Card Set Information
Biochem of the Lung
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
what happens if mucus is hypersecreted in conducting airways?
cough and production of sputum
plugging of airways, gas trapping, reduced gas exchange
what is mucus secreted by?
submucosal glands and goblet cells
what are the three functions of mucus?
protecting respiratory epithelium
entrapping inhaled particles and microorganisms
providing anti-inflammatory, antibacterial, and antioxidant substances
what are the two layers of mucus and their functions?
: allows free movement of the cilia (low viscosity)
: (on top of sol-layer and cilia, high viscosity) traps particulate matter
where would you find a high concentration of CFTR?
secretory organs (pancreas, sweat glands, reproductive glands)
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)
what is the primary function of type I alveolar cells?
gas exchange (surface of alveolar)
what is the major function of type II alveolar cells?
what is the surfactant layer of the alveolar lumen composed of?
90% phospholipids, half of wich is dipalmitoyl-phosphatidylcholine (DPPC)
10% surfactant proteins
when does the synthesis of surfactant from type II alveolar cells begin?
24 weeks in utero and continues for life
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
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)
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)
what is the function of surfactant proteins SP-A and SP-B?
required for formation of tubular myelin
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
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)