Lecture 3 - Blood vessels, circulation, and lymphatics

I've run dr. Mike here now let's tie types of blood vessels we have in our body so what I've drawn up down the bottom is we have the larger blood vessels that are coming from the heart that we term arteries okay so remember here's the left-hand side of the heart the important thing about the left-hand side of the heart is that it's delivering blood to the body so this is where blood gets injected from the heart through the aorta and then you can see it gets distributed to all these various parts tissues this includes the coronary arteries the brain the gut the renal system the muscles and the skin plus other areas of the body and that means that the large vessels that exit the left hand side of the heart are under high amounts of pressure because that left ventricle contracts really really hard in actual fact the strongest pressure coming out of that left ventricle is 120 millimeters of mercury that's quite a strong contraction in actual fact if you want to measure that not in mercury but measure that in water would be around about three meters of water that means if that left ventricle contracted under its highest pressure it could squirt water around about three meters out all right now this is an artery right here and arteries what you need to know about other is comprised of elastic tissue really important point elastic tissue why because when it's under high pressure it needs to stretch and the important part about stretching is that it recalls snaps back into place so that means that arteries are filled with elastic tissue and they are compliant really important point as you get older sometimes they can harden stiffen and then become less compliant which means they don't stretch very well under high pressures which means they're more likely to be damaged under higher pressures hence why people as they get older can have stiffened arteries but also increase the likelihood of damage to those arteries forming atherosclerosis and that can lead to a plaque being built up and that plaque can detach a thrombus can form and now that's a clot that can potentially travel to the brain stroke the heart heart attack okay so arteries compliant elastic tissue as we move from arteries they branch off into these multiple smaller blood vessels called arterioles now there's arterioles as you can see here they lead into capillary beds but an important point about arterioles are they have heaps amount of is elastic tissue no it's smooth muscle they have huge amounts of smooth muscles surrounding them then why is this important it's important because you can tell muscle to contract and if you've got muscles surrounding a tube and you tell that muscle to contract it narrows the hollow inside of that tube now think about it bloods moving through here if it wants to go let's say to the gut but the muscles constrict and limit the amount of blood going in it means the blood backs up backs up backs up if you do have to multiple areas of the body you're gonna increase the amount of blood in the systemic circulation and increase the pressure just like having a hose and putting your thumb on the end of the hose the pressure increases right and so what that does is it increases the pressure so arterioles have lots of smooth muscle and this makes them resistance vessels I said arteries have elastic tissue they're compliant you've got arterioles have smooth muscle and they are resistance vessels they can play around with blood pressure now what we have right in the middle here are the capillary beds now this is the site of exchange or exchanging gases were exchanging nutrients we're exchanging metabolic waste products and you can see that capillary beds are porous and they that means they have holes in them and you can have different types of capillary beds and different sized pores okay so for example you can have these sinusoidal capillary beds and they are located in areas where you need mass exodus of fluids proteins cells this can happen in the bone marrow for example their sinusoidal but at most of the tissues they're just porous holes that are so small that not even proteins or cells can leave them simply the fluids the ions the gases and the waste products can go back and forth so that means that capillaries are porous and they're the site of exchange then we move on the other side of the capillary bed where we have venules and then veins okay venules gather all that blood that's just been exchanged at the capillary beds and they've then put them into a vein or multiple veins larger vessels that go back to the heart and we know from there it goes to the lungs to get that oxygen now venules and veins have a thinner wall then you'd find with the arteries and arterials but what you'll find is they can be larger in diameter and what you'll find is because of their thin walls and their larger diameter it means they can hold most of the blood most of the blood in the circulation is actually sitting in the venous system which makes them capacitance vessels okay so what do we have now so just to summarize we have arteries elastic tissue compliant arterioles smooth muscle resistance capillaries porous exchange venules and veins thin walled wider diameter capacitance vessels holds most of the Bloods so that's a quick run-through of the blood vessels of the body in this video we're going to have a look at capillary exchange so capillary exchange happens at capillary beds and this is the exchange of bulk fluids out of the capillaries and once this fluid has exchanged out of the capillary it's able to via the process of diffusion hand over the oxygen hand over some of the nutrients that's required for the tissues and also the tissues need to hand over to that fluid carbon dioxide and also some metabolic waste products like urea for example so basically we have and you need to remember this when the heart contracts like when that left ventricle contracts it's pushing out oxygenated blood which has nutrients in it add a left ventricle into the aorta now remember where this blood goes once it goes out via the aorta the aorta branches into all of it aeolic branches and these continue to branch like a tree now as these arteries because it's leaving the heart as they branch they get smaller in diameter but they become more numerous okay and all of these branches end up feeding all the tissues of the body now every minute that Hart's going to contract a relaxed contract and relax contracture relax every minute