0:00 I ninja in this video we're going to go specifically over again external respiration but we're going to focus in on what next we already talked about ventilation and perfusion where you have a video on that if you haven't seen that one go watch that one after that now we're going to focus on thickness and surface area of the respiratory membrane now I didn't really talk about this yet but what is defined as this respiratory membrane the respiratory membrane let's actually write this up your respiratory membrane is going to be made up of the alveolar cells so you know you're going to have these certain types of alveolar cells lining the alveoli we'll talk
0:45 about that in a little bit but specifically you're going to have alveolar cells so you're going to have alveolar cells add with that I'll just mention them now and there's two types type 1 and type 2 type 1 is more of a simple squamous okay they're simple squamous which means they're very very thin and flat these are the ones that are involved in the gas exchange process the other one is more of a simple cuboidal and this is the one that's actually involved in more of the surfactant production which has to do with surface tension we'll have another video on that so that's one component of the respiratory membrane so one component of the respiratory membrane is the alveolar cells the second part of
1:31 the respiratory membrane is going to be the basement membrane so you know on every underneath the actual epithelial cells so let's say this is the epithelial cell lining this if I were to just show you here in a simple way there's a thin connective tissue lining that's going to be right here in between the blood vessel okay and the actual alveoli so this right here is our basement membrane or our basal lamina right so this is going to be the basal lamina now separating and now if I take this if I take the alveolar cells the simple squamous and the actual simple cuboidal and I take this basal lamina to connect tissue that's going to make up my respiratory membrane and then surrounding that it's going to be the
2:17 capillaries which is going to have this endothelial cell lining now so let's write that down so if the alveolar cells type 1 and type 2 and the other component of it is going to be this basal lamina this basal lamina or basement membrane right so that's kind of like a basement basement membrane and then these are surrounded by the alveolar cells in the basement membrane are surrounded by these pulmonary capillaries that's what makes up the respiratory membrane now on average the respiratory membrane is a specific size we don't want it to be too sick and the reason why is because if it's too thick that's a that's a big big barrier difference in a big separation
3:02 so the bigger this membrane is that's the farther that the co2 has to travel from the blood to the alveoli and that's a farther distance that the oxygen would have to travel from the alveoli to the blood so we don't want it to be too thick now what's the average thickness the average thickness of the respiratory membrane it has a good range certain literature will say it's about 0.5 to 1 micrometer in thickness okay you know they might even range out to about 2 micrometers but generally it's about 0.5 to 1 micrometers now this respiratory membrane the thickness of the respiratory membrane is going to have a very very important effect on this gas exchange process so like I'm saying here let's say that I take this respiratory membrane and let's
3:47 say it's thick a really really thick respiratory membrane does they have a really really thick respiratory membrane okay if I have a very thick respiratory membrane what's going to happen to the gas exchange well if it's a thicker respiratory membrane it's going to have a longer distance so it's a longer distance for the gaseous state to actually move across so let's say here's my co2 and it wants to move over here and let's say here's my oxygen and once it wants to move over here when they move down their partial pressure gradients again they're moving across this endothelial cells which are the summer and the interlining of these capillaries through the basal lamina which is that basement membrane and then the alveolar cells into specifically this alveolar space
4:32 if this basilar member I'm sorry if this respiratory membrane is thicker that's a farther distance it's going to have to travel and that's going to alter the gas exchange process that's going to throw off the ventilation/perfusion effect too so again this external respiration is influenced by the thickness of the respiratory membrane if it's really really thick okay then there's going to be decreased gas exchange so as a result here what would be the result of this so Bloods coming in and the Bloods coming out there's going to be a what abnormal gas exchange and so in simple a think about it like this and let's look at a situation would you have a sick respiratory membrane that's the first question we should actually evaluate this what's what would
5:19 be the problem in which a patient would have a thick respiratory membrane you know there's two good reasons to good reasons that you should think about let's come over here for a second you know in individuals who have what's called a left-side heart failure congestive heart failure so let's say that you have left-side heart failure and you know you have cardiomyopathy and over time the heart starts actually becoming very hypertrophy and after that it starts actually dilating and it starts becoming very very weak and it can't pump if the left ventricle isn't able to pump some of this blood out into the actual systemic circulation what happens it starts really building up and as it starts building up where does it start going it starts backing up back into the pulmonary circulation as this blood starts backing up into the
