This paper examines the nature and function of surfactants, amphiphilic compounds that reduce surface tension in liquids and at interfaces. It focuses specifically on pulmonary surfactants — the protein-fat mixtures produced in the lungs — explaining how they coat the alveoli to prevent collapse and enable breathing. The paper discusses fetal lung development, the consequences of surfactant deficiency in premature infants, and the clinical use of artificial and animal-derived surfactant therapy. It also briefly acknowledges associated risks, such as pulmonary hemorrhage, while affirming that the benefits of surfactant therapy substantially outweigh these concerns.
Surfactants are organic compounds that are amphiphilic, meaning they contain both hydrophilic groups (the "heads") and hydrophobic groups (the "tails"). Because of this dual nature, surfactants are composed of both water-soluble and water-insoluble components. They diffuse in water and adsorb at water-air interfaces or oil-water interfaces.
Surfactants are therefore compounds that reduce the surface tension in liquids, between solids and liquids, or the interfacial tension that occurs between two liquids. For this reason, surfactants act as wetting agents, detergents, dispersants, emulsifiers, or foaming agents.
Within the human body, surfactants occur as a mixture of proteins and fats produced in the lungs. They act as a coating for the alveoli, preventing the alveoli from sticking together when a person breathes out. Without this coating, the lungs would not be able to expand. Pulmonary surfactants therefore reduce surface tension within the lungs, enabling the alveoli to expand — in this respect, the surfactant acts as a biological detergent within the lungs.
The alveoli are tiny sacs found in the lungs where oxygen is captured from inhaled air and transferred into the bloodstream. They are very small, and their surfaces are moist. On any wet surface, water molecules are naturally attracted to one another, causing surfaces to stick together. Surfactants are important in the alveoli because, when they combine with the water present there, they reduce the surface tension of that water, allowing the alveoli to remain open (Lynch, 2010).
Approximately three to four weeks before birth, the lungs begin producing surfactants. When a baby is born and takes its first breath, the fluid-filled alveoli must open in order to allow air in. Without the presence of surfactants, this would not be possible. This is the reason why infants born prematurely typically experience difficulty breathing.
Premature infants are born before their lungs have had sufficient time to produce adequate amounts of surfactant. Low surfactant levels result in poor lung function, producing lungs that are stiff and prone to collapse, along with an increase in the amount of fluid within the lungs — all of which makes breathing extremely difficult.
"Breathing problems caused by insufficient surfactant"
"Clinical outcomes and risks of surfactant treatment"
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