Transcript for:
Understanding Gas Exchange Across Organisms

what's up everybody so in this video we're going to be talking about gas exchange just like this little fishy here with these cheeks all blown up so there's a lot that we're going to talk about in this video but I think it's all super interesting I really like this topic as you can see we're going to break it down like this the most important part will be the whole human or mamalian lungs we're going to talk a lot about that in this video so let's just get started so what is gas exchange so you need to remember right on Earth on the planet there are many kinds of organisms and we're all made up of cells right some organisms are made up of one cell we call them unicellular whereas others like me and you and this fat Superman here are multicellular we're made up of many many cells right but all of us if we're we're aerobic If an organism is aerobic okay aerobic aerobic means this aerobic means an organism needs oxygen to make energy we know we need oxygen right for cell respiration to make ATP right you you're going to learn about cell respiration in another video at some point but cell respiration is the process that happens in our mitochondria that helps us make ATP and we need ATB ATP or energy for everything right otherwise nothing can happen and you'll die so any aerobic organism anyone this is an organism that needs oxygen to make energy right any aerobic organism needs to do gas exchange so what exactly is gas exchange SO gas exchange um refers to the process by which oxygen from the environment is taken in um from the external environment and carbon dioxide is expelled from organism so it's literally as the name implies exchanging gases oxygen in carbon dioxide out but the process um differs a little bit depending on what organism we're looking at right a fish will do it different than me and you we will do it different from a unicell organism right so that's why we're going to break it down into we're going to talk about gas exchange in terms of these different kinds of organisms so first off the most the easiest one is going to be single cell organisms so single cell organisms gas exchange real simple because they're only made up of a one cell it's very easy they just have to directly exchange gases with the environment so around them there will be oxygen carbon dioxide and the oxygen will just defuse in and the carbon carbon dioxide will just defuse out right whenever needed right so it's very simple with a single cell organism they can do it directly with the atmosphere they don't need some crazy mechanism when the oxygen um when there's a when when there's a gradient a lot of oxygen in the outside and there's little oxygen on the inside when they need it it will just diffuse in when they have made a lot of carbon dioxide as waste product it will just diffuse out right very very simple so that's for single cell organisms but when we think about multicellular organisms so say an organism has a lot of cells this unfortunately isn't possible because say we want this oxygen to reach this little cell here it has to travel from here through all these cells to get here and that doesn't happen that's way too slow so it's way it's not efficient so therefore for a single cell organism directly with the environment is real simple and it works but if you have a lot of cells like me and you right we have so many cells we can't just directly do gas exchange with the environment it doesn't work because we have cells deep in the center of our body that also need oxygen and that will never happen if the oxygen had to diffused through our whole body to get there so therefore organisms like me and you multicellular organisms we're adapted we have the respiratory system right we have all these systems that can help us function properly that can help our cells stay alive right we have many of these systems now the one that's going to help us do gas exchange is called our respiratory or respiratory system right you must have heard of that one like the lungs and L sort of stuff so now um coming into this right we just talked about what gas exchanges and how single celled organisms do it so how do organisms like me and you do it mamalian lungs how do we do it any organism with lungs how does it how does this gas exchange happen it's far more complicated right far more complicated as you'll see but it makes sense so let's use this guy here Holland right if you don't know him is this the famous football player doesn't matter we're going to look at his lungs and see how it works we're going to look at the big picture and then we're going to go into the detail if you understand the big picture then the details are really straightforward so let's look at let's break him apart we can see this is his thorax right you can see his ribs here this his these all these ribs this sternum we're going to label all of these things later so don't worry about it and just giving you the big picture now we can see this is his torax right the lungs are there hidden behind his ribs so so how does it work let me show you we know we're made up of cells right it's super super important to understand that right we're made up of billions of these cells now our cells need to make energy to survive ATP right now like I said before organisms that are aerobic like me and you we need oxygen to make ATP to survive right we need oxygen so how does our cells get oxygen because I just told you that we cannot do it like this it would take forever for oxygen to come from the outside world diffuse through your skin into your body into your deepest cell in your body right it'll take forever so we have a system let me show you we actually have um right we have a lung we have a respiratory system and it doesn't work alone it works with another system called our cardiovascular system right this is all Our arteries our veins all these blood vessels they're going to work together the lungs doesn't get this oxygen to you to to your cells by itself it needs to work with this other system called our cardiovascular system or um just our vessels okay so how does it do it so we know remember this is a big picture so we're going to go into the specifics later just try to understand this big picture we know our respiratory system right here is going to inhale it's going to bring in oxygen let's say okay let me show you it's going to bring in oxygen and once the oxygen comes into our lungs it will go from our lungs into these little vessels okay the little vessels let's say it brought in oxygen now oxygen can go through these vessels because we know these vessels these blood vessels they transport all these nutrients oxygen and all these things around our body right they want to bring these this oxygen and the nutrients to our cells that needed so that these cells can do aerobic respiration now remember most of our oxygen is carried inside our red blood cells okay so this picture isn't realistic right these are the red blood cells it would actually be inside the red blood cells most ly so then these red blood cells would come to our cells okay and drop off the oxygen because now our cells can use this oxygen to make ATP but you need to understand this when our cells make ATP using oxygen a byproduct a waste product is carbon dioxide so actually we make carbon dioxide as a waste product so our cells will make all these carbon dioxide and the carbon dioxide is a waste product that will be sent back into the blood and our bloodstream will now carry carbon dioxide to our lungs so our lungs can do what exhale it get it get rid of it right because our cells want oxygen and it's going to get rid of carbon dioxide right that's important to understand that's the big picture so you can see why we need to do gas exchange we need gas exchange because we need this oxygen so our cells can do cell respiration and we need to get rid of our carbon monoxide and our lungs can exhale it that's gas exchange that's the big picture if if you understand this then that's perfect that's what you need to if you understand this big picture the rest of the video will be really really easy okay so let's get into the next part so oh yeah I wanted to show you this more clearly I want to emphasize right gas exchange does not only depend on your respiratory system it also really depends on your cardiovascular system right so if we look here at this guy right who knows this guy this guy is Eddie Hall right he's a one of the world's strongest men he was the World's Strongest Man actually in 2007 not that anyone cares but let's look inside of him to show this idea better that these two body systems our lungs I mean our respiratory system and our cardiovascular system work together okay this is very important but don't worry too much about the cardiovascular system what I'm about to show you don't worry about it there's a whole chapter where you're really going to learn all the details of this I just really want to get make sure you understand the big picture here okay so here we have this guy again here is the what the lungs here we got the heart right in the middle between the two Ls lungs okay I want to um make this clear so I told you our cells of our body let's say our lower body our legs our abdomen all of that just what what they just did was cell respiration they keep using this oxygen so they use it up so the oxygen level is going to drop and they're making carbon dioxide as a byproduct so the carbon dioxide is going to cre increase in our vessels so these are little vessels coming back towards the heart from the lower body okay and they're going to be low in low in oxygen because they just used it all and they're going to be high in carbon dioxide because they made this byproduct the same thing with our upper body right we got to bring um our whole body does cell respiration so all these vessels will bring back this so-called dirty blood as I would like to call it because it it doesn't have any Oxygen anymore and it's high in carbon oxide we kind of want to get rid of it to be honest so it comes back to the heart see these two vessels come back to this heart now