so throughout this video you're going to be hearing um you know the sounds of like like a like a loud sound at the background that's because they are cutting down the trees outside uh the my house so it's gonna be a little bit annoying so I hope you can you know uh Soldier poo that distraction all right I'm sorry about that so in the previous video we were talking about how complex multicellular organisms will need a transport system to minimize the diffusion distance to ensure that these cells inside the body will be able to receive substances such as oxygen as I'm representing on the left and the transport system of the multicellular organisms consist of three components where it's the heart blood vessels and blood but what I've drawn on the left is just a kind of simplified representation okay so how does this actually how does the transport system look like in the uh memo the first thing we are going to do is we are actually going to draw out the pump okay and this is the pump and what's the name of the pump again the name of the pump is referred to as be hot okay and what's the function of the heart the function of the heart is just to generate pressure so it's able to push the blood to the entire body okay whatever it needs to push it to now remember one of the functions of blood is to carry oxygen blood does not just carry oxygen it carries a lot of other substances but let's just focus on one function of the blood okay the blood needs to carry oxygen and you know for a fact that the blood is like liquid and it's red in color why is it red in color we will talk about it later but the point I'm just trying to make is blood takes on the liquid form okay in our body and for the most part it needs to carry oxygen to the cells so in this case over here because the blood is a liquid it needs to be contained inside a vessel and the name of the vessel and the vessels are referred to as something called blood vessels so as you can see here I'm just throwing out the blood vessel and what is happening is just gonna blow it out okay now in reality the blood vessels there's not just one blood vessel there are many different types of blood vessels by the way but I'm just giving a simplified version of it so what the heart will basically do is the heart will pump the blood as I'm just highlighting it in pink and the blood is now as you can see it is moving okay as the heart pumps it the blood moves and when the blood moves all the way towards let's say an organ or a cell okay it moves to the cell let's just basically say a cell in the body like a neuron notice that the blood for the blood to give oxygen to the neuron the blood cannot just leak out okay this cannot happen this is wrong what is supposed to happen is the blood remains inside the blood vessels but the oxygen inside the blood vessels will diffuse into the cell into the neuron for example and when the neuron actually uses up the oxygen it produces carbon dioxide through a process known as respiration the neuron cannot retain the carbon dioxide because too much carbon dioxide is dangerous for the cells so the cells will give back the waste product to the blood vessel so what is supposed to happen the blood is now going to be I'm going to highlight the blood in a different form where I'm going to color it as a blue color to show you that the blood has a lack of oxygen and the blood needs to be oxygenated again so what does the body do the body basically brings the blood back to the heart but it goes over to the other side we will talk about the heart having two sides in a different video but the point is as the heart keeps beating the blood just keeps moving as it keeps moving it will then enter the heart and as it enters the heart it fills up the heart and the heart just keeps moving and it pushes the blood out of the heart now when it pushes the blood out of the heart it has to push it to another organ all right which organ will actually make the blood oxygenated again okay because as you can see here the blood which I've represented in blue is deoxygenated that means they are not full of oxygen okay they don't have oxygen and the blood needs to be oxygenated right so in this case over here it will then just basically go to something referred to as the organ called the lungs more specifically it will go to a tissue known as the alveolus okay but we will talk about alveolus in the later chapter but what exactly happens in the alveolus so in the lung alveolus again the blood cannot just leak out the blood has to remain contained inside the blood vessel but as you breathe your lung alveolus is now full of oxygen and the oxygen will diffuse into the blood and the carbon dioxide that was earlier inside the blood will diffuse into the lung alveolus and this process will actually make the blood oxygenated again now once the blood has become oxygenated what do you think needs to happen based on this diagram as you can see this here what needs to happen to this blood vessel so the blood vessel so where does this Blood go right now correct it will have to return to the heart it fills up the heart and then it gets pushed out again to other parts of the body instead of just putting neuron I will just basically call this the rest of the body and alveoli or gas exchange surfaces right so it goes to every part of the body like the brain the livers the intestines and all uh the purpose of that is to just give oxygen to the body cells pink color is just represented as oxygenated blood and of course the blue color over here I'm going to represent it as deoxygenated blood as we can see so to describe the mammalian circulatory system the mammalian circulatory system is referred to as something called sa closed double circulatory system now what does it mean as a closed double circulatory system the first important thing to understand is why is it referred to as closed the reason why it is closed is because the blood always remains inside the blood vessels it does not leak out if that happens that's called a hemorrhage or an internal bleeding and that's not supposed to happen Okay that's not good so and then comes the next spot the concept of it being double now why is it called double circulatory system is a bit of an interesting one because the blood passes through the heart twice in one complete circulation so what do I mean by that as you can just basically trace the movement of blood it passes through the heart once goes to the rest of the body comes back to the heart twice and then finishes up the loop I'm gonna do that again for you to see it maybe I'll put it in a different color okay maybe in green so let's say this is the beginning B and just by presenting that as the beginning goes to the heart once out rest of the body twice and then ends over here as one complete circulation that is why it's called the double circulatory system now the circulatory system also consists of two very important movements the first important movement which I've represented in a green color over here as you can see like this this is referred to as something called as the pulmonary circulation so the pulmonary circulation which comes from the word palmol Palm Palma which is Latin for lungs which means to say it has something to do with the lungs all right so pulmonary circulation just basically means it is the movement of the blood from the heart to alveolus back to the heart that is the pulmonary circulation the next one is basically referred to as the one I'm going to be representing it in a purple color goes from here here and then comes back to the heart and that is referred to as something called systemic circulation the systemic circulation is what happens when from the heart it goes to the rest of the body and then it goes back to the heart so the purpose of pulmonary circulation is basically to make the blood oxygenated from deoxygenated it becomes oxygenated the purpose of systemic circulation is to provide oxygen and other substances to the body cells that's basically it