this is going to happen around about 72 times okay so every run about 72 beats of your heart per minute every contraction pushes out approximately about 70 mils of blood so 70 mils pushing out just could your stroke volume every contraction pushes out 70 mils times 72 beats in a minute means that in a time span of one minute your heart will push through five liters of blood okay so this is on both sides of your heart so remember the left hand side of your heart deals with oxygenated blood and delivers it to the whole body every minute the left-hand side of your heart will deliver five liters of blood to the tissues of your body the right-hand side of your heart deals with deoxygenated blood and therefore this blood needs to get to the lungs and again every minute this side of your heart will push out five liters of blood so if we just have a look at what I've drawn here on this side of the whiteboard you'll see we've got the heart if we have a look at the left-hand side of the heart when it contracts pushes blood out of the aorta the aortic branches into all of it aortic branches and then further branches into smaller arterioles and these arterioles will then lead into capillary beds and these capillary beds could be capillary beds of the coronary arteries cerebrovascular capillary beds capillary beds of the gastrointestinal tract of the renal system of the muscular skeletal system and also the skin you can't these are just potential places that this blood could go through now remember as it gets to the capillary bed the capillary bed is the site of exchange and that's exchanging gases oxygen carbon dioxide and also nutrients and waste products then on the other side of this capillary beds we have veins okay veins will always go back to the heart and you can see they all come together and these veins will get back to the right hand side of the heart by the vena cava whether that's the superior or the inferior vena cava now to the right hand side of the heart it will contract and push that deoxygenated blood where to the lungs to get oxygenated and again this Bloods coming through two capillary beds of the lungs if we look at this portion so the blood that's going to the body every minute five liters if we look at this portion go into lungs every minute five liters but here this blood is partitioned to various tissues now why am i bringing this up when we're talking about capillary exchange because when the Bloods push down the left hand side huh it's under a particular amount of pressure okay and in one of the previous videos I've spoken about blood pressure and I spoke to you about the fact that a normal blood pressure is 120 over 80 120 is the systolic value so 120 is telling me that when the heart contracts under systole this is the pressure that the blood exerts on the walls of your arteries 120 millimeters of mercury the bottom value 80 is the diastolic value and this is the amount of pressure within those arteries when the heart is relaxing okay now saying 120 over 80 is important clinically but to know what the mean arterial pressure is I told you that you need to take the diastolic value and add a third of the pulse pressure now if you're unsure what that means go back to the previous video looking at blood pressure and that will explain it all but mean arterial pressure is 93 millimeters of mercury that's just saying that going through the arteries of the body the mean pressure that the blood is exerting on the walls is 93 millimeters of mercury and as this 93 millimeters of mercury starts the move through these various branches the pressure drops and by the time the blood reaches the capillary beds it's no longer 93 millimeters of mercury by the time the blood reaches the capillary beds the pressure of the blood inside the capillary beds is 13 millimeters of mercury between 30 to 35 okay now what does that mean it means that Bloods going to move through these small arterioles until it gets into a capillary bed and you know capillaries are porous that means they have holes in them and you can see these little holes through this computer in bed okay now this blood is getting through and by the time it reaches what we call you can see one side of the capillary bed upjohn red the other side of John in blue because one side is the arteriole end and the other side is the venous end because remember arterial blood is oxygenated venous blood is deoxygenated which means that here we have that stuff coming out and here it's no longer oxygenated so Bloods being pushed out of here exchanging gases so pushing out oxygen taking in carbon dioxide and here we now have deoxygenated blood and this blood is ultimately leaving the tissue and going back to the heart and then two lives so as this blood is coming through as it gets into the part Tyrael end of the capillary there is a blood pressure that's pushing out and this blood pressure is like I said thirty millimeters of mercury now remember pressure that we measure in blood vessels is simply as the blood moves through the vessel blood is pushing on the walls of those arteries there's no holes in the walls of arteries they're not porous so blood cannot leak out okay as those arteries branch out even further and gets smaller in diameter they turn into arterioles and again arterioles don't have holes they don't pause so blood cannot be pushed out but as when those arterioles branch off into these smaller capillaries that's when they have these holes in these pores and therefore as the blood comes through and pushes on the walls it can leak out and so once we get to the capillaries we now have 30 millimeters of mercury pressure pushing on the walls and that means that this fluid this blood fluid has been pushed out of the capillaries okay like 30 millimeters of mercury pressure now the important point is this you can see that there's little holes in the walls of the capillaries these holes are of a particular size okay now what is in blood you need to remember what's inside of blood it's not just a fluid inside blood we have red blood cells we have platelets we have white blood cells we also have what proteins okay so all these substances of the blood is coming through now these holes are too small to let white blood cells red blood cells platelets and proteins out okay they're too small so you remember diffusion remember that in diffusion if you have a concentration difference of a substance on one side of a membrane compared to the other side of a membrane but this concentration