one of the reasons why cardiovascular is such a big chapter is because besides the heart which is a huge achievement in both lab and lecture we also have all these blood vessels so blood vessels if you look at this picture here okay our circulatory system or cardiovascular system is what we call closed-circuit meaning the blood is somewhere in your body in a tube some animals or I guess well I mean they are animals but especially a lot of insects which we don't always think of as animals even though they are they have what's called an open circulatory system if you cut open a grasshopper blood just like leaks out the blood isn't in a blood vessel whereas all of your blood is that's why sometimes they'll do exploratory surgery and they'll open your body up there shouldn't be just like pooling blood in your body cavity that would be a sign that you've torn a blood vessel so your blood should be somewhere in the heart or in these blood vessels and so the blood is going to flow like this from your major arteries to your arterioles to your capillaries to your venules and to your veins so we start off with really big vessels we get very very small arteries arterioles capillaries capillaries are the smallest and then we get bigger as we get back to the heart so if you remember from lab the aorta is the largest artery in the body that's pretty big the superior and inferior vena cava the superior inferior vena cava also being very very large but a capillary bed is microscopic like if you've ever got a paper cut and it didn't really bleed it just kind of oozed because you've really just cut into those capillaries so in lab we'll focus on this a lot arteries away from the heart veins towards the heart that rule always works 100% of the time now remember in lab a lot of times arteries are represented by red because we're showing that oxygenated blood and veins are represented by blue because they tend to be deoxygenated blood but remember the red and blue rule doesn't work with the pulmonary arteries and veins because there are the exceptions to that but arteries always away veins always towards arteries 99% of the time have oxygenated blood that's why we're leaving the heart and veins are usually in a skanky blood which is why we're coming back to the heart so the blood vessels themselves have three layers the tunica like a tunic is a clothing that you wear we have the Tunica intima which is the most internal we have the tunica media which is the middle layer and the Tunica externa or adventure which I would use external external because external that's a lot easier the Tunica intima otherwise known as the internal I prefer interna because I think intimacy and of creepy it reminds me of department stores where they Karl call the underwear aisle the intimates that's creepy it's just underwear but if you think about your underwear right now it is your most delicate layer right because that is the layer of clothing that's touching your boy or girl parts and so you don't want it to be made of plywood or metal because it would rub it up all day so it's the same thing here this is the layer that's touching your blood and your blood is very very delicate so we want to make sure that this layer is not hurting your blood stream and hurting your blood cells at all so we call this the Tunica interna or intima but it's basically just those squamous cells that we saw on a mp1 so we call this endothelium that's the lining is called endothelium so this it's very very smooth because we don't want any place for these guys to get stuck right so it's just like the pipes in your house you want them to be really really smooth so you don't get clogs so we want to prevent the platelets whose job we'll talk about in our next unit but his job is for blood clotting and the red blood cells themselves we don't want them to get damaged we don't want the platelets to have any excuse to get stuck and start clotting when they don't need to we want to make sure the blood is flying through your blood vessels because remember we only have a minute to go from the heart to the vessels and back the tunica media this is the middle layer so this one is really the kind of impressive layer under the microscope which we'll see in lab it's mostly smooth muscle so remember smooth muscle you can't control that it's not voluntary it's involuntary so you can't speed up or slow down your blood by thinking about it if you get pissed off and your blood pressure shoots up you can't just instantly stop that so smooth muscle we don't have to think about this so it's mostly smooth muscle in this middle layer which is how I remember it media muscle but there is some elastic tissue because when you get pissed off you need your blood vessels to react really quickly right you don't have an hour for your vessels to change based on whether or not you got to run from a lion Tiger bear oh my or if you're pissed off so we regulate this sympathetically vasoconstriction versus vasodilation we saw on a previous slide so we need our cells to be able to respond when our blood pressure surges we need to be able to open up our blood vessels when there's a huge amount of blood we need to be able to kink those hoses to ship that blood around your body very very quickly so the point is we just need these tubes to respond so the Tunica interna is the most delicate one cell layer thick the tunica media pretty thick and beasty because it has all that muscle and so you can kind of see this comparison in this picture as we add the Tunica externa which again is what I call it so this is the outer layer so this is like if you've looked at your garden hose how it has that outer kind of thick plastic coating on it we want to kind of protect our blood vessels right so this is mostly collagen so remember collagen is a really thick protein rope we want the outside of both our arteries and our veins to be relatively tough because we don't want to pop these guys just like you don't want to pop your garden hose also we need that kind of tough outer coating because we're gonna need to attach these where you need to stick these to your organs you don't want your organs like you don't want the blood rolling away from your organs right so if you look at the brain models and lap they have blood vessels on them we want to make sure the blood vessels are staying to the brain because the brain always needs fed so the order of the blood vessels through