Circulatory and Immune System Breakdown

Hello, BISC 132. This is the beginning of Recorded Lecture 5.1, starting off on the circulatory system. So, we've actually talked about circulatory systems before in previous chapters. We compared and contrasted open circulatory systems. circulatory systems and closed circulatory systems in various groups of invertebrates and vertebrates. So there's a bit of this in the chapter that I'm skipping because we've done this already. For the rest of this chapter, what we're going to be talking about is closed circulatory systems. circulatory systems. So we've said all we need to say about open in previous chapters. So let's start by talking about blood. So there are three main components to blood. Platelets, small things here, blood cells coming in all sorts of different types and sizes, and you can't see it here, but it's everything else that they're suspended in plasma. So blood, if we're talking about whole blood, that refers to plasma. plus blood cells, plus platelets. All three of these things together make up blood. So let's start by talking about plasma. Plasma is defined in the key terms as the liquid component of blood that is left after the cells are removed. So this is the liquid component. So unsurprisingly, it's mostly water. But there are other things in plasma as well. You should think of this as really as small stuff. So plasma also contains nutrients. You know, stuff like glucose that your body is circulating around to get from one place to another. Wastes, stuff like urea that we'll talk about in a later chapter that circulates in the bloodstream and it's part of the plasma. Hormones, you know, signaling molecules that your body is using to send messages from place to place. Ions, stuff like the carbonate-bicarbonate buffer that is used to buffer pH in the blood. Again, maybe you're seeing a pattern here. These are all, you know. you know, fairly small molecules. We're getting a little bit bigger here. Proteins, including fat carriers and many other proteins. In fact, some hormones are proteins. But again, these are definitely much smaller than a cell, part of the plasma. Proteins are part of the plasma. And then clotting factors. This is another protein we'll talk about a little bit when we talk about clotting. And this brings us to another term that you'll see brought up when talking about blood and blood products. And that's the term serum. Serum is basically plasma that doesn't clot. So the key terms define serum as plasma without the coagulation factor. So when these things have been removed or destroyed somehow, we call this serum instead of plasma. So, okay, that's straightforward enough. Let's talk about the cells next. So there are actually two different types of cells, red blood cells or erythrocytes and white blood cells. And you can see many different types here. and this is definitely not even naming all of them, but all these other ones called leukocytes. So red blood cells, abbreviated as RBC, also known as erythrocytes. Erythrocytes have kind of a weird shape. I always think of this horrible butterscotch candy, the Werther's Original, as sort of a shape of an erythrocyte. The other very strange thing about them is they don't have a nucleus. So don't memorize this, but this. this is showing that during their development, of course, early on, they have a nucleus, but as they differentiate at a certain stage, they actually eject their nucleus and, you know, continue on as a cell without a brain, essentially, a cell without a nucleus. And we had discussed this in the last chapter, that their job is to carry hemoglobin, which carries oxygen. So I guess you don't need a nucleus to do that if you're just a bag filled with protein that's... carrying oxygen so these erythrocytes disc shaped with no nucleus and they contain hemoglobin which carries o2 that's a good enough summary there so what about all these white blood cells well i'm going to kick the can down the road and not really talk about these at all i'm going to save it for the immune system chapter so white blood cells abbreviated wbc also known as leukocytes involved in the immune system we will get into more of of their function of the different types when we we get to that chapter so that's it for now all right so we've done plasma we've done cells the only thing left is platelets so as you can see here platelets are much smaller than a cell they are not cells they are cell fragments and you could see this even more clearly when you look at how platelets are made so here's the megakaryocyte that is making these and yeah it rips off pieces of its membrane a little bit at a time and that's how platelets are created so cell fragments their job of Along with some of the proteins that are present in plasma, their job is involved in clotting. So if you have a wound or something like that that breaks the wall of a capillary, your plasma, your blood is going to start... leaking out into the surrounding tissue. And that is, uh, that's no good. Um, so if you have a hole in anything, the first thing you want to do is patch that hole so you can prevent leaking. And so, um, platelets along with, um, you know, fibrin. a couple of other proteins that are present in plasma but not serum, are going to form a clot that's going to plug up this hole. So platelets are cell fragments involved in clotting along with proteins. Okay, so that was just talking about blood as far as what it is and what its components are. Let's now talk about circulation, how this blood moves around. Now this is kind of a complicated process, but... But I think by breaking it down step by step, it's not going to be as intimidating as it looks. And so this is a never-ending circuit. And so there really isn't a beginning or an end. But arbitrarily, let's start in the body and the head. So what I'm calling step one, but again, this is all arbitrary. Blood in the body and the head loses its O2, which should make sense. That's the job of blood, or one of the many jobs of blood, is to give the O2 that it has been. storing to these tissues that need it so the o2 is given to surrounding tissues the blood is now what is called deoxygenated it's it's given away its o2 and this deoxygenated blood is drawn the color blue so and in this figure but i mean every every circulation physiology blood flow you know figure that i've seen in any textbook ever seems to to follow this convention that you know here we have the the blood in the body or the blood in the head you know getting rid of its o2 giving it to the surrounding tissues and and now it's blue i i making a fine point of this your blood is always red your uh if you have pale skin sometimes your blood can look blue in in certain places but that has to do with how light is filtered through the layers of your skin your blood is never actually blue it's always red uh but it is a convention that is convenient for these figures that deoxygenated blood is drawn the color blue. So, okay. Now, we can guess what needs to come next. I mean, this deoxygenated blood needs to get oxygen so it can do this whole process again. But there are going to be a few steps before we can do this. So, step number two, blood enters the heart through