difference will want to balance itself out okay so if I can draw it up here very quickly if I'll have a container and I'll still put a membrane in between a semipermeable membrane and I was to fill both sides up with water and on one side of the membrane has to put some substances some particles and on the other side I don't put any particles well under diffusion these particles on this has this sign so sign a compare to site B the particles on side a would want to diffuse from its high area of concentration towards its low area of concentration okay but there's a membrane here and this membrane will not let these particles through so it cannot diffuse across from A to B but there's osmosis and osmosis is the movement of water through a semipermeable membrane from an area of high water concentration to an area of low water concentration what that means is basically this these particles on site a exert a pull okay they exert a pull of that water from side B to slightly so that means in order to balance out the concentration of both sides these particles pull water towards me okay what happens to the water volume on this side it starts to rise up okay so think about that in regards to the blood we have the blood moving through and it's exerting pressure on these walls at 30 millimeters of mercury there's holes here so the fluid can leak out at 30 millimeters of mercury but we have substances inside that cannot move out these substances substances sorry what a diffuse out of the vessel but they cannot there is a semi permeable membrane in between so what that means is these substances exert a pull back in they exert a pull because there's a high concentration of particles here and the low concentration of particles here so they actually exert a pull now of all these particles I said red blood cells platelets white blood cells proteins which of these exert the strongest pull the answer is for proteins now the next thing is which proteins you should know what the most abundant protein is within the blood it's called albumin and this albumin protein is very important in in eliciting a pull of the fluid back in okay yeah the strength of this pull the strength of the pull is 20 millimeters of mercury now I want you to have a look at this we have a push out of 30 millimeters of mercury and a pull in at 20 millimeters of mercury when you have two pressures opposing each other the stronger pressure will always win what if you have two people pushing against each other and you say - one of you said one of them push harder than the other person that person is going to win okay they're exerting more force so if you have a look at these two which one is exerting more force the 30 millimeters of mercury pushing out that overpowers the 20 millimeters of by what's the difference 10 millimeters of mercury okay what that means is at the arteriole end of a capillary stuff gets pushed out okay there's a pull back end but overall stuff gets pushed out now all the stuff that gets pushed out this is fluid this is a bulk push of blood fluid coming out and in this fluid it has gases because they're small enough to get through in the fluid anna has substances like glucose they small enough to get through these gaps as well and then this fluid can exchange with the tissues now as we move across from the arterial oh because remember Bloods moving through like this is coming through pushing out as we moved from the arteriole into the venous end I want you to think about what happens to this pressure if you're at a hose and you were to connect that hose to a tap and you turn that tap on add a particular pressure so you turn it on let's say you turn it on halfway and you had a look at the hose let's say the hose is 10 meters in length you look at the other end of the hose and water squirting out that end at a particular pressure okay let's say you two now put holes in that hose so let's say every meter for the 10 meter hose you put a hole hole hole hole and you have it turned on at halfway and you have a look at what's happening at those holes you see water squirting out right now let's say you have a look at the hole that's closest to the tap the water's going to be squirting out of that hole at a particular pressure at a particular height as we move down what do you think so just think about what's going to happen to the pressure of that water pushing out those holes is the pressure going to increase or decrease is the water going to push out at a higher distance or less well think about how is it turned on what is pushing out at a particular height closest to but because that water's leaving the pressure drops distal to that and then the next one squirts out but it's a little less and then the next one drops a little less so the pressure decreases as you move down the hose because those holes are reducing the pressure as a moving throat that's what happens in capillaries so as we move from the arterial and stuffs getting pushed out to the pressure in here drops and that means that the venous and the pressure drops enough that it ends up being I push out on 15 millimeters of mercury now these substances such as and I'm just going to draw the albumin is continually moving through so it's still on this side of the venous end of the capillary okay so this substance ISM these substances are moving through so these proteins are still exerting a pull of the floor back in and this pool is still around about 20 millimeters of mercury so have a look now if you were to measure the pressures against each other which one now wins well 15 out 20 in the pull in now wins the difference five millimeters of mercury so what that means is at the arteriole end we have a bulk flow or a net flow of fluid being pushed out and then when we get to the venous end we have a net flow of fluid being pulled back in and the reason why this is important is because the fluid that's on this end is handing over oxygen and substances like glucose and then let's continue continuing past and then on this end the tissues handing it carbon dioxide and waste and why is that perfect because this is where the floor gets pulled back in and can get taken back to the heart perfect perfect perfect perfect now the push out and the pull in have names which you need to know okay so the push out remember I've drawn it in red so the push out is called the hydro static pressure and basically it's blood pressure right because it's the pressure of the blood being pushed in the walls of the arterial end of the capillary