Respiratory | Surface Tension & Surfactant in Alveoli

I ninja nerds in this video we're going to talk about surface tension and surfactant all right what is surface tension how would you define surface tension so surface tension is really actually better define we look at it inside this actual alveoli but right now we'll put like a little definition for right now surface tension is actually occurring because of two things so surface tension is caused by two things one thing that causes surface tension is there's you know inside of the alveoli you have a lot of water looks just a little bit good looking like a nice thin water layer right here and then inside of that you're actually have a lot of air a lot of the nitrogen the oxygen the carbon dioxide molecules that you're going to be in here well there's an interaction and interplay between the water layer and the air layer and we'll talk about in more detail but because of that interplay between the two there's a certain amount of tension because what happens is the water molecules don't want to interact with the air and they dive deep down closest to the actual alveolar cells type 1 and type 2 and because of that it creates this tension because the again the water molecules do not want to interact with the dissimilar gas molecules okay so it's due to this air gas okay I'm sorry water air water air interaction okay so this air water interaction okay and we'll explain that more detail and the second thing is because of the air water interaction what this causes is whenever the actual water molecules dive down into the deeper layers of the actual water layer it creates the shrinking of the alveoli and when I wants to shrink the alveoli I want the alveoli to recoil and collapse and produce the smallest size possible and so again another thing with surface tension is it tries to promote the actual collapsing of alveoli all right okay so that's how we would define surface tension and again it can even add on to this it's basically a cohesive interaction between the water molecules so it's a very strong cohesive intermolecular force reaction between the water molecules and then instead of them the water molecules acting with the air they react with themselves and produces a tension because the tension it tries to shrink the alveoli and tries to collapse the alveoli and causes them to assume the small size possible but for us to better understand this let's take this alveolar line what we're going to do is we're going to take a section of that alveoli so we're going to take this blue part which is the respiratory membrane we're going to look at the alveolar cells here and then the water and air interaction so let's go ahead and drop down here okay so here we're going to have this blue layer that's basically the basal lamina the basement membrane then we're going to have these alveolar cells now you know alveolar so there's actually two types of alveolar cells two types there's type 1 and type 2 simple as that right so you have what's called type 1 and if you read them in certain textbooks they also call pneumo sites I'm just going to call them type 1 alveolar cells but again you can call type 1 pneumo sites or type 1 alveolar cells and the type 1 alveolar cells are the ones that are primarily involved in gas exchange so in other words whenever the oxygen is actually moving from what the alveoli into the blood and whenever the co2 is moving from the blood to the alveoli that's what it's contributing to our cancer contributes in gas exchange all right the second one is type 2 and type 2 before I do this it's not just important to know their actual their function it's important to know their shape which one of these because obviously I could have said any one of these can be type one and any one could then type two the type one are these squamous like epithelial cells the cuboidal like epithelial cells is type two okay and there are more type one than there is type two so the type one or more abundant type 2 is less abundant so again I should under put under this this is actually squamous epithelial cells epithelial cells okay type to alveolar cells are going to be this cuboidal one and they contribute to a protein lipid complex called surfactant so they play a role in producing this Cantus actual lipid protein detergent complex called surfactant and we'll talk about him and they are cuboidal cuboidal epithelial cells okay okay so now we got all that mumbo-jumbo out of the way I want to explain something here okay so bear with me it's kind of a tough topic for some people but I'm going to do my best to explain to you I'm going to represent again I told you that there was a water layer right here right so there's a water layer here that's actually interacting between these epithelial cells and the air so let me draw here these circles and what these circles are representing here they're representing the water molecules now water molecules are interesting because they can interact with one another right and when they interact with one another they exert a certain amount of force it's kind of like an inter inter molecular reaction right so these intermolecular attractions or reactions between each other is very interesting so let me draw a couple more circles here and then we'll see what I'm talking about with these reactions and forces and cohesive interactions okay so we got a lot of water molecules right here all of these brownish colored circles are