let me bring this clear so they come back to the heart now the heart what the heart's going to do is the heart is going to now pump this blood to the lungs because we want to change this we want to increase the car the amount of oxygen and decrease the amount of carbon dioxide right so what the see what they do is now the heart's going to pump it so this blue arrow represents blood that is low in oxygen okay low in oxygen so and high in carbon dioxide so basically the heart pumps into both lungs now the lung is going to do the cool part lung is going to do this so the lung right we know he can this guy Eddie Hall he can inhale oxygen right so he can bring oxygen into his lung so now we know this oxygen can go into this Blood that's been sent by the heart guys because this heart sent this dirty blood to the lungs now the lungs will see ah there's low oxygen high carbon dioxide so now he's going to in inhale and all this oxygen is going to go into this Blood now and all the carbon dioxide he's going to Exhale because it's high carbon dioxide low oxygen so he's bringing more oxygen in and he's getting rid of all this bad carbon dioxide okay because that's what our lungs can do bring the oxygen oxygen in carbon dioxide out because in our lungs there's High oxygen and low carbon dioxide so that's perfect because so this oxygen can go into this blood and the carbon dioxide can come out of the blood into the lungs so we can exhale it so now basically the respiratory system cleaned up our blood okay cleaned up our blood now now our blood has a lot of oxygen and all that and low carbon dioxide so it's going to send it back to the heart now the heart has all the has blood that has high oxygen low carbon dioxide and it's going to now pump it to your whole body your upper body your lower body it's going to pump it everywhere for your cells to now use it because it's fresh in oxygen and everything like that that's perfect okay so this is really important to understand so I'm going to put it here in words so understand that our two body systems work together in gas exchange okay very important all the respiratory system does so you're breathing system is helps bring air into our body so oxygen and all that oxygen in and our carbon dioxide out that's what our respiratory system does and our cardiovascular system is going to help distribute this oxygen that we brought in to all our cells and help get rid of and help bring all the dirty blood out of our body bring it back to the lungs so our lungs can get rid of it okay so very important these two systems work together not one alone okay so now perfect let's go into the details so now let's first we're first going to look at the structure and then we're going to go deep into the function so tell me here here we have the thorax right the thorax is basically your upper body except for your arms and your head okay your thorax your chest area try and label these as much as you possibly can at the moment okay this one up here I admit is a bit confusing but just label what you notice here okay the diagram is not that great so we know mouth and nose why do we care about the mouth and the nose because that's what's bringing in our air we can Brea breathe in through our mouth cuz our mouth right here we can bre breathe it in through our mouth here this little uh Pink part and our nose up here can bring in air and they all join to the same pipe so your mouth and your nose connect to the same pipe so you can bring in air if you close your mouth you can bring in in air through your nose and it will go to the same pipe that that it would lead to if you breathe in through your mouth right so if you're sleeping maybe you don't eat your mouth because you're not doing a lot of exercise your body doesn't need ATP so you only need some oxygen right you don't need to um ventilate or breathe as much okay so the important part to understand is they connect to the same pipe both the nose and the mouth now we're going to label this pipe on the on the next slide so don't worry about it for now we're looking at the most outer structures here so what's this little bone here this little bone here right in the if you feel your chest is a hard hard bone okay this is your sternum okay very important you can see your sternum is connected to all these things here you called your ribs right your ribs now your ribs um in fact the part of your ribs close to the sternum connecting directly to the sternum is not actually made up of bone it's made up of cartilage okay so it's a bit flexible this is good because if you could punch right in the chest at least there's some flexibility it won't break instantly okay so just know this is still your ribs it's just this part is made up of cartilage a more soft flexible part okay um it's also very useful that this is cartilage because it allows when you breathe you know when you breathe your your chest expands so if it was just bone it wouldn't be able to expand so your chest cavity wouldn't be able to expand so much so because this part is a bit elastic it can expand much more now and then there's this huge muscle here at the bottom I'm going to drag it out for you okay kind of like this you can see it's like a dome shape okay it's like a dome sort of shape Dome like okay this is your diaphragm okay and it's you're going to see in this video it's so important it does a lot it's very important in breathing okay and then we got these muscles in between our ribs so you see the ribs um all these ribs they're connected this rib will be connected to this rib with some muscle and this one will be connected to that rib with some muscle these um muscles in between these ribs have a special name okay they're called the inter Coastal muscles and why does that make sense inter means in between Coastal means ribs okay so in between our ribs muscles very simple okay cool that's a lot of the key outside structures that we can see very obviously so now let's go deep and label some more things because you need to know these structures very clearly so you can label them for whatever test you got um and then we can go into function because if you understand structure function is a breeze okay now we're going deeper so let's say we're removing okay basically doing this we're removing the the bones the all the muscle now we're getting to our lungs okay we're lungs and we're going to see how it looks like inside when we slice open our lungs what does it look like what's all the branching going on and all that okay that's what we're doing now so let's label some stuff so what's this pipe remember when it comes the air comes in through your mouth and nose it goes into this pipe here and down here this is your trachea trachea very important behind it is your esophagus that's where the food goes down so your food doesn't go down this one just the air okay if food goes down here you'll you'll cough and choke and all that sort of stuff okay so traum um now this just basically it's lung right it's very simple now when this trachea goes down notice that it branches into two right here it comes down it Branch one to the right lung and one to the left lung what do we call these big branches they have a name broni so this will be the main bronchus the broncus okay we call the broncus the trachea the bronchus now this bronchus will Sprint into more broni and then eventually when they get very small we give them another name like these very small branches call them bronchioles okay very important so you can understand so far when our air comes in they pretty much all they're going through is pipes so the biggest pipe is going to be our trachea then we get into a smaller pipe broni and then even smaller bronchi and then eventually bronchials very small little pipe so we can see if we zoom in here the bronchials like even smaller branches and ultimately what you need to understand is that they lead to these final thing here this final thing here these little balls you see these little pocket pockets of air they're called Oli you must have heard of this if you haven't then that's good we're going to talk about it now um let me show you let's zoom in want to make this clear oh sorry so if we zoom in uh here let me show you yeah g to put in the right spot okay so you notice uh this diagram is very simplified in reality there would be a lot more vessels so these red and blue things are just blood vessels right they carry your your oxygen your carbon dioxide your nutrients and notice they're being sent to the Alvi okay you can see this one is being sent to the Alvi this one is coming out of the the blue one's coming away from the Alvi but there's a lot of these little alveoli so let's label them first these little pockets of air okay Alvi very important structure so you can see here in this diagram this little part here that I'm showing you now you can see it's made up with all these little cells connected to each other forming a little bubble right this is your alvioli and then this little part here with all the red blood cells in surrounding the alvioli like like you can see in this diagram that's your vessels okay your arteries your veins don't worry we'll learn all about arteries and veins in some other video I'm not going to kill you with that now now it's important I'm going to show you why all this blood vessels around the Alvi is very important you probably un maybe have an idea already why we're going to talk about it when we get to function we're just in structure now so notice the very end we start off with this very big one it branches and branches and branches and branches and branches the bro bronchioli and then finally we get to these little pockets of air right you can see in this diagram called alvioli and these alvioli are supplied by a lot of little vessels right a lot of little vessels and notice very important not very important just interesting fact you have 300 million of these little balls in your lung so it's very important a lot of people even um even me when I was younger I really thought our lungs was pretty much just a pipe connected to a big bag but see it's not like that it's not like a big plastic