okay but pull in which I drink blow so I'm just going to drill the blue arrow here the pull in is called colloid osmotic pressure and I told you it's the pull of the proteins in the blood pulling that fluid back in yeah let's just think clinically for one second what if we were to increase the size of these gaps in the capillaries let's say they're now big enough for proteins to move out so that means that as the blood comes through 30 millimeters of mercury pressure pushing out not just fluid comes out but also the proteins come out as well if the proteins leave the capillaries is there any pullback in no so that means we have all this bulk flow out including proteins and there's no proteins to move to the venous end so there's no pull back in which means fluid just continues to accumulate outside the capillaries in an area called the interstitial meaning between the tissues this is edema so when you see a patient who has fluid buildup at the bottom of their legs or at the periphery this is edema and it can be due to one of the reasons a widened between the endothelial cells of your capillaries think about inflammation inflammation is just injury or damage occurring to vascularized tissue everyone's had some form of inflammatory response let's say you've cut your hand what happens you've got the four cardinal signs of inflammation you've got the redness you've got the swelling you've got the heat and you've got the pain okay these have been known for thousands of years but what's one of those that we need to remember swelling so you cut yourself you always notice swelling at the site why because when you damage cells of your skin these cells explode their guts and inside there's histamine and histamines are chemicals that creates larger gaps in your capillaries why why would we want this because if I want to cut myself whatever cut me let's say it was a nail what if there's bacteria on that nail I now have bacteria in my teen decision okay how am I supposed to attack it and kill it if all my white blood cells are in my capillaries well histamine opens up the gates and white blood cells can come out and attack the bacteria kill it off but what that also means is fluid comes out but this is good as well because the fluid sort of washes it away and die looks it okay now you may think that of all the fluid under normal situations of all the food that's given that gets pushed out on the arterial side that it all gets pulled back in that's not the case there is a small percentage of this fluid that once it gets pushed out you cannot get pulled back in now this is enough even though it's a fraction of the fluid it's enough that at the end of the day if we could not find a way to pull that fluid back in if we could not pull that forward back in our blood pressure drop enough that would die at the end of one day so it means that on the floor that can't get pulled back and we do have a mechanism we need to get that fluid back how do we get it back the lymphatic system so we have lymphatic vessels as well around our tissues and the lymphatic vessels help bring back that lost fluid from a capillary exchange and drops it back into our Veda supply so I hope that this made sense looking at capillary exchange I run dr. Marc here in this video we're talking about pressure but more specifically we're talking about one part of the blood pressure equation which is really important something called systemic vascular resistance also known as total peripheral resistance I know sounds like a mouthful and doesn't seem to make sense from the beginning but let's have a quick look when we look at blood pressure or blood pressure is is the amount of force exerted on the walls of the blood vessel when the blood is moving through so for example this is the left hand side of the heart which delivers blood to the whole body as you can see the heart the brain the GRT the rain or the muscle the skin and multiple other aspects now in order for the blood to get from this left ventricle or chamber it needs to travel through these blood vessels to get there and it does so when that left ventricle contracts now when it contracts it squeezes blood which obviously pushes blood and as that blood pushes through it's going to put pressure on the walls of these vessels and that simply is blood pressure now we know here from the left ventricle to the aorta that the blood pressure is going to be around about 120 millimeters of mercury under its strongest contraction okay that's pressure now this blood pressure we can gather from an equation which involves cardiac output which is the amount of blood we eject every minute and multiply that by what we're talking about today the systemic vascular resistance now let's have a look what systemic vascular resistance actually is when this blood moves through from the aorta the large elastic vessels and then goes to all the areas where it branches off to different tissues of the body these smaller arteries we term arterioles these are the arterioles here and something i've told you about in the past is that arterioles have huge amounts of smooth muscle in the inside layer of their walls so that means all of these arterioles have smooth muscle around them all right now what does that mean well it means that muscle can contract and if you've got muscle lining a tube and it contracts it narrows the hollow inside of that tube which means less blood can move through now an interesting thing is when we talk about pipes and fluid movement especially in the bloodstream if I have a pipe of a particular length and then I have the size of that pipe in regards to having the diameter of that pipe you would think that we have now have the amount of blood that can go through but in actual fact it is to the power of 4 so that means 1 over 2 times 2 times 2 times 2 that actually means 1/16 that means instead of having the amount of blood when you have the diameter of the vessel you decrease the amount to 1/16 only 1/16 of the amount of blood gets through so that means when I constrict any of these particular arterioles I significantly alter how much blood goes past going to the various tissues of the body to feed it right now let's think of an actual scenario that happens in our body you are walking in the park late at night you hear a rustle in the bush and then all of a sudden a big dog jumps out starts barking at you what happens you get scared you activate that fight or flight system that we turn the sympathetic nervous system now when you