representing water molecules so it's a thin water layer so this right here is the water layer this is the water layer here's the cell layer and then up here I'll represent it with a couple different types of I'll represent up here you're going to have some oxygen you're gonna have some co2 you're going to have some nitrogen stuff like that this is your gas layer or your air layer right so this is where the air is now here's what's really cool these water molecules exert a force on one another so look at the top that where the surface tension is really taking places here at the top layer so if you have to remember any of these layers try to remember the top at least first or second layer look what happens here if we go to the second layer in the third layer look at this this guy can exert a force or it can interact it can have an intermolecular attraction with this water molecule you can have an intermolecular attraction to this water molecule and it can have an intermolecular interaction with this molecule as well as with the one above it same thing for this guy it could react with this guy react with this guy react with this one and react with this one watch here's the problem all of these molecules because of their having this net interaction in other words this one has a nice interaction with this guy nice interaction with this guy next interaction with this guy a nice interaction with him here's the problem ready look at this guy look at this one on the top he can interact with the guy next to him he can interact with the guy on the side of him and he can interact with the guy below him but he has no interaction with the person above him there's no the actual water molecules do not want to interact with the gas so you know what they do they're very greedy you know about vectors look at this vector this vector and this vector they'll cancel each other out so these will cancel each other out if these two vectors cancel each other out where would the net vector be pointing downwards that's where the water molecule is going to want to go it's going to want to interact with the water molecules below and so guess what these water molecules will start doing these water molecules not just this one but this one here this one here this one here I come over here this one here this one here this one here and you get the point that look at all these net vectors this one's pointing gun this one pointing down this one's pointing at and if I even did this one this one's pointed out these water molecules will start diving to the bottom as these water molecules on the top and even some of the actual and maybe a layer below as they start diving to the bottom what happens to the layer it gets thinner as this layer gets thinner so watch this let's say that I actually have this layer here I take this layer I put it up here right so now I have here here's my air water interface and again this Brown is supposed to represent my actual water molecules right and let's say originally here was actually the water molecules right but what were the water molecules trying to do the water molecules are trying to go and drop down to the lower layers as they try to drop down to the lower layers right so that these water molecules start trying to drop down to the lower layers so for example let's say I take these water molecules they're going to start diving down well they're not going to be here they're going to start trying to move downwards they're going to try to get closer to these guys so as they start trying to get closer to these guys they try to pull the water layer down same thing with this one over here these will try to pull the water layer down so as they try trying to pull this water layer down what's happening it's actually shrinking it's actually shrinking and getting smaller and smaller and smaller it's trying to keep dropping and going down to the bottom layer as these water molecules keep trying to go down and drop to the bottom layer it makes this layer thinner okay as this layer gets thinner it actually starts causing alveoli to develop some type of tension so as this layer gets thinner the alveoli starts actually collapsing and as the alveoli starts collapsing it starts trying to push the air out okay so let me explain water line because these water molecules right here they have an interaction to the side of them and interaction to the other side in an interaction below but nothing to interact with above this will not allow for the alveoli to expand because the water layer can't go up okay it has nothing to interact with so because of that because the water does not want to interact with the gases it goes deeper down into the bulk layers of the water down here to the bottom layers as it drops down to the lower layers it makes this layer thinner as the layer becomes thinner it creates a specific type of tension and that tension is called surface tension and as that tension starts increasing it tries to pull on the alveoli tries to make the alveoli collapse you know there's a guy his name was Al aplis and he was working on spheres and he came up with this concept he came with this concept that we can determine the pressure that whenever the surface tension is increasing there's a certain amount of pressure that's being alveolus trying to exert and push on the air to push the air out they call it a collapsing pressure he devised this formula which says the change in pressure you know this is lifeless Lawyer