bag that's getting air you have all these branches leading to alveoli it's way different than you may have thought now I want to emphasize something so you can see these vessels right surrounding your alveoli they have these red blood cells and these vessels themselves remember they're made up of cells you can see little pipe being formed by all these little cells now same with your alveoli it's it's a little bubble formed by these cells there's two cells that you need to know about for the Alvi that make up the alv you could have probably already seen it these smaller cells and these bigger ones okay I'm going to give them some names type one and type two pyes we're going to talk all about their functions and everything later just for structure now type one would be these smaller cells they make up the majority of the Alvi and then the bigger ones that are very rare they're type two pneumocytes and they're called pneumocytes why because pumo means lung and sites means cell in some other language okay so very important this is all just structural so don't worry about function at all at the moment okay very good so what do we got now in terms of our human okay our gas exchange in mammals we get the big picture how these two systems our cardiovascular system and our respiratory system work together we know the basic out out structure we know this deeper structure very important now let's get into some function that's what we really came for right so function is pretty cool so you need to learn a key word called ventilation so our respiratory system um can do a key function called ventilation ventilation is the process of bringing air in and bringing air out of our lungs okay not out of our bloodstream not out of ourselves out of our lungs so ventilation is just a process very key A lot of people get it confused between ventilation and gas exchange so ventilation is bringing air into our lungs and bringing air out of our lungs whereas gas exchange is bringing um air or oxygen into our into our body so our bloodstream to to go to our cells and bringing carbon dioxide out of our bloodstream out of our body okay so gas exchange is a broader term gas exchange describes bringing air into our body and into our cells and then and and out of our cells and out of our body whereas ventilation is only referring to the part of bringing air into our lungs and out of our lungs you're ventilating when you hyperventilate right you probably heard that before when you bring air too air in and out of your lungs too quickly okay now let's get into this okay remember we got our alveoli okay so remember we're looking now here at an Alvi remember this little bag here is our alveoli we're going to look at the function now so I want to the reason why we have these vessels here is because they're very important remember I told you before let's go back to that um here your lower body or the your whole body keeps using this oxygen to do cell respiration and makes carbon dioxide as a byproduct right so that's that's perfect that's what we wanted to do so this Blood this dirty blood is going to go to the heart okay and the heart is going to pump it to the lungs so that so that it can get cleaned up so that it can pick up some oxygen and get rid of this carbon dioxide that we don't want so when we look at this picture here we can see this vessel here is bringing blood from the heart so this is going to be the blood that doesn't have um that has um uh this is the dirty blood as we call it right why because it has low oxygen and high carbon dioxide so we're going to put it here so this blood coming towards this lvi has going to have low oxygen high carbon dioxide which is why we make the blood blue normally what makes your blood the what makes your blood cells red is being is oxygen being in them so when your cells when your blood cells do not have oxygen in them or they have low oxygen then they're kind of Bluey okay when they have a lot of oxygen they're red so we can see this dirty blood coming from your heart to your lungs specifically to your alvioli they're going to have low oxygen and high carbon dioxide right but that's perfect now what's going to happen remember remember this the inside of your alvioli what's in there what's in there high oxygen low carbon dioxide because this guy this person Holland whoever is inhaling a lot of oxygen okay and he's going to Exhale the carbon dioxide so in here we have a lot of oxygen and low carbon dioxide so that's perfect so we can see there's a gradient right we can see it let me show you we can see there's a concentration gradient inside of the alvioli there's a lot of oxygen in this blood vessel this dirty blood there's low carbon there's low oxygen so there's a gradient we can see this is perfect so the oxygen will um passively diffuse into this vessel to go into the red blood cells and the same way in Reverse this high carbon dioxide inside this blood so and there's low carbon dioxide inside the Alvi so the same way it will diffuse out down the concentration gradient right so let me show you so remember we have a this this oxygen which we can inhale and this carbon dioxide that we will exhale let put it here okay so remember we're inhaling all this oxygen so there a high oxygen in in the Alvi because of the concentration gradient difference remember remember really understand this this is the dirty blood coming from our cells that used up all the oxygen and made a lot of carbon dioxide is byproduct our heart pumps into the lungs because it wants to clean it up it wants the lung to put a lot of oxygen into it and remove all this carbon dioxide and that's exactly what happens we get here um because of the gradient the oxygen goes into the vessels and the carbon dioxide comes out um right that's that's very important the carbon dioxide is going to come out let me put that also here so the carbon dioxide hope this diagram is clear for you guys so the oxygen comes in diffuses in because of the concentration gradient at the same time don't remember this don't misunderstand this diagram um the carbon dioxide doesn't come out after the oxygen comes in this all happens at the same time okay it all happens gradually throughout here until all the red blood cells are fresh okay so don't think that oxygen is coming in first and then carbon dioxide is coming coming out okay this happens at the same time okay so because of the gradient oxygen goes into the vessel carbon dioxide comes out and that changes our blood that cleans our blood now our oxygen I mean now these vessels have a lot of oxygen and a low carbon oxide what does that mean that means they're perfect they're ready now to go back to the heart because now the heart can take this fresh blood and pump it all across our body for all our cells to use again because it's fresh in oxygen so our cells can use it again to do cell respir a and make ATP right it's perfect so we call this process gas exchange okay this process here that happens in the alvioli is gas exchange bringing the oxygen the gases into and out of our bloodstream with the external environment because right this Alvi is connected to the outside world right if we follow these pipes along it's connected to the external environment so this gas exchange is exchanging these gases from the outside environment to inside our body inside our bloodstream that's gas exchange and remember ventilation is just bringing air into into and out of the lungs okay very important so that's really really really the trickiest part to understand about this whole mechanism let me quickly re recap it so we got all our trachea so we got our trachea we got our bronchi we got our bronchioles and alvioli our Alvi is where this gas exchange process is going to happen and it's very much connected to our what our cardiovascular system right our dirty blood is going to get delivered so if you look at this picture here so these vessels right in reality they're being sent to the Alvi because the blood is dirty and they want the Alvi to do gas exchange to make the blood um fresh and ready to go back to our cells okay back to our heart and then back to all our cells so that's very important I hope you understand this concept and understand that concentration gradient is very important here okay the gases diffuse down their concentration gradient from where there's a lot of one so a lot of oxygen here to little oxygen a lot of carbon dioxide to little carbon dioxide okay that's very important so now let me just a quicker water you need to understand that alvioli um the reason why alvioli is is so good at gas exchange is for four reasons we know it's really good at gas exchange we saw it here in this in this slide so Alvi are really good at gas exchange for four reasons one because they're really thin have you have you noticed the ovoli is one cell thick one cell from the alvioli space here to the bloodstream the alvioli itself is one single cell thick so that's very efficient because that means the gas so if we take the oxygen has such a small distance to travel before it gets into the bloodstream it just has to pass the Alvar membrane and then the capillary or the vessel membrane that's it okay so that's one key feature of the alvioli that makes it so good for gas exchange okay it's got very thin walls second the alviola has a great abundant blood supply all these capillaries all these little vest vessels right these tiny little vessels supplying it it's called capillaries okay they're everywhere right when we look at this picture here they're every single lvi is being supplied of bloodstream if there was no bloodstream what would happen guess what would happen if there was no bloodstream all the oxygen would come in here and it would have nowhere to go right there's nothing picking it up nothing taking it it's like a taxi coming to your house but no one getting into it it's useless right so our bloodstream the fact that the alvioli are so abundantly supplied by Blood these little capillaries makes it very efficient for this oxygen to be collected and the carbon dioxide to be sent to the Alvi to be gotten rid of right very important thirdly