veins. So, okay, there are going to be a few terms as we go through this process. of blood circulation. A vein is defined in the key terms as a blood vessel that brings blood back to the heart. So if it's traveling toward the heart, it's traveling in a vein. Just know that. So blood enters the heart through veins into the right atrium. So this is the first of four chambers that we are going to bring up, the right atrium here. And again, these are also color-coded. They're blue because they're dealing with deoxygenated blood. Now, you might be looking at this as I, you know, confidently move my mouse around the right atrium and think, this is on the left. What's going on here? Well, another convention in every textbook ever is when you're looking at a heart, you are looking at the heart of a person. Imagine this being a person, you know, like this standing in front of you, you know, facing you. So this is their right side, even though it's on your left. left and this is their left side uh even though it looks to be on your right so anyway sorry if that's confusion confusing but that is just the way it's done you are looking forward at the heart of a person who's looking forward at you so okay this deoxygenated blood is coming in through veins into this atrium so we're actually going to see a couple of atria again there are four chambers in the heart keep this in mind blood enters heart through atria so anytime blood is coming in into the heart the chamber is an atrium chamber atria is just plural okay so again we know what's what's supposed to happen this deoxygenated blood is supposed to go to the lungs so it can get oxygen but before it can do that um we need some power to send it to the lungs so this this low low pressure chamber this atrium where the blood just entered after making its long journey throughout the body it's got to move to a different chamber so so it can be pumped to the lungs. So this deoxygenated blood moves from the right atrium to the right ventricle. Blood is pumped from the right atrium to the right ventricle. And importantly, there is a valve here that makes sure that this movement is one way. We don't want backflow. We definitely don't want this system going in reverse. So there is a valve here that ensures one way movement. By the way, yeah, there are names for this valve and the other valve. There are names for these veins and arteries and stuff. I'm skipping over a lot of details that I don't think are important in an intro course. So yeah, just remember that what I... I have on these slides is what I want you to be familiar with for an exam. So, okay, we are now in the right ventricle, and finally, we're able to go to the lungs. So, blood, reminding you this is still deoxygenated, is pumped through an artery to the lungs. So, an artery is the opposite of a vein. It's defined in the key terms. A blood vessel that takes blood away from the heart. So, veins go to the heart, arteries go away. Deoxygenated blood pumped through an artery to the lungs. lungs and blood exits the heart through ventricles so again we are in the the right ventricle now going toward the lungs you can this will this will bring you a long way towards uh towards you know being able to answer any test question if you remember these two statements blood always enters in an atrium through atria and blood always exits through a ventricle so here on in the right ventricle we can we know where it's going it's exiting the heart because it's a ventricle. So at this point, we're at the lungs. And in the lungs, the blood is going to pick up O2 from the surrounding air. So now we're going to go from deoxygenated to oxygenated. So there we go. At the lungs, blood obtains O2. It is now oxygenated. And again, it's now drawn the color red. It's always red, but oxygenated blood is now drawn the color red. So, okay, we... Logically, we know what's about to happen or what's going to eventually happen. This blood that has O2 is supposed to deliver it to the body. But just like we saw before, in order to make that trip, you've got to go back to the heart again. So this oxygenated blood is going to come into the heart now on the left side. Remember, blood always enters in an atrium. So here comes in from the lungs into this left atrium. Atrium. So oxygenated blood enters the heart from the lungs at the left atrium. And again, we know that if we're going to exit, it's going to have to be through a ventricle. So before this blood can make its exit to the head and the body, it's got to move from the left atrium to the left ventricle. And once again, there's a valve here that makes sure that this movement is one way. So blood is pumped from the left atrium to the left ventricle. Valve ensures one way movement here. and uh again we know what's going to happen this is the a ventricle so it's about to leave the heart it's oxygenated blood so we know it's not going to the lungs it's supposed to go to the the head and the body and that's exactly what happens here blood oxygenated is pumped from the left ventricle to the head and the body and and from there it's going to deliver uh it's o2 and that's right where we started again blood in the body and head losing its o2 and then you know the whole process repeats itself. Another thing that if you keep in mind will help you remember what each of the four chambers does. Again, I said blood enters through atria and exits through ventricles. Also keep this in mind, the right side always deals with deoxygenated blood and the left side of the heart always deals with oxygenated blood. So again, the right side, whether it's the atrium receiving deoxygenated blood or... sending out deoxygenated blood. The right side is always blue, drawn blue. It's always dealing with deoxygenated. And the left side, again, whether it's receiving or sending out, it's always dealing with oxygenated blood. So keeping this in mind will help you a lot as well. Now, there are actually three different circuits that exist in blood circulation. So this is just some terminology here. The pulmonary circuit... is what we call the part of this journey that we talked about from the heart to and from the lungs. So yeah, this is the pulmonary circuit here from the heart to the lungs to get oxygen, then back to the heart again. The systemic circuit is the other one we saw from the heart to and from the body. So there's the systemic circuit going to the body and the head, losing it. It's O2 and then back to the heart again. But I just said there were three circuits and this is only showing two. So what could the third possibly be? The third is called the coronary circuit, which is... easy to forget about but the heart needs blood the heart is a muscle the heart is working very hard and the heart muscle itself needs to be supplied with oxygenated blood the blood in this This chamber, well, first of all, only half the heart gets to have oxygenated blood, but it's not really getting a chance to absorb this O2 as it's flowing through these chambers. So we need to have veins and arteries connected to the heart itself. This is called the coronary circuit. From the heart to and from the heart. Kind of a weird way to say that, but yeah, the heart muscles must have veins and arteries themselves. And