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Diffusion of Gasses through the Respiratory Membrane

Final Exam - Dr. Carter
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What are the 6 layers of the respiratory membrane?
1) the fluid lining of the alveolus (including surfactant)
2) alveolar epithelial cells
3) epithelial basement membrane
4) interstital space
5) capillary basement membrane
6) capillary endothelial cells
What are the 4 factors that dictate confusion?
1) pressure gradient
2) thickness of the membrane
3) surface area of the membrane
4) diffusion coefficient
What do the 6 layers of the respiratory membrane represent?
the distance a gas molecule must travel to move from the alveoli to the blood or vice versa
By what process do gasses pass through the respiratory membrane?
diffusion
What are the 4 factors that dictate diffusion?
1) pressure gradient
2) thickness
3) surface area
4) diffusion coefficient
What is the partial pressures of O2 and CO2 in the alveoli (PA)?
104mmHg and 40mmHg
What are the partial pressures of O2 and CO2 in the blood prior to gas exchange (Pv)?
40mmHg and 46mmHg
What are the partial pressures of O2 and CO2 in the blood after gas exchange (Pa)?
100mmHg and 40mmHg
List 3 clinical examples of increases thickness of the respiratory membrane and describe each one.
1) pulmonary edema - a build up of excess fluid in the interstital space between the alveoli and the capillary
2) pulmonary fibrosis - a build up of fibrous tissue in the interstital space
3) pneumonia - a build up of inflammatory fluid and cells in and around the alveoli
How does emphysema affect diffusion of gases in the lungs?
it decreases the overall surface area of the respiratory membrane by destroying the alveolar septa
Why does CO2 diffuse more efficiently than oxygen?
CO2 is 20 times more soluble in water than oxygen is
What does Fick's Law describe?
the volume and rate of diffusion of gases across the respiratory membrane
What is hypercapnia?
increased partial pressure of CO2 in the blood
What is hypoxemia?
decreased partial pressure of O2 in the blood
Which will occur first, hypoxemia or hypercapnia? Which will be corrected first?
hypoxemia; hypercapnia
What is pulmonary capillary transit time?
the time that a RBC is in contact with the respiratory membrane
If cardiac output increases, what will happen to pulmonary capillary transit time?
it will decrease
Why isn't PaO2 an appropriate indicator of PAO2?
even though they are close to the same under normal circumstances, there are many factors influencing the transport of gases across the respiratory membrane and if there is pathology, the difference between PaO2 and PAO2 will increase