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Veins of the cardiovascular system

Overview of the main veins of the circulatory system.

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Hey everyone! This is Nicole from Kenhub, and in this tutorial, we'll be looking at the veins of the cardiovascular system.

So as you may already be aware, the cardiovascular system is responsible for transporting and recycling the blood around the body. Carried in the blood are a range of substances including oxygen for respiration, nutrients for our cells and waste products that have to be removed for cells to function properly. You can therefore see why the cardiovascular system is so vital for our bodies to work normally.

The cardiovascular system comprises of the heart highlighted here and the blood vessels of which are there are two main types. So, generally, the vessels that carry oxygen-rich blood from the heart to the rest of the body are known as arteries while the vessels that carry deoxygenated blood from different parts of the body back to the heart are known as veins.

There are a couple of exceptions to this rule which include veins that do carry oxygenated blood to various regions of the body but we're not going to worry about these for this particular tutorial. In this tutorial, we're just going to focus on the veins that carry deoxygenated blood which mainly consist of the major veins of the body. But, of course, if you wanted to learn about those other veins such as the veins that carry oxygenated blood, please be sure to check out our other tutorials covering these on our website at kenhub.com.

So, before we look at any veins in particular, it's important that we're aware of what a vein actually is and how they differ from the arteries in their structure and their anatomical arrangements. So, we're just going to put our model to the side for a moment and bring in this lovely schematic diagram to demonstrate some of the layers of the veins and their relationship to the skin and where they are in the body.

So as I mentioned, this diagram here roughly represents a cross-section through the skin and up top, we can see the superficial veins which are, of course, located just beneath the integument, otherwise known as the skin, and between the layers of superficial fascia. We then have the perforating veins which cross the superficial fascia – and you can see that in blue just on our right here – and these perforating veins drain into the deep veins.

So one little thing about the deep veins is sometimes the deep veins are arranged so that they accompany an artery and these are known as the venae comitantes of that artery and they pretty much piggyback on the artery's pulse so that the blood could be moved through the veins. So another way of saying that is that they ride on either side of the artery as you can see in this image here and they used the pulse of the arteries to pump the blood back up towards the heart, and this is because the blood pressure in veins tends to be a lot lower than in arteries and so sometimes they need a little help.

Also distributed throughout the veins are structures known as valves, and these prevent the blood from moving in the wrong direction, mostly back down towards the earth as we want the blood to be heading back towards the heart further helping the blood to move through the veins efficiently. So a useful point to note is that during this tutorial, I'll be mentioning the tributaries of the major veins and these are basically just the smaller veins that drain into a larger vein as you can see in our diagram on our right.

So as we mentioned earlier in this tutorial, we'll be introducing the major veins of the body starting furthest away from the heart in the lower limbs followed by the abdomen and the pelvis then by the upper limbs followed by the head and the neck and finally we'll finish back up in the thorax where the blood eventually returns to the heart.

And, of course, let's start by looking at the veins of the lower limb. So just before we go on to talk about the veins of the lower limb, I just want to divide this image up a little bit. We're going to divide it into deep veins and superficial veins and you can see that the deep veins are on the left of our image which is on the anatomical woman's right while the superficial veins are on the right of our image which is on the anatomical female's left. And we're going to start with the deep veins. So as you follow me, you'll be able to see us going down the model's right leg before we move on to look at the veins that are in the left leg.

Alright, so beginning with the deep veins, let's start by talking about the posterior tibial vein which you can see highlighted in green and these veins are formed by the union of the medial and lateral plantar veins just around about here, and these veins are actually venae comitantes which we mentioned earlier in the tutorial. So, if you remember, it means that the posterior tibial veins piggyback off the pulse of the posterior tibial artery which runs alongside it, and you can see the posterior tibial artery in red down the bottom. Another thing to mention about the posterior tibial vein is that these veins receive tributaries from the veins of the calf muscles, some superficial veins and also from the fibular veins.

The posterior tibial vein then drains into the popliteal vein highlighted here just superior to the posterior tibial vein which we'll cover a little bit later on in this tutorial. And if we hop over to the other side, we can see the anterior tibial vein. And the anterior tibial veins are the venae comitantes of the anterior tibial artery which is just here and running lateral to that is the deep fibular nerve in yellow. The anterior tibial veins receive tributaries from the dorsal pedis veins as well as the veins of the anterior lower leg. So, the anterior tibial vein, just like the posterior tibial vein we just saw before, drains into the popliteal vein which is highlighted here again in blue.