or blood through the vessels basically goes like this so we've done all the hard Anatomy and lab hopefully by now but the blood leads those ventricles it's gonna shoot out the arteries so see they're gonna shoot out the aorta to the rest of the body or the pulmonary artery to the lungs it's then gonna branch off into smaller arterioles capillaries venules veins and then back to specifically the right atria of the heart so the best way to think about blood vessels is to think about roads you go the fastest on an interstate right the interstate 70 miles per hour I usually go 80 because that's how I roll but the point is I'm going the fastest during my commute home I'm going the fastest on the interstate so arterial blood is like that especially the aorta this has the highest fastest pressure blood in your body because you just came off that left squeeze of the heart so these major arteries these are the ones that you watch a good horror movie and somebody gets sliced they're gonna bleed out so these arteries are all about getting the blood as quickly as possible from point A to point B like an interstate people don't take take interstates for the scenic route right you don't expect to see a lot on an interstate but that's the point you want to get where you're getting so I take interstate 74 to route 49 so I would call route 49 an arterial I'm still going pretty fast the speed limits 55 I usually go about 64 so I'm still going at a pretty nice clip but it's more scenic right in the sense that I can turn off of 49 like every other mile or so there's a turn-off whereas on the interstate sometimes you'll go 20 miles without it branching off so arteries are like this the blood is moving so fast because we don't allow it to slow down because there's not a lot of places to quote-unquote exit that's why interstates are fast whereas highways are still pretty fast but we have a lot more opportunity to get off the main road well your arterioles there's a lot more branching of blood coming off those arterioles to ultimately get us to capillaries so capillaries you can think of like your driveways but the only difference being in your driveway usually stop right capillaries are like UPS man during Christmas time where they slow down and kind of throw the package out like they slow down almost to stopping but they'll have time so Bloods the same way you never have blood just completely stopped in your body and so the capillary beds are like your driveways in the sense that that's where you're driving the slowest I would hope would be your driveway but you're actually never stopping so at this point the capillaries is where we actually deliver stuff so you could be driving on the interstate next to the UPS guy he's not gonna give you your package from Amazon the only place that happens is in your driveway so the only place you actually get exchanged in this case getting the oxygen and the nutrients from the blood and having the blood pick up your carbon dioxide and other waste is happening at the capillary so we're gonna spend a lot of time on that so now we've delivered all the good stuff that's what the arteries arterioles and capillaries are all about now it's time to get the skank get the trash back to the heart so now if I'm leaving my driveway to go back to work I'm gonna speed back up right so venules the blood speeds up a little bit now it's never gonna be as fast as the arteries and arterioles the venous system is never gonna be as fast as the beginning but it will speed back up so the venules is like getting on like a side street in your neighborhood and then the veins like getting back on a highway our ultimate goal to return to the heart so this is a closed circulatory system somewhere your blood is in one of these vessels the general rule for arteries remember a and away so it's trying to be clever here highlighting it but then you have black and white notes so there goes my Teacher of the Year award but arteries in a way this always works okay so some other characteristics of arteries they have the thickest walls of all of your blood vessels and they have a lot of elastic or elastin in them so they can snap back whenever we need them to we need these guys to respond very very fast we need them to have a thick wall because just like a garden hose you don't want to spring a weak arteries also have the highest blood pressure so your exam will cover things like this like who's got the highest blood pressure where's the blood the slowest where's the blood the fastest who's got the most blood so you want to keep in mind as we go through this section the notes those are characteristics you want to know so the reason why arteries have the highest blood pressure is simply they're the closest to the heart they've just left the heart it's never going to get any better than that right the heart is what pumps blood so if you don't have that pumping you're not gonna have blood pressure so the average pressure in the arteries is also affected by cardiac output remember cardiac output is just a nerdy way of saying how many millimeters of blood does the heart pump per minute so obviously if you have a bigger heart you're gonna have higher blood pressure so if you're a bigger person you'll probably have higher blood pressure than a child who has a smaller cardiac output and also blood pressure is affected by peripheral resistance we will address peripheral resistance on another slide but for now if you think about being on a water slide versus a slide in a park especially on a hot summer day I don't know how many times I've heard kids go down a dry slide and you hear that squeak cuz like their skin is like scraping down the slide it's a terrible sound right so that slows you down versus if you're on a water slide you don't have that resistance of the slide because the water helps kind of lubricate you right you're not really making contact with the slide so this would be resistance if you walk across the room versus dragging your feet that would be resistance so ideally because of that Tunica intima that endothelial lining of the blood vessels ideally nothing sticks to that so it should be very very quick the blood shouldn't have a lot of resistance when you're pumping it however if you're starting to get a lot of cholesterol built up and your arteries are starting to get kind of clogged that's gonna cause resistance just like when you're trying to pump water through