change in pressure is equal to two times the tension and you know this tension is surface tension let's write that next to it this is specifically the surface tension and then this is going to be over what this will be specifically over radius and where represent radius is R okay so piece right here is supposed to represent pressure okay but specifically it's a type of pressure what do we say as these layers get thinner because of the water molecules diving to the bottom layers because they have no interaction with the gas molecules above them only the water molecules below them cause this layer to get thinner and as it create causing this layer to get thinner it develops a certain type of surface tension between the water in the air as it does that the alveoli starts trying to collapse as it tries to collapse it tries to push air out that's the whole desire to push air out when it does that the pressure by which it pushes the air out is this pressure so it's called a collapsing pressure okay so we technically holiday collapsing pressure okay so let's say let's actually explain this a little bit more than let's see how tension can affect this collapsing of the pressure so for example let's say that I take this formula and form two different forms so I put P here and I put two times the tension over the radius for this one and I put over here in a different color I put this one in this maroonish color I put pressure equals two times the tension divided by the radius so in this situation if the surface tension increases what can we devise from this thing if the surface tension increases okay because of the air-water interaction because of the air water interaction because the water molecules on a dive to the bottom layer it creates a tension what do they can do the pressure so in increase in the actual surface tension increases the collapsing pressure of the alveoli increases the collapsing pressure of alveoli what are we saying come here surface tension it wants to collapse the alveoli that's all it is and if we understand that what a surface tension is do the air water interaction and as the water molecules dive to the bottom layer because there's nothing for them to exert their intermolecular force or interaction above they're going to drop down make the layer thinner which is going to create a tension that tension can cause the alveoli to collapse and then in the opposite if you decrease the tension if you by some situation decrease the tension we'll talk about how we decrease the tension our body has a beautiful way of doing that and it's called surfactant if you have the surface tension decreased what is that going to do okay we'll think about the formula if you decrease this number what we'll do to the this number it'll decrease the pressure so they'll actually decrease the collapsing pressure so tension and pressure this collapsing pressure are directly proportional right oh the alveoli sweet deal and again whose law with this this was lapis law of a sphere but in this case we're talking about the alveoli okay now you know since we're here let's see how the radius is affected by and that's where we have this diagram okay let's say for some situation you have this alveoli and let's look at the difference look at this one and look at this one let's say that this alveoli by some reason isn't getting properly inflated because it has a lot of mucus buildup so let's say that this is a mucus plug right here kind of pretty nasty but you got them big old mucus plug here and this mucus plug is occluding or it's blocking some of the air flow down into this area so if it's blocking the air flow so air is coming here so flow so air flow as the air is flowing it's going to want to come down here but there's going to be a lot of friction and resistance right so this area will become very under-inflated it's going to be not very very well inflated so it's going to be you know how to call ventilated if we say ventilated and we actually say it's below of the normal ventilation we say it's hypo ventilated so we can say that this alveoli is hypo ventilated and let's say that this alveoli it's getting a decent amount of air okay it's getting a decent amount of air so this one let's say for right now it's normally ventilated just for right now and then we'll see something that's really interesting here okay so phase one is having this mucus plug in this one's you can normally no really ventilated watch what can happen look at the radius difference here look at the radius difference look it from this point here so now you take you know take radius you take half of the diameter so if we come from here to this point here that's our radius so the radius here and I come from here and I take the radius here this one must have a much larger radius right let's just say for example this radius is 2 centimeters even though that's not good it's going to be a much smaller than that but anyway this is going to be 2 I'm sorry this should be let's make this one bigger let's make it 2 times that they get 4 centimeters let's apply lapis as well to this so lapis is law says that pressure the collapsing pressure is equal to 2 times the tension divided by the radius if this in this situation let's do this in a different color let's do this one in this blue so pressure is equal to two times the tension divided by the radius and this situation here the radius is very low because it's under ventilated if the radius is very very low what