 So what I will do is I will start teaching Laplace law, see Laplace law says if anybody knows what is Laplace law it says pressure is equal to tension twice of tension divided by radius isn't it or we can look at it into tension is equal to pressure into radius. So depending on how we look whether we are looking at the pressure or whether we are looking at the tension that we have to be very clear the equation is in inter relationship. So while we look in respiratory system we are looking into the pressure developed into the alveoli but when we are talking about the cardiovascular system especially the heart and when we are talking about the capillaries then we are talking about the tension developed. In maturation also we are talking about the pressure developed. So respiratory system and maturation we have bothered about the pressure developed and when we are talking about cardiovascular system we have bothered about the tension in the ball. So when we are talking about heart tension in the wall of the ventricle and when we are talking about the vessels tension in the wall of the capillaries or other vessels as in case of aneurysms. So just I will tell you for example in respiratory systems for that I've already made one video Laplace law in respiratory system that you can see after the discussion gets over that in respiratory system we say pressure is equal to twice of tension divided by radius. Why we say so? Because alveoli actually it is in contact with the air and if there is a thin lining of fluid and whenever there is like even contact with air and thin lining of the fluid there develops a surface tension. So here tension is developing because of this difference air and water difference is there. So that causes the tension actually pulls the balls of the alveoli. So if there is a tension tends to pull the ball of the alveoli together it is just like the layer of that on milk what top layer forms whenever it is in contact with this air. So that top layer forms that is because of the pull of the molecules due to the surface tension. So similarly alveoli there is pull on the ball of the alveoli. Now if there is pull on the ball of the alveoli so the diameter of the alveoli is like trying to reduce it is not reducing because everything is being held by the connected tissue okay but it is trying to reduce so what happens that inside the pressure is going to increase okay. So try to understand this here tension is causing development of the pressure inside the alveoli. So when the pressure increases now how much pressure is going to increase depends on the size of the alveoli that's where we are bringing in the radius okay. Now suppose there is a large alveoli and there is a small alveoli now with this formula pressure is equal to twice of tension into radius can anybody tell me pressure is equal to twice tension into radius. Where tension is the same in which of the alveoli pressure will be more a smaller alveoli or larger alveoli? Smaller alveoli and who's radius is less? Who's radius is less? It is the smaller alveoli whose radius is less isn't it? It is the smaller alveoli whose radius is less. So pressure will develop more in the smaller alveoli so suppose there are there are two alveoli side by side and obviously all the alveoli are connected. So suppose there are two alveoli side by side, then tension is almost same in both. But just because of the difference in the radius smaller alveoli is going to develop more pressure and if you know where does the air move, where does the water move, it always moves from high pressure to low pressure. So by that logic what will happen? Air will move from the smaller alveoli because of the higher pressure into the larger alveoli, understanding. So all the smaller alveoli will M2 into larger alveoli because if you see everything is relative, some alveoli will be the smallest, some alveoli little large and then the other will be little larger. So anything which is a smaller, they will slowly slowly empty into the larger alveoli. So what will happen? The lungs will become a big alveolus. They will not have a small small alveoli and which will be very damaging because ultimately the surface area for diffusion of the gases is going to decrease. That is the reason that lungs is having so many small small alveoli that increases the surface area, understanding. So based on the Laplace law, what we are seeing here is surface tension is developing the pressure. See how I am looking at the equation and taking this tension is equal to P into R equation because of the surface tension pressure is developing and because of the surface tension pressure is developing and sorry pressure is equal to 2T by R equation we are seeing, pressure is equal to 2T by R ok. So because of the surface tension pressure is developing and radius is less it is in denominator so pressure will be more ok. Hopefully I have made it clear that how this all smaller alveoli if we see by Laplace law all small alveoli are going to enter into large alveoli. Am I clear? Type S. If I am clear, give me a thumbs up or type S ok. So now this is counteracted by surfactant in our body because if surfactant was not there then only all these alveoli are going to empty into the this larger alveoli. So what surfactant does? We are saying that pressure is more right. So what surfactant does is it decreases more tension, it decreases more tension in the smaller radius. It is like everywhere 8 8 surfactant are there right. So in a smaller radius this 8 surfactant molecules will be more effective in reducing the tension right. So radius is less let me tell radius is less