Hello everyone. The purpose of this lecture is the circulatory system. More specifically, what we're going to go through is the different vessels that run to and from the heart.
All of these are going to be identified as arteries and veins. So we've already learned about the different types of vessels that we can have based on their different layers and structures. What we're focusing on here is the arteries, which run away from the heart, and the veins, which run toward the heart.
And hopefully as I paint this picture for you, you're going to get a better idea of how vessels run from the heart. and to the heart in that pathway of blood flow. And hopefully it creates a more unified whole picture for you as to how the blood circulates throughout the body and what it feeds. So arteries and veins, they are going to run again to all parts of the body and the exception in terms of the color is the lungs. So you might remember again that red is going to be representing our oxygen rich or oxygen high arteries.
Blue is going to represent our oxygen-poor, or oxygen-low, veins. And that color-coding system is going to take place throughout the entire body, with the exception, again, of the pulmonary arteries and the pulmonary veins, because the arteries running away from the heart to the lungs are oxygen-poor. We're going to the lungs to pick up more oxygen. The veins coming back into the heart are actually gonna be oxygen-rich.
And so, with the exception of the pulmonary system, the systemic circulation, the arteries are going to be red and the veins are going to be blue. So let's first focus on arterial circulation. So when we talk about the arterial circulation, we're talking about the arteries.
So we're going to be focusing on the red vessels first. Now we are going to be flowing out of the heart and where we're going to be flowing from first is the aorta. The aorta, before we get to our arrows here, let me just take a step back, here is our aorta. The ascending aorta is the part that goes upward. So this is the ascending part of the aorta, also known here as the aortic trunk.
Then this portion is called the aortic arch, and then we have our descending aorta. So I just want to give you an idea here of the different parts of the aorta and what we can identify them as. Now from the aorta, you might remember from our lecture recording, talking about the blood flow to the heart itself.
Remember we have to feed the cells of the heart. We are then going to go from the ascending aorta, or aortic arch, and we're going to go to the right coronary artery. So it's what we see here, again in red, and to the left coronary artery. The left coronary artery is just this part here, and remember, this is gonna come around the bend.
We'll have our circumflex artery. We're not even talking right now about the marginal artery that we can see here, or the anterior interventricular artery, but those are there as well. From there, we're going to talk about the aorta and what branches off from it outside of the heart.
So now we're going to focus on, here is the aorta, the aortic arch. There is a special first branch. So if we come back to the previous slide, you might have noticed we have three branches coming off of the aorta.
That is what we're focusing on now. So this very first branch, second branch, and third branch. So the very first branch, that's the one we're seeing here, we call that the brachiocephalic trunk. The brachiocephalic trunk is going to branch off into two separate arteries. This is the right side of the body.
Just to orient you, here is our left side of the body. Notice again on this model that we're seeing and looking at, we can see more of the superficial on one side compared to the other. So we will not be able to see on our models all of the arteries represented on the right and the left sides. But hopefully you'll see that. I will draw your attention to that.
There are rights and lefts for the majority of these arteries that we're going to be focusing on. We'll just only see them on the right or the left side. So again, coming back from our aortic arch, the very first branch is the brachiocephalic trunk. That is going to divide into two arteries. One is the right common carotid artery.
Now again, there's going to be a left, but right now this one specifically is the right common carotid artery. Whenever you hear common, that often means that it's going to further branch. into more specific arteries, but our common is where we start.
That's one sub-branch, so to speak, of the brachiocephalic trunk. The other branch coming off of the brachiocephalic trunk is the right subclavian artery right here. The right subclavian artery, you hear sub below, clavian is clavicle, so this one is going to run below the clavicle.
So those are the two branches coming off of our very first kind of shoot-off of the aorta, the brachiocephalic trunk. Again, brachiocephalic trunk goes to the right common carotid artery and to the right subclavian artery. The next branch that we have coming off of the aorta is the left common carotid artery.
So where we had the brachiocephalic trunk that branched into two things, including the right common carotid artery, our second branch off of the aorta is just simply the left common carotid artery. And again, you hear common. We're gonna find that that further branches later. And then the third and final branch is going to be the left subclavian artery, which is what we see here.