does that do the collapsing pressure it increases the collapsing pressure so the decrease in the radius is going to do what the decrease in the radius of this alveoli is going to increase the collapsing pressure of the alveoli oh that is not good and goodness our body has different ways of dealing with this you know and I'll explain it in just a second but just for the heck of it look at this radius let's say that this radius is a little bit larger all right it's a little bit larger okay and let's let's say for a second normally our body doesn't do this but it usually we have ways of protecting this if this radius drops down really low and the collapsing pressure of the alveoli becomes too high what would it do to this alveoli collapse it if it collapses this alveoli where would the air go it would go over into this guy and as the air starts flowing some normal air is coming this way but then we add in some extra air from this alveoli because this alveoli collapses so this alveoli collapses it provides some extra air to flow over here so what is normally ventilated but then it gets extra air from this collapsed alveoli what would happen to this alveoli it would become above ventilation hyperventilated right so we become hyper ventilated all right what happens to the radius then let's say that the radius even increased let's say it was originally four and because of the alveoli emptying some of his actual air in here let's say I went up to like five or something like that let's say that all the air went over and so what goes up to about five centimeters okay if that's the case then we know that the radius is really really what really really high if the radius of this is really really high what is that going to do the actual collapsing pressure it's going to decrease the collapsing pressure so in actual increase in the radius does what to the collapsing pressure increase in the radius of the alveoli decreases the collapsing pressure of alveoli now I told you this normally doesn't happen right it can happen in certain alveoli in the lungs but our body has a way to be able to prevent this from happening in between these alveoli we have these pores that are connecting the adjacent alveoli let's do this in a nice little color let's do this one in this red look at this here's a pore I know I'm really really accentuated the pore here but it's just for you guys to get the point that these two alveoli are connected it's kind of like gap junctions in a way so what does that mean then that means that some of the air that's in this alveoli can flow over here right some of the air that's in this alveoli can flow over this alveoli and some of the air from this alveoli can flow over into this alveoli you know what this helps this helps to maintain proper ventilation normal ventilation between the two alveoli it's amazing I did it just blows my line so this is actually called the alveolar pores um sometimes even call it the pores of Kohn most of them some dude named cone to figure that out but anyway what are these alveolar pores doing they're basically allowing for proper adequate equilibrium of movement between gases between the two alveoli to maintain a nice alveoli structure right so that there is no collapsing of the alveoli so that's one thing another thing that's also preventing this from happening its surfactant and we'll talk about that one more thing though before we talk about surfactant look at this so if this guy is getting under Bentley if you guys remember from the ventilation/perfusion coupling video look at this let's do this one and this pink marker here remember ventilation was V over Q and it was normally going to about 0.8 we solved that what happened what's happened to the ventilation here it decreasing so if it's decreasing what's that going to mean then okay if it's not getting a lot of air into this area that I'm not going to be able to offer a proper amount of exchange even though there's no let's say that there's normal perfusion which is representing as our Q normal perfusion coming through here normal amount of blood flow but this thing is it's under ventilated it's not going to be able to offer a proper gas exchange there's not going to be enough oxygen to exchange so what's going to happen here there's going to be an inadequate oxygen exchange in this situation so inadequate exchange of gases this is super important because if you can't exchange gases you can't get oxygen into the blood and you can't get co2 across into the lungs to expire which can lead to hypoxia and it can lead to maybe even respiratory acidosis so very serious situation obviously what would happen if this is hypo ventilated and you this is decreasing this numbers decreasing what do I have to do to fix it what we said we would actually decrease the perfusion so what happens is they have later they were constrict and you guys remember opposite scenario if this is hyperventilated apply the formula V over Q is equal to 0.8 what's happening this one it's over ventilated if it's over ventilated then what can happen let's assume here that there is normal perfusion originally we always have to think about things before everything's being compensated but normal perfusion coming through here so the Q isn't changing yet but if it's being hyperventilated there's too much oxygen in here to be able to deliver to the actual blood there's not enough blood here to become adequately oxygenated so that's the case then because