I referenced this earlier. earlier there are names for all of these things but we're definitely not not going to worry about this level of detail in an intro course so there's one last topic in this chapter that I think is worth worth discussing before we move to the next chapter and that is comparing and contrasting vertebrate circulatory systems so this This the circulatory system that we've been looking at so far is what we see in mammals and and birds. This four chambered heart, everything we just went through. That's how mammals do it. that's how birds do this it's called double circulation because it is you know basically a figure eight the systemic circuit the pulmonary circuit um those are the two main big circuits so it's called double circulation this is defined in the key terms uh flow of blood in two circuits the pulmonary circuit through the lungs and the systemic circuit through the organs and the body so four-chambered heart double circulation everything we just talked about mammals and birds so how is this different Well, in reptiles, let's move from mammal bird circulation to reptile or most reptiles. See if you can spot the difference. So a lot of this looks very similar. You have a systemic circuit here. You have a pulmonary circuit here to the lungs. If you've got a sharp eye, you might notice the difference is here in the heart. So in the mammalian and bird heart, the. The chambers that hold oxygenated blood and the chambers that hold deoxygenated blood are completely separate from one another. It looks like they're mixing here. It's actually just crossing over. They're completely separated from one another. You don't want blood with oxygen in it and blood that doesn't have oxygen in it to mix with one another because then you'd end up sending red blood cells with no oxygen to the body and head and that's a waste. Or you would send red blood cells that have oxygen. to the lungs which would be a waste so they're completely separated here but in most reptiles they're not there's a septum that incompletely divides this chamber and you have a little bit of mixing it's sort of drawn purple here uh in between oxygenated and deoxygenated blood this is obviously not great uh but it it is the way it is in most reptiles so most reptile have a three-chambered heart. There is a partial septum. This is like the fifth time we've seen the word septum in this course. A septum is just a wall or a barrier or whatever. So there is some mixing of oxygenated and deoxygenated blood. This is very bad, but you know, it is what it is. And this is still a double circuit. This is still double circulation, but you have this mixing. Now let's move from reptile heart. We're kind of going backwards evolutionarily. So things are getting more. primitive and more simple as we go back let's move from reptile to amphibian spot the difference this mixing is even worse without even a partial septum to divide this chamber this is uh a fully you know three chambered heart where there's a lot of mixing of oxygenated and deoxygenated blood and that's really not great as far as efficiency goes so amphibians have a three three chambered heart no septum at all mixing of oxygenated and deoxygenated blood that's bad like I said in the last slide and this is still double circulation though okay moving backwards again from amphibians down to fish whoa this is completely different so there's no mixing oxygenated and deoxygenated blood because fish circulation has just two chambers to the heart one atrium and one ventricle and so uh instead of making a a figure eight of one loop to and from the lungs or the gills in this case and another loop to and from the body in a single loop this blood is pumped from the ventricle to the gills to acquire oxygen to the body to deliver oxygen and then back to the heart again. So fish have a two-chambered heart with a single circuit circulation. So let's review this again. So this is the simplest way to have a heart, and these are the simplest vertebrates with two chambers. It is kind of an upgrade to do this in two loops. It allows you to, you know, pump more effectively if you're making two different circuits here. So this is kind of an upgrade, even though there is some mixing, and obviously, you know, we see a further upgrade in the partial septum of reptiles and then we see sort of the peak performance of the heart uh in the complete separation what we see in mammals and birds so again i thought this was this was interesting uh to explore the differences in circulation among these vertebrates all right that does it for circulatory system now on to the immune system okay this is going to be a big chapter and so uh we can actually do divide the immune system into two basic halves or two parts, the innate immune system and the adaptive immune system. Let's start with the simpler one and we'll get more complicated as we go through. So the simpler of the two is called the innate immune system. So the innate immune system, I'm double underlining this because there are going to be several things that are a part of this and I'll underline those. So just my way of organizing. The innate immune system has limited path. Pathogen specificity. So pathogen is a term I'm going to use a lot in this chapter because a pathogen is a bad thing. Something trying to cause disease. The key terms define this as an agent. That's very vague. Usually a microorganism that causes disease in organisms that it invades. So I'm being vague like this because this could be a bacterium. This could be a eukaryotic parasite. This could be. be a virus. So all of those things, some of those are alive, some of those are not alive, virus is not alive. All those things fall under the heading of pathogen. If it's trying to harm you, it's a pathogen. So again, using this word a lot in the chapter. So the innate immune system is not very limited or specific about the pathogens that it deals with. It fights against pathogens, certainly, but not in a very specific way. The innate immune system is, however, very immediate uh the the other immune system is going to take a little bit longer but this is much faster but not as specific so the first part of this i'm going to talk about is actually the largest organ of the human body it's a fun trivia question here and he guesses the largest organ is the skin uh so google image search supplying supplying some skin here if you didn't know what this looked like uh looking more closely at a patch of skin here Oh, hey, I was talking about receptors last time I used this slide, but there's a lot going on here. The part that has to do with the immune system, though, is the outer layer, this thick layer of epithelial tissue, as well as the sweat created by sweat glands and excreted here. It provides a barrier to entry. So the skin is just a physical barrier that prevents stuff from getting in. Right. If we want to zoom in even further here, oh, don't sweat all the detail here, but there's a lot of stuff going on other than just epithelial cells. So you have oils here and you have sweat, which is at a low pH. This creates an environment that's actually not a great place to live, even though this is a lot of available real estate. It's pretty inhospitable