So again, just to summarize, there's three different major branches coming off of the aorta. The first is our brachiocephalic trunk, which branches into the right common carotid artery and our right subclavian artery. We have then our left common carotid artery, which gets its own branch. And then finally, third, we have our left subclavian artery. So, you might notice that the right common carotid artery and the left common carotid artery are both running up towards the head and towards the neck.
And that is what they're going to feed in terms of the blood. The left subclavian artery and the right subclavian artery are going to feed blood to the arms and to those thoracic regions. Now, going from the left common carotid artery and the right common carotid artery, we're now specifically focusing on the right side.
And so we're going to follow that common carotid artery on the right side to the more specific branches that I mentioned previously. When it comes to the right common carotid artery, which we can see here, this first branch that we can see is the only branch that we can see, unfortunately, because this side is showing us some of the deeper structures. This is going to be the right internal carotid artery.
So it's running... inwards and the internal one is actually going to run towards the brain and feed the vessels of the brain. We're gonna see that a little bit later.
As for the right external carotid artery, you can't see that in this slide, you can't see it in this image, so I wouldn't be able to expect you to identify it. Same thing for the left side, we cannot see it on the left side either. So what we've identified so far, I just want to give you a pictorial representation and I know it's a little bit fuzzy, but from the heart we went to the aorta and aortic arch we identified that there was three branches coming off we had the brachiocephalic trunk which branched into sorry about that branched into the right common carotid artery and the right subclavian artery we then had our branch to the left common carotid artery and then finally to the left subclavian artery We further find that the common carotid arteries can branch off into the right internal carotid artery, the left internal carotid artery, the left external carotid artery, and the right external carotid artery. Our attention now is going to go towards the brain and feeding the brain.
What we actually have coming off of the Subclavian arteries are vertebral arteries. So you might remember that the vertebrae are posterior. And so that is what's being represented here.
We're going to come up and feed the brain posteriorly from the right and left vertebral arteries. Anteriorly, or more anteriorly at least, we have the right and left internal carotid arteries. Those are going to feed the more anterior portions of the brain.
So going forward, you're going to see that I will be referencing In the next and coming slides, the vertebral arteries and the right and left internal carotid arteries. So in order to feed the brain, what we have is a circle. And the reason that we have a circle is that if there were to be a blockage at any point, the blood could flow around the circle, pass that blockage to still get to areas of the brain to feed those cells.
Remember that the brain contains special, precious neurons, and we want to make sure that we can continue to feed the cells of the brain with blood flow, even if there is a blockage. So in order to meet that need, we have what is called the cerebral arterial circle, so a circle of arteries, also known as the circle of Willis. So as I previously mentioned to you, there are two different regions through which we are going to feed this circle of Willis.
The first is the internal carotid arteries, the right and left internal carotid arteries. which are branching off and come from the common carotid artery. And then we have our right and left vertebral arteries. Again, these are branches of the subclavian arteries.
We're not yet going to focus in this slide on the vertebral arteries. First, we're going to focus on our internal carotid arteries. So our internal carotid arteries are only being represented just right in these specific regions.
And the reason for that is we're coming from an inferior portion coming up through the neck and the head to make our way to the circle of Willis. that we're seeing here. So just where I'm pointing, that's the internal carotid arteries.
Because we're in an inferior view here, this is the right side, this is the left side. So this is anterior at the top, posterior at the bottom. And again, just to kind of orient you, these will be the vertebral arteries that we'll talk about. So this is the posterior side of the cerebrum. Now coming around the circle of Willis, we have different specific portions we need to be able to identify.
First, in the most anterior portion, so these two branches that we're seeing, these are the anterior cerebral arteries. So what you can hear in the name, they're anterior, and they're feeding the cerebrum. So these are the right and left anterior cerebral arteries.
I will help you by saying right anterior, left anterior, right posterior, and left posterior on the exam, so you can help yourself to be oriented. In between the right and left anterior cerebral arteries, we have the anterior communicating artery. It is all of this region in between, so it's specifically this part of the circle of Willis.
Kind of more medial, between the anterior and what we're going to find are the posterior cerebral arteries, we have the right and the left middle cerebral arteries. So if I point it here, this is the right middle cerebral artery, this is the left middle cerebral artery. Coming back to what we learned before. We have the anterior communicating artery, and that is between the right anterior cerebral artery and the left anterior cerebral artery.