there's not enough red blood cells coming through this area to get oxygenated they'll still get oxygenated but they're still going to be a lot of air here in the lungs so they get gets wasted so because of this there's a lot of air being wasted okay because of this situation whereas in this one if there's an inadequate exchange of gases because there's not going to be enough oxygen and co2 moving across so in this situation there would be a waste of what the blood coming through that area the Bloods can get wasted because there's going to be no use for so again that's why just to clarify here again if the ventilation is low what does that mean for the amount of oxygen that's going to be in its alveoli that means that the partial pressure of oxygen going to be low so if you want if you want blood to come here here it's not going to get properly ventilated so I want to decrease my perfusion to be able to bring it back to normal right so that's why you would actually do what you would constrict these capillaries because if blood flow came through here it would be a waste of the blood you don't want to waste the blood you want to send it to areas where it's properly ventilated so it can actually get enough oxygen okay so in this situation when the partial pressure is low constrict those pulmonary capillaries and send it away from that area but again that can cause a lot of problems in the body and then the opposite of this situation it's hyperventilated so what does that mean for the partial pressure of oxygen in this area that means it's high so what are you going to want to do to the actual capillaries here we said if the ventilation is highway together do the perfusion increase the perfusion so what would you do to the capillaries you would dilate the capillaries and as you dilate them you'd have more blood flow coming in here so that the air the extra area that you have in here wouldn't go waste it okay all right that takes care of that thing now one last thing before we talk about surfactant it's just really interesting thing that happens if remember how we said that this alveoli if the pressure was really really high it would collapse theoretically right but we do have these mechanisms to try to prevent it but it still can't happen if this alveoli collapses because of this increase in surface tension you know what happens as it collapses it creates like a vacuum like a vacuum and it pulls fluid you know what's the most abundant fluid inside of the blood plasma water all right so there's a lot of water flowing here in the blood plasma when this collapses it creates like a vacuum and pull some of the water out of the pulmonary capillaries and in here into the actual alveoli what does that do as the water is getting pulled into this alveoli and what's going to do it's going to put water in here in the alveoli which can affect gas exchange but not only that as water is accumulating what's happening to that respiratory membrane it's getting thicker what did we say was the relationship between the thick respiratory membrane and gas exchange the thicker the membrane that decreased the gas exchange that's another problem so what are the three things that surface tension can really really pick us up it can cause collapsing of the alveoli if the surface tension is really high right what else could it do it also could create unequal ventilation right of these alveoli and on top of that if these alveoli do collapse what will it do it'll pull water into the alveoli that are actually collapsing and create a lot of pulmonary edema all right and that can be a bad thing okay so that takes care of surface tension now the question is how does our body deal with it surfactant okay let's come back over here to this diagram for a second so if we look over here we had these water molecules diving to the bottom well guess what the type 2 alveolar cells come to the rescue okay surfactant surfactant let's actually talk about surfactant right over here so surfactant is actually going to be a lipid protein complex right so surfactant is a lipid protein complex now you might ask okay well how much of it is living at how much of this protein don't worry we're getting there all right it's 90% lipids and it's about 10% proteins okay so let's look at before we do anything let's look at the structure of this actual surfactant and then after we talk about the structure let's talk about when it's synthesized okay and then what it does so it's talked about the structure when it's synthesized and what it does okay first off let's look at the lipid component so the lipid component over here let's see let's draw the lipid component in this bluish color here there is actually going to be these two fatty acid tails that are connected and these fatty acids are approximately 16 carbons and links so what do you call these sixteen carbon fatty acid structures and they call it well if it's one you call it the actual what you call it the palmitoyl right it's called as a palma tog group the other one is going to be another palm tog group so we call this collectively a dye palma tile by the acid group right so so far we have dyed palma tile all right then we have another thing we have this next thing we look at this this right here is actually going to be consisting of a phosphatase fossil to dial group here so the faucet at a loop is actually going to be hydrophilic so this part here is actually hydro philic and this part here the dipole metoya