surface area so have you noticed if you look at this our lungs right are not like a plastic bag if you measure the surface area of a big bag if you if you thought your lung was just a big bag and you measure the surface area so you go 40 um * 40 * 6 you know surface area um this is just a stupid example you'll find that the bag like this has this surface area okay but actually our lung if we add up all the surface area of all of our um 300 million alveoli if we add up the all the little surface areas of these little alveoli we get a way bigger number so the surface area the amount of surface that there is for the oxygen to to um to get into bloodstream is way bigger in the in our in our alvioli compared to how a normal bag would be so that's why the alviola is very very efficient they have a super insane large surface area a large area for these oxygen carbon dioxide to reach um a a a bloodstream okay very important and then lastly moist because the alola are slightly moist moist moistness I don't know if you love that word or not but moistness um encourages diffusion it makes the fusion a little bit easier if it was very dry it wouldn't work as well don't worry about the reason why um it's not important for you guys so just know these four reasons that really make Alvi super unique and super good at gas exchange they're very thin they've got a super crazy blood supply to pick up all the gases and they got a very large surface area Okay because of all this branching and all these little lvi everywhere and it's moist okay now we're going to um now that we have gotten that out of the way we need to come back to these type one and type two pneumocytes okay so remember I told you before this little Alvi this little bag is made up of two kinds of cells this one these small ones that are numerous they're type one and these big ones that are type two okay and there are some differences between them that you need to know so you see this little thin layer this little watery mucousy layer guess which cell makes it type two or type one the answer is type two so type two that's one unique feature about type two to it is the one that makes the surfactant now what on Earth is the point of this little surfactant what on Earth can it possibly be so surfactant is really really important for this reason let me try and show you an example so you know a balloon if you blow up a balloon right and um you open the balloon so you can make a small hole it will just um deflate like this until it becomes collapsed right like this right so the thing is in a way our alvioli are like little balloons but the problem is you um our alvioli are not allowed to collapse if they collapse like this we would not be able to in um we would not be able to breathe okay have you ever tried to blow up a balloon that hasn't been blown up yet like this a collapsed one it's really really hard but once you get it um blown up a little bit like this then the rest is very easy right you've noticed that it's the same with our Alvi if they are collapsed like this it's very hard for us to inflate them again so they can never become collapsed so this little fluid the surfactant it reduces surface tension okay so even though even when we exhale and we try and get rid of the air the alvioli will never collapse they will always stay something like this they will never collapse because of this surfactant so understand that the surfactant is made by these type two pyes and the surfactant is like a phospholipid protein it's made up of phospholipids and proteins and it's very important very very important because it reduces surface tension that means it cannot collapse that means when we try and get rid of the air when we exhale we can get rid of the air but the alvioli will stay patent it will stay open it won't just collapse okay okay so that's very important that's what surfact does reduces surface tension remember this it pops up in many many multiple choice questions okay so just remember alveoli should never collapse okay so what are the differences between type one and type two okay I'm going to go quickly over this so type one majority as you can see in the diagram type Tye two is the minority know this for a four or five mark question type one is smaller as you can see type two are larger um type one is made for gas exchange SO gas because the these type one cells are very small it's a sort of distance for gas exchange to happen across the type one cells as opposed to the type two cells because they're very big so if the gases had to travel across this bigger cell it would take longer it would be less efficient so type one is made for gas exchange the process we just mentioned and then type two is primar suited for surfactant secretion which is very important for what reducing surface tension okay type one cells they are a little bit like stem cells you know what stem cells are these are little cells that can divide and divide and become other cells so these stem like they they're undifferentiated so they have the potential to become anything it's like you when you're a teenager you have the potential to become a football player an engineer um homeless anything right you have the potential for anything so these type one cells they are stem cells they they have the potential to divide and divide and they can even um um they can divide and divide oh sorry I'm I'm I'm mistaking you the type one cells they cannot divide they cannot divide the type two cells are very special because they are stem cells as I just said that means that they have the potential to become any other kind of cell so when these type one cells die because they can't divide by mitosis to replace themselves then this type two cell is special because it can divide and become a type one cell so it's kind of like a little stem cell it has a potential to become a type one cell as well if needed okay very important so know these four differences between type one and type two what num numos sites okay very important it's also a very high heel topic it comes up a lot okay awesome so now I want to say what we've done so what we've done so far um in this video uh is we've done the intro to gas exchange talked about vaguely what gas exchange means we've talked about uh how gas exchange work in these single celled organisms and we've talked now a lot about gas exchange in melan lungs specifically we've looked at the big picture we talked about how the respiratory system is so important our cardiovascular system is important and they both work together to make this happen right and we've talked all about the structure of our respiratory system and we've started talking about the function we've talked um uh we've talked about the the gas exchange specifically we talked about exactly about about how gas exchange happens in the Alvi now we're going to talk about ventilation how our body manages to actually bring in the air into our lungs because remember we we saw here ventilation is the process of bringing air into and out of our lungs how does that happen it can't just happen by Magic so how does it happen let's talk about that so the lungs themselves so these guys right here let me show you these guys right here have no muscle so how how do they expand then how do they get bigger and smaller how do they how do they suck air in and how do they push air out that's very important the lungs themselves have no muscle so the lungs themselves cannot move okay it's something else that makes the lungs move muscles like the diaphragm that we talked about before this guy he's going to be responsible for making that long move and then um our intercoastal muscles these that we mentioned here they're going to be responsible for making ventilation happen and maybe even abdominal muscles your abs but those we're not going to focus on those because those um if you've done a lot of exercise before you'd notice when you use your abdominal muscles if you've ran like five keters or something and you're tired you notice your abs are moving your stomach is moving in and out because your abdominal muscles are also trying to get um ventilation it's also trying to help you in addition to your diaphragm and intercostal muscles but when you're just sitting here picking your nose watching my video you're probably only using these two the diaphragm in and the inter Coastal muscle so we're really going to focus on these two okay these to the abdominal one know that it exists but um it's not important for what you need to know okay so to understand to understand ventilation you need to understand this concept if you done if you're a physics student or a chemistry student you maybe already know this but most of you are just bio students so you this is not something you would like focus on in biology so I want to give you a quick overview on this and it's going to help you understand ventilation a lot let me show you you okay so notice this little picture here we got a we got a um a glass turned upside down or whatever you want to think about it I Tred to make it like the respiratory system this is like the diaphragm and this is the lung okay just um whatever how however you want to see it so if you take this thing this little layer so this layer here this wooden layer or whatever is making sure no air can escape okay so if you move this wooden layer up up up up up what's going to happen to all the gas inside here is it going to become more pressure or less pressure so as you push this push this little barrier up up up up you're creating a smaller volume right smaller volume whenever you decrease the volume of a of a specific container so you force this thing to make the area smaller and there's and the and this air can't escape anywhere then the pressure is going to increase okay very important so the smaller the volume the higher the pressure is going to be here a lot of pressure okay the same for the reverse okay so if we take the reverse scenario if we make this box bigger we give more volume what's going to happen now the pressure is going to be reduced I see pressure as like how compact how um how much um how much is going on inside that area okay