activate the sympathetic nervous system and you get scared you can feel your heart beat harder stronger faster but also if you looked into a mirror you look white now why do you look white when you get scared because your sympathetic nervous system which is the home of adrenaline gets released into your body and this adrenaline goes to the arterioles of the skin which has lots of muscle and it tells it to constrict the blood vessels feeling your skin can strict now 5% of all the blood that exits your left ventricle 5 percent goes to the skin which means when they constrict that blood doesn't go to your skin so you turn pale and backs up into the system another thing that happens is you jit your gastrointestinal tract when you're scared you don't need to use that so the muscles there constrict as well in the arterioles and 25% of your cardiac output or blood that comes out of your left ventricle every minute goes to your GRT so now 25 plus 5% 30% of your blood volume gets shunted back into this systemic system now again when you put your thumb on the end of a hose this is what you're effectively doing here the pressure backs up in increases so it backs up backs up backs up increases and what have we now effectively done simply by changing the diameter of these tubes with increased blood pressure so systemic vascular resistance also known as total peripheral resistance if you decrease the diameter of it you're going to increase the resistance you increase the resistance you increase blood pressure now this is diameter but you can also change systemic vascular resistance by changing the length of the tube the length of the blood vessel okay now think about this you have a 10 meter long garden hose at home and you turn it on you see at the other end water squirting out at a particular pressure now if you were to keep that tap turned on at the same pressure yet you lengthen that tube to a kilometer what do you think the pressure would be on the other end of that tube would it be coming out at the same pressures the 10 meter tube no it wouldn't the pressure would be decreased because the longer a blood vessel is the more the blood gets stopped by it as it moves through right so there's more resistance therefore what you get is a problem that means in order to think about this if I had instead of a 10 kilometer long blood vessel I had a 1 million kilometer long blood vessel it means that at the other end of that vessel the pressure is going to be lower with my heart just pumping normally so my heart would need to respond by pumping harder just to get the same pressure on the other end just to get these tissues fed when's a clinical example that this is going to happen in individuals who are obese the larger your body mass the longer your blood vessels for every kilogram of fat that you put on your body you need to generate at least a thousand kilometers of blood vessels which means the heart in response needs to pump harder just to get the same amount of pressure getting to your tissues that means there's more strain in your heart over time that means increased likelihood of cardiovascular disease all right so that's length but you can't change length in the short term you can in them you can change diameter in the short term through the sympathetic nervous system can't change length in the short term that's overtime increasing body size and viscosity is the last way you can alter system vascular resistance viscosity is how many things are in your blood how thick is your blood now how do you change this where you can change this with the number of red blood cells okay so some people can have polycythemia which is too many red blood cells that makes your blood thicker which means if the Bloods thicker it's harder to move through and it increases systemic vascular resistance or you can have anemia and it's thinner and it's gonna affect systemic vascular resistance or you could blood dope with erythropoietin EPO as some cyclists have done in the past and that will also make your blood more viscous and again increase systemic vascular resistance alright so and when it comes to blood pressure your blood vessels themselves diameter like the viscosity have a very important role in altering that blood pressure now another way that you can alter the diameter of your blood vessels I said short term constriction in the long term you can see your kidneys require 20% of your cardiac output really important if that drops for any particular reason your kidneys actually respond by releasing a hormone called renin which then stimulates the release of another hormone called angiotensin ii and that tells the skin to constrict or at least tells the blood vessels to the skin to constrict and it backs the blood up increasing pressure again saying hey skin doesn't need it I need it and it backs up that's the renin-angiotensin-aldosterone system and I'll do an entire video just on that in this video we're going to take a quick look at blood pressure now blood pressure is the pressure or the force that the blood and your vessels exerts on the walls of that vessel okay now how do we generate this sort of pressure well today we're going to have a look just at the left hand side of the heart because the left hand side of the heart deals with oxygenated blood that it needs to deliver to the whole body you know that when that left ventricle contracts pushes blood up into the aorta and the aorta branches numerous times and ultimately leads to capillary beds of the tissues for the tissue to get fed now without the right amount of pressure behind the blood pushing it through the blood will not get to the tissues and put use at the sites in which it needs to meaning it won't be able to feed those tissues so blood pressure is required for perfusion in order for the blood to feed the tissues at the appropriate sites and you know that that left ventricle when it contracts needs to send the blood to the top of your head to the tip of your toes so there needs to be a relatively high amount of pressure being generated from that left side of the heart the reason why we're not talking about the right hand side the heart today is because when that contracts it's just sending the blood to the lungs now yes that's important but the lungs are not very far away from the heart other so when the right-hand side of the heart contracts it does not generate a huge amount of pressure in order to get the blood to the lungs we want to talk about what we call the systemic blood pressure and