which is consisting of the fatty acids this is hydro phobic that's going to be super critical here for when we explain this mechanism the last thing is it does have one more thing connected to it it's actually going to have these like choline groups which is an essential vitamin like nutrient so they actually completely call this whole name here they call it fossa to dial kohli so there's this phosphatidylcholine group which is going to be consisting of this polar head like structure with these actual essential vitamin like nutrients structure is called choline but you know that's not it there's proteins many different proteins coming off of this soccer here let's show these protein and let's do these ones in blue here there's actually going to be specifically I'll boom in which is the same male demon that you see within the blood plasma okay there's going to be another one which is going to be IG a antibodies immunoglobulins right for the passive immunity I'm sorry what's a part of our actual innate immunity length of the structure right and then what else we're going to have then we're going to have these able proteins and there's mainly four four types four types of April proteins there's actually going to be type a B C and D we call them surfactant protein type a surfactant protein type B surfactant protein type C and surfactant protein type D okay now that we have all of this let's go ahead and see the next thing so we've said what's the first thing we're going to look at we look at the structure of surfactant we know that it's 90% Levitz 10% proteins the lipid component is the dye palmitoyl group which is hydrophobic then what else is going to have its going to have these 16 carbon fatty acid change with a dipole metal group then it's gonna have this pink head which is the faucet to the coaling group which is hydrophilic it's a little bit more polar then it's going to have these 10% of proteins right albumin IgE antibodies and able proteins type a Type B type C type D okay what's the next thing we said we said when is it made and how is it like secreted that's the next question so you're the fetus during the gestational period around the 24th week so around the 24th week let's come over here so around the 24th week of gestation the actual fetus starts producing this protein lipid complex called surfactant so around the 24th week of gestation the surfactant production begins and it actually is a very slow process very very slow process but by the time the female gets closer to the 34th week of gestation mr. fact in production starts going really high so in the beginning parts like 24 25 26 27 28 the actual surfactant reduction is kind of low but as she starts approaching the 34th to 35th week of gestation then the actual surfactant production increases so look let's say right here the stir factor production as we get closer to the 35th week increases so surfactant surfactant production increases right as we get closer to the 34th week now some of you might be like okay well why is it slow in the beginning and then a lot more as we get closer to the 34th week as the female approaches this 34th week getting closer to that she starts producing a hormone in the hormone within the zona fasciculata it's called cortisol Jenna the woman is actually producing a hormone called cortisol and cortisol you know it's actually a glucocorticoid so it's one of the glucocorticoids she can also produce other different types of glucocorticoids cortisol though one of the google corticoids can actually help to stimulate this process but primarily it enhances the actual the cortisol levels become very very high as the female approaches as she starts getting closer to the 34th week so because the cortisol levels start increasing as you're closer to like the 29th 30th 31st 32nd 33rd 34th week the actual surfactant production starts increasing why is that important because you know in certain people if they actually are prematurely born they aren't able to produce enough surfactant so let's say the individual is born before the 34th week like maybe like a little bit closer to like on a thirty second 31st week that can cause a decrease the monitor and available and it can freeze was called infant respiratory distress syndrome we'll talk about why that's important but again I want you understand when it's produced it's produced during the actual gestational period and it's dependent upon hormone levels like cortisol now when this is actually made it's made by the type 2 alveolar cells so let's see how it's actually secreted so here's our type 2 alveolar cells over here these type 2 alveolar cells when they start making it they store them inside of these actual like large globules inside of our actual alveolar cells and when they're stored in these like look at this I'm going to draw some circles here they're like these big big globules of surfactant this whole big globules of surfactant they look like big old bodies you know what that's called that's called lamellar bodies and then what happens is whenever the actual type 2 alveolar cells exocytosed the actual surfactant would specifically it's in this form called lamellar bodies it comes out in like this tubular like fashion and when it comes out in this tubular fashion this tubular like structure here is called tubular myelin so what if this hair structure called it's called tubular myelin so again lamella bodies is the actual bigger will globular structure inside