that's pressure so we can see when the volume is made smaller the pressure is going to be larger right this is relatively intuitive right this is kind of logic right when we make it bigger we make a bigger space now all these things have more space to move there's not so much pressure right this is Bo's law so an increase in volume will lead to a decrease in pressure and vice versa so if we think about this like our lung we think about this like our diaphragm that's moving up and down we're going to look at how the diaphragm works and all that so don't worry but um if we look at this say our diaphragm moves up and compresses our lungs what's going to happen if this is high pressure here where does and we make a let's say we make a hole right here what do you think is going to happen if we make a hole right here where's the air going to go it's going to burst out right why because where there's high pressure um a pressure will go from where there's high pressure to where there's low pressure so if you compress this and make this area very high pressure and the outside is less pressured then as soon as you make a hole the air will just explode out and the molecules will go from where there's high pressure to where there's low pressure right so what about this what if we make a hole in this one so let's say we make this we drag this down we reduce the pressure a lot and to a point where the pressure inside here is actually lower than the pressure in the outside world what's going to happen air will then come in because the particles will go from where there's high pressure to where there's low pressure so in this scenario the pressure is higher in the outside so it will come into this area with lower pressure so that's very important understand boils law okay an increase in volume will lead to a red in pressure and vice versa this is important with our lungs if you imagine these are our lungs say we compress our lungs we make them higher pressure with our muscles then that's going to force air out from higher pressure to lower pressure if we expand our lungs we make them bigger that's going to lead to lower pressure in our lungs sucking air in from the outside where there's higher pressure air okay that's very important so now let's actually look at the real lungs and make this make sense okay here we go okay so remember diaphragm is one of the key muscles in in gas exchange okay and I want to show you something when the diaphragm contracts it gets flat okay so you can see it's a nice Dome when the diaphragm contracts it moves down and becomes flat so because the diaphragm is attached to the lungs remember this the diaphragm is directly attached to the lungs because it's attached to the lungs when it contracts it pulls the lungs down making them bigger making them expand okay so based on that logic how does inhalation work how do we inhale okay I'm going to show you step by step here just because just because I know this is what you guys want okay so inhalation is how we inflate our lungs so what's going to happen the diaphragm is going to contract as it contracts what happens it becomes flat okay when it becomes flat it pulls the lungs down with it increasing the volume remember from boil law when we increase the volume what do we do we reduce the pressure okay so when we reduce the pressure now the pressure in the outside world in our environment in the atmosphere will be higher than the pressure inside our lungs so the pressure the air will then rush in from the outside to the inside of our lungs naturally okay so you see what I mean so what about the opposite so what about exhale so when we exhale our diaphragm will become a dome it will relax when it relaxes it's going to push the lung compress it it's going to push it up so it's going to compress it a bit okay so when it becomes a dome so we decrease our long volume when we decrease the long volume what do we do again when we decrease the volume we increase pressure if we increase increase pressure now there will be higher pressure in the lung compared to the atmosphere so what's going to happen lower pressure outside compared to the inside so the air will flow out of the lungs so that's how our diaphragm Works make sure you understand this it comes up a lot in multi multiple choice or even long answer questions okay so that's the diaphragm for you let's do the next one so let's do our inter Coastal muscles okay that's because we only need to know those two the diaphragm and the inter coal muscles so you actually need to know two things we actually have two inter Coastal muscles and I'll show you a picture later but how this works is like this so our we have external intercoastal muscles and internal intercostal muscles so the external intercostal muscles work like this so if you look at our r they will attach in this direction you know putting your hands into your pockets it's in that direction so remember the way you put your hands into your pockets from the back forward like like this from the top down like this when you put your hands into your pockets that's how the external intercostal muscles attached onto your onto your ribs okay like this between this rib and that rib so and it's going to happen and that will happen in between each rib everywhere okay and it's the external inter Coastal muscle is the most outer layer so the the internal interco coal muscles we'll see a diagram later will be below the external interco coal muscles that's why we call it that way so the external inter Coastal muscles are on the outside the most external and then the internal inter Coastal muscles will be deeper we'll see a picture later but let's first focus on this external one so if we assume that it attaches in this direction in between each rib then how is when this muscle contracts how is it going to change the shape of the lung let me show you pretend this guy is pulling a rope so this is right this is a muscle right we know muscles um we know muscles contract so if he's going to say this guy is pulling it like Pretend This Pretend This thing is Contracting as Pretend This guy's like pulling this rope okay pulling this muscle if this muscle is Contracting this way what's going to happen to the ribs let me show you so normally if we look from the side here's our spine here's our ribs attaching to what the sternum okay now if we have this external interal muscle contract rting or this guy pulling this rope what's going to happen to the to the C to this um to the thorax what's going to happen to the rib cage it's going to rise look it's going to rise up right you can imagine when this guy pulling this rib on this rope it's going to lift it up right so it's going to rise up by rising up we actually increase the anterior to posterior distance see it's nice and small here now it's much bigger so now we increased the volume of the lung remember the diaphragm when it contracts it moves up or down so we increase the volume of the lung vertically down we make it we make it bigger downwards whereas for this one we make it bigger forwards okay so we increase the volume by making a larger distance from front to back or back to front right that's important so you can see here when the external interos muscle contracts we raise the rib cage like this let me show you so the external intercal muscles when it contracts it will raise the ribs just like this you can imagine um and that will cause reduced pressure increased long volume so reduce pressure which again according to boils law means what if we have reduced pressure that means air will flow in so that'll help us respire don't worry I'm going to have a diagram just like this as well for this one just tring to show you quickly now the opposite One internal intercostal muscles how do they attach so they're the opposite so they're deeper remember but they don't attach like you put your hands into your pocket they don't attach in this direction they attach the opposite so you can imagine what happens when this muscle contracts let me put a guy here for you guys what happens when this one contracts imagine a guy hanging on a rope here what's going to happen to the rib cage the opposite so we're going to go we're going to depress the we're going to go in this direction instead of raising the ribs like this image is showing we're going to pull the ribs down so we're going to reduce this distance even more okay so the exact opposite so when this muscle contracts we depress the ribs we don't raise or Elevate them we depress them that's going to cause increase pressure because we're making the volume even smaller and that's going to force the air to go out okay so I hope I hope these little guys if you don't understand and remember external inter Coastal muscles is like putting your hands into your pocket that direction and you can imagine if you don't understand how the muscles will do anything think about a guy pulling a rope how's that going to what's going to happen to the rib cage when the external intercal muscle is contract it will raise the rib cage like this when the internal ones contract it will depress it it will sink it down squeezing the lungs okay okay so let's let's look at the word form of that because I know you guys love this part so using the external intercoastal muscles what's going to happen we're going to contract remember the picture when this one contracts we raise the ribs okay we raise the ribs by raising the ribs what do we do we increase the lung volume from anterior posterior we make it bigger front to back so there's more space for the lungs by doing so we reduce the pressure and ACC according to Bo's law by reducing the pressure now we're going to have lower pressure inside the lung compared to the outside world so the outside world's atmosphere will be higher pressure forcing the air to come into our lungs okay the opposite for exhalation okay not going to talk about that because you should understand it like basically when I'm just going to show it for this one and for next one I won't so when this one doesn't contract the external inter coal muscle the the distance will be smaller so the volume will be smaller so