a hose if there's like a clot if a clog built up in there the waters not gonna flow very well but we will address it better later on so this little picture right here is basically what we'll see in lab right you need to be able to tell the difference between an artery and a vein under the microscope and it's so easy in this drawing it's easy as well because look how thick the muscle in the artery is versus the vein also arteries tend to keep more of a straw-like shape whereas veins if as this little microscope picture shows they kind of collapse on us a little bit but veinous blood isn't flying through your body really really fast think about the last time a nurse drew blood from your arm you didn't paint the walls with your blood it wasn't shooting out of there it was pretty slow so it doesn't have to have as thick of a wall so we have the intima layer or interna we have the media we have the externa so the inside layers the thinnest and its whole goal is to just make sure we don't have friction we want to make sure the cells are flying through there just like the water in your in your sewer line at home the tunica media muscle it's the thickest layer and this helps regulate blood pressure and then the external layer like that plastic coating on the garden hose nice and thick and beasty because of the collagen fibers arterials so these are branches off of arteries like highways are branches off of arteries so arteries are of interstates so arteries are crazy fast okay the blood is flying through there like I'm flying on that interstate but when I exit onto the highway I'm still going pretty fast so this blood is still pretty fast we have a lot more arterioles than arteries if I gave you a map and I gave you crayons and I told you to color in all the interstates that wouldn't take you very long if I gave you another cult color and I told you to color in all the highways that's gonna take you a little bit longer if I gave you another crayon and told you to draw in all the neighborhoods and driveways you're gonna need a snack because that's gonna take you a while so it's very much relating to that we're trying to branch out right and reach every house in America with our roadway system well with our arterial system we are trying to reach out and feed every cell in your body so the arterioles goal is to carry the blood from the major arteries to the capillaries which remember are like your driveway so every cell in your body has a capillary next to it because every cell in your body has to have blood so arterioles have a tunica media but it hardly has any smooth muscle so it's a lot thinner and we will feel this on the cadaver if we haven't already when you squeeze an artery on cadaver you can feel how muscle it is when you feel when you squeeze a vein they're kind of pathetic so same thing with arterioles arterioles are a little bit thinner than arteries and so when you can if you squeeze an arteriole you can tell that it's just a lot thinner but it's because the Bloods not as high pressure so it doesn't have to be so flow of blood is slower than an arteries but that's like saying I'm on the highway going 55 that's slower than 70 that's true it is slower but it's still pretty fast blood pressure is less the further you get from the heart the more blood pressure goes down so blood pressure is never going to be as high as it is in the arteries but it's still pretty high in the arterial just not as high you one of the assessments of health that they do is take your pulse so they take your pulse at the doctor you may take your pulse occasionally my Fitbit watch takes my pulse but what is pulse it's basically the expanding and recoiling the expansion and the shrinking of your arteries the walls themselves in response to blood pressure change so it's basically your left ventricle right because we really care about that left side contracting because that's what's feeding our body so a common place to take pulse is your radial pulse this is your left ventricles contracting it's usually between 60 and 80 beats per minute the heart rate and so 72 is just kind of a number I threw in there 60 to 80 being normal but pulse is kind of a bass ackwards way of checking your blood pressure if your blood pressure is nice and strong your pulse will be nice and strong if you're low if you have low blood pressure your pulse will be weaker I have extremely low blood pressure so it's very hard for me to get my pulse in my radial artery but I can always get it in the carotid in my neck although capillaries are the smallest by far they're arguably the most important as far as physiology because capillaries are the smallest blood vessels this is where exchange occurs so just like if I order a pizza I don't care if the pizza man has to take a highway or an interstate to get to my house because where I'm gonna give him money and get my pizza where we are gonna have that exchange is in a capillary is in my driveway so the capillaries are where the blood is going really really slow it's not stopped it never stops but it's practically stopped it's very slow and there's enough time for things to leave the blood and things to come back to the blood so the good stuff leaves bad stuff comes back so this is the connection between your arterial system and your venule system basically the connection between clean happy blood and dirty skanky blood so your capillaries are just one layer so they're very very thin they just have that single cell layer of simple squamous cells those little squashed cells that we call endothelium so that's just like your underwear it's the thinnest layer of clothing you're probably wearing right now so at first that sounds bad that thin is bad but it has to be thin because otherwise things can't diffuse through it so if I light a candle and put a bucket over it what's the point you can't smell the Yankee Candle goodness so same thing here it's like if I have oxygen that needs to leave my blood how can it do that if my blood vessels xxx cells thick so it needs to be thin to do its job but the price we pay is yes your capillaries are weak and they get damaged really easily that's what a bruise is you see a bruise because blood has leaked out of your capillaries because you tore them capillaries also contain what's called fenestrations which i think is a fantastic word fenestrations but they're just pores they're just little holes you don't want holes in your