the systemic blood pressure is generated by the left hand side of the heart specifically the left ventricle so what I've drawn up here is the left hand side the heart so I've got the left atrium and look at the left ventricle and you know that the left ventricle leads to the aorta and that VA orders going to branch numerous times and that's going to branch again into arterioles okay so I want you to remember that this is left hand side of the heart left atrium left ventricle Ayana and all these branches and these are arterioles ultimately go into capillary beds okay now when the blood from the pulmonary vein fills that left ventricle it's now oxygenated because pulmonary vein means from heart from lungs so this is oxygenated blood coming from the lungs going into the left atrium contracts pushes blood through the bicuspid or mitral valve into the left ventricle and you know that the walls the muscular walls of the left ventricle are extremely muscular okay so when this muscle contracts it squeezes and pushes blood up through the aortic semilunar valve into the aorta now important point when the left ventricle contracts this is known as sisterly mechanic so contraction is referring to systole when this left ventricle relaxes that's called diastole so contraction systole relaxation diastole let's write that down systole it's a contraction diastole relaxation but so you must keep that in mind now Bloods filled that left ventricle now that left ventricle contracts so that systole and what happens when that left ventricle contracts as that left ventricle contracts the blood gets pushed up through the pulmonary semilunar valve it goes into the aorta now when it contracts it produces a certain amount of pressure and I told you that pressure is the force of the blood on the walls of the vessels this pressure that's generated in this left ventricle under systole under contraction is 120 millimeters of mercury okay now this pressure gets transmitted into the elder so 120 millimeters of mercury gets transmitted into the aorta and because the aorta is very stretchy the aorta starts to bulge out so what you can see is this left ventricle contracts systole create a pressure inside that left ventricle of 120 millimeters of mercury that blood with a pressure behind it of 120 millimeters of mercury is pushed into the very distensible very stretchy a order and 120 millimeters mercury stretches the a on around okay that is what we call the systolic blood pressure and therefore it's a hundred and twenty millimeters of mercury okay now when that left ventricle relaxes when that left ventricle relaxes the pressure inside this left ventricle drops and that means these valves closed because the blood that's here in the aorta wants to come back down there's no more pressure behind it so the blood that's pulled here wants to come back down but luckily the aortic semilunar valves closed now the other thing is this because that a order was stretched out under systole just like a rubber band would be when this ventricle relaxes this rubber band reclaims and comes back in now as this rubber band recoils and comes back in what do you think happens to the blood that's pulled here it gets pushed forward okay now because even though the left ventricles relaxed it means that because of the stretch ability of the aorta that the blood could continually be pushed through so basically if contraction blood comes out descends that pressure on the wall is 120 millimeters of mercury then when the ventricle relaxes the aorta comes back in it recalls back in and continues to propagate blood through this pressure that's propagated from the recall of the aorta is the distillate pressure and so the distillate pressure is about 80 millimeters of mercury okay the dystonic pressure is about 80 millimeters of mercury now hopefully that makes so that's why when you measure your blood pressure so remember the aorta branches off one of the branches is the brachiocephalic branch okay and the brachiocephalic branch is going to come down into the subclavian and the subclavian is going to come down into the brachial and you're gonna have your brachial artery and what do you do you measure blood pressure from the brachial artery whatever pressure is in that brachial artery is reflecting the pressure of the aorta and what that aorta has generated okay and when you do this I want you to think about when you measure do manual blood pressure readings you have that cuff and you wrap the cuff around the patient's arm and you pump that cuff up you put pressure in the cuff because if you have your brachial artery with blood moving through you know that Bloods moving through in a fashion like this contract up Bloods being pushed through a understands left ventricle relaxes recoils continues to push blood through that's why blood doesn't squirt through your arteries like this blood is consistent push their own assistant Lee continues to push nicely so push through when it contracts continues to get pushed under relaxation okay 121 it's contracted 80 millimeters of mercury when it's relaxed now if we have a look at this blood vessel you're going to have pressure being placed upon the walls of this blood vessel the brachial artery and you're going to wrap a cuff around and pump it up now when you pop that cuff up what's it feel like feels like it's getting tight up on your arm and that means that the cuff starts to if we had this cuff wrapped around the vessel as you pump up the pressure it starts to push on the artery now remember what's the outward force on this artery well under systole it's 120 millimeters of mercury so under systole of 120 millimeters of mercury pushing out on this vessel so what do we need to do in order to close this vessel up if we wanted to close this vest on block it all the way up we need to put equal to more pressure in the opposite direction that makes sense 120 millimeters of mercury pushing out we need to put a hundred 21 millimeters of mercury pushing in and that's what we do we pump the cuff up to about 160 170 millimeters of mercury just to make sure and that means that it's fully occluded the pressure going in is beating the pressure coming out and what do you do you take the stethoscope and you put it on the brachial artery and you listen and now what you hear is nothing when it's fully occluded fully blocked okay but then what do you do you slowly release the pressure of the cuff and the cuff starts to come out and out and out and now now as soon as the cuff