of the cell when it's pushed out of the cell by exocytosis when this comes out of the cell by exocytosis it becomes this structure called tubular myelin why am I telling you this because tubular myelin imagine I take a big old string of tubular myelin as I take a big old string a tube of the myelin let's say after 10 here's a circle here's a circle here's a circle another one another one ok you get it this part of the tubular myelin that's a surfactant molecule and that's one two so this would be surfactant one surfactant to subtracted three surfactant for surfactant five you get the point this tubular myelin structure is consisting of many many surfactant molecules ok so we talked about its structure we talked about when it's produced we talked about how it's actually released now let's talk about what is doing and how it's actually the rending surface tension ok let's bring that molecule and put him right here so now what I'm going to do is I'm going to get rid of these here for a second and now look what happened to you I'm going to put this guy right here and I'll put another one right over here you put another one right over here I'm going to put another one right there now watch what happens this was the phosphatidylcholine group what was coming off of the phosphatidylcholine group you're having me die palmitoyl groups right which are the 16 carbon fatty acids and then what's so significant about this all right look at this so as if you guys remember the water molecules what were they doing if we follow this water molecule right here it was exerting a force to the side to the side and down but nothing to exert what above look at this Acrobat here this faucet to the cooling group it actually can interact with the water molecule but to the side it can interact with the molecule to this side and it can even interact with the water molecule below now you might be saying okay well they're still no matter what there's no snow force upwards guess what yes there is you see this part here what do we say this part was this was a die palmitoyl fatty acid group this guy palmitoyl fatty acid group is hydrophobic it does not want to be in the water what does that mean it's going to want to be staying out here and because it wants to stay out here is going to create a force that's trying to pull and pull and pull this actual surfactant molecule upwards as it does that what happens then as this pulls this upwards it decreases the surface tension because now what's going to happen some of the water molecules might come back up to the surface so as this is pulling this up some of the water molecules might come back up to the surface here what happens to the actual water layer it goes back to its normal thickness when it goes back to its normal thickness because of the surfactant what does that do to the tension it decreases the surface tension okay so again surfactant molecule here is having interactions with all directions around him and because of the hydrophobic fatty acid tails it's pulling the surfactant molecule upwards as it does that some of these water molecules here on the bottom bulk layers go upwards and draw themselves upwards to interact with the actual surfactant molecules as that does that what you're going to do to the cohesive interactions with all of these other water molecules it's going to decrease the cohesiveness it's going to break up those intermolecular forces and it's going to allow for the water molecules to move up to the top and allow for this actual water layer to expand when the water layer expands the surface tension decreases okay now now that we know that let's see really quickly here how this surfactant eliminates all of these problems okay well let's look at this situation right here first surfactant was produced what was the purpose of surfactant to decrease surface tension if it decreases the surface tension what's going to happen here actually we already have it right over here we already have it right over here and look the surface the actual surface tension decrease what cause of this surface tension to decrease surfactant okay and why because surfactant was actually going to be decreasing the cohesiveness of the water molecules and trying to pull the actual water molecule from the bottom upwards to decrease the surface tension and allow for the alveoli to expand so once to decrease the collapsing pressure of the alveoli okay now let's see how this affects the radius okay this one's a little bit more tricky let me do this right over here for a second let me make two small alveoli down here in the bottom let me get this out of the way here okay look at this let's say here I have this alveoli here with a small radius and I have this alveoli over here with a really big radius and again what was this layer right here let's say this layer right here come on drawn blue was the water layer this is the water layer right here and that was actually creating that surface tension between the air water interface what did we do to treat this issue we brought in surfactant right as we bring in the surfactant molecules let's say that let me show the surfactant in this pinkish color I suppose to factor molecules to pretend it's actually coating this air water interface and it's coating this air-water interface look at what i'm doing what do you notice is different right away you see how this actual surfactant layer is easily coded it's very good it's very nice and dense around all of