arteries just like you don't want holes in your garden hoses right you don't want holes in your big veins because you don't want to be leaking blood in your arm so the only time you want this exchange the only time you want these Holies is the capillary bed so this is the only blood vessel where it change of gases and nutrients occurs between the blood vessels and the tissues so some characteristics they have the smallest diameter of any blood vessel but have the greatest area so this sounds really complicated okay but it's not so diameter is if you're looking through a straw grossberger straws are a lot bigger than McDonald's straws so it's just a size thing it has a bigger hole so capillaries if you're looking through them like a tube they have the tiniest hole so they have the smallest diameter but they have the greatest area if I go back to that crayon example it would take you a lot more time to color in all of the driveways and side roads in Illinois versus the time it would take you to outline all the interstates you could probably outline all the interstates in just a few minutes but it'll probably take you several several days to color in every single driveway so capillaries because there's a capillary next to every cell on your body you have more of these than anything else so area is like just a measurement of space so you have more of these than anything else but the tubes themselves are really tiny they also have capillaries also have the lowest velocity of blood flow so that just means speed like I said the blood is almost completely stopped in the capillary but it has to be because we gotta have time for things to leave the capillary and time for things to come back so capillaries form what are called capillary beds just like your neighborhood probably has multiple streets so those suburbs suburbia is like branches of different roads with different names right so they form these big networks a capillary shunt which will see a picture of is where we don't get any exchange of blood so it's like the fastest way to send blood through a capillary so the whole point of a capillary is exchange but you can control this which will see the picture so this is my sad attempt to draw these fenestrations so this is just showing you one side of the capillary bed and I was basically just trying to show these little holes we need these holes so things can get out but it's just like making coffee when you make coffee you want the coffee flavored goodness and the water to get through but you don't want the chunky Funky's to get out so it's the same thing here we don't want our blood cells to leave our blood but we want like the oxygen so these holes are big enough for certain things to get out but certain things can so the more metabolically active your tissue the more capillaries basically that means the more active at issue is the bloodier it is so if you remember from A&P one muscle incredibly bloody if you eat steak and you see all that blood right muscles are ATP horse they're using so much energy every single day that they need good stuff brought to them and they need their waste constantly picked up whereas if you remember the skin doesn't have any capillaries at all the capillaries are below the skin in the connective tissue but as far as the epidermis especially it can't be vascularized it can't have a blood supply because it's to protect you it's on the outside but skin just pretty much lays there right so why does it need to have a huge blood supply so the more active you are you're going to need more energy which means you need more blood so this is the picture talking about those capillary shuns so this picture here is showing you that network of capillaries remember I said it kind of looks like a neighborhood so this looks like a lot of suburban neighborhoods I've been in so on the left side there you have the arterial on the right side you have the venule so this color is showing us how we change from red to blue it's to illustrate how in the beginning we have all that oxygen we drop it all off and as we move through the neighborhood we've picked up the trash so it's a good illustration of that but blood is very very important and sometimes you can't send blood everywhere in the body at the same time so you can control if you're sending blood out into the neighborhood do these little shunts so when this would be valuable say you've just eaten a meal well I would want to open all of my capillary beds to my intestine so I could absorb a whole lot of stuff so I would want to do the picture on the left if I had just ate but if I haven't eaten in a while I probably wouldn't want to send all that blood out to the intestines on the right side there right because what a waste why send blood out to a neighborhood if there's no nutrients to pick up so consequently sometimes if a lion tiger Barrow Maya's chasing you you may need to send more blood out to your arms and legs for example to survive an event so you can borrow blood from parts of your body by kind of shutting it off with these capillaries sphincters now you can't shut it off forever of course but it's something that maybe you could skip temporarily just to keep blood where it's needed at the time so the hardest part of this chapter is capital air exchange I think so again I was trying to draw so we have the blood vessel itself the capillary bed itself and it's got holy Holies so we need to exchange good stuff out to the tissues bad stuff in but the blood itself has the stuff right so you eat and you breathe you're getting all the nutrients all the oxygen everything else inside that blood so this goes back to a and p1 so if you remember the cell membrane the cell membrane was fat which men it was nonpolar and water is polar so if you remember if you're on Polar's team you hang with polar things if you're on non Polar's team you hang with non Polar's thing it's a team so basically oil and water don't mix right we know this but this related to diffusion diffusion is the movement of molecules from high to low concentration molecules don't like to be crowded well things that dissolve in fat things that are lipid soluble can diffuse in and out of your bloodstream through the vessel walls anytime that anytime they want because those cells are made of fat so they're gonna say okay fat come on in so the good news is this is a lot of stuff this is some of our nutrients and some of our waste