Making our way towards the back, as I mentioned, another type of vessel that is going to be feeding the circle of Willis is going to be our vertebral arteries. Again, these are branches coming off of the subclavian arteries. So we have our specifically right vertebral artery and our left vertebral artery.
They're going to come together in the basilar artery, so think basal behind, and those are going to come up to the circle of Willis. The branches coming off on the posterior side are the right and left posterior cerebral arteries. The final and only other part that you need to be able to identify is the right and left posterior communicating arteries. So there's only one anterior communicating artery.
But here in between the middle cerebral arteries and the posterior cerebral arteries, we have our right and left posterior communicating arteries. This is a different view. So now what you're looking at is instead of looking at previously the cerebrum itself, we're now looking down into the cranial cavity. So to orient you, this is your right side.
You're looking down into the cranial cavity. This is your left. And so here instead we're seeing the circle of Willis represented. This right here is the, because we're on the left side here, the left anterior cerebral artery and the right anterior cerebral artery. Sorry about that.
We then have our anterior communicating artery right in the center. We have coming in just where we're pointing, those are going to be our left and right internal carotid arteries. The little branches or nubs coming off. are the middle cerebral arteries. So this one is the left middle cerebral artery.
This is the right middle cerebral artery. We have, let me just remove this so you can see a little bit better, our posterior communicating arteries. So this is our left posterior communicating artery. This is our right posterior communicating artery.
These very first branches represented here are the posterior cerebral arteries. So again, on our left side, left posterior cerebral artery, right posterior cerebral artery. Then we have our basilar artery, and then we have our vertebral arteries.
So left vertebral artery and right vertebral artery. Don't worry about any of these other little branches. So don't represent or don't think about any of these other little ones.
All of the rest you can identify. So big thing here, make sure that you orient yourself. I will probably also provide you direction for this one as well, so you know left and right. So we are done with the blood flow for the brain. We are going to come back to the subclavian arteries and talk about feeding the upper limb.
Remember that our right and left subclavian arteries are going to branch towards the upper limbs. From there then, the major vessel that is going to feed the upper limb is the auxiliary arteries. This model that we're seeing here is of a left limb and so that's why I have bolded for you the left auxiliary artery. You remember the auxiliary region as being the armpit region and so that's where we are with this artery.
So we're feeding the shoulder, we're feeding the thoracic region. This is going to further branch into the right and left brachial arteries, specifically the left brachial artery here because we are in the left limb. If we were in the right upper limb it would be the right brachial artery.
So we only have one brachial artery per limb, left if we're in the left limb, right if we're in the right limb. The brachial arteries then are going to further branch. Right at the, you might remember the antecubital region, we're then going to go from the cubital fossa and down to the ulna and the radius. The ulna side, remember the ulna is going to be closest to us.
And so right here in red, you can see the left ulnar artery. Again, left because we are in the left limb. On the radial or radius side. we can see the left radial artery.
Again, left because we're in the left upper limb. What happens as we come down to the palm is we actually have anastomosis. We come together.
And so right there, you have a palmar arch. Because this is the left limb, it is the left palmar arch. And from that palmar arch, we have branching off to the digits, and these are known as our digital arteries.
So just to kind of summarize and take a step back, We go from the subclavian artery to the brachial artery to the ulnar artery and the radial artery, the anastomose together at the palmar arch, and then that goes to the digital arteries. Now we're going to talk about the major blood flow from the aorta. So we covered the upper limbs, we've covered the head, now let's talk about going to the abdominal and thoracic regions. I mentioned that we have the ascending aorta as it comes upward, we have the aortic arch, and then we have the descending aorta which goes downward. What we label the descending aorta within the thoracic region is the descending thoracic aorta.
We know that this is within the thoracic region partially because we can see what was remnant of ribs here, so you can see some ribs, but also we're going to use the diaphragm as our marker. If we are superior to the diaphragm, we are in the thoracic region. and so this is the descending thoracic aorta. It goes downward, so it's descending. If we go past, again, the diaphragm, then we call it the descending abdominal aorta, because then we are in the abdominal region.
So, descending thoracic aorta there. This is now going to be below the diaphragm. So what we can see here is the descending abdominal aorta. So this big, big vessel descending abdominal aorta.
