pneumonia, and human immunodeficiency virus , adult respiratory distress syndrome, pulmonary oedema, other diseases specific to infants chronic lung disease of prematurity, and surfactant protein-B deficiency , interstitial lung diseases sarcoidosis, idiopathic pulmonary fibrosis, and hypersensitivity pneumonitis , pulmonary alveolar proteinosis, following cardiopulmonary bypass, and in smokers. These limitations must always be considered when interpreting ex vivo studies of pulmonary surfactant.