products it's fatty acids of course I mean they're clearly on fast team but the biggest thing is the oxygen carbon dioxide so thank goodness right that oxygen and carbon dioxide can just zip in and out of your blood vessels all day long they don't have to wait in line other substances that dissolve in water so water of course is is polar but also table salts the example I gave us here table salt clearly dissolves in water and you get the na and the CL so if you're on waters team it's not that we don't want you it's just you can't just come right on in you got to go through these little pores these little sinister ations but then there's also things like your blood vessels or sorry your blood cells or the plasma proteins that are just simply too big we don't want them to ever move though right I don't ever want my blood cells to leave my bloodstream because then it's not blood anymore just like I don't ever want coffee grounds in my coffee you also have these proteins that float around in your blood which are call plasma proteins we will get into the details of this in the next chapter when we talk about blood for now these are just proteins that have to stay in the blood so there's two kinds of pressure when we talk about capillary exchange this slide is something that you'll want to read on your own after we explain this so I'm a little ahead of myself with this but if you look at this slide it talks about hypertonic and hypotonic so if you don't remember that we're gonna review it and you may want to come back to this slide same thing with this slide this is explaining and defining things that we're about to do so this is another slide I would come back and read after we're done with our drawings so you will want to get a piece of paper because we are gonna draw something and you really want to draw this I wouldn't print it I would draw it so this I want you to draw or you know highlight it and whatever if you want to just use the picture that's provided but it is kind of nice to draw it so the thing with this is is this is capillary exchange and it is complicated but if you draw it and think about it it's not too bad so you may want to pause me to get this drawn and then we'll explain it but the key is you've got to pay attention to color so it doesn't have to be blue red and green but you need three different colors you also want to label the key so you want to know what your colors stand for so blue is gonna be water osmotic pressure red is gonna be hydrostatic pressure and green is gonna be the net pressure so you want to make sure you you write your key it's also really important that the blue arrows at the top all stay the same size and it's really important that the red arrows start all big and get small you want to label the arterial side and the venule side and then I would write the word capillary in between like this whole tube is the capillary so I would maybe add that this is something I stole from the internet and they didn't so I would pause me and get this strong so once you have it drawn okay we want to understand this and we're gonna have two pictures so you're gonna draw another picture as well but this is the more simple one so if you look at the arterial side that is the side that's closest to the heart remember your heart is your pump so the blood is gonna be pumping really hard on that side and not so much on the venule side so we'll start with the red arrow so hydrostatic pressure hydro means water right hydrostatic pressure is blood pressure so anytime you see hydrostatic pressure in physiology I want you to think blood pressure now that doesn't work in like physics and it doesn't work in chemistry but who cares about that we care about this class so hydrostatic pressure for us is always blood pressure so that is why the arrow starts out all big and gets small because you're on the arterial side you're closest to the heart so when that heart squeezes you're never gonna get any better blood pressure then closer to the heart it's just like if I turn on a garden hose next to my house I'm gonna feel that water shooting in that hose right away but if I have my hose stretched clear across the road or clear across my there may not even be water trickling out on the other end right so the closest you are to the tap you're gonna have more water the closest you are to the heart you're gonna have more blood pressure so as you move through that capillary bed the arrow gets smaller as you move further from the heart blood pressure goes down so that's the first thing to understand as blood is moving through your body blood pressure is gonna go down it's never gonna be as high as it was in the aorta the second thing to notice is the little blue arrow at the top that arrow is never changing in size that arrow is representing what we call osmotic pressure and this goes back to tonicity so if you don't remember hyper and hypotonic I define it on the next slide so hypertonic is the solution with more solute less water so I always remember hyper kids are hopped up on sugar somebody needs to give them some water whereas hypotonic hypotonic is more water less sugar so water always goes from where it's crowded to where it's not so water always goes from hypotonic to hypertonic always water is always attracted to solute that's how you kill poor little slugs you pour salt on a slug it's gonna suck the water out because the water inside the slug is gonna be drawn to that solid so a good thing to remember is water always goes from hypotonic to hypertonic so that's what this blue arrow is representing the blue arrow is representing water in your body in your tissues that is attracted to the blood stream water will always be attracted to the blood because another word you may want to add to this drawing blood is always hypertonic so you may want to write hypertonic in the center of this capillary so water is always gonna want to go from hypo to hyper so water always wants to come back so you have a tug-of-war happening here when that water that's in your blood hits the capillary bed he's crowded in there right he has all that high blood pressure just like if I just like if I put 500 people in a classroom you'd be desperate to leave so the water in the capillary bed is desperate to leave because it's real high pressure and crowded in there so it wants to leave but the water in your tissues want to be in the blood so it's a tug-of-war it's just like