From there, let me just remove my little diaphragm, we have our right and left common iliac arteries. So when we say iliac, hopefully you hear ilium in that, and common tells us that they are going to branch. So just to orient us, this is our right side, this is our left, because we are looking at a model, and it is in anatomical position to us. And so we have our right common iliac artery and our left common iliac artery.
Each one of those is going to branch into internal and external iliac arteries. So if I just take these away, the internal iliac arteries are going to run inward and the external iliac arteries are going to run externally. So here again we have our right and our left.
internal iliac arteries, which are coming off of the common iliac arteries, and we have our right and our left external iliac arteries. This is a chest plate which we've used before to identify the different muscles. You are looking at the internal view.
So you might remember identifying the diaphragm here, transversus abdominis, transversus thoracis up here. We are going to see vessels that are only being represented on the left side. So this is going to be...
just like we'd see it in our own body. So this is our left, this is our right, and we only see these vessels represented on the left side even though we have them on both the right and the left. So first we have our internal thoracic artery.
Remember we're looking at the internal portion of the chest plate here and that's on the left side. So all of this right here is the left internal thoracic artery running in between the ribs here And here, and here, and here. These are on the left side, though we do also have right, but they're on the left side, so these are the left anterior intercostal arteries. Why are they anterior? Because they're on the anterior side of our body.
We'll find that we also have posterior intercostal arteries, which run posteriorly. Represented, well, not really represented, but what would be right here and is not represented, this would be our superior epigastric artery. Superior is because it's superior and it's above the stomach.
So it's not shown here, but that's where it would be. And then we have represented below the inferior epigastric artery. So superior epigastric artery is superior to the stomach.
Inferior epigastric artery is inferior to the stomach. So just to give you an idea where we've been coming from. We fed from the subclavian artery up above to the right and left internal thoracic arteries to the anterior intercostal arteries and the superior epigastric artery. Our right and left external iliac arteries actually feed the inferior epigastric artery. So we're kind of coming from above and below here to feed these parts of the body.
Coming back to our thoracic cavity, remember we have our descending thoracic aorta. In addition to what we identified on the previous slide of the anterior intercostal arteries, we also have our posterior intercostal arteries. So that is what you're seeing represented here. All of these would run posteriorly on the body. So posterior.
intercostal arteries. This is the left side, so specifically what we're seeing here are the left posterior intercostal arteries. We are now focusing our attention on the abdomen and providing blood flow to the different organs that we find within the abdominal region.
So what we find at the very top of this region, so again just to orient us here's the diaphragm, there is a circle of vessels here that are going to feed different organs. This little cluster of vessels is called the celiac trunk. So each of these represents a little nub.
If you haven't caught on yet, all of these are just little cut versions of the vessels. You're not seeing the whole thing for ease of use. So each nub represents a vessel.
Collectively though, this is the celiac trunk. And then inferior to the celiac trunk, we have the next little nub, which is the superior mesenteric artery. Skip these, and then we find the inferior mesenteric artery.
So celiac trunk. superior mesenteric artery, inferior mesenteric artery. We're going to come back to these ones here in a second. As for the celiac trunk, there are three little nubs that were represented.
The one that is at the very top comes up and around to feed the stomach. It is only up and above on the left side, not on the right, and so we call this the left gastric artery. We're going to learn about different parts of the stomach.
We call this the lesser curvature. The greater curvature is the bigger curve that's on the bottom of the stomach, but this is the lesser curvature, and that's where we see the left gastric artery feeding in. The next little nub that we have of the celiac trunk is the splenic artery, and the splenic artery is feeding the spleen, and so that's what we are seeing here. The final nub that we have, sorry I keep going back, is to the liver.
You might remember the liver has hepatocytes, and so it's this is the common hepatic artery. Common because it does branch. There is a left and right hepatic artery, which we can see right here, but this is the common hepatic artery, which is going to again supply the liver.
So coming back, if I identify the little nubs, again at the very top we have our left gastric artery. Towards the side over here, this is where our spleen would be. So we have our splenic artery and then we have our liver. common hepatic artery.
So whether or not you were previously familiar with where the spleen was, the spleen is going to be on our left side, our liver is going to be on our right, and so you can kind of see those nubs going in those different directions to help guide you. We also mentioned the superior and inferior mesenteric arteries. So right here is the superior mesenteric artery, okay? The superior mesenteric artery, so it's not just a little nub, it is going to feed a couple different things.
