Pulmonary surfactant
Pulmonary Surfactant
Pulmonary surfactant (pronounced: puhl-MON-uh-ree SUR-fak-tant) is a complex mixture of lipids and proteins that is secreted into the alveolar space by Type II alveolar cells. Its main function is to reduce the surface tension at the air/liquid interface in the lungs, thus preventing the alveoli from collapsing at the end of expiration.
Etymology
The term "pulmonary surfactant" is derived from the Latin pulmonarius (meaning "of the lungs") and the English word "surfactant" which is a portmanteau of "surface active agent".
Composition
Pulmonary surfactant is composed primarily of phospholipids (about 80%), the most important of which is Dipalmitoylphosphatidylcholine (DPPC). The remaining 20% is made up of other lipids and proteins, including surfactant proteins A, B, C, and D (SP-A, SP-B, SP-C, SP-D).
Function
The main function of pulmonary surfactant is to lower the surface tension at the air/liquid interface within the alveoli. This prevents the alveoli from collapsing at the end of expiration and thus maintains the patency of the alveoli. It also contributes to the host defense mechanisms of the lungs by opsonizing inhaled pathogens and facilitating their clearance by alveolar macrophages.
Clinical Significance
Deficiency of pulmonary surfactant in premature infants leads to Respiratory distress syndrome (RDS), also known as hyaline membrane disease. This condition can be treated with exogenous surfactant therapy. Mutations in the genes encoding the surfactant proteins can lead to various forms of interstitial lung disease.
Related Terms
- Alveoli
- Type II alveolar cells
- Surface tension
- Dipalmitoylphosphatidylcholine
- Surfactant proteins
- Respiratory distress syndrome
- Interstitial lung disease
External links
- Medical encyclopedia article on Pulmonary surfactant
- Wikipedia's article - Pulmonary surfactant
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