if you've ever been to a big city and some people want to get on the train and some people want to get off or some people want to get on the elevator and some people want to get off there's a tug-of-war somebody's got to win same things happening here so that's what the little green arrow is representing somebody has to win so in the beginning of the capillary bed the red arrow is winning blood pressure is winning because there's way more water that's wanting to rush out of the blood than the water that's coming back so if I pay a bill I get paid and say I have fifty dollars and I pay a bill that's $20 I'm still ahead right so on this case way more waters leaving that's coming back so who's winning blood pressure there's more water leaving than coming back blood pressures gonna win at the end of the capillary bed it's reversed so now as the red arrow shrinks as it moves to the capillary bed blood pressures gone down as a room empties or as an elevator empties or as a Train empties we're not as excited to leave remember molecules want to go from where they're crowded to where they're not everything wants to go from where they're crowded to where they're not in the beginning of the capillary bed the water inside the blood is crowded at the end of the capillary but it's not so it wants to leave but it's not like running out of the elevator whereas the blue arrow if you look at it has never changed in size though the desire of the water to come back to the blood has never changed so now the blood coming back wins so the point of this is in the beginning of the capillary bed you're gonna lose water at the end of the capillary bed you're gonna gain it this is good because in the beginning remember that's good blood that's clean blood that has tons of oxygen and it has tons of sugar at the end of the capillary bed we are bringing back water from the tissues that have a lot of waste so we're gonna look at this in a different way with another picture you on your drawing if you didn't remember those words I would write this down on your drawing so this relates to osmosis that's why it's osmotic pressure it's the movement of water from high to low concentration just like anything else if I'm number 10 in line at Walmart and they open up a new line I'm hauling ass and knocking over old ladies you don't have to make me move I'm gonna move so hypotonic is the solution with less solute or water hypertonic solution with more solute less water like I said previously I always remember hyper kids are hopped up on sugar somebody needs to give them some water so water always always always always goes from hypo to hyper because all that saying is water goes from where there's more water to less if you didn't learn this in a mp1 or in biology you have to learn it now capillary exchange and the urinary system works on this completely we will use these a lot now as you look at this I know you're like wow fancy but this is the drawing that I always put on the board and so instead of doing something fancy I thought I would just give you the exact thing I guess my face-to-face class so this is the capillary bed so I know that because I've got those fenestrations right so I would draw this as well because if you draw it you kind of get a better feeling for it so this is what we just did we're just adding some stuff so remember I said blood was hypertonic so that means there's a lot of stuff dissolved in your blood so if you look at my little drawing here I've got red blood cells which I abbreviated RBC's I have plasma proteins which I just have read it abbreviated PP we've got some white blood cells in there to fight infection so the point is blood has blood in it right duh but it also has these big plasma proteins that have very important functions that will eventually get to but for now all these chunky Funky's inside your blood make blood hypertonic so remember if I'm water I'm always gonna think the blood is a good idea I'm always gonna want to be in the bloodstream so on the arterial side if you start there on the left you're closest to the heart that's why I drew a heart so that's going to be the highest blood pressure in this drawing will be on the arterial side so we've got very high blood pressure we also don't have hardly any friction so if you walk across the floor and you lift up your feet versus dragging it if you lift up your feet you have less friction right so blood we have that inner lining of the blood vessel to do everything we can to reduce friction but as long as blood is making contact with the vessels there's gonna be some but ideally it's really slick so there's not a lot of friction like a water slide but there's still some but we haven't dragged our feet quote-unquote in the capillary bed yet the blood hasn't had time to really go through the capillary so on the arterial side pressure is really really high friction is really really low so in the beginning of the capillary bed water is gonna want to leave remember from your last drawing blood pressures going to win so we call this filtration just like when you make coffee filtration is favored it's happening on the arterial side because blood pressure is so high which remember is hydrostatic pressure so the water is still coming back to the blood but more water is leaving and so who's the winner chicken dinner remember the little green arrows from our last drawing in the beginning of the capillary bed filtration winds filtration is favored and so it's gonna send out water with all those nutrients with all those hormones with all that oxygen the beginning of the capillary bed is about feeding your tissues we want to send all the good stuff out so we do this and as we move through the capillary bed if you remember that previous picture where it changed from red to blue towards the end of the capillary bed it flips blood pressure now goes down because remember the farther we get from the heart blood pressure goes down so we've now moved through the capillary bed blood pressure is lessened so the water inside the capillary bed isn't as crowded anymore and doesn't have as much desire to leave we also have a lot of friction by this point which is slow which has slowed the blood down which is why capillaries have the slowest blood in your body so both of these factors mean the water that's inside your blood stream doesn't really want to leave it will but it's not that excited but remember the water that's