because of the oil and the sweat and the locals. So I reference... these way earlier in the quarter in our chapter on prokaryotes but we have a lot of normal flora normal bacteria and fungi that make their home in this environment and so the normal flora with the sweat and the the oils make this just a place that's not a great place to live so the skin is an inhospitable environment for pathogens that's a good way to put it low ph and the normal flora crowd out pathogens just make it difficult for them to get a foothold here. Now as great as the skin is, this cannot cover our entire body. We need entrances and we need exits. So to cover those parts of the body, we have what are called mucosal epithelial surfaces. So these are epithelial cells that secrete mucus. This is the nasal epithelium we're looking at here, but most mucosal epithelium. are the same way you got these cells and then you have a layer of mucus that they have secreted as like an additional layer of protection for these cells so mucosal epithelial surfaces are entrances and exits of the body cells secrete mucus and enzymes the mucus just you know traps and destroys things the enzymes a lot of times are specific well not too specific but will actually destroy pathogens the the one that comes to mind your eyes so that's another entrance to the body technically make an enzyme called lysozyme that targets peptidoglycan remember that compound it's part of the bacterial cell wall so they're going to trap and destroy pathogens and again this is part of the innate immune system this is all very generic mucus is going to trap just anything that gets stuck in it and you know those enzymes have to have a bit of specificity but bacterial cell wall that's definitely not a specific species of bacteria. So this is the to whom it may concern part of the immune system. So what about the cells? What about leukocytes? So there are some leukocytes that are involved in the innate immune system in addition to these epithelial cells. One way in which leukocytes involve themselves in innate immunity has to do with pattern recognition receptors and pattern recognition receptors. pathogen-associated molecular patterns. Okay, so the immune system as a whole becomes a lot of alphabet soup after a while, so I'm going to try to go through this as simply as I can. So here's the leukocyte. It's a macrophage. It has a pattern recognition receptor, or PRR. Let's break this down. Pattern recognition receptor. So it's a receptor. It recognizes something. It binds to something. Pattern recognition means it binds to some specific pattern. So the pattern recognition receptors are on the leukocytes. The patterns that they are capable of binding are on the pathogens. So here's a bacterium, for example. The PAMP is a pathogen-associated molecular pattern. So again, it's a pattern-associated... on a molecular level with a pathogen. A PAMP is basically a bad thing. A thing that you associate with a pathogen, it's never a good thing. More alphabet soup. Lipopolysaccharide, LPS, is one of those PAMPs. It's bad stuff. It's found on gram-negative bacteria. We do not have this in our bodies. So if you encounter lipopolysaccharide, that's bad. That's always going to be associated with a pathogen, with something bad. So let me write down what I have so far. So pattern recognition receptors, or PRRs, present on some leukocytes, for example, macrophages. We're not going to learn the names of all the leukocytes, but this is an important one, the macrophage. So the PRR on something like a macrophage binds to a pathogen-associated molecular pattern, or PAMP. on, again, common pathogens. So there's some specificity here, but this is all still kind of generic for common pathogens. So what happens when this recognition happens? Well, again, that tells this macrophage, hey, something bad is happening here. And so it's going to send out a bunch of signaling molecules called cytokines, more alphabet soup, interleukin-8, interleukin-1, tumor necrosis factor alpha. My point is, these are cytokines. So this binding leads to the release of cytokines and eventual phagocytosis of the pathogen. So cytokines are defined in the key terms. These are signaling molecules used by the immune system. Oh, I'm sorry, I'm reading the wrong thing. Chemical messenger that regulates cell differentiation, proliferation, gene expression, and cell trafficking to affect immune responses. It's kind of wordy. It's a... It's a message. It's a signaling. molecule that tells the immune system to do something. So anyway, PRR binds to PAMP, cytokines are released, phagocytosis. So this is how your immune system deals with viruses and bacteria. These cells will eat the pathogens. They engulf the pathogen and destroy it from the inside, sending it to the lysosome, if you remember that organelle back from BISC-130. So that is how... That is how these leukocytes deal with a specific pathogen. And again, there's some specificity here because it's only something that happens to have this common danger pattern on it. But it's also very generic. Any gram-negative bacterium, any species or whatever, anything that has LPS, for example, is going to be destroyed through this process. So that's why this is the innate immune system. It's pretty generic for what you're going to fight against. So another way in which leukocytes can be involved here is at the site of injury. So phagocytic leukocytes, which they're leukocytes that do phagocytosis, that includes neutrophils and the macrophages. So macrophages are kind of smart. They recognize stuff, but they can also eat things. They can also fight. So phagocytic leukocytes like neutrophils and macrophages can be brought to the site of injury. injury by cytokines. So here's a wound site. Again, you've been stabbed with something. Obviously, there's, you know, some blood leaking out here and all the stuff we talked in the last chapter about clotting. But also you get some pathogens that, you know, make it past, you know, this primary barrier, this primary line of defense. We got, we got to bring in some, some cells to try to deal with this. So the damaged cells will actually send out cytokines that recruited them. that bring these leukocytes to the site of injury, and they're going to do phagocytosis on the bacteria or the viruses that have managed to get past the skin. So this is called inflammation when this happens, when you have the site of an injury. Also in the key terms, localized redness, swelling, heat, and pain that results from the movement of leukocytes and fluid through opened capillaries to a site of infection. So a lot of the symptoms... of just like, ah, man, it's so swollen and it's hard to move if you have an injury somewhere. A lot of that is due to your immune system. You're bringing stuff into that site to try to deal with these pathogens and just bringing a bunch of stuff in is going to lead to swelling and heat and redness there. Okay, so that is not, definitely not the end of the immune system, but, and not even the end to the innate immune system. system but this is a good cutoff point this is typically where i've run out of time in lecture 5-1 this is the end of lecture 5-1 more immune system stuff in the next lecture