6:04 pulmonary circulation some of that fluid might start oozing out out here into this alveolar spaces and as it starts moving losing out water might accumulate out here and as some of this plasma fluid sightmark might start accumulating here what starts happening to the lungs they may start becoming very waterlogged and edematous right a lot of edema if that's happening what's it doing to the respiratory membrane it's making it thicker that's a larger distance that the co2 and oxygen want to travel that'll throw off the actual gas exchange in what way people who have left-side heart that are usually they have dis neon they're you know a shortness of breath one of the main reasons why is if you have this abnormal gas exchange what's happening there's going to be if there's not a lot of gas exchange here not a lot of oxygen is going to be moving over so the partial pressure of
6:50 oxygen is going to be a little bit lower because it's not going to be able to as much is going to be moving across co2 isn't going to be moving across the membrane as much also so what's going to happen to the partial pressure of co2 in the blood it's going to go up so this person can develop hypoxia but particularly we call this hypoxemia and technically they call it hypoxemic hypoxia and then the condition in which they're inadequate you know the ventilation perfusion process and obviously if you have a high co2 that can cause respiratory acidosis I'll have another video on but that's the whole purpose here to understand that concept of the thick respiratory membrane now what about another reason ok another another reason could be due to pneumonia so if you also could have besides less high heart failure let's say that that's one possible reason another reason could
7:38 be pneumonia and in pneumonia you know there's certain types of bacterium like the micro bacterium Klebsiella different types of bacterium that can cause sorry not micro bacterium NECA actually causes tuberculosis specifically they may be like Klebsiella or Legionella bacteria and they start damaging this into this epithelial tissue and the surrounding areas as that starts happening what happens you know whenever there's tissue damage you'll release histamine and other mediators of inflammation what will happen to the blood vessels in that area there start dilating as they start dilating blood starts actually flushing through this area very very and large amounts and starts leaking out right there's a lot of permeability because of the histamines and the variety kinds and all those things and so the blood vessels are dilating and a lot of fluids leaking out into these spaces what's happening then that respiratory membrane
8:24 is becoming thicker the distance is long a longer distance for the co2 and the oxygen to move across which we call this abnormal gas exchange and that's why people have pneumonia are also going to have that shortness of breath or hard time breathing right all right but that gives us that point so any situation in which the respiratory membrane is very thick in other words what I mean it's greater than about one well technically like I said we it can range to about maximum of two micrometers but usually if they little bit greater than about three micrometers we say it's a very question 4 remembering and it can cause these certain types of abnormal gas exchange you can imagine in the same way that if the respiratory membrane is very thin ok we're not going to go over any pathologies here but it's just to understand the concept what if we have a thin respiratory membrane for whatever
9:09 reason it's just to get the concept across if we have a very very thin respiratory membrane and that means that there's not going to be a large distance that this oxygen and co2 have to move across so what's going to happen then a lot of co2 will move into the respiratory membrane and actually across the respiratory membrane and into the alveoli and a lot of oxygen will move into the blood so this is the case then you're going to have really good gas exchange but it might be a little bit more than normal right so if you have high amounts of oxygen being exchanged here your partial pressure of oxygen might be really high and the partial pressure of co2 here might be very low and it could cause depending upon the situation if your co2 levels are really really really low this can cause a condition called respiratory alkalosis but again we're just talking about this
9:56 in normal situations just imagine comparing just comparing contrasting what does the thickness have to do with this external respiration process if it's thin in other words it has to be what less than what less than about specifically 0.5 micrometers right so let's say it's less dense point 5 micrometers and thickness if it's less than point 5 micrometers in thickness what's going to happen it's a thinner membrane there's less distance for the co2 to travel less distance for the oxygen to travel and then the gas exchange will have high amounts of oxygen leaving it and low amounts of co2 leaving it okay that covers that concept so again the respiratory membrane sticker is going to impair the gas exchange if the respiratory membrane is thin it's
10:41 also going to affect the gas exchange but there's going to be more gas exchange this one's going to have low gas exchange there's only the high gas exchange but you'd like to have it right within this range of 0.5 to 1 micrometers because it allows for the perfect amount of gas exchange across the respiratory membrane for just the right amount of co2 to move from the blood into the alveoli in just the right amount of oxygen to move from the alveoli into the blood okay now that covers the thickness now we have to talk about the surface area now surface areas are also very very important for this ventilation process for this external respiration so let's say I take two different alveoli okay this one has a small surface area
11:27 and this one has a large surface area okay so say this one has a large surface area and this one has a small surface area you can imagine something here let's say that again oxygen is moving from the alveoli into the blood and co2 is moving from the blood into the alveoli the larger the surface area what's going to happen to the exchange we'll think about it like logically I can have more oxygens being exchanged across this large surface area some more surface area the more oxygen that can be exchanged and also the more