in your tissues is very attracted to the hypertonic blood and it's going to want to come back so on this side of the capillary bed we call this reabsorption because your reabsorbing back into the bloodstream so reabsorption is favored because now osmotic pressure is going to win hypotonic to hypertonic is going to win but this is good because now we are sucking up water that has carbon dioxide and all of those waste products so this is capillary exchange it's the guy showing up giving you a pizza and you give him money the blood squirts out the good stuff in the beginning because filtration is favored and reabsorbs sucks up the bad stuff in the end you this slide just reviews exactly what I just said so if you draw both of these pictures and go through this either with my voice or just reading this over and over again so osmotic pressure in the capillary is caused by cells and plasma proteins so that's just tonicity so blood remember is hypertonic because it has a lot of stuff in it otherwise it wouldn't be blood right it would just be water so especially at the end of the capillary bed that osmotic pull is important reabsorption wins at the end of the capillary bed because all of that water that has all that dissolved waste waste is going to want to come back to the blood now we will see the lymphatic systems roll with this but that is more our next unit but basically the lymphatic system is there to absorb any excess water so if you send too much water out to your tissues like if you eat a lot of salt and your fingers get swollen your lymphatic system will help suck up that excess fluid hydrostatic pressure remember blood pressure anytime you see hydrostatic pressure it's blood pressure so this is happening more in the beginning of the capillary bed in the beginning of the capillary bed remember that water that that water in your blood is pounding into the capillary bed because it just came off of an arteriole it's closer to the heart so it's gonna force the water out of the blood but that's good because that's taking the good stuff so in the beginning of the capillary bed hydrostatic pressure wins at the end of the capillary bed osmotic pressure wins at the beginning of the capillary bed you're sending stuff out we call that filtration at the end of the capillary bed you're reabsorbing it you're sucking it back up so this is just a comparison of the two processes we just saw filtration versus reabsorption so filtration is caused by hydrostatic pressure blood pressure reabsorption is caused by osmotic pressure the fact that water always goes from hypo to hypertonic filtration the more blood pressure the more filtration it's just like when you make coffee the more water you put in the reservoir the more coffee you're gonna get this plug pushes things out into what's called the interstitial space which is just the space between the cells basically you're just pushing the fluid out with all that good stuff to feed your cells whereas reabsorption is affected by the more concentrated your blood the more reabsorption so the more water you send out if you look at the blood that's left behind it's going to be even more and more hypertonic if it's lost a lot of water which it does in the beginning of the capillary bed the blood concentration is going to go up and so if I can go from number 50 in line to number one I am really haulin ass right if I can go from 50 to 30 I'm still gonna move but I'm not gonna move as fast so the more concentrated the blood the more hypertonic the blood is the more water is going to reabsorb but that's good right because if you're really dehydrated you'd want that water to come back so when it pulls that water back from the interstitial spaces from the tissues it's going to have all those waste products in it so if we go back to that first drawing with the green arrows how do you know which way the fluids gonna move it's a tug-of-war somebody has to win life's not a tie life's not about participation somebody wins and somebody loses it's how it always is right so it's the same here if blood pressure wins filtration occurs if osmotic pressure wins reabsorption occurs somebody has to win either there's more people getting on the elevator than off or vice versa somebody has to win in healthy people the beginning of the capillary bed we send the blood out or sorry we send the water in the blood out and at the end of the capillary we bring the water back in the beginning of the capillary we send out all the good stuff at the end of the capillary we pick up all the bad but not everyone is normal and healthy right so starvation I'm not talking about me right now I haven't had lunch and I'm quote-unquote starving I'm talking about people that are profoundly starving so starvation and osmotic pressure starvation if you're not you're to the point where you haven't eaten in like three weeks if you're malnourished if all you've had in three weeks is rice you're not getting enough protein you will get what's called edema edema is swelling this is because if you're starving you're gonna need to use those proteins for other things I'm not gonna make proteins that are floating around in my blood if I can't even make skin right it's just like your bills you're gonna keep your heat on before you're gonna pay your cell phone bill because priorities right what keeps you alive if you're starving you're not gonna make those plasma proteins well remember plasma proteins are what make the blood extremely hypertonic so if I'm water I'm only coming back to that blood at the end of the capillary bed because I'm attracted to it well if you don't have those proteins the water's not gonna have the incentive to come out so it's actually gonna pull water out of your bloodstream we call this called Yodle osmotic pressure which is a real nerdy way of saying protein osmotic pressure because colloid all comes from collagen so this is why sometimes like your tissues will swell is cuz of edema sometimes things will pull water out of your bloodstream for example salt but in this case people that are starving will end up with if you've ever seen those little kids with the pot bellies like their arms and legs are stick-thin but they have the little potbelly when I was a kid I thought that was fat and I would ask my mom well why do they have fat bellies if they're starving well it wasn't fat it was water it was water getting pulled into that peritoneal space because