So there's a bit of this in the chapter that I'm skipping because we've done this already. For the rest of this chapter, what we're going to be talking about is closed circulatory systems. circulatory systems.

So we've said all we need to say about open in previous chapters. So let's start by talking about blood. So there are three main components to blood. Platelets, small things here, blood cells coming in all sorts of different types and sizes, and you can't see it here, but it's everything else that they're suspended in plasma. So blood, if we're talking about whole blood, that refers to plasma.

plus blood cells, plus platelets. All three of these things together make up blood. So let's start by talking about plasma.

Plasma is defined in the key terms as the liquid component of blood that is left after the cells are removed. So this is the liquid component. So unsurprisingly, it's mostly water. But there are other things in plasma as well.

You should think of this as really as small stuff. So plasma also contains nutrients. You know, stuff like glucose that your body is circulating around to get from one place to another. Wastes, stuff like urea that we'll talk about in a later chapter that circulates in the bloodstream and it's part of the plasma. Hormones, you know, signaling molecules that your body is using to send messages from place to place.

Ions, stuff like the carbonate-bicarbonate buffer that is used to buffer pH in the blood. Again, maybe you're seeing a pattern here. These are all, you know. you know, fairly small molecules.

We're getting a little bit bigger here. Proteins, including fat carriers and many other proteins. In fact, some hormones are proteins.

But again, these are definitely much smaller than a cell, part of the plasma. Proteins are part of the plasma. And then clotting factors. This is another protein we'll talk about a little bit when we talk about clotting.

And this brings us to another term that you'll see brought up when talking about blood and blood products. And that's the term serum. Serum is basically plasma that doesn't clot.

So the key terms define serum as plasma without the coagulation factor. So when these things have been removed or destroyed somehow, we call this serum instead of plasma. So, okay, that's straightforward enough. Let's talk about the cells next.

So there are actually two different types of cells, red blood cells or erythrocytes and white blood cells. And you can see many different types here. and this is definitely not even naming all of them, but all these other ones called leukocytes.

So red blood cells, abbreviated as RBC, also known as erythrocytes. Erythrocytes have kind of a weird shape. I always think of this horrible butterscotch candy, the Werther's Original, as sort of a shape of an erythrocyte.

The other very strange thing about them is they don't have a nucleus. So don't memorize this, but this. this is showing that during their development, of course, early on, they have a nucleus, but as they differentiate at a certain stage, they actually eject their nucleus and, you know, continue on as a cell without a brain, essentially, a cell without a nucleus.

And we had discussed this in the last chapter, that their job is to carry hemoglobin, which carries oxygen. So I guess you don't need a nucleus to do that if you're just a bag filled with protein that's... carrying oxygen so these erythrocytes disc shaped with no nucleus and they contain hemoglobin which carries o2 that's a good enough summary there so what about all these white blood cells well i'm going to kick the can down the road and not really talk about these at all i'm going to save it for the immune system chapter so white blood cells abbreviated wbc also known as leukocytes involved in the immune system we will get into more of of their function of the different types when we we get to that chapter so that's it for now all right so we've done plasma we've done cells the only thing left is platelets so as you can see here platelets are much smaller than a cell they are not cells they are cell fragments and you could see this even more clearly when you look at how platelets are made so here's the megakaryocyte that is making these and yeah it rips off pieces of its membrane a little bit at a time and that's how platelets are created so cell fragments their job of Along with some of the proteins that are present in plasma, their job is involved in clotting. So if you have a wound or something like that that breaks the wall of a capillary, your plasma, your blood is going to start... leaking out into the surrounding tissue.

And that is, uh, that's no good. Um, so if you have a hole in anything, the first thing you want to do is patch that hole so you can prevent leaking. And so, um, platelets along with, um, you know, fibrin. a couple of other proteins that are present in plasma but not serum, are going to form a clot that's going to plug up this hole. So platelets are cell fragments involved in clotting along with proteins.

Okay, so that was just talking about blood as far as what it is and what its components are. Let's now talk about circulation, how this blood moves around. Now this is kind of a complicated process, but... But I think by breaking it down step by step, it's not going to be as intimidating as it looks.

And so this is a never-ending circuit. And so there really isn't a beginning or an end. But arbitrarily, let's start in the body and the head. So what I'm calling step one, but again, this is all arbitrary. Blood in the body and the head loses its O2, which should make sense.

That's the job of blood, or one of the many jobs of blood, is to give the O2 that it has been. storing to these tissues that need it so the o2 is given to surrounding tissues the blood is now what is called deoxygenated it's it's given away its o2 and this deoxygenated blood is drawn the color blue so and in this figure but i mean every every circulation physiology blood flow you know figure that i've seen in any textbook ever seems to to follow this convention that you know here we have the the blood in the body or the blood in the head you know getting rid of its o2 giving it to the surrounding tissues and and now it's blue i i making a fine point of this your blood is always red your uh if you have pale skin sometimes your blood can look blue in in certain places but that has to do with how light is filtered through the layers of your skin your blood is never actually blue it's always red uh but it is a convention that is convenient for these figures that deoxygenated blood is drawn the color blue. So, okay. Now, we can guess what needs to come next. I mean, this deoxygenated blood needs to get oxygen so it can do this whole process again.

But there are going to be a few steps before we can do this. So, step number two, blood enters the heart through veins. So, okay, there are going to be a few terms as we go through this process. of blood circulation. A vein is defined in the key terms as a blood vessel that brings blood back to the heart.

So if it's traveling toward the heart, it's traveling in a vein. Just know that. So blood enters the heart through veins into the right atrium.