One of them is the pancreas. So the pancreas is kind of represented back here. You can kind of see it there.
We also are going to feed the small intestines. Now the small intestines have been removed in this image. So all you're seeing is the large intestines. But all of the small intestines would be filling in all of this space. And you can see they're cut here, but these are all small intestine arteries.
And then specifically, we're going to feed the right large intestines. Not the left, just the right large intestines. So again, With the superior mesenteric artery, we feed the pancreas, we feed the small intestines, and specifically the right large intestines. So when we look at a model of the superior mesenteric artery, where we're going to see it represented is here.
Again, it's going to branch up towards the pancreas. It's going to branch towards the right large intestines, which is being represented here. And again, it will also branch to these small intestines. Alternatively, the inferior mesenteric artery, which is represented lower down here, it specifically supplies the left large intestines. So where the small intestines is entirely supplied by the superior mesenteric artery, we actually feed the large intestines on the right and the left sides with different arteries.
The left large intestines, represented here, is fed by the inferior mesenteric artery and the Right large intestines, represented here, is being fed by the superior mesenteric artery. Coming back to other abdominal organs that we would have and what feeds them, from the descending abdominal aorta, remember that's all of this that we have here, we also have renal arteries. The renal arteries are feeding the kidney.
You only see the kidney on this side. Ideally, there'd be a kidney here too. And so the right and the left renal arteries feed the kidneys.
We also have suprarenal arteries. This one is showing you right here. and it's going up to the suprarenal glands which are important for our endocrine system. Same one, there's one right here.
These suprarenal arteries are above the kidneys. Coming back to those little nubs that I told you to ignore previously, these are our gonadal arteries. They are going to run to our reproductive organs.
Both of them actually run down to the reproductive organs, but one is shown at length, the other one is cut into a nub. But both of these are gonadal arteries, right and left gonadal arteries. That brings us to our lower limb.
So from the right and left external iliac arteries, which we covered previously, we're going to come into the femoral region with our femoral arteries. I've bolded left because this is a left limb. So we have our left femoral artery and that can further branch into our left deep femoral artery.
So you can't actually see it here and I wouldn't expect you to be able to identify it. If we were able to remove sartorius here, we would be able to better see this little branch which is the left deep femoral artery. From there we're going to make our way down and when we get to the popliteal region we have our popliteal artery.
So right here is the popliteal or popliteal artery. It is then going to branch to the tibial side. Remember those that tell us the truth we keep close to us.
We are on the posterior side of the lower limb so this is the left posterior tibial artery. And if we turn the leg around, and we are on the anterior side, we can see the left anterior tibial artery. So both on the tibial side, one is posterior, the other one is anterior. That brings us to our venous circulation. So what we just focused on was all arteries, all running away from the heart.
Now we're going to talk about venous circulation. So in our path of blood flow, we're gonna make our way back to the heart. Most are companion vessels. So we talked about companion vessels in lecture. Remember that they would be side by side with the artery.
And they'd be named the same as the artery with the exception that they're blue and they're called a vein. We're going to just talk about the exception to the companion vessels that we have for the most part. So now with our veins, we're making our way back to the heart.
Again, some of the exceptions we have, drainage of the brain. You might remember the dural sinuses. Those are coming back for us now. There's also some exceptions in the thoracic cavity, some exceptions superficially in the upper and lower limbs and is in the digestive system as well.
And we'll focus on the liver. So feeding back into the heart, we are going to have the inferior vena cava, which we can't see here. It would be more inferior in this view.
What we can see is the superior vena cava. And so remember, we're coming back into the heart. We're coming this direction back into the heart. What the superior vena cava is, is a fusion of the two vessels that I just drew over, and those are the brachiocephalic veins. So we have our right brachiocephalic vein, and we have our left brachiocephalic vein.
Making our way up, or kind of away from the heart to make our way back down, we have these vessels right here and here. What these are... jugular veins and more specifically internal jugular veins.
So our jugular veins, these are the internal right and left internal jugular veins, we also have right and left external jugular veins. We again don't see that represented on the left right side excuse me we only have the left so here is our left external jugular vein, our left internal jugular vein, and our right internal jugular vein. Each of these is going to feed into our subclavian veins.