in smaller alveoli and hence tension is also less in a smaller alveoli less in a smaller alveoli due to due to what? Due to surfactant. So same surfactant is able to act better in the smaller alveoli hence the pressure development is same in smaller and larger alveoli. So that is how we look into Laplace law in respiratory system. So please understand tension is developing the pressure. This is the key line. Tension is developing the pressure in the alveoli. Now let us move on to another aspect that is the heart. Very very very important heart it is extremely important because there is concentric hypertrophy and eccentric hypertrophy and how it affects the functioning of the heart, how it increases the tension that is very important because that increases the myocardial oxygen demand and cardiac failure how it helps. So now in heart how we see is that tension developed in the wall of the heart. So we are looking at opposite tension developed in the wall of the heart is equal to pressure and radius. Why we look like this because in heart the muscles contract right when the muscles contract there is a huge development of pressure inside the ventricles. So I told you whenever there is development on the pressure it is like it is pushing the walls. Pressure is going anywhere any container you see what is there molecules are there and what they do they like they like hit on the wall. So that is creating a wall tension similarly when you inflate a balloon what happens if the when the balloon inflates it creates a stretch if you touch it you will feel the tension on the wall of the balloon isn't it. So here pressure is creating the tension on the wall of the ventricle more the pressure more the tension developed on the wall of the ventricle and it is very important concept which is important for oxygen demand oxygen demand okay in the ventricles in the heart. So I will give you an example whenever there is hypertension what happens to overcome the hypertension which is the afterload now the ventricle has to develop more pressure it has to contact more because of which the pressure inside increases then only the blood will overflow so pressure should be more so that the blood overcomes that and moves out. So but who is feeling the weight of this pressure it is the wall of the ventricles who are feeling the weight of the pressure understanding so that is known as wall tension. Now how much tension can it bear how much tension can it bear there is a limit isn't it. So now here comes the concept of thickness so I will give you one extended formula where tension is equal to P R divided by H divided by thickness divided by thickness okay so more the thickness less the tension is developed okay so in simple words in understanding may we see that when the pressure is high tension developed the out of our force will be more so if the wall is thick it will be able to bear that pressure so they they are like the counteracting forces which are acting isn't it and that is what is happening in hypertension what happens that is adaptive concentric hypertrophy is happening so whole this whole muscle hypertrophies there is increase in the thickening of the wall of the ventricle and that helps in bearing the stress which is happening on the wall okay understanding now that is one concept so is that good in hypertension of the concentric hypertrophy happens tension is relieved fine everything is fine but that doesn't happen because after a certain limit heart starts dilating also right so that is that is increasing radius happens and that is because adaptation there is always a limit whenever we talk about physiology there is always a limit to which the body can work to which the adaptation can occur afterwards that the limit is crossed okay and then the maladaptation starts so after that what happens that there is a increase in the radius also because there is some fibrosis going on along with the hypertrophy some fibrosis interstitial fibrosis that you will study in pathology that also happens and there is increase in the radius and then radius increases what happens tension also increases okay so let us quickly and two lines I will tell whenever in respiratory system what we saw tension is developing the pressure and because of this there is movement of the air when we are looking in cardiovascular system how we are looking for the movement of the blood we need pressure development okay you see how I am changing the language in respiratory system tension causes development of the pressure and this will lead to movement of the air if not stopped thankfully surfactant is there which prevents that in heart for the movement of the blood more pressure is developed but this creates tension if this creates wall tension understood have you got it this language is very important that what you are looking looking at in cardiovascular system we talk about wall stress this is wall stress more the wall stress more is the oxygen demand and then high chances of myocardial infarction in concentric hypertrophy or in eccentric hypertrophy whenever there is there is increase in oxygen demand and if it is not met it can lead to myocardial infarction am I clear in cardiovascular in heart if is it clear then please type yes okay harsh was there I think harsh is there or not is coming and going fine no issue so that was about heart now let's come to blood vessels blood vessels what is there same as I told you that in cardiovascular system we have to talk about wall tension so whenever blood is flowing by it is flowing it is due to pressure all the blood vessels have some pressure inside it right so this