this air water interface while this one is more distributed has a lot of breaks in certain points of the actual surfactant molecules what does that mean them if something has a larger radius a very large radius okay this is diameter but you imagine half of this is the radius here let's just do it anyway fix this here this point here this is the radius if you have a large radius their surfactant actual distribution is going to be less if the surfactant distribution is less across this alveoli what does that mean for the actual surface tension there's going to be a little bit more surface tension here so this alveoli is going to want to collapse a little bit more even though the radius is much larger isn't that amazing and the last thing if the surfactant is actually if this has a small radius very small radius the surfactant distribution is going to be nice and condensed and concentrated in this area so that's the case the sir the actual surface tension is going to decrease and then if you look at the situation now here they had a decrease in radius right if there was a decrease in the radius what did that do decreasing the radius increase the collapsing pressure well if you decrease the radius how can we fix that what did we say surface tension right we actually would do what we would decrease the surface tension that's what we said we would allow for the alveoli to expand and that would help to decrease this collapsing pressure and then what do we say with this last one we said here the radius was really really big and when the radius is really big what does that want to do to the pressure it decreases the collapsing pressure and whenever you try to decrease this collapse in pressure that's great but let's keep everything even we want equal alveoli so how does that happen what do we do the surface tension what do we do we increase the surface tension because it's not going to be surfactant is not evenly distributed and because of that surface tension increases what does that do to the actual collapsing pressure it brings it up a little bit Amun tries to bring both of these two into homeostasis equal amount so there's no we don't want this one to collapse and this one not to collapse we want them to equally have this equal flow of gases between the two okay now that is how the surfactant is working in this situation if this individual is not able to produce surfactant you can imagine how hard it would be for these alveoli to expand if this individual that that little infant who was born prematurely and wasn't able to produce enough surfactant if that infant was born early she doesn't have this surfactant if she doesn't have this surfactant what's the whole thing that's going to happen she doesn't have sir fact there's gonna be a lot of surface tension what do we say a surface tension would do it would want to collapse the alveoli it would create unequal alveoli it didn't want to pull water into the alveoli right that's the whole purpose surfactant trying to present prevent all of those things if the baby is born prematurely she doesn't have surfactant and all of those things can happen and in order for this baby to breathe they have to put her onto a child on a mechanical ventilator to be able to push air into the baby so that the baby can actually inflate the alveoli because the alveoli constantly want to collapse and when the baby is born and when a baby is born the country umbilical cord and then there's decrease in oxygen levels inside of the baby and that triggers hypoxia activates the respiratory centers with inside of the baby and triggers the babies to do what activate some of the muscles right and when the muscles are activated what happens they contract and try to bring air in what does that call it's called the first cry well in this individual it's still going to do the same thing they'll cut the umbilical cord if they have infant respiratory distress syndrome they'll cut the cord they'll still have a poxy up it'll trigger the actual nervous system to trigger inspiration but when they come to inspire the alveoli don't want to open because they have to have so much that takes so much energy and so much work to open up those alveoli that babies have a hard time breathing and they go into distress and have to put them on the ventilator right last thing I want to mention here is these April proteins April protein a and April protein D are really important because what they help to do is they play a role in your optimization reactions so they play a role in optimization this one here as well as D and if you guys remember what optimization is it's where you tag these proteins could tag specific types of foreign matter and trigger them for phagocytosis so that's pretty cool so there's a little bit of actual immunity Pro component whereas B and C they play a role in the distribution the rate of the distribution and spread of the actual surfactant so they play a role in the spread the rate of which the surfactant is spread so spreading of surfactant all right in engineers we talked about a lot of information this video I hope you guys enjoyed I hope it made sense I really really do if it did please hit the like button comment down the comment section hit that subscribe button our ninja nerds as always until next time

Channel: Ninja Nerd

Views: 528,213

Keywords: surface tension, surfactant, alveoli, respiratory

Id: gjLCu8qe2nI

Length: 46min 32sec (2792 seconds)

Published: Wed Jul 12 2017