00:01
Okay, we have a series of questions talking about gas exchange, mostly focusing on co2, but also something about oxygen.
00:09
So the first one here is which statement accurately describes alveolar exchange of oxygen.
00:16
Okay.
00:16
So again, oxygen, we want to go from the atmosphere, right, into the lungs, and we want that diffuse into our blood, right? we need to supply our tissues with fresh oxygen.
00:36
So we want to take in oxygen from the respiratory surface into the circulatory system.
00:43
So let's look at our choices.
00:45
Oxygen diffuses from blood to the alveolus.
00:47
That's the wrong direction, right? we don't want to go from blood to the lungs with oxygen.
00:52
We want to go from the atmosphere into the blood.
00:57
So a is incorrect.
01:00
B hasn't going the same direction from blood to the alveolus.
01:03
We want to go from alveolus to the blood.
01:06
So that leaves us with c and d.
01:09
C is oxygen diffuses from alveolis to the blood because the alveolaris has a lower partial pressure.
01:16
D is oxygen infuses from the alveolaris to the blood because the alveolaris has a higher partial pressure.
01:23
Remember, if we're not going to spend energy to move something, we have to go with its gradient, right? and that could be a concentration gradient or in this case a partial pressure gradient.
01:36
So we go from high pressure to low pressure.
01:43
So if we need to move from the alveolus to the blood, we need the alveolus to be high and the blood to be lower, right? so that should give us with d as the answer.
02:03
59, now we're taking that oxygen and going through the systemic capillaries.
02:07
This is going from blood to our tissues, right? so what's going to happen with the exchange there is that, again, we need to go from high oxygen partial pressure in the blood to lower partial pressure of oxygen in the tissue if we want that exchange to proceed without the expenditure of energy.
02:36
So the partial pressure of oxygen in blood increases as it goes from arterials to vanials.
02:42
So that would mean that it's picking up oxygen in the capillaries, meaning it's pulling oxygen from the tissues.
02:49
We certainly don't want to do that because our tissues need it.
02:52
The partial pressure of oxygen on blood remains the same as it goes from arterials to vanials.
02:59
Remember, we've got, let me change colors for you here.
03:03
Blood goes from arterials to capillaries to vanials.
03:15
And this is where the exchange takes place, namely, we give off o2 and we take in co2.
03:26
So we give oxygen to the tissues and we get co2 and other waste products from the tissues, right? so we would expect the partial pressure of oxygen to change as we do that process.
03:36
So it can't be b, right? so the partial pressure of oxygen in blood decreases as it goes from arterials to vanials.
03:46
This is what we would expect, right? it's dropping off oxygen in the capillaries.
03:50
So the partial pressure of oxygen in the arterials should be lower than the partial pressure of oxygen in the vanials because we're giving some up in the capillary beds.
04:07
Which reaction involving co2 predominates within erythrocytes in the pulmonary capillaries of the lungs? okay, so again, we're in the lungs, so we want to give up co2 to the lvoi.
04:26
We want to get rid of that waste.
04:29
It needs to diffuse.
04:33
So the best way to do this is to make it a gas as co2, right? rather than some of the other forms that it's in that we'll discuss in a second.
04:45
So at the lungs, we want co2 to be, or we want our carbon dioxide waste to be in the form of co2.
04:53
So it readily diffuses out of the capillaries into the alveoli, right? so, a is co2 combines with water to form by carbonate ion and carbonic acid.
05:03
Okay, that's making it more complex, and especially an ion and an acid will not pass through the membrane.
05:10
So that's not how we're going to get rid of it.
05:13
Hco3 negative disassociates into hydrogen ions, carbon monoxide, and oxygen.
05:20
Okay, so be careful here.
05:21
Carbon monoxide actually competes with oxygen and would bind to hemoglobin...