This is the vein that I've mentioned a few times already – the popliteal vein. Now, this vein is named for the fact that it passes through the popliteal fossa which is just a fancy anatomical term for the pit at the back of your knee. And as we saw, the popliteal vein is formed by the union of the anterior and the posterior tibial veins just about here. So if we take another look at our image of the popliteal vein from a posterior view – and here you can see it highlighted in green – I can better show you how it receives tributaries from the small saphenous vein along with two veins from each head of the gastrocnemius muscle – and the gastrocnemius muscle is highlighted in blue. The popliteal vein then pierces the adductor magnus muscle after which it continues as the femoral vein which we can see on this image highlighted in blue, and we'll cover this a little bit later in the tutorial when we get to it.

The femoral vein is the continuation of the popliteal vein as we saw earlier and like some of the other veins, it accompanies an artery by the same name – the femoral artery – and receives tributaries from the medial and lateral circumflex femoral veins, part of which is highlighted in blue just here. It also receives tributaries from the great saphenous vein here and from the deep femoral vein.

So, one very important thing to note that even though the femoral vein is drawn on the side of the body that's meant to be showing the superficial veins and the femoral vein is sometimes mistakenly classified as a superficial vein, it's actually considered a deep vein of the lower limb. So, this is important to know as it sometimes can mistakenly lead some doctors to refuse thrombolysis or other such treatments during the treatment of deep vein thrombosis but it's actually a deep vein so please don't forget that. And the last thing I want to say about the femoral vein is that it drains into the external iliac vein which is highlighted in blue just here posterior to the inguinal ligament which we can see just here in this image which has some of the other anatomy surrounding it.

And now we're finished talking about the deep veins of the lower limb, let's move on now to talk about the superficial veins of the lower limb. And as we mentioned before, these veins are drawn on the left side of the body and on the right side of our image, and the vein that's highlighted in green in this image is known as the great saphenous vein, sometimes aptly referred to as the long saphenous vein. And the great saphenous vein actually happens to be the longest vein in the human body. As you can see, it arises around about here as a continuation of the medial marginal vein of the foot and on its journey upwards, it receives tributaries from many veins of the leg particularly those in the tibial malleolar region and the calf. Finally, the great saphenous vein drains into the femoral vein which as you can see is just here.

Let's move on now to the small saphenous vein – also sometimes referred to as the short saphenous vein – is a continuation of the lateral marginal vein which is located around about here on the lateral part of the foot but it's not really visible on this image. And, in fact, the lower half of the saphenous vein is not visible on this image as it runs down the posterior aspect of the leg but you can follow the vein as we pointed out with the arrow. So, the small saphenous vein begins behind the lateral malleolus just here passing lateral to the calcaneal tendon and ascending between the superficial and deep fascia in the distal third of the calf to continue upwards as we can see on our image here in green.

This vein receives tributaries from many of the superficial veins of the lower limb which we can then see on our model's left leg just here, and again like the anterior and posterior tibial veins, the small saphenous vein also drains into the popliteal vein which we can see here more from a posterior view – and you can see it highlighted in blue just here. And it's worth noting that the small saphenous vein also has many branches that communicate with its larger neighbor – the great saphenous vein.

Moving on now from the lower limb, we'll now talk about some of the major veins of the abdomen and the pelvis, and we're just going to pick up with the external iliac vein as this vein is, of course, the continuation of the femoral vein. The external iliac vein receives venous blood flow from the inferior epigastric vein, the deep circumflex iliac vein, and the pubic vein. The external iliac vein courses on the medial side of the external iliac artery before joining with the internal iliac vein just here, which we'll talk about next, to form the common iliac vein. But first we're going to talk about the internal iliac vein. And here we can see only part of the internal iliac vein and though it might look small here, it's actually considered to be the main vein that drains the pelvic region. And the internal iliac vein receives tributaries from the veins that drain the organs of the pelvis and from some venous plexuses.

Next on our list, we can see the common iliac veins highlighted here, and as we've already seen, these veins arise from the union of the external and internal iliac veins. They're also direct tributaries of the inferior vena cava, and as the left and right common iliac veins technically unite to form the inferior vena cava, they're considered to be tributaries of origin.