12:13 co2 that can be exchanged so the whole concept here is that this is directly proportional just like the thicknesses so we can say here if there is a increase in the surface area it's directly proportional to what an increase in the actual exchange process so increase in surface area will offer the increase in gas change the directly proportional whereas if you think about this one what happens if the respiratory membrane is thick so the thicker the respiratory membrane what's going to happen to the gas exchange it is
12:59 inversely proportional right so it's inversely proportional to the what to the actual gas exchange process and we already understand that because the thicker the respiratory membrane though what happens the more distance that these guys have to travel that can impair that process now what about a small surface area well let's think about this now if I take you know usually your lungs are having these things you have what's called an alveolar duct and then generally the alveolar ducts is these things which are called alveolar sacs I like to think of them literally like popcorn okay now just generally this is kind of like the nice surface area of the alveoli they're going to these alveolar sacs which are made up of individual alveoli they're
13:45 just perfect surfaces they have a lot of surface area but in certain situations there's an enzyme there's an enzyme because you know there's a lot of elastic fibers in this area there's an enzyme called a last case you know neutrophils let's say here I have a neutrophil neutrophils in certain situations they produce a lot of this enzyme in certain types of inflammatory situations like maybe you're exposed to you know maybe you're smoking maybe its genetic whatever it could be you produce a lot of elastase and again this is usually coming from individuals who are like smoking a lot but and the reason why you'll see why this can happen I'll explain in a second is when you produce this elastase normally what it does is is it comes over here and it breaks this elastic tissue up of the alveolar membranes if you break this elastic
14:32 tissue up what happens to the surface area it decreases because now look all these little alveolar chambers were contributing to a large surface area if you take this thing get rid of all of these and just make this one big alveolar chamber you make this just one big alveolar chamber here no individual alveoli for the next surface area that's going to decrease surface air so this one has more surface area this one has less surface area and whenever you don't have this actual as much surface area it's going to affect the actual gas exchange process if there's a decrease in surface area there's a decrease in gas exchange so this the last taste enzyme is normally degrading these elastic fibers within
15:18 the alveoli so come over here for a second so again I told you there was neutrophils here right and I said that these neutrophils are normally producing this elastase in zyv right they're producing this enzyme called elastics and I told you that this chemical can build up whenever there are certain situations like smoking or maybe even genetic factors right but let me explain why this enzyme is normally inhibited we have a molecule that our lungs are producing called and our body's abundant in alpha 1-antitrypsin alpha 1-antitrypsin is a specific type of produce and what it can do is it can come over here and it can
16:04 inhibit elastase and then the last days can't break down this actual tissue this elastic tissue which helps to maintain the normal elasticity of the lungs and allow for the the right amount of surface area but in certain situations like cancer maybe where you've switched off the gene to produce alpha 1-antitrypsin so maybe some type of cancer which gene that switched off the gene so there's a gene switch off so now you can't produce this alpha 1-antitrypsin or because you know in this cancer could be due to what could be to do smoke smoking you know so people who smoke tobacco and certain things like that so stop smoking those stogies smoking can do that what else can do that you know certain
16:50 types of predispositions so maybe you might be more genetically predisposed and there could be other situations too but that's that's good enough so just predisposed maybe to this genetically or smoking it can activate the specific gene to shut this antitrypsin production off if you shut the antitrypsin production off what happens to the elastase then it starts building up because now you have nothing to degrade it as the elastase starts building up what is that going to start doing then it's going to start breaking down all of this look it comes all over here and starts destroying all of these alveolar membranes and now the surface area is decreasing significantly because when you have all of these little alveoli they contribute to more efficient gas
17:37 exchange now getting rid of it look I just have one big fat chamber okay and what's that going to do so it's going to throw off my sir this area so this condition is called emphysema okay so it can happen to people who smoke right more calm and individuals who smoke but this is the type of COPD control a chronic obstructive pulmonary disorder and if you think about this is going to decrease the surface area so if you have a smaller surface area what is that going to do to the gas exchange well I have less surface area not as much co2 is going to move out of the blood and then not as much oxygen is going to move from the lung into the blood and then what's going to happen to the gas exchange it's going to decrease and so that is going to have a bad effect on
18:24 the body right so there's going to be a decrease in gas exchange so all of these things play a role in our gas exchange process are this external respiration so again quick recap while all this ventilation perfusion plays a very very important role in external respiration and so this thickness and surface area what's the normal thickness of the respiratory membrane about point five to one micrometers but again certain literature might say about - what is the respiratory membrane made up of alveolar cells primarily in this case type one simple squamous which makes up like 97% of them the other remaining small percentage of them is simple cuboidal which is going to produce the surfactant then you're going to have this basement membrane which is kind of like a connective tissue with a little connective tissue which is going to be in between the alveoli and the
