Surfactant

Surfactant


SURFACTANT

  • Soap-like substance secreted by type-II pneumocytes of alveolar epithelium
  • Major role in maintaining the lung compliance.

Embryological facts on surfactant:

  • Surfactant synthesis occurs in 24 – 28th  week of gestation
  • Amniotic fluid appearance in 28 – 32nd week.
  • Pre-term conditions – Deduction in 28th week.
  • Mature levels of surfactant after 35th week

Composition:

  • Surface-active lipoprotein complex (phospho-lipo-protein)
  • Main surface tension lowering phospholipid in surfactant
  • Dipalmitoyl-phosphatidylcholine (DPPC) (dipalmitoyl-lecithin)

Other substances present include:

  • Phosphatidylglycerol
  • Neutral lipids
  • 4 Surfactant proteins (SP – (A to D)
  • Carbohydrates
  • Other phospholipids.

Mechanism of action:

  • Breaking water molecule inside alveoli:
  • Water molecule lining alveoli exert elastic contractile force
  • Resulting in alveolar collapse
  • Surfactant breaks this surface tensional force of water molecules.

Functions:

  • Acts on alveoli
  • Reduces surface tension of fluid-lined alveoli
  • Prevents lung and alveolar collapse
  • Increases lung compliance
  • Prevents pulmonary edema

Special physiological effects:

  • Reduction in alveolar surface tension.
  • Reduces collapsing tendency of alveoli & lungs.

Alveolar stabilization:

  • Is a property of alveoli to reduce natural tendency of smaller alveoli to collapse into larger ones.
  • Also, reduces tendency of alveolar interstitial fluid transuding out to alveolar space
  • Reduces alveolar elastic recoil.

Effects of surfactant deficiency:

  • Decreased compliance
  • Increased elastic recoil
  • Hyaline membrane formation
  • Atelectasis
  • Interstitial edema

Conditions associated with surfactant:

1. Acute Infant Respiratory Distress Syndrome (IRDS)

  • Also referred “Hyaline membrane Disease” (HMD)
  • In premature infants
  • Glucocorticoids accelerate surfactant production in premature lungs

Cause:

  • Due to Immature functional surfactant system
  • Insufficient production of surfactant dipalmitoyl lecithin

Treatment:

  • Corticosteroid administration to pregnant women.
  • Transplacental transport to fetus promote,
  • Accelerated fetal lung maturation.
  • Production of surfactant.

2. Cigarette smoking:

  • Decreased surfactant
Exam Question
 

SURFACTANT

  • Soap like substance secreted by type-II pneumocytes of alveolar epithelium

Embryological factors of surfactant:

  • Surfactant synthesis occurs in 24 – 28th  week of gestation
  • Amniotic fluid appearance in 28 – 32nd week.
  • Pre-term conditions – Deduction in 28th week.
  • Mature levels of surfactant after 35th week.

Composition:

  • Surface-active lipoprotein complex (phospho-lipo-protein)
  • Main surface tension lowering phospholipid in surfactant
  • Dipalmitoyl-phosphatidylcholine (DPPC) (dipalmitoyl-lecithin

Mechanism of action:

  • Breaking water molecule inside alveoli
  • Surfactant breaks surface tensional force of water molecules.

Functions:

  • Acts on alveoli
  • Reduces surface tension of fluid-lined alveoli
  • Increases lung compliance

Special physiological effects:

  • Reduction in alveolar surface tension.
  • Alveolar stabilization: 
  • Is a property of alveoli to reduce the natural tendency of smaller alveoli to collapse into larger ones.

Effects of surfactant deficiency:

  • Decreased compliance.
  • Hyaline membrane formation.

Conditions associated with surfactant:

1. Acute Infant Respiratory Distress Syndrome (IRDS)

  • Also referred “Hyaline membrane Disease” (HMD).
  • In premature infants.
  • Glucocorticoids accelerate surfactant production in premature lungs.

Cause:

  • Due to Immature functional surfactant system
  • Insufficient production of surfactant dipalmitoyl lecithin

Treatment:

  • Corticosteroid administration to pregnant women.
  • Promote accelerated fetal lung maturation.
  • Production of surfactant.

2. Cigarette smoking:

  • Decreased surfactant
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