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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 .
They are also a member of the lecithin group of yellow-brownish fatty substances occurring in animal and plant tissues. Dipalmitoylphosphatidylcholine (lecithin) is a major component of the pulmonary surfactant, and is often used in the lecithin–sphingomyelin ratio to calculate fetal lung maturity.
For sphere-like structures like alveoli, water molecules line the inner walls of the air sacs and stick tightly together through hydrogen bonds. These intermolecular forces put great restraint on the inner walls of the air sac, tighten the surface all together, and unyielding to stretch for inhalation.
Surfactant protein B is an essential lipid-associated protein found in pulmonary surfactant.Without it, the lung would not be able to inflate after a deep breath out. [5] It rearranges lipid molecules in the fluid lining the lung so that tiny air sacs in the lung, called alveoli, can more easily inflate.
Lecithin (/ ˈ l ɛ s ɪ θ ɪ n / LESS-ith-in; from the Ancient Greek λέκιθος lékithos "yolk") is a generic term to designate any group of yellow-brownish fatty substances occurring in animal and plant tissues which are amphiphilic – they attract both water and fatty substances (and so are both hydrophilic and lipophilic), and are ...
A pulmonary alveolus (pl. alveoli; from Latin alveolus 'little cavity'), also called an air sac or air space, is one of millions of hollow, distensible cup-shaped cavities in the lungs where pulmonary gas exchange takes place. [1] Oxygen is exchanged for carbon dioxide at the blood–air barrier between the alveolar air and the pulmonary ...
The secretion, called pulmonary surfactant, reduces surface tension, allowing for bronchioles to expand during inspiration and keeping the bronchioles from collapsing during expiration. Club cells are a stem cell of the respiratory system , and also produce enzymes that detoxify substances dissolved in the respiratory fluid.
The ion channels CFTR, and ENaC work together to maintain the necessary hydration of the airway surface liquid. [10] An important factor is the rate of mucin secretion. The mucus helps maintain epithelial moisture and traps particulate material and pathogens moving through the airway, and its composition determines how well mucociliary ...