The inferior vena cava – the vein formed by the uniting of the common iliac veins I just mentioned – is the largest vein in the human body and it transports venous blood from the abdomen and the lower body to the right atrium of the heart. And let's just bring in an image of the heart and have a look at the right atrium itself. And in this image, you can see how the inferior vena cava connects to the right atrium. A little bit more about the inferior vena cava, as you might expect, the inferior vena cava receives several tributaries along its course. It's situated in the retroperitoneal space posterior to the abdominal cavity and it runs along the right side of the vertebral column.

Moving on, let's now talk about the gonadal veins which are obviously different in males and females. And, of course, the ovarian veins drain the ovaries in females. As you can see, the left ovarian vein drains into the left renal vein just here while the right ovarian vein empties directly into the inferior vena cava – and you can see that in green on the model's right and our left just here. Similarly, the testicular veins drain the male gonads and also similarly to the ovarian veins, the left testicular vein opens into the left renal vein while the right testicular vein drains directly into the inferior vena cava. And in this image, we can, of course, only see the right testicular vein and therefore that's the one that drains into the inferior vena cava.

Next, let's have a look at the renal veins just here, and as you may already know, the term "renal" refers to the kidneys, and so we can assume that these veins must have something to do with, well, the kidneys. Sure enough, these veins do drain the kidneys and, like we just saw now, receives venous blood from the left gonadal vein. So, these veins lie anterior to the renal arteries and because of the position of the inferior vena cava, the right renal vein is shorter than the left renal vein and both the left and right renal veins empty directly into the inferior vena cava.

Now you may remember at the beginning of the tutorial that I mentioned that there are some veins that have a slightly different function – for example, veins that do carry oxygenated blood. And this venous system that I want to talk about is the hepatic portal venous system which you may or may not have heard of before.

So before deoxygenated blood from the abdominal region of the gastrointestinal tract makes its way back to the heart, the blood has to pass through the liver and it does this through the hepatic portal venous system which includes the following five veins – the splenic vein, the superior mesenteric vein, the inferior mesenteric vein, the hepatic portal vein which as you can see goes directly into the liver as well as the hepatic vein which itself drains the liver – and here in this diagram, you can see the flow of blood as I just mentioned. You can also see the hepatic arteries here behind the veins in red.

And coming back to our regular image of the anatomical woman, you might have noticed in previous images that there's this one section that's highlighted in purple and that, of course, is our slightly more anatomically correct version of the hepatic portal veins.

And to start off our section on the hepatic portal vein, I want to start with talking about the splenic vein which you can see in green on our right just here and, of course, from the name, you can infer that it has something to do with the spleen and you would be inferring correctly as this vein drains the spleen which is roughly indicated just here. The splenic vein also drains part of the stomach as well as part of the pancreas. The splenic vein also receives tributaries from the pancreatic veins, the left gastroomental vein and the short gastric veins as well as the superior mesenteric vein. It also runs alongside the splenic artery and joins with the superior mesenteric vein to form the hepatic portal vein which is just here and we'll look a little bit more closely at the hepatic portal vein in a little bit but for the moment, we're going to look at the superior mesenteric vein.

So, you might have heard the term mesentery before and if you have then you'll know that the word "mesentery" refers to the connective tissue that anchors the intestines and other organs to the abdominal wall so that they remain in place. And the superior mesenteric vein receives tributaries from pretty much across the whole digestive system including the jejunum and the ileum of the small intestine, the pancreas, the duodenum and the colon as well as the greater curvature of the stomach. The superior mesenteric vein is an indirect tributary of the inferior vena cava and joins with the splenic vein here to form the hepatic portal vein.

Let's move on now to talk about the inferior mesenteric vein, and the inferior mesenteric vein is here in green and it drains the large intestine specifically the descending colon, the sigmoid colon and the rectum via several tributaries. The inferior mesenteric vein goes on to drain into the splenic vein just here and this goes on to drain into the next vein we're going to talk about which is the hepatic portal vein. And the hepatic portal vein as we've previously seen arises here from the union of the splenic vein and the superior mesenteric vein. The term "hepatic" refers to the liver and so, sure enough, we can infer that this vein must have something to do with – you guessed it – the liver. And as we mentioned earlier, this vein functions to transport nutrient-rich blood from the gastrointestinal tract, the spleen, the pancreas and the gallbladder to the liver for metabolic processing. So after the nutrient-rich blood from the digestive organs has passed through the liver, it exits via the hepatic vein. Now, three main parts of this vein along with several minor veins serve to drain the liver and eventually come together to form a direct tributary to the inferior vena cava.