the pressure will be higher and so on okay okay the internal so notice here here this diagram the extal intercal muscles the direction is from the back forward like you put your hands into your pocket look at their muscles look at the the the look at the direction of the fibers okay now look at this one the internal COA muscles opposite okay downwards backwards the direction is the is the opposite okay so here's the little words for you guys I hope it makes sense I'll talk about the first one so how do we um when when this muscle can when this muscle is useful for um exhalation because when the in internal interco coal muscle contracts what happens when this one contracts we depress the ribs let me show you we depress the ribs we decrease the lung volume and when there's decreased volume there's increased pressure so there's higher pressure inside the lungs lower pressure outside causing air to flow out of the lungs okay that's very important so from from all this the two very important muscles you need to understand for that does ventilation is diaphragm and intercostal muscles make sure you know these flow diagrams it makes very much sense if you just use use the logic okay make sure you write them out like this all the detail because they're very important they can be asked in Long longer questions or even multiple choice as you'll see later in this video okay that's very important so now we got everything there nailed let me show you we're now at this point we finished big picture structure function all the functions Al L has that you guys need to know about we're going to go into this one now okay okay okay spirometry so you need to learn about spirometry spirometry is really really interesting it's really really simple actually as well basically it's a little machine this little machine measures um the volume of air when you when you're breathing okay so when you you you know when you inhale you can see the Curve will go up when you exhale the Curve will go down because on the left here the y- axis we have the volume the amount of air in your lung whereas here we have time okay so as time goes on you can see so what they do in this test is interesting so for example you can see with this person for the first 20 seconds they just asked the person to breathe normally so you can see they're just normally breathing inhaling the volume increases exhaling inhaling exhaling but then here at this point they ask the person to inhale as deep as they can so you can see now the volume inside their lungs increased drastically and now they went back to normal and now they went their normal breathing again and then at this point this person was asked to Exhale as much as they possibly can so you can see the volume inside the person's lung decreased a lot so all of these little Peaks and curves have names so we need to know them so know that the spirometry this is used to measure the amount of air that is exchanged during breathing okay as well as your respiratory rate that's important okay it's used a lot especially for athletes to see their performance or even for diseases so they use this a lot so for example if you have asthma then your spirometry results will look different from a normal person because in asthma maybe you can't exhale as well or inhale as well as a normal person so these curves will look different so it's used for assessing performance for athletes or used for disease people like people with COPD that smoked their whole life or asthma anything like that it's very useful okay so now let's label some things so I want to label first these little normal curves the normal breathing we call that your tidal volume okay your tidal volume because titles like the like the ocean's waves they come in and they come out it's normal it's always the same it's the constant tital volume okay it's not high it's not all effort or no effort it's just the normal tital volume waves coming in waves coming out okay this is your normal breathing then we can have see this one we have this when you inhale as much as you can okay we can see we give that a name we call that your inspiratory reserve volume but notice the volume is from the peak of your title volume to the peak of your of your maximum capacity okay so it's the inspiration Reserve volume because when you normally Inspire see when you normally Inspire let's say you get to this point that's normal inspiration so this whole Gap would be your inspiration reserve the amount of air that you um have left that you can still breathe okay because this peak here is the amount that you normally inhale just by existing so this little thing this little thing this part here would be the reserve the amount that you have left the amount the capacity that you have left to inhale more okay in addition to normal that's inspiratory Reserve volume okay okay so pay attention it's not from here to up there it's from your normal inhale point to your maximum the reserve that you have left the capacity that you have remaining after a normal inhalation a tital volume okay and then the same in Reverse would be your expiratory resolve Reserve volume so when you're normally your tital volume you inhale you exhale now the amount that you have left that you can still push out if you try your best that's called your expiratory reserve volume the capacity the capacity that you have left to Exhale after a normal exhalation okay now from the very bottom so your expiratory reserve volume Peak to your inspiratory reserve volume Peak that has another name it's called your vital capacity the total ability the the if you inhale completely until exhaling completely that amount of volume that's your vital capacity okay you need to know these four okay it's very very important so I have some questions for you here so what is the title volume if we look at this person okay we can see here uh one 1,00 2,000 millit so in between here this would be five so every two blocks is 500 so if we if we try to measure the title volume every two so two blocks will be 500 so for this one their title volume will be 500 milliliters so what is their inspiratory Reserve volume make sure you know the abbreviations as well sometimes they ask those so we can see here every two blocks is 500 right so um we can just look here from 2,000 to 4,500 so how do we get from 2,000 to 4,500 it's going to be 2,500 so this person's inspiratory Reserve volume is 2,500 okay what is there expiratory Reserve again you can calculate that here from 1,500 to 500 so that's going to be 1,000 so what is their vital capacity you add it all up it's going to be 4,000 so make sure you know spirometry why it's why it's used why it's important you know all these values and how to read it okay and how to calculate something just like I asked you great here is the here is is a slide on all the word um how CU I I Define them for you using my own words but I know you want them written down so here they are for you written down okay okay awesome so we're done now with um mammals we're done with humans we're going to go into fish now but it's very simple fish is super you almost need to know nothing so it's going to be really quick okay fishies okay here we got it I made it really nice and easy for you guys okay so got some dead fish cuz why not got some alive fish cuz why not and then we have a fish here and we're looking from the top so you can see the eyes and we're looking from the top important so what's unique about fish fish don't have lungs right that's very important that's what distinguishes mammals mammals have lungs right so fish have something else called gills and it's really cool because it works pretty interestingly so we know how does a fish breathe so important to understand a fish still uses oxygen it's just they extract the oxygen from the water where humans extract the oxygen from the air with our lungs um fishies will extract it from the water so look here what happens so the water is flowing into the fish's mouth okay and then it's going to go into their into their mouth and it's going to go and flow out through the gills now the gills what it basically is is a bunch of capillaries so remember if we if we think about the humans alvioli um right it it was surrounded by a lot of these capillaries right that um that that has a dirty blood right that has dirty blood so you can imagine let's say this fish's gills these capillaries here have a lot of dirty blood and they want to be cleaned they want to remove the the carbon dioxide and they want to gain oxygen so this water that's going to flow in inside the water you have dissolved oxygen and stuff like that so think about it let me show you using this image uh here's the Gill so we're looking here at single Gill when the water flows it has oxygen in it so the Gill is going to have low oxygen because remember this fish it cells did respiration and everything so its blood a lot of its blood will have low oxygen and high carbon dioxide just like humans when we do when we do sell respiration so in this scenario now the gills will have dirty blood so now the water flowing through will drop off fresh oxygen and take away the carbon dioxide it's going to be diffusion right the water is going to have higher oxygen than the fish's gills so it's going to dissolve in and then the fishes gills will have a lot of carbon dioxide that's going to diffuse out into the water okay so that's pretty much how gas exchange happens in fish because they don't have lungs so instead they use these gills that's the basics that you need to understand here's a little picture to help you so water flows through the fish's mouth past the gills and back out the gills are these little structures that has a lot of capillaries and blood just like the just like humans right and then as I said um this happens here okay so make sure you understand this it's really really interesting how it works for fish much different from then humans but the concept is the same we have dirty blood and then instead of water I mean instead of air like in humans that go into the Alvi and clean the blood now the water is going to bring the oxygen okay instead of the air