has come out enough that a little bit of blood can squirt through what does that mean if the cuff has come out enough that a little bit of blood can squirt through that means that the pressure inside the vessel is just overcoming the pressure of the cuff which means I'm no contraction and assistant Li there's a certain amount of pressure coming through and it's overcoming the cuff now that's your systolic reading so when you have your stethoscope on this thing as you releasing the pressure you'll hear a sound and that is going to be your systolic though you look at the reading the reader on the swing my manometer you have a look at the reading and that's giving you systolic value then you continue to release the pressure and you'll keep hearing these sounds until the sounds stopped when the sounds stopped that means the vessel is fully open and there's a constant flow of blood through as soon as you stop hearing that sound that's your diastolic value its meaning that this little and the smallest amount of pressure being generated in this vessel is even able to get passed okay that's measuring your manual blood pressure now last thing I want to talk about is when we look at blood pressure you need to think of the calculations that go towards it now I told you that 120 over 80 is the normal blood pressure whatever that may mean but I want to talk about what things can alter blood pressure okay now I'm gonna do another video on the things that can alter blood pressure but I just want to introduce in the last 1 minute of this video this very important little equation which is blood pressure is equal to cardiac output times systemic vascular resistance what does this mean it means the blood pressure the pressure that the blood is exerting on the walls of your artery is equivalent to cardiac output this is the amount of blood being pushed out of your left ventricle over time how much blood has been pushed out of your left ventricle over time blood quantity basically volume systemic vascular resistance well this is the systemic blood supply here and it's referring to vascular meaning blood vessel resistance so how much resistance are these blood vessels putting on the blood behind it now this is important because your arterioles have smooth muscle wrapped around them and this smooth smooth muscle can either constrict or dilate if this smooth muscle constricts what do you Cap'n's the blood pulls backwards and the blood pressure increases if they dilate more blood can be pushed through and the blood pressure on the walls back here are less okay so the amount of blood coming out of the heart multiplied by the amount of resistance being experienced distal to the arteries can regulate blood pressure in the next video I'm going to talk about this in detail because all the antihypertensive drugs that we give our patients well either alter carry out output or it will alter systemic vascular resistance I hope that made sense hi everyone dr. Mike here and in this video we're going to talk about blood pressure and how some of the common blood pressure medications actually work so remember that a normal blood pressure is around about 120 over 80 now all blood pressure is is the force of the blood on the walls of the vessels inside now if somebody has hypertension it means that they've had constant blood pressure measurements and they've been higher than this 120 over 80 now the problem with this is that if you have high blood pressure over time it can damage the walls of the blood vessels this makes sense if you increase the pressure within a hose increases the likelihood of the walls of that hose getting damaged so we want to decrease blood pressure if somebody is hypotensive so that means chronically increased blood pressure so how does this work well let's have a look at the equation for blood pressure blood pressure equals cardiac output times something called systemic vascular resistance let's have a look what is cardiac output this is simply the amount of blood your heart pumps out per minute so how could we calculate that it's simple you take something called the stroke volume this is the amount of blood pumped out purse per contraction stroke volume and you multiply it by how many times your heart contracts in a minute so stroke volume a single contraction how many times per minute stroke volumes usually about 17 milliliters heart rates are at about 75 beats per minute this ends up being between 4 to 5 liters of blood every single minute this is cardiac output now what you do is you multiply this by something called systemic vascular resistance this is also known as total peripheral resistance sounds like a big term but it's very simple it's basically talking about the resistance that your blood encounters as it moves through the pipes as it moves through the vessels there's three ways that you can alter systemic vascular resistance one you can change the diameter of a blood vessel if you decrease the diameter of a blood vessel it's more difficult for blood to move through and that increases the peripheral vascular resistance you could lengthen a blood vessel so if you were to take a blood vessel and tell it to grow longer and you may be thinking why would a blood vessel grow longer if somebody were to put on weight well there's more body mass blood vessels need to reach distal parts of the body blood vessels get longer and that actually increases systemic vascular resistance that changes blood pressure and then the third way is you can have your blood and you can make it more viscous make it thicker now how can you make your blood thicker well something called EPO erythropoietin some people can dope themselves with EPO to increase the amount of red blood cells increasing the amount of oxygen that's transported around but it increases the sluttiness or viscosity of the blood increases systemic vascular resistance the easiest one to change what do you think blood vessel diameter okay our sympathetic nervous system fight-or-flight changes blood vessel diameter very very quickly so I could probably wipe these two out all right now let's have a look can i cap put so the amount of blood pumped out per minute times the diameter of a blood vessel gives you basically your blood pressure now if you break down stroke volume the amount of blood pumped out per contraction down into blood volume itself and contractility what we now have are the four values or readings which we want to alter to alter blood pressure what are they again well we want to