So now that we're finished talking about the veins of the abdomen and the pelvis, let's move on now to talk about the veins of the upper limbs. So in keeping with the direction that the venous blood is traveling, we're going to be starting at the distal ends and then working our way up and as with the lower limbs, the upper limb veins can be divided into superficial and deep veins, however, unlike our lower limb veins on our image, we've reversed it. So, our deep veins are on the left side of the body which is our right while the superficial veins are on the model's right which is our left. And since we started with the deep veins in the lower limb, we're going to start with the deep veins again with the upper limb which means we're going to be starting with the veins that are on our right.

So, the first vein of the upper limb that we're going to look at today is the ulnar vein highlighted in green, and the ulnar veins are the venae comitantes of the ulnar artery. They receive tributaries from the deep palmar venous arch just here and also communicate with the superficial veins of the wrist. The ulnar veins unite with the radial veins at the level of the elbow joint just here to form the brachial veins.

Now hopping over to the other side of the forearm, we can have a look at our next vein which is called the radial vein. And the radial veins run up the lateral side of the forearm here – another venae comitantes of the radial artery. Similar to the ulnar vein, the radial vein receives tributaries from the vessels of the deep palmar venous arch and then as we've just seen, unites with the ulnar veins just here to form the brachial veins.

Moving back again to the deeper veins, we can see the brachial vein I have mentioned a couple of times already highlighted here and as we saw, the brachial veins are formed by the union of the radial and the ulnar veins at the anterior cubital fossa which is anatomical lingo for the pit of your elbow and you can find it just here. So, the brachial veins themselves are also venae comitantes of the brachial artery and they receive many perforating branches from the anterior and the posterior compartments of the arm. They go on to join with the basilic vein around about here and continue upwards to form the axillary vein.

Let's now have a look at the axillary vein which I've mentioned a couple of times before. And as we've seen already, this vein arises from the union of the basilic and brachial veins just here and also receives tributaries from the cephalic vein. As you can see, this vein is pretty short and it increases in size as it descends and it ends at the lateral margin of the first rib which is just here where it becomes the subclavian vein. And, of course, now moving on to the subclavian vein as we just saw, it arises from the continuation of the axillary vein and goes on to unite with the internal jugular vein just here to form the brachiocephalic vein which is just here.

Alright now that we're finished talking about the deep veins, I want to move on to talk about the superficial veins of the upper limb. And the first vein I want to talk about is the basilic vein which is a good site for venipuncture and the basilic vein receives venous blood flow from the dorsal venous network of the hand as well as the ulnar side of the arm and, as we've seen, eventually unites with the brachial veins just here to form the axillary vein.

Another vein that I wanted to have a look at is the median cubital vein and this is a small vein that connects the basilic vein and the cephalic vein to create a sort of wonky H-shape as you can see in our drawing. Now due to its location close to the surface of the skin, this vein along with the basilic vein as we mentioned before is the most common site for venipuncture and it's also a site for the introduction of cardiac catheters during a procedure called cardiac catheterization.

The next vein I wanted to talk about is the cephalic vein, and the cephalic vein runs superficially from the hand all the way up to the axillary vein where it joins with the axillary vein in an area outlined just here known as the clavipectoral triangle, and from there, it becomes the subclavian vein.

Moving over to the lateral part of the arm just briefly, in this image, we can see the cephalic vein running pretty much the entire length of the upper limb, and this superficial vein receives venous blood flow from the dorsal venous network of the hand and the lateral aspect of the arm and the forearm. Again, due to its superficial location, the cephalic vein is another one on the list of veins to be considered good for drawing blood which you can see in our image.

So, now normally, this is the point where we would enter the thorax territory but before we go into more details just here, we're just going to hop upwards and look at the major veins of the head and the neck.