So this is the first of four chambers that we are going to bring up, the right atrium here. And again, these are also color-coded. They're blue because they're dealing with deoxygenated blood.

Now, you might be looking at this as I, you know, confidently move my mouse around the right atrium and think, this is on the left. What's going on here? Well, another convention in every textbook ever is when you're looking at a heart, you are looking at the heart of a person.

Imagine this being a person, you know, like this standing in front of you, you know, facing you. So this is their right side, even though it's on your left. left and this is their left side uh even though it looks to be on your right so anyway sorry if that's confusion confusing but that is just the way it's done you are looking forward at the heart of a person who's looking forward at you so okay this deoxygenated blood is coming in through veins into this atrium so we're actually going to see a couple of atria again there are four chambers in the heart keep this in mind blood enters heart through atria so anytime blood is coming in into the heart the chamber is an atrium chamber atria is just plural okay so again we know what's what's supposed to happen this deoxygenated blood is supposed to go to the lungs so it can get oxygen but before it can do that um we need some power to send it to the lungs so this this low low pressure chamber this atrium where the blood just entered after making its long journey throughout the body it's got to move to a different chamber so so it can be pumped to the lungs.

So this deoxygenated blood moves from the right atrium to the right ventricle. Blood is pumped from the right atrium to the right ventricle. And importantly, there is a valve here that makes sure that this movement is one way. We don't want backflow. We definitely don't want this system going in reverse.

So there is a valve here that ensures one way movement. By the way, yeah, there are names for this valve and the other valve. There are names for these veins and arteries and stuff. I'm skipping over a lot of details that I don't think are important in an intro course. So yeah, just remember that what I...

I have on these slides is what I want you to be familiar with for an exam. So, okay, we are now in the right ventricle, and finally, we're able to go to the lungs. So, blood, reminding you this is still deoxygenated, is pumped through an artery to the lungs.

So, an artery is the opposite of a vein. It's defined in the key terms. A blood vessel that takes blood away from the heart.

So, veins go to the heart, arteries go away. Deoxygenated blood pumped through an artery to the lungs. lungs and blood exits the heart through ventricles so again we are in the the right ventricle now going toward the lungs you can this will this will bring you a long way towards uh towards you know being able to answer any test question if you remember these two statements blood always enters in an atrium through atria and blood always exits through a ventricle so here on in the right ventricle we can we know where it's going it's exiting the heart because it's a ventricle.

So at this point, we're at the lungs. And in the lungs, the blood is going to pick up O2 from the surrounding air. So now we're going to go from deoxygenated to oxygenated.

So there we go. At the lungs, blood obtains O2. It is now oxygenated. And again, it's now drawn the color red.

It's always red, but oxygenated blood is now drawn the color red. So, okay, we... Logically, we know what's about to happen or what's going to eventually happen.

This blood that has O2 is supposed to deliver it to the body. But just like we saw before, in order to make that trip, you've got to go back to the heart again. So this oxygenated blood is going to come into the heart now on the left side. Remember, blood always enters in an atrium. So here comes in from the lungs into this left atrium.

Atrium. So oxygenated blood enters the heart from the lungs at the left atrium. And again, we know that if we're going to exit, it's going to have to be through a ventricle.

So before this blood can make its exit to the head and the body, it's got to move from the left atrium to the left ventricle. And once again, there's a valve here that makes sure that this movement is one way. So blood is pumped from the left atrium to the left ventricle. Valve ensures one way movement here. and uh again we know what's going to happen this is the a ventricle so it's about to leave the heart it's oxygenated blood so we know it's not going to the lungs it's supposed to go to the the head and the body and that's exactly what happens here blood oxygenated is pumped from the left ventricle to the head and the body and and from there it's going to deliver uh it's o2 and that's right where we started again blood in the body and head losing its o2 and then you know the whole process repeats itself.

Another thing that if you keep in mind will help you remember what each of the four chambers does. Again, I said blood enters through atria and exits through ventricles. Also keep this in mind, the right side always deals with deoxygenated blood and the left side of the heart always deals with oxygenated blood.

So again, the right side, whether it's the atrium receiving deoxygenated blood or... sending out deoxygenated blood. The right side is always blue, drawn blue.

It's always dealing with deoxygenated. And the left side, again, whether it's receiving or sending out, it's always dealing with oxygenated blood. So keeping this in mind will help you a lot as well.

Now, there are actually three different circuits that exist in blood circulation. So this is just some terminology here. The pulmonary circuit... is what we call the part of this journey that we talked about from the heart to and from the lungs.

So yeah, this is the pulmonary circuit here from the heart to the lungs to get oxygen, then back to the heart again. The systemic circuit is the other one we saw from the heart to and from the body. So there's the systemic circuit going to the body and the head, losing it.

It's O2 and then back to the heart again. But I just said there were three circuits and this is only showing two. So what could the third possibly be?

The third is called the coronary circuit, which is... easy to forget about but the heart needs blood the heart is a muscle the heart is working very hard and the heart muscle itself needs to be supplied with oxygenated blood the blood in this This chamber, well, first of all, only half the heart gets to have oxygenated blood, but it's not really getting a chance to absorb this O2 as it's flowing through these chambers. So we need to have veins and arteries connected to the heart itself.

This is called the coronary circuit. From the heart to and from the heart. Kind of a weird way to say that, but yeah, the heart muscles must have veins and arteries themselves.