19:11 endothelial lining of the capillaries the pulmonary capillaries and you're going to the pulmonary capillaries surrounding this that's making up the respiratory membrane whenever it's thicker what do we say - thicker the respiratory membrane it's inversely proportional to the gas exchange right so thicker the respiratory membrane the less gas exchange is occurring okay then we said surface area the more surface area you have the more gas exchange going to occur across that surface area and this is due to what's the difference between this look if I have a whole bunch of alveoli like I showed you before a whole bunch of alveoli right here versus just one big circle like that approximately the same size this has more surface area because I can have
19:57 more capital Aries serving each one of these individual alveolar lives so I'm going to have more gas exchange well this one might just have only what see the point so the point is that this has more surface area more surface area more gas change because they are directly proportional so if there's more surface area there's going to be more gas exchange less surface area less gas exchange and again what could cause this situation where you could be converting from more surface area to less surface area this could be in the situation of emphysema where there's some type of destruction in the elastic tissue and the alveolar chambers become larger okay and then also the thickness of the respiratory membrane can be occurring due to pathological conditions such as left-side heart failure where the blood backs up into the pulmonary vessels and
20:44 then does what starts leaking out and causes edema or in the situation of pneumonia because pneumonia can have bacteria like Legionella or Klebsiella different types of bacteria that damage the tissue and caused an inflammatory reaction that causes widespread bay so that localized dilation and that localized dilation is going to cause increased permeability and there's going to be a lot of fluid leaking out and as the fluid leaks out what happens to that respiratory membrane it gets thicker which again throws off the gas exchange process okay now why is all of this important generally as blood is flowing through here I just flowing through here we talked about this whole external respiration process you know external respiration let's say here we're going to go over this in more detail when we talk about partial pressure greetings let's say here on the x-axis I have
21:29 times I have time and we're this is going to be the time flowing through the pulmonary capillaries okay so the time and let's say specifically flowing through pulmonary capillaries okay in seconds and then on the y-axis I'm going to have the partial pressure of oxygen okay so let's say that I go here at zero then I go to 0.1 second then I go to 0.2 seconds then I go over here to 0.3 seconds and then keeps going point four seconds and eventually I get all the way over here to like point eight seconds okay the graph is going to kind of take on this type of structure in general
22:15 it's usually going to start off here and let's say that we actually mark our y-axis here let's say here is about a hundred millimeters of mercury let's say here it's about 50 so here it's about 25 millimeters of mercury okay what can happen is let's follow this graph up as I'm going up okay usually we start you know usually when you're coming through here the blood flowing it's already at about 40 okay that's the partial pressure of oxygen generally so I'm usually I'm starting here look how fast it takes for us to get to 100 and then it stays the same from that point on look at that that's insane right so it doesn't take long for the actual the oxygen the blood flowing through the pulmonary capillaries to get
23:01 oxygenated look if I kind of follow it up here it kind of goes about right here so you know what that is it's like in between point two and point three it's approximately about 0.25 seconds that's how long it takes for the blood flowing through the actual pulmonary capillaries to go from 40 millimeters of mercury to 100 millimeters of mercury because that's what we're reaching we're reaching 100 millimeters of mercury but this is normal you know what happens in situations in which there is actually the thickness you know that thickness is increasing of the respiratory membrane then as the blood is flowing through this area because the actual respiratory membrane is too thick as the blood is flowing through they could get all the way you know generally the blood only takes about 0.75 seconds generally only
23:48 takes about 0.75 seconds for the blood that flows with the pulmonary capillaries in situations like pneumonia or left-side heart failure what happens is is they can actually let's say I draw the graph now in the new graph so I draw this new graph here and pink they start here at 40 but look what happens they never reach it they never reach 100 millimeters of mercury they never reach full saturation that the maximum amount of oxygen saturation on the hemoglobin and that's because of that thickness of the respiratory membrane so it's going to throw off the oxygenation they could go the entire your time point seven five seconds and still never reach the maximum saturation the maximum partial pressure of oxygen to take to our tissues and this can cause hypoxia okay
24:34 so just want to give you a little correlation of that concept as the blood is flowing to the pulmonary capillaries iron is yours in this video we covered a lot of information again we talked about the thickness of the respiratory membrane and the surface air the respiratory membrane and certain clinical correlations I hope all of this made sense I hope you guys did enjoy it in the next video we're going to put it all together and we're going to go over a very large process of where we're going to talk about partial pressure gradients and solubilities okay in the next one you click up on the right hand corner and the icon that'll take you to the next video I'll see you guys soon