pressure so suppose this is the vessel right this is the vessel so inside there is pressure what it will do it will it will create a push on the walls right what a wall is very thin what a wall is very thin will it be able to bear this will it be able to bear this yes or no it will break right because it's a push force it will just damage the vessel right it will just damage the vessel and the blood will flow out right now do you know what is the thickness of capillary wall capillary wall it is single cell thick capillary single cell thick then how is it able to bear this pressure how is it able to bear this pressure it should break but that doesn't happen why because capillary diameter is also very less it is its radius is also very less so again you see the equation tension is equal to pr yes very good so the tension is equal to pr divided by thickness right so if thickness is less but its radius is also less so very less tension develops on the walls so that isn't done on the contrary if you see it in the larger vessels in the larger vessels what happens they are having big radius and that is the reason that larger vessels should be thick also so that is the reason that thickness prevents it otherwise if they are of large radius and the pressure you know the pressure is also more then it is going to break the walls of the large arteries so that is why the walls of the large arteries need to be thick so that the tension developed on the walls is less okay so now you understand that even though capillaries are lesser in sorry thickness is less still they are able to withstand the pressure inside the capillaries okay so just because this concept of how we are looking into the equation in respiratory system development of the pressure due to tension in cardiovascular system development of the tension due to pressure understanding okay one example of this is an aneurysm actually in aneurysm what happens so there is weakening of the wall okay it's like wall breaks right so wherever there is weakening because of the pressure what will happen will it be able to be a distress no it will not be able to be a distress and due to this it expands it's like it balloons up in a particular area right so what is happening radius has increased so thickness has decreased and radius has increased so it becomes like a positive feedback thickness has increased due to thickness has decreased due to damage because of that radius has increased it has ballooned up and now the tension developed for the same pressure will be more see see the equation pr divided by thickness thickness decrease tension more radius increase tension more okay so what will happen more tension developed so it is going to damage the wall further if it is damages the wall further then radius is going to increase further so it is kind of a positive feedback right it cannot be stopped and ultimately the vessel ruptures in aneurysm so that is the physiology based on the Laplace law behind the aneurysm okay then coming to maturation where it is you will see the Laplace law again in maturation we have to see in terms of how it is happening in respiration okay because development of the pressure leads to maturation pressure is detected as stretch in maturation for maturation also I have made one video so two Laplace law video already exist on the channel that is Laplace law in respiratory system and Laplace law in maturation both exist so you can have a look in that in cardiovascular system I still need to make and I think after this I can easily make the video on cardiovascular system there I will also talk about in what happens in concentric hypertrophy what happens in eccentric hypertrophy so some components of applied also I will put up so what I was saying in maturation what happens as filling up occurs it is like a balloon right if you fill a balloon with water what will happen it will stretch right so it is a tension which is being developed on the walls okay now so we are looking again pressure is equal to twice of tension divided by radius so that tension starts developing so pressure starts increasing in the urinary bladder okay filling tension increases it's like it becomes taut like this so because of this tautness pressure increases but it is a smooth muscle a smooth muscle has a characteristic of stress relaxation so whenever there is a feeling it relaxes a little bit so it is like that radius is going to increase so even tension is increasing radius is also increasing and hence pressure is not changing but everything is up to a certain limit only right so pressure is not going to change up to a certain limit and that is why that um um this maturation is delayed only starts um after a certain level okay so that was the main applicant respiratory system more authorotical that you will read about it because surfactant is there so it doesn't allow laplace law to operate there but we study like if surfactant was not audio as per a system it exists in this um this um aneurysm as let me know and once again hirsh thank you and i i'm so delighted that my videos are helping students and that was the um concept here that i want to give quality videos to the students and and concept based videos so that they see and they apply the physiology to their learning and not just about writing notes and just getting marks okay thank you thank you hirsh i just wanted to thank you once and any questions are there i will take now have you understood hi simran vasudev have you understood laplace law and i hope that this switching great i like it this topic was selected by you only i think no okay then bye thanks for joining