so that's very important I hope you understand this part you don't need to know really the focus is the human lungs and the respiratory system of the mammals so the you just need to know a tad bit about the fish just this is fine just the basic concept important okay the concept of the concentration gradient right oxygen going from where there's a lot to where there's little carbon dioxide from where there's a lot to where there's little okay make sure you understand that that's it for fish okay we're done with fish for today okay what about plants so plants is also really really interesting okay I see now we have reached the hour congrats to you if you have reached you're still here at this point there's only a couple things left and then we got some questions it is a huge chapter to be honest but a lot of interesting things I think okay let's look at the plant so to understand the plant we got to look at its structures right right so look at this Leaf if you cut this Leaf we take a transverse cut so we cut it and we look at um the thickness of the leaf we can see what it's made of so right now we're looking at the thickness of the leaf we're looking at um this is the top of the leaf this is the bottom of the leaf we're looking at what it's made up it's super thin right so let's see what's going on here we can see let's label some stuff you by the way you need to know how to draw this in a two-dimensional way at least for your test and need to be able to um label all the structures and and uh talk about what they do okay so first notice these cells these are called epidermis okay these these cells are called epidermal cells or epidermis okay these cells are near the top okay you can see they're also near the bottom okay the difference is these are upper epidermis cells because they're near the top of the leaf and these are um lower epidermis cell they're near the bottom of the leaf so these epidermis cells what they can do is is they can one of their jobs is to make this little liquidy layer on top of it this waxy layer fatty layer called the waxy cuticle and this waxy cuticle is super important um it is uh because it's very lipid it's very it's made up of lipids is very hydrophobic it is very good at preventing water loss because water doesn't like fat and this is really it's a fatty layer so water when the cell is um um has a lot of water in it this prevents water loss so the plant doesn't get dehydrated as quickly because this fatty layer we know water doesn't like fat so water's not going to DARE go through there right that's very important now look at this um these cells here below the epidermis these cells are more cylindrical more they're bigger and they're closely stacked together just like the epidermis now these are very cool notice they have so many of these um chloroplasts these are chloroplasts by the way remember these are the things where photosynthesis happen so what's unique about these these paliside These are paliside mesop cells cells okay these cells are very tightly stacked and they have a lot of chlorop chloro uh chloroplast and these chloroplast what's important about them is they like to do photosynthesis so these cells are located near the top of the leaf so that they're closer to sunlight because we know sunlight is going to shine on top of the leaf so if these cells were very far down they wouldn't be able to capture light as well so they're located here on purpose near the top of the leaf so they so these chloroplasts can capture the light and do photosynthesis that's very important and you can see there are so many chloroplasts because they are very good they're very good cells for doing photosynthesis because they're near the top of the cell near the top of the leaf so they can capture sunlight very efficiently now below that layer we got these cells that are not so tightly stacked you can see they're not so tightly stacked they're more like distributed randomly and there's a lot of gaps and spaces in between them these are called the me the spongy mesopo like a sponge like a sponge you can compress it there's a lot of spaces in between the sponge right that's why I like to remember that one now the sponge mesophyll is important because this is an area these cells are very good at gas exchange because they can basically just release the gases into these empty spaces whereas these cells can't because there's no space in between them so these are very nice because they can um this Spong a mesop layer because gases can very easily go into these empty spaces and move around and eventually leave the leaf leave the leaf through this little hole here which we call the sto okay the sto so you can see the bottom of the leaf also had this has this epidermis and every now and then the um this epidermis layer has a little hole in it which we call the sto and the two cells um I mean the cells surrounding the hole is called the guard cells okay it's like they're guarding this hole okay very important uh good good good now lastly we got a lot of little pipes it doesn't look like it in this picture but they're basically you know like in humans we have vessels are these veins these are like the vessels and arteries and veins of plants okay we call them we learn about this a lot more another chapter so don't wor too much about it uh there's two there's two kinds of these vessels one is called a xylm and one's called a flm okay and basically what they do is they are like the vessels of the humans they carry nutrients and oxygen and things in and water in um up in down the the plant okay to all the cells um okay great so here is basically the actual um word form of what I just said okay because I said a bunch of stuff but here's the word form for you guys okay so look at this one again the spongy mesophile so remember unlike this Palisade mesophile which has a lot of chloroplast efficient for photosynthesis these have very little because they're too deep they're near the bottom of the leaf so when sunlight comes the sunlight doesn't reach them as well so there's no point in them having a lot of chloroplasts okay but yeah they're better for gas exchange because a lot of SPAC is for the gas TR okay great now here I told you you need to to know how to do a 2d drawing so here's a little example uh it doesn't even have to be as um if you can do this see it's very very simple if you can just draw 2D diagram um of this transverse section of a leaf just like this you'll get a 10 out of 10 trust me so just know how to I Really emphasize it know how to draw it okay because they may they are allowed to ask you how to draw um a transverse section of a leaf okay cool okay last little bit and then questions okay so you know we go back to this gastic change happens here through this stom okay we know water vapor you know water can be gas form or liquid form so water vapor is the gas form of water it can leave through here oxygen can leave through here carbon dioxide can come in and whatnot because remember um plants can do two things they can do cell respiration so they can use oxygen to make ATP like like humans can but they can also do photosynthesis so they can use um use carbon dioxide and make glucose and uh and and all that sort of stuff right they can do both photosynthesis and carbon dioxide and cell respiration okay so you need to know about a word called transpiration so you know sweating sweating in humans is just the loss of water from our skin right now transpiration in plants is basically the loss of water from the leaves and the stems via the stomata so essentially transpiration is just plant sweating okay so you need to know a little bit more about that let me show you so if we have the soil here we have some water in the soil we have the roots here we have the stem and the leaves and all that transpiration is basically this so we know um the official definition is the evaporation of water through the open stata but how does it work let me show you so when we have the water water can be sucked up by the roots right we know that's what the roots of a of a plant can do do now the water will enter this little pipe remember I told you there are two of these pipes one of them is called a xylm and the xylm is going to transport the water water so the xylm is it's going to enter the xylm okay and it's going to move up the xylm it's going to move from the xylm to the leaves or wherever whichever cells need the water now the now the water will evaporate into the empty spaces so let's put that here so remember when we look at the structure of a leaf we just we just looked at it here right um the cells will use it and whatnot and water will be evaporated all these gases will come into the spongy mesil these spaces and the only way they can leave or do gas exchang is by the sto okay so when we look look at transpiration which is again um the the evaporation of water remember not oxygen or carbon dioxide it's water so we can see here step five water will evaporate into these empty spaces of the leaves and then and then transpire out of the stamata so remember our stamata so stamata here's our stamata look at this these are the epidermis cells right if we go back to this picture uh it's different view from this view it's a side view so you can't really see well but if you look from the top of the leaf and with a microscope or something you see a lot of small holes um uh the guard cells which surround the hole and then surrounding the guard cells is all the epidermis cells right so if we look at this here here if we look at the top of the leaf we don't look from the side then we can see this we've got the sto the hole and then surrounding the sto are the two cells called the guard cells they control the opening and closing of the stom so they can make they can close it or they can open it when needed and then surrounding the guard cells everywhere else is the epidermis the epidermal cell so that's how it looks like this is the sto the little hole here so finally the water can transpire so if we zoom in here the water can can leave this little hole this little hole here same as this picture here it can leave this little hole here