And I referenced this earlier. earlier there are names for all of these things but we're definitely not not going to worry about this level of detail in an intro course so there's one last topic in this chapter that I think is worth worth discussing before we move to the next chapter and that is comparing and contrasting vertebrate circulatory systems so this This the circulatory system that we've been looking at so far is what we see in mammals and and birds. This four chambered heart, everything we just went through. That's how mammals do it. that's how birds do this it's called double circulation because it is you know basically a figure eight the systemic circuit the pulmonary circuit um those are the two main big circuits so it's called double circulation this is defined in the key terms uh flow of blood in two circuits the pulmonary circuit through the lungs and the systemic circuit through the organs and the body so four-chambered heart double circulation everything we just talked about mammals and birds so how is this different Well, in reptiles, let's move from mammal bird circulation to reptile or most reptiles.

See if you can spot the difference. So a lot of this looks very similar. You have a systemic circuit here. You have a pulmonary circuit here to the lungs.

If you've got a sharp eye, you might notice the difference is here in the heart. So in the mammalian and bird heart, the. The chambers that hold oxygenated blood and the chambers that hold deoxygenated blood are completely separate from one another. It looks like they're mixing here. It's actually just crossing over.

They're completely separated from one another. You don't want blood with oxygen in it and blood that doesn't have oxygen in it to mix with one another because then you'd end up sending red blood cells with no oxygen to the body and head and that's a waste. Or you would send red blood cells that have oxygen.

to the lungs which would be a waste so they're completely separated here but in most reptiles they're not there's a septum that incompletely divides this chamber and you have a little bit of mixing it's sort of drawn purple here uh in between oxygenated and deoxygenated blood this is obviously not great uh but it it is the way it is in most reptiles so most reptile have a three-chambered heart. There is a partial septum. This is like the fifth time we've seen the word septum in this course.

A septum is just a wall or a barrier or whatever. So there is some mixing of oxygenated and deoxygenated blood. This is very bad, but you know, it is what it is. And this is still a double circuit.

This is still double circulation, but you have this mixing. Now let's move from reptile heart. We're kind of going backwards evolutionarily.

So things are getting more. primitive and more simple as we go back let's move from reptile to amphibian spot the difference this mixing is even worse without even a partial septum to divide this chamber this is uh a fully you know three chambered heart where there's a lot of mixing of oxygenated and deoxygenated blood and that's really not great as far as efficiency goes so amphibians have a three three chambered heart no septum at all mixing of oxygenated and deoxygenated blood that's bad like I said in the last slide and this is still double circulation though okay moving backwards again from amphibians down to fish whoa this is completely different so there's no mixing oxygenated and deoxygenated blood because fish circulation has just two chambers to the heart one atrium and one ventricle and so uh instead of making a a figure eight of one loop to and from the lungs or the gills in this case and another loop to and from the body in a single loop this blood is pumped from the ventricle to the gills to acquire oxygen to the body to deliver oxygen and then back to the heart again. So fish have a two-chambered heart with a single circuit circulation. So let's review this again.

So this is the simplest way to have a heart, and these are the simplest vertebrates with two chambers. It is kind of an upgrade to do this in two loops. It allows you to, you know, pump more effectively if you're making two different circuits here.

So this is kind of an upgrade, even though there is some mixing, and obviously, you know, we see a further upgrade in the partial septum of reptiles and then we see sort of the peak performance of the heart uh in the complete separation what we see in mammals and birds so again i thought this was this was interesting uh to explore the differences in circulation among these vertebrates all right that does it for circulatory system now on to the immune system okay this is going to be a big chapter and so uh we can actually do divide the immune system into two basic halves or two parts, the innate immune system and the adaptive immune system. Let's start with the simpler one and we'll get more complicated as we go through. So the simpler of the two is called the innate immune system. So the innate immune system, I'm double underlining this because there are going to be several things that are a part of this and I'll underline those.

So just my way of organizing. The innate immune system has limited path. Pathogen specificity.

So pathogen is a term I'm going to use a lot in this chapter because a pathogen is a bad thing. Something trying to cause disease. The key terms define this as an agent. That's very vague.

Usually a microorganism that causes disease in organisms that it invades. So I'm being vague like this because this could be a bacterium. This could be a eukaryotic parasite. This could be.

be a virus. So all of those things, some of those are alive, some of those are not alive, virus is not alive. All those things fall under the heading of pathogen.

If it's trying to harm you, it's a pathogen. So again, using this word a lot in the chapter. So the innate immune system is not very limited or specific about the pathogens that it deals with. It fights against pathogens, certainly, but not in a very specific way.

The innate immune system is, however, very immediate uh the the other immune system is going to take a little bit longer but this is much faster but not as specific so the first part of this i'm going to talk about is actually the largest organ of the human body it's a fun trivia question here and he guesses the largest organ is the skin uh so google image search supplying supplying some skin here if you didn't know what this looked like uh looking more closely at a patch of skin here Oh, hey, I was talking about receptors last time I used this slide, but there's a lot going on here. The part that has to do with the immune system, though, is the outer layer, this thick layer of epithelial tissue, as well as the sweat created by sweat glands and excreted here. It provides a barrier to entry.

So the skin is just a physical barrier that prevents stuff from getting in. Right. If we want to zoom in even further here, oh, don't sweat all the detail here, but there's a lot of stuff going on other than just epithelial cells. So you have oils here and you have sweat, which is at a low pH. This creates an environment that's actually not a great place to live, even though this is a lot of available real estate. It's pretty inhospitable because of the oil and the sweat and the locals.

So I reference... these way earlier in the quarter in our chapter on prokaryotes but we have a lot of normal flora normal bacteria and fungi that make their home in this environment and so the normal flora with the sweat and the the oils make this just a place that's not a great place to live so the skin is an inhospitable environment for pathogens that's a good way to put it low ph and the normal flora crowd out pathogens just make it difficult for them to get a foothold here. Now as great as the skin is, this cannot cover our entire body.

