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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. The normal surface tension ...
Lamellar bodies are then secreted into the liquid-air interphase surface of alveolar through membrane fusion initiated by influx of Ca2+. [2] Released pulmonary surfactant acts as a protective layer to prevent alveolar from collapsing due to surface tension.
Type II cells (granulous pneumocytes) in the alveolar wall contain secretory organelles known as lamellar bodies or lamellar granules, that fuse with the cell membranes and secrete pulmonary surfactant. This surfactant is a film of fatty substances, a group of phospholipids that reduce alveolar surface tension. The phospholipids are stored in ...
DPPC is a variant of phosphatidylcholine. Its structure includes both a hydrophilic "head" and hydrophobic "tails", and it is this arrangement that makes it able to reduce the surface tension of the water layer. The choline radical constitutes the polar hydrophilic head; it is oriented towards and extends into the alveolar liquid.
As water molecules pull together, they also pull on the alveolar walls causing the alveoli to recoil and become smaller. But two factors prevent the lungs from collapsing: surfactant and the intrapleural pressure. Surfactant is a surface-active lipoprotein complex formed by type II alveolar cells.
Increased pulmonary compliance may be associated with COPD and emphysema due to loss of alveolar and elastic tissue. Pulmonary surfactant increases compliance by decreasing the surface tension of water. The internal surface of the alveolus is covered with a thin coat of fluid. The water in this fluid has a high surface tension, and provides a ...
Pulmonary surfactant is a soap-like chemical synthesized by type II alveolar pneumocytes and is of various lipids (80% phospholipids, 5-10% cholesterol, and ∼10% surfactant-associated proteins). This biological fluid reduces surface tension and lines the aqueous layer covering the alveolar surface of the lung.
The function of this complex is to reduce surface tension in the alveolus and prevent collapse during expiration. The protein component of surfactant helps in the modulation of the innate immune response, and inflammatory processes. [7] Alveolar sac region of the lung - TEM. SP-A2 is a member of a subfamily of C-type lectins called collectins.