now when the stoma is open not only can water leave but the other gases can also come in and out we can't control we can't prevent them from okay so that's important know what transpiration is so when the water leaves through the sto right when the water leaves through a stom that will cause more water to be sucked up because as soon as something leaves that makes space for another water to come in so it's a continuous sort of cycle that allows water to be brought up okay now you need to know three things what can affect transpiration so I just told you transpiration is when is the evaporation of the water through the stata okay this water vapor through the stata the sweating of the plant so what can affect it there are three things that can affect and you should know it um firstly um daylight or night during daylight the stomato are open where at night they are closed so during the day they can sweat why does this make sense because during the day there's light light stimulates photosynthesis photosynthesis is going to cause all these gases to be made water to be made so water it's going to so the at the same time this the the leaf will need to lose some water by transpiration so that's why it can open now once it's open what can increase and decrease transpiration so once this once it's open things that can increase transpiration will include heat high temperature can increase transpiration uh low humidity can increase transpiration and high wind can increase transpiration low temperature high humidity and no wind will decrease it okay so we're going to see how now so here we have our stomata with the guard cells okay and then the epidermal cell surrounding it so how does temperature affect it so think about it inside the stomata inside the leaves a lot of water high temperature causes increase kinetic energy increase movement um increase evaporation so so the so the water one will want to evaporate and leave this leave the the leaf through the stom okay so high temperature causes increased in increased um as you can see here high temperature causes increased evaporation transpiration I mean low temperature does the exact opposite okay what about this so low um low humidity meaning remember humidity is the presence of water vapor in the air right when it's very wet the air is wet so let's say the area around the leaf is very dry so the humidity is very low this will increase transpiration because now there's a gradient remember gradients concentration gradients exist everywhere so let's say there's a lot of water here in the stoma that wants to leave and there's nothing on the outside it's very dry this will this will stimulate transpiration because now there's a gradient a high gradient and nothing on the outside so it'll easily want to leave high humidity on the other hand will do the opposite think about it if we have a lot of water vapor it's very humid now there's a high concentration the outside and a low concentration on the inside so the water vapor will not want to leave okay it will not want to transpire so transpiration will be reduced so that makes sense so high humidity reduces transpiration low humidity increases transpiration okay what about wind so imagine there's wind so imagine there's this Leaf now with the sto and there's a lot of wind and the wind is just wiping it's blowing away all of the all the water vapor around it what's that going to do the more wind there is the more we're blowing away all of these um water water vapor droplets so what are we doing we're reducing the concentration on the outside so we're giving it so we're allowing the water to be able to leave because we reducing the conc conentration on the outside so the inside concentration is higher so now there's a concentration gradient so the water would want to leave to the outside right that makes sense so that's why wind is actually good at increasing transpiration if there's no wind then guess what then we'll have all of this High concentration all this humidity that is reducing the concentration gradient so that the water does not want to leave okay so that's this little image here so first you need sunlight to open the stata and um if it's um in the darkness if in the darkness none of this will even affect anything because the Stato has closed so these things only impact transpiration if the stamata is open so during daylight okay that's very important but don't worry too much we're going to talk a lot more about PL stuff in another chapter this is just the level of stuff they wanted you to know in this video okay so no transpiration gasic how gas exchange Works in Plants through the STA know the structure know how to draw it know what transpiration is basically sweating in Plants know how it works that these water exit through the stata along with all the other gases um and know the things that affect it know the things that increase it know the things that decrease it they love this for multiple choice or even long answer questions so here is a little table where I summarize it because I talked a lot these are the factors This Is How They affect transporation and this is this is and this is the mechanism of how they do it let's do some questions guys we're at the question phase so if you're still here you're an absolute Legend means you're absolutely dedicated man so let's do this let's do the questions which are the following features of Alvi adapt adapt them to do gas exchange a single layer of cells yes because that decreases the fusion distance a film of moisture yes I told you moisture increases gas exchange it helps and the dense network of capillaries yes the Alvi have all of these vessels all these capillaries to pick up um to pick up the gases and and and deliver them to the Alvi so all three of these are useful so the answer is going to be D what is the purpose of pulmonary surfactant promotes capillary growth nope decreases surface tension remember that's very important surfactant what's it made by it's made by the type two pneumocytes okay so they decrease surface tension C adheres alvioli and capillaries no stretches the inside surface of the alveoli no okay so very important this one comes up a lot answer is B so which conditions are correct for inspiration so think about inhaling okay try it by yourself and I'll tell you what the answer is okay so the answer is a because your external inter Coastal muscles remember when they contract your ribs are raised your rib will get raised right your ribs are raised remember that little picture when your rib is raged you decrease what you increase the volume so you decrease the pressure okay and that allows air from the outside environment to come into your lungs so the answer is a so why not b okay internal inter coal muscles is not let me think about this one when it contracts oh yeah this one the internal intercal muscle is not used for inspiration right when this one contracts you cause expiration you you you depress the ribs forcing um the pressure in the thorax to increase and therefore forcing the air out of the lungs so this one isn't used um in when it contracts it doesn't do inspiration it does um expiration okay diaphragm the diaphragm when it contracts it will become flat and that will increase the volume of the lung which will decrease the pressure so not increase the pressure okay the abdominal muscles you can think about these yourself um when you are um when you've just ran and done a lot of exercise um when you're exhaling your abdomen contracts right and when it contracts it will increase the pressure in your lungs because it's going to it's going to press your um it's going to make your lungs smaller right so but don't worry about the abdomen one for this syllabus they really only care about the interal and diaphragm H you will get this question right even if it was like this because You' know what's the right answer without even looking at the option D okay during expiration how does air pressure in the lungs compare with the atmosphere so when you expire that means you're compressing the lungs making them have higher pressure than the outside environment so that the air can Will flow from your lungs to the outside world right so the answer is going to be a okay last one here last multiple choice one here what happens to the external and internal interal muscles when um and the diaphragm and Contracting so all three muscles try it by yourself let me show you so the answer is going to be D okay because when you inhale your external inter coal muscle contract raising your ribs R increasing the volume reducing the pressure so that air can come in your internal Coastal muscles will need to relax because normally when your internal inter Coastal muscles contract that will cause exhaling and your diaphragm when it contracts it will become flat um bringing the lungs down making them bigger causing air to flow into your lungs right so the answer is going to be D see they love these they love these questions on the uh ventilation so obviously these questions I showed you is just some of the questions that you should know about I didn't have any questions on plant or fish but um uh make sure you still find questions for those okay so don't just stop here and here's a big question for you guys on ventilation this is a past paper question I just wanted to show it to you guys so you can see how the mar scheme looks like so to explain the mechanism you can read through these every single time there's a semicolon that means one point so you can see from this question there are one two three four five six seven eight eight 9 10 11 12 possible points you only need seven and you can get full marks okay so a lot of the IB questions work like this there's actually a lot of things you can say um and um a lot of possible things you can say you only need to say the amount needed for the points okay okay so I hope I hope this video was useful it was really a lot but look at what we covered the whole chapter gas exchange single cell organisms mamalian lungs fish plants questions and answers so that was it for this video I really hope it was useful and I'll see you in the next one