alter blood volume this is gonna alter blood pressure we want to alter contractility alters blood pressure alter heart rate alters blood pressure alter the diameter of a blood vessel alters blood pressure remember you increase any of these things you're going to increase blood pressure now the drugs that we use to decrease blood pressure are going to tell the diamond of a blood vessel to dilates get larger it's going to tell the heart rate to slow down it's going to tell contractility to be more efficient and it's going to tell blood volume to decrease so this is how blood pressure works and how our most common blood pressure medications work hi everybody dr. Mike here in this video we're gonna look at the aortic branches what is the aorta the aorta is that large vessel that exits from the left hand side of the heart that left ventricle now as you can see from the left ventricle we've got the aortic trunk and coming out of the aortic trunk there's a number of different branches we've got one branch here one branch here and one branch here let's have a look at these branches before the aorta descends down through the diaphragm into our abdomen these three branches are this first branch here is what we termed the brachiocephalic the brachiocephalic now the reason why it's called the brachiocephalic there's two words here brachio which means arm and cephalic which means head so this blood vessel is going to go and feed the head and the arm how does it do it well from this branch you've got one that descends down this way and one that goes up this way that we turn the common carotid so let's label this one common carotid an actual fact is going to be the right common carotid what's this well this is called the right subclavian now it's good the subclavian sub meaning below clave ian is referring to the clavicle because what we've got here is the clavicle and it goes behind the clavicle okay now moving a little bit to the left we've got a branch of the aorta here and this is going to be the left common carotid so we've got the right common carotid there with the left common carotid here and because their common carotid they get a branch off and give smaller branches and these smaller branches include the internal and external carotid what's important about the internal and external but it's pretty easy first of all is that the one in the middle there in turn all the ones on the outside they're the external carotid well it's important the internal carotid they supply eighty to eighty-five percent of the brains blood okay the brain gets eighty to eighty-five percent of its blood from the internal carotid not the external the external gives blood to the face and neck okay now what we're moving onto here is what we call the left subclavian which means its sister is the right subclavian over here we're gonna have the clavicle that it moves behind and let's write it up this is the left subclavian now once it's gone underneath the clavicle and it's into our arm up arm it is called the brachial so we're gonna have the left and right brachial I'll just write it up here left brachial and this is that blood vessel that we often do a manual blood pressure reading from okay the brachial artery now there's a couple more branches for the subclavian I'll just very quickly say two that are clinically important they get a branch off right and when they branch off let's branch it off over here so we don't get in the road these two branches I want you to think about this remember this is the forearm that's sorry this is at the top of the arm here and this is going down towards the forearm and it branches off you have the anatomical position with the thumbs facing most laterally and if your thumbs can turn in a circle that means it's turning in a radius so the radial artery is the most lateral and the ulnar is the most medial so that means we have the radial artery here right radial and this is going to be right on our okay why is this important because you can take a pulse from the right radial common radial commonly it's quite easy to do now let's continue with the aorta now the a always going down it's gonna be a couple of branches that get to feed the esophagus feed at various particular areas but doesn't matter we're going down we go through the diaphragm okay so we're going through the diaphragm and as we go down through the diaphragm there is a very quick or I should say immediate branch that comes off which is called the celiac trunk now this is the like I said the celiac trunk and the celiac trunk has three branches that come off which I've done a video on okay these branches are going to feed the liver the stomach the spleen the pancreas the lowest part of the small into the lowest part of the esophagus and a very minor part of the small intestines that's what the celiac trunk does now below the celiac trunk we've got another branch called the superior mesenteric that comes off and the superior mesenteric the superior mesenteric artery that's going to give blood to most of the small intestines a little bit of the large intestines now basically nearly either side of this you're gonna have a paired artery coming out and that's going to be the renal artery that's going to give blood flow to the kidneys the paired renal arteries then below that we're going to have the inferior mesenteric artery and the inferior mesenteric artery it's going to give blood to the rest of the large intestines rectum up to anus inferior mesenteric then as we go even further down we're going towards the legs now what we get is some branching off and now what we're getting is the common iliac arteries left and right common iliac and they're gonna have various branches to them which is going to include the femoral artery now these are the major branches of the aorta okay we've got the left ventricle pushing up the aortic arch which is three main branches at the top then it goes down into the abdomen with celiac trunk superior mez tarek renal artery's inferior mesenteric and then branching for the common iliac as we go into our pelvis and legs so these are the most common branches of the aorta you

Channel: Dr Matt & Dr Mike

Views: 21,440

Keywords: blood, vessels, arteries, veins, lymphatics, circulation, pressure, stroke, volume, cardiac, output, systemic, vascular, resistance, lymph, capillary, exchange, arteriole, diastolic, systolic, nursing, medicine, anatomy, physiology, cardiovascular

Id: oJ6ebQclqHI

Length: 59min 28sec (3568 seconds)

Published: Mon Jun 22 2020