the water wasn't returning to their bloodstream because they don't have the proteins so starving person their blood is not very hypertonic so there's no reason for the water to come back so this is an actual scientific diagram from your textbook that's showing the arterial and the venule and the capillary bed in between and this is showing just some numbers about pressure so it's like the elevator thing if you look there on the Left 33 out 20 in so I'm losing 13 right so even though 33 people leave the elevator 20 people are getting back in so overall I've lost 13 so at the beginning of the capillary bed filtration is favored but that doesn't mean water's not coming back water always wants to be in the blood it's just we're sending more out so who's the winner chicken dinner on this example 13 so we're losing 13 pressure of water consequently at the end of the capillary bed we have water coming back and water stew leaving we still have an exchange but who's the overall winner in this case now reabsorption so in the beginning of the capillary bed we send more water out at the end we reabsorb more water so after we leave the capillaries we now get into venules so these arise from the capillaries and merge to eventually become veins so the whole job of venules to drain those capillaries remember right now this blood is dirty now we got to get it back to the heart we're gonna have lower pressure because we're further from the heart so it's always gonna be lower the farther you go down from the heart blood flow is very slow so the velocity of the blood is very slow but it's still faster than capillaries so this is like you're leaving your driveway and you get on your side street you're starting to pick up the pace a little bit veins carry blood back to the heart remember a in a way for arteries veins back to the heart so these have three layers but that media is very very thin there's not as much muscle because you don't have that much pressure in the veins the veins have the lowest blood pressure in your entire body because the blank the veins are as far from the heart as you can get so even though the superior and inferior vena cava are attached to the heart there is far from the heart as you can get if we're talking about blood flow so these have the lowest blood pressure because of that they have the greatest lumen that's just the space so if you're looking through a grossberger straw has a huge space a huge lumen the walls are very very thin you can actually collapse your veins and veins because they have such low blood pressure they need a little bit of help so to keep blood flowing you have valves in your veins so a good way to remember is valves start with v and veins start with st. with v so it's all about keeping the blood flowing especially since gravity your arteries have it great right because they've got the pressure of the heart to give them a good squirt and gravity works for them to send the blood down to my feet is way the hell easier than bringing it all back so the valves have to help out your veins as the blood goes arteries arterioles capillaries and then that's all the good blood that we're then dumping into the venous system so blood pressure is slowing way down so veins have a hard time because how is the blood gonna get back to the heart it can't rely on blood pressure because veins have hardly any blood pressure at all because they're so far from the heart so veins have to have some fancy this is a really good chart to look at to compare arteries arterioles capillaries venules veins and the vena cava ultimately so first of all if we look at the top picture that's showing the vessels so you can see arteries they branched arterioles they branched capillaries they branched venules they branched veins total area you don't have very many arteries whereas if you look at that middle diagram how it's peeking at capillaries remember I said if you needed crayons to color in your driveways you have way more driveways so if we're talking about area you have way more of the tiny vessels than you do the big vessels just like we have way more smaller roads than we do big roads velocity of the blood this is the speed of the blood so it's never gonna get any faster than the aorta and your major arteries those have the fastest blood in your body those are the interstates of your body the blood is pumping from the force of the heart look how much it drops off speed with capillaries it's almost at a standstill but that's where exchange occurs right my Domino's guy has to get off the interstate to bring me my pizza to my driveway but then notice how the blood speed picks up a little bit but even when we're in the major veins even when we're in the vena cava it's nowhere near where it was in the beginning this picture is illustrating blood pressure so the aorta is the highest and then it drops off from there all the way down to look at the vena cava it's practically zero you practically have zero blood pressure in the vena cava but remember those vessels are as far from the heart as they can get because they're the ones that are bringing the blood back so the farther you get from the pump of the left ventricle especially the worse off your blood pressure vanes need some help they're Fighting Gravity they don't have that thick muscle layer how do we get this blood back to the heart well you got to move around the answer is always exercise the answer is never Takeda tequila and Twinkies it's always exercise but you got to move around those of you that work in nursing homes know that when people are immobile they get swollen they get a demo which is swelling because one of the major ways you bring blood back to your heart is squeezing your major skeletal muscles especially in your legs and your butt gravity gravity helps the veins the superior vena cava right if I'm draining blood from my head gravity helps otherwise the lower part of your body has to have these little valves which we're about to see and it's basically to keep the blood from sliding back down the veins but we'll see a picture of it breathing eating helps moving your lungs moving your respiratory organs including your muscles and your abdominal that's gonna squeeze that diaphragm and help push the blood up and then if you get really desperate your nervous system can kink your hoses your nervous system can constrict the veins which will hopefully get them to squirt a little better