So we have our right subclavian vein, our left subclavian vein, which feed into our right brachiocephalic vein and our left brachiocephalic vein, finally branching into our superior vena cava to drain into our heart. So there it is, superior vena cava. Let's go to the blood in the brain now.
and talk about the dural sinuses. Hopefully you remember looking at the dural sinuses a little bit and identifying them in lecture. Remember that these are between different layers of the dura mater that we identified before, and we eventually are going to have CSF dump into some of these veins.
So on this model, hopefully again you can just use this as recollection and kind of remind yourself. We have our superior sagittal sinus. We have our inferior sagittal sinus. We have our straight sinus, which is almost like stabbing in between the cerebellum and cerebrum. And if we look at our different view here, again we're looking down into the cranial cavity.
We have our right and left transverse sinuses. You can only see the right. represented here, okay?
We have our sigmoid sinus, which kind of has an S shape to it, represented here. And then we have our cavernous sinus, which is this braided structure right here. So what we are feeding into will be the right and left internal jugular veins, but we don't see that represented in these models.
So again, if we were to follow the path of blood flow from the brain, we would go into the right and left internal jugular veins, then we'd have our right and left external jugular veins, we'd go into the subclavian veins, then to the brachiocephalic veins, then to the superior vena cava to go back into the heart. One kind of special vessel that we have for the venous flow in the posterior thoracic wall is the hemiozygous vein. So before we get to that, we have our posterior intercostal veins.
You might remember we had our posterior intercostal arteries. Those are companion vessels. But our hemiozygous vein runs this direction. So all of this one right here, that's the hemiozygous vein.
On the right side, instead of a hemiozygous vein, we have an azygus vein, which will help us to actually drain this vein and eventually get back to the superior vena cava. but again specifically on the left side we have our hemiozygous vein and there's our superior vena cava which we will eventually drain into while there are exceptions for the superficial drainage of both the upper limbs and the lower limbs i'm only going to give you three vessels that i want you to know and they're specifically for the upper limb First, we have our left basilic vein. And the left basilic vein is left because we're in the left limb.
So this is our left basilic vein. We have our left cephalic vein. And we find that these two vessels are actually going to anastomose at the left median cubital vein.
So this one right here. Okay? What you saw me pointing to as well is our left subclavian vein, which is going to be all where all of these vessels are going to drain into to bring us back to eventually get to the superior vena cava. So all you need to know again, let me just review, we have our left basilic vein, we have our left cephalic vein.
Up at the top we are going to eventually drain into the left subclavian veins and anastomosis of the basilic vein and the cephalic vein are at the left median. cubital vein. The main venous exception that we want to note for the gastrointestinal tract is the liver.
What we have available to us for the liver is the hepatic portal system. What the purpose of the hepatic portal system is, is to take all of the blood from the digestive tract organs. So think the intestines, the spleen, all of these different organs that have blood that has now received nutrients and toxins from our digestive tract. and to take that blood and shunt it to the liver so that it can be detoxified before we allow it to go to the heart and to be recirculated throughout the body. So the liver is gonna serve as a filtering agent for us, that's its function, but again we want to shunt all of the blood from digestive tract organs to the hepatic portal system to get to the liver.
The specific vein that's going to come into the liver with all of that blood is the hepatic portal vein. So all of the other veins that we're going to discuss again are going to dump into the hepatic portal vein. to go into the liver and then allow us to finally go to the inferior vena cava to be able to go back to the heart.
So as far as the hepatic portal system, what do we have? We have the inferior mesenteric vein. You might remember that there is the inferior mesenteric artery as well. We have our superior mesenteric vein, which is the companion vessel to our superior mesenteric artery. And then we have, if we turn this around, we have our splenic vein.
coming from the spleen, and we have our hepatic portal vein. So all of these different veins, the inferior mesenteric vein, superior mesenteric vein, notice again these are coming from the small intestines and the large intestines, with all of the nutrients and toxins that would come from our digestive tract, those are gonna join along with the splenic vein to come to the hepatic portal vein. That will dump into the liver, which will then detoxify that blood before it goes to the inferior vena cava to go back to the heart.
That is it for our circulatory system. So hopefully all of that makes sense. If you have any questions, feel free to reach out.