if the total atmospheric pressure is 760.00 mm hg, what is the partial pressure of co2? This is a topic that many people are looking for. khurak.net is a channel providing useful information about learning, life, digital marketing and online courses …. it will help you have an overview and solid multi-faceted knowledge . Today, khurak.net would like to introduce to you Gas exchange 2- Partial pressures O2 & CO2. Following along are instructions in the video below:
We want any kind of gas exchange to happen at all then the bottom line line is we are going to have to set up some kind of partial pressure between the alveoli and the blood and the blood and the body cells. So im going to draw you a picture. What i know i know i continually shock.
You with my strategies for teaching anatomy and physiology. This strategy is going to involve drawing a mouse with a trachea and uh novelists because you know dont you think they kind of look exactly like this not even close. This is a diagrammatic view of the alveolus because i want to fit everything on here.
So heres what else im going to draw i need a blood supply. So this right here is where im going to do um external respiration between the alveolus and the blood. And then im also going to do internal respiration between the blood oops.
I need to get a little bit closer between the blood please im going to show you my arrows in just a second and the body cells. So as we already know because we dealt with the concept of capillary exchange. We know that every single cell has to be within diffusions distance of the capillary or the cells going to die so you can imagine this little red vessel here is a capillary and heres my organization first of all this is the atmosphere.
So this is the air that youre breathing our blood flow is going to go this direction. So i would imagine that this is going to be blood dirt blood. Thats coming in contact with an alveolus in the lungs and then its going to travel to the body and heres a capillary thats in contact with some body cells.
And then the blood of course after it drops off its oxygen and picks up its carbon dioxide. Its going to come back to the lungs and we can throw in all the anatomy. We can go to the correct places in the heart can follow it all around.
But right now lets just focus in on whats going on how what are the partial pressure gradients that are going to motivate internal respiration and external respiration and heres a scoop. Im going to tell you were going to keep track of po2.
I dont think i want it to be green. I think were going to do po2 in red and well do pco2 in blue. There is oxygen in our atmosphere.
Thank goodness for that and so we can throw a partial pressure. We know that number its actually about 160 millimeters of mercury. All my partial pressure units are going to be in millimeters of mercury.
Im going to stop putting my units on here just to save us a little bit of time. But do not forget that thats what that were talking about millimeters of mercury and know that if you ever give me numbers without units. It will be a sad story and you probably wont get credit.
So dont leave off your units. This is wild are you ready for this amazing fact i mean we talk about carbon dioxide concentrations in our atmosphere carbon dioxide is a greenhouse gas something we should definitely be concerned about do you know how much carbon dioxide is in the atmosphere what the partial pressure is 025 millimeters of mercury you got to be kidding me that isnt very much carbon dioxide in the atmosphere at all now imagine im going to take a nice fresh breath of air and im going to divide my alveolus in half just so we can keep track of after external respiration has taken place. What our new numbers are so relax.
Because watch how this is going to work obviously the entire quantity blob of air from the atmosphere is going to go into the entire alveolus. Im dividing it in half. So you can imagine the change thats going to happen over time so this error this fresh blob of air whose characteristics.
Ive given you over here. Im going to throw it into this half of my alveolus and now im going to tell you that my partial pressures of my gases is different. Now.
Po2 is actually about 100 millimeters of mercury look. I did it i couldnt help it and pco2 is about 40 and im telling you which ones.
Which based on the color okay seriously what happened thats the fresh air that i just breathed in why did my po2 go down and my piece co2 like went up by a whole bunch. How why what happened remember that there was that whole chunk that blob of air in your lungs. That you cant ever breathe out.
So you arent ever going to have an inhale that is purely atmospheric concentrations you have leftover air in there that is highly concentrated with carbon dioxide and not so much oxygen in that air so we can accept that when we mix with that residual air that you can never actually breathe out these are my new partial pressures inside the alveoli at the beginning of a breath. So you take a breath. Fantastic and now inside my alveolus these are my partial pressures.
Its probably relevant right now to say okay. Whats the partial pressure of the blood thats coming back from the cells. This is the used up blood the cells have sucked out as much of the gases.
The oxygen as they possibly can and theyve had as much of the carbon dioxide as possible sucked out of them and so watch this inside venous blood that has come from the cells. We have a partial pressure of carbon dioxide of 46 millimeters of mercury and oxygen is at about 40 millimeters of mercury. Okay.
Why what did the cells do its like its like thirsty cells sucked all the oxygen out of the blood down to 40 millimeters of mercury now. Gases move down their partial pressure gradient. Do you agree with that absolutely so what direction is oxygen going to move.
We dont have to think very. Long to go oh well of course. Oxygen is going to move from 100 millimeters of mercury down to 40 millimeters of mercury.
Whats going to happen to the partial pressure in the blood. When this happens well the partial pressure of the blood is going to increase and in fact because of some amazing mechanisms that well talk about later on in this lecture.
After external respiration is complete the blood and the alveoli have effectively changed concentrations. Theyve switched so the alveoli now have notices after external respiration has occurred. The alveoli have only 40 millimeters of mercury of oxygen.
Whereas the blood now has 100 which just is more oxygen molecules dissolved in that blood what do you suppose has happened the carbon dioxide dude carbon dioxide is going to move down its partial pressure gradient its going to move out of the blood and into the alveolus and it switches right down. I mean it makes perfect sense. So we end up with 46 in the alveolus and 40 in the blood.
And that travels to the cells. Now whats going to happen in the cells well your cells. Dont ever like end up with a partial pressure of oxygen thats high theyre constantly saying.
We need more oxygen they use up the oxygen that theyre exposed to so. The po2 in the cell. Usually really ends up being about 40 and you can imagine that the more active a cell is the more it uses up oxygen in its environment.
The lower that partial pressure is going to go so so that can vary depending on the metabolic activity of the cell. But check out whats going to happen to if if your cells essentially hang out at about 40 because they are using the oxygen thats available to them then the oxygen inside its going to come around at the beginning of the capillary. Were going to have oxygen at about 100.
But by the end all the oxygen has been sucked out of the blood and into the cells and theyre just using. It thats how we end up with 40 millimeters of mercury when we head back to the alveoli carbon dioxide on the other hand carbon dioxide shows up the blood shows up with a partial pressure of 44 carbon dioxide and your cells again theyre chronically producing carbon dioxide so essentially you can imagine that theyre producing it enough to be a partial pressure of about 46 so the carbon dioxide is going to continually diffuse in in the end game you end up with about 46 millimeters of mercury in that old used up capillary blood. Which travels to the alveolus for external exchange external respiration happens here.
Internal respiration happens here cellular respiration is happening in here does that work for you you might be like dude numbers ahh the numbers are handy then the numbers help you visualize the push for why this gas exchange happens at all there are several factors were going to look at this diagram and look at several factors that can affect gas exchange. Internal and external gas exchange. .
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