equilibration between the alveoli and the arteries.
And so that means that the pressure of gas in the alveoli
is going to be what is going to determine the pressure of
oxygen in the blood, and that's what is important.
So then, the arterial blood is going to be taken to the organs, and
the organs are going to take the oxygen, and dump CO2.
And so you'll see that the pressure in veins of oxygen has now
gone down to 40 millimeters of mercury.
So a lot of it has been dumped, and that now our pressure of
CO2 in the veins has increased from 40 to 46 millimeters of mercury.
And we'll be talking much more about these pressures, and
about how these gases are carried in the blood in future sessions.
So, we've talked about ventilation.
We've talked about minute ventilation, but
now we've also considered alveolar ventilation.
How much fresh air is getting to the alveoli, because that's what matters.
We've also talked about how that means you're going to have to
consider dead space where we've got
anatomical dead space, which is the only kind of dead space we've considered so
far, which is just the conducting zone of the respiratory tract.
Later we'll consider a little bit areas of the lungs that are not well ventilated or
perfused, which is also going to be included when we talk about physiologic
dead space, and that's going to occur in just even normal lungs where we
don't have perfect ventilation or perfusion in different areas.