Chapter 39 - Guyton Flashcards
The pressure is directly proportional to the ____________ of the gas molecules.
concentration
How is the alveolar air composition different from atmospheric air?
it is humidified, higher carbon dioxide, lower oxygen
What two factors control oxygen concentration in the alveoli?
the rate of absorption of oxygen into the blood and rate of entry of new oxygen into the lungs by the ventilatory process
As alveolar ventilation increases, what occurs to alveolar PCo2 and PO2?
PCo2 - decreases; PO2 - increases
Respiratory unit
respiratory bronchiole, alveolar ducts, atria, and alveoli
Because of the extensiveness of the _______ ______, the flow of blood in the alveolar wall has been described as a “sheet” of flowing blood.
capillary plexus
Factors that affect the rate of gas diffusion.
thickness of the membrane, surface area of the membrane, diffusion coefficient of the gas in the substance of the membrane, and partial pressure difference of the gas between the two sides of the membrane
What is the physiologic shunt?
venous blood passing through the pulmonary capillaries that does not become oxygenated
What is the ventilation-perfusion ratio?
ratio of alveolar ventilation to alveolar blood flow (Va/Q)
Under normal conditions, the alveolar air Po2 averages ___ mm Hg and the Pco2 averages __ mm Hg.
104; 40
What creates physiologic dead space?
ventilation is high but blood flow is inadequate (ventilation of these alveoli is wasted)
What results from abnormalities in ventilation-perfusion ratio in the upper and lower lung?
at the top of the lung, there is a moderate amount of physiologic dead space (more ventilation, less blood flow) while at the bottom of the lung, there is physiologic shunt (less ventilation, more blood flow)