We need entrances and we need exits. So to cover those parts of the body, we have what are called mucosal epithelial surfaces. So these are epithelial cells that secrete mucus. This is the nasal epithelium we're looking at here, but most mucosal epithelium. are the same way you got these cells and then you have a layer of mucus that they have secreted as like an additional layer of protection for these cells so mucosal epithelial surfaces are entrances and exits of the body cells secrete mucus and enzymes the mucus just you know traps and destroys things the enzymes a lot of times are specific well not too specific but will actually destroy pathogens the the one that comes to mind your eyes so that's another entrance to the body technically make an enzyme called lysozyme that targets peptidoglycan remember that compound it's part of the bacterial cell wall so they're going to trap and destroy pathogens and again this is part of the innate immune system this is all very generic mucus is going to trap just anything that gets stuck in it and you know those enzymes have to have a bit of specificity but bacterial cell wall that's definitely not a specific species of bacteria.

So this is the to whom it may concern part of the immune system. So what about the cells? What about leukocytes?

So there are some leukocytes that are involved in the innate immune system in addition to these epithelial cells. One way in which leukocytes involve themselves in innate immunity has to do with pattern recognition receptors and pattern recognition receptors. pathogen-associated molecular patterns.

Okay, so the immune system as a whole becomes a lot of alphabet soup after a while, so I'm going to try to go through this as simply as I can. So here's the leukocyte. It's a macrophage.

It has a pattern recognition receptor, or PRR. Let's break this down. Pattern recognition receptor.

So it's a receptor. It recognizes something. It binds to something. Pattern recognition means it binds to some specific pattern. So the pattern recognition receptors are on the leukocytes.

The patterns that they are capable of binding are on the pathogens. So here's a bacterium, for example. The PAMP is a pathogen-associated molecular pattern. So again, it's a pattern-associated... on a molecular level with a pathogen.

A PAMP is basically a bad thing. A thing that you associate with a pathogen, it's never a good thing. More alphabet soup.

Lipopolysaccharide, LPS, is one of those PAMPs. It's bad stuff. It's found on gram-negative bacteria. We do not have this in our bodies. So if you encounter lipopolysaccharide, that's bad.

That's always going to be associated with a pathogen, with something bad. So let me write down what I have so far. So pattern recognition receptors, or PRRs, present on some leukocytes, for example, macrophages.

We're not going to learn the names of all the leukocytes, but this is an important one, the macrophage. So the PRR on something like a macrophage binds to a pathogen-associated molecular pattern, or PAMP. on, again, common pathogens.

So there's some specificity here, but this is all still kind of generic for common pathogens. So what happens when this recognition happens? Well, again, that tells this macrophage, hey, something bad is happening here. And so it's going to send out a bunch of signaling molecules called cytokines, more alphabet soup, interleukin-8, interleukin-1, tumor necrosis factor alpha.

My point is, these are cytokines. So this binding leads to the release of cytokines and eventual phagocytosis of the pathogen. So cytokines are defined in the key terms. These are signaling molecules used by the immune system.

Oh, I'm sorry, I'm reading the wrong thing. Chemical messenger that regulates cell differentiation, proliferation, gene expression, and cell trafficking to affect immune responses. It's kind of wordy. It's a... It's a message.

It's a signaling. molecule that tells the immune system to do something. So anyway, PRR binds to PAMP, cytokines are released, phagocytosis.

So this is how your immune system deals with viruses and bacteria. These cells will eat the pathogens. They engulf the pathogen and destroy it from the inside, sending it to the lysosome, if you remember that organelle back from BISC-130. So that is how... That is how these leukocytes deal with a specific pathogen.

And again, there's some specificity here because it's only something that happens to have this common danger pattern on it. But it's also very generic. Any gram-negative bacterium, any species or whatever, anything that has LPS, for example, is going to be destroyed through this process.

So that's why this is the innate immune system. It's pretty generic for what you're going to fight against. So another way in which leukocytes can be involved here is at the site of injury. So phagocytic leukocytes, which they're leukocytes that do phagocytosis, that includes neutrophils and the macrophages.

So macrophages are kind of smart. They recognize stuff, but they can also eat things. They can also fight. So phagocytic leukocytes like neutrophils and macrophages can be brought to the site of injury.

injury by cytokines. So here's a wound site. Again, you've been stabbed with something.

Obviously, there's, you know, some blood leaking out here and all the stuff we talked in the last chapter about clotting. But also you get some pathogens that, you know, make it past, you know, this primary barrier, this primary line of defense. We got, we got to bring in some, some cells to try to deal with this. So the damaged cells will actually send out cytokines that recruited them.

that bring these leukocytes to the site of injury, and they're going to do phagocytosis on the bacteria or the viruses that have managed to get past the skin. So this is called inflammation when this happens, when you have the site of an injury. Also in the key terms, localized redness, swelling, heat, and pain that results from the movement of leukocytes and fluid through opened capillaries to a site of infection.

So a lot of the symptoms... of just like, ah, man, it's so swollen and it's hard to move if you have an injury somewhere. A lot of that is due to your immune system. You're bringing stuff into that site to try to deal with these pathogens and just bringing a bunch of stuff in is going to lead to swelling and heat and redness there. Okay, so that is not, definitely not the end of the immune system, but, and not even the end to the innate immune system.

system but this is a good cutoff point this is typically where i've run out of time in lecture 5-1 this is the end of lecture 5-1 more immune system stuff in the next lecture

Transcript for:Circulatory and Immune System Breakdown

Transcript for:
Circulatory and Immune System Breakdown