Lecture 51.txt

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Lecture 51.txt
2010-10-27 18:05:05
Biochem Lung

Biochem of the Lung
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  1. what are the two main functions of surfactant in the lungs?
    • decrease the surface tension of alveolar epithelium - easier to expand during inflation, prevents collaps during deflation
    • hydrophobic barrier between air and alveolar cells - keeps fluid in and air space intruders out
  2. what happens if mucus is hypersecreted in conducting airways?
    lower/respiratory airways?
    • cough and production of sputum
    • plugging of airways, gas trapping, reduced gas exchange
  3. what is mucus secreted by?
    submucosal glands and goblet cells
  4. what are the three functions of mucus?
    • protecting respiratory epithelium
    • entrapping inhaled particles and microorganisms
    • providing anti-inflammatory, antibacterial, and antioxidant substances
  5. what are the two layers of mucus and their functions?
    • sol-layer: allows free movement of the cilia (low viscosity)
    • gel-layer: (on top of sol-layer and cilia, high viscosity) traps particulate matter
  6. where would you find a high concentration of CFTR?
    secretory organs (pancreas, sweat glands, reproductive glands)
  7. what are four important functions of clara cells?
    • unciliated secretory cells
    • precusors of ciliated cells
    • primary site of airborne xenoblotic metabolism
    • synthesis and secretion of proteins involved in immune defense (IgA)
  8. what is the primary function of type I alveolar cells?
    gas exchange (surface of alveolar)
  9. what is the major function of type II alveolar cells?
    produce surfactant
  10. what is the surfactant layer of the alveolar lumen composed of?
    • 90% phospholipids, half of wich is dipalmitoyl-phosphatidylcholine (DPPC)
    • 10% surfactant proteins
  11. when does the synthesis of surfactant from type II alveolar cells begin?
    24 weeks in utero and continues for life
  12. what are the 7 steps of pulmonary surfactant synthesis in type II alveolar cells?
    • 1. surfactant components synthesized - lipids on smooth ER, proteins on rough ER
    • 2. golgi complex modifies and secretory vesicle form lamellar bodies
    • 3. contents of lamellar bodies secreted by exocytosis, constitutive secretion but can be increased by mechanical stimuli (deepened respiration
    • 4. surfactant unfolds to form tubular myelin (TM)
    • 5. surfactant is integraded into the expanded surface monolayer during inhalation
    • 6. surfactant is compressed forming closely packed monolayer of DPPC during exhalation
    • 7. excluded material forms small aggregates which are endocytosed by alveolar macrophages (8) or endocytosed and recycled by type II alveolar cells
  13. what is the function of surfactant proteins SP-A and SP-D?
    • formation of lamellar bodies
    • regulate secretion and re-absorption of surfactant phospholipids
    • stimulate immune response by binding to microorganisms and promoting their phagocytosis by macrophages
    • (they are hydrophilic poteins)
  14. what is the function of surfactant proteins SP-B and SP-C?
    • inserting phospholipids into the surfactant monolayer
    • promote spreading of surfactant lipids
    • (they are hydrophobic membrane proteins)
  15. what is the function of surfactant proteins SP-A and SP-B?
    required for formation of tubular myelin
  16. what test is used to predict lung maturity and the risk of NRDS?
    • amniocentesis to determine the PC/SM ratio (phophatidylcholine/sphingomyelin)
    • PC/SM less than 2 suggests immature ling and elevated risk of RDS
    • also, and immunoassay for SP-A can be used
  17. what is given to mothers at risk for pre-term delivery when the PM/SM ratio is low?
    glucocorticoid (stimulates type II cells to produce surfactant by increasing surfactant synthesis)