So just bringing in an image of the brain for you. So as you can see, I've brought up a lovely left lateral view of the brain and you may already be aware that the brain is a pretty demanding organ when it comes to blood supply. So it's pretty unsurprising therefore that the venous networks draining the brain and its surrounding membranes can seem a little bit complicated. But, of course, like a lot of things, once you get to know it, it's not so complicated especially once you understand the very unique arrangements of the veins of the brain. But, of course, the last thing we want to do is to overwhelm you so we're not going to be covering the venous networks of the brain in detail during this tutorial. But, of course, if you would like to learn more about this at any time, please feel free to go to Kenhub as we've got plenty of resources to help you out.

So, let's come back to our image of our lovely anatomical woman, and in this image already, we can see some of the veins surrounding the brain just here and moving down towards the neck, we come across the first major vein in this area that we're going to be looking at which is the internal jugular vein. Now, this vein is the largest of the three jugular veins providing major venous return from the brain, the upper face and the neck. Now, these veins are formed by the union of the inferior petrosal sinus and the sigmoid sinus either in or distal to the jugular foramen which is one of the openings into the skull. In other words, the internal jugular veins receive their venous blood flow from the major veins that drain many of the structures within the skull including the brain.

So next we have the external jugular vein which is highlighted just here in green and it's the other major vein of the neck that I'll be looking at today. The external jugular vein is formed by the uniting of the retromandibular vein and the posterior auricular vein within the parotid gland of each side around about here. And the external jugular vein receives additional tributaries from the veins that drain the external cranium and the face.

Okay, so they're the major veins that I wanted to talk about to you today with regards to the head and neck, and now that we're finished talking about those guys, I want to move back on down the body and have a look at the major veins of the thorax. And the first vein in this section that we wanted to talk about is this little squiggly vein that's highlighted in green just here which is known as the internal thoracic vein. And the internal thoracic veins are venae comitantes of the internal thoracic arteries, however, the venae comitantes of the internal thoracic veins actually merge to form a single vessel that continues medial to the internal thoracic artery.

The internal thoracic veins receive tributaries from several sources including the thymus, the intercostal spaces, the diaphragm, the pericardium and the mediastinum and continue until they open into the brachiocephalic veins which happen to be the next veins that we're going to be talking about.

So let's take a look at the brachiocephalic veins in more detail, and these large veins are paired and we can see clearly that the left brachiocephalic vein differs in appearance to the right brachiocephalic vein, and as we've previously seen, both veins are formed by the union of the internal jugular vein and the subclavian vein just here. Now, of course, both veins receive tributaries from the internal jugular vein, the subclavian vein, the vertebral vein, and the internal thoracic vein. They also go on to unite and form our next vein which is the superior vena cava.

So, the superior vena cava or the SVC for short is a relatively short valveless vessel with a large diameter and as we just saw is formed by the union of the left and right brachiocephalic veins which are just here. It receives venous blood from the upper limbs, the head and the neck and just like its lower-down neighbor – the inferior vena cava – the SVC opens directly into the right atrium of the heart.

So let's bring back our image of the heart that we used before – there we go – and just like we did before, you can see how we can get a better view of the superior vena cava and how it opens up into the right atrium.

And that's the last vein I want to look at today so thanks for sticking with me but we haven't finished just yet. The last thing I want to talk about is the clinical notes. And the main thing I wanted to talk about clinically is a condition called deep venous thrombosis. You may have heard of it before as people who have blood clots when they're flying and you would be right. A DVT is essentially a clot that forms within the deep veins. Now, DVT can affect people of all ages but the risk of developing DVT increases with age leading to an inactive, sedentary lifestyle and being overweight as well as being pregnant or having a family history of developing blood clots just to name a few.

Some individuals that develop DVT may not have symptoms but for those that do, symptoms include swelling in the affected leg as we can see in the image just here as well as pain and tenderness. So treatment of DVT includes giving the patients anticoagulants such as heparin or warfarin to thin the blood and to reduce the risk of the clot growing in size. And sometimes, we used compression stockings to help relieve the symptoms.

Alright, now that we're finished the tutorial, I'm just going to briefly recap what we looked at today. So, first of all, we looked at the deep veins of the lower limb and the first vein we looked at was the posterior tibial vein which has venae comitantes as well as the anterior tibial vein which is lateral to the posterior tibial vein. We also talked about the popliteal vein which runs through the popliteal fossa and the femoral vein which is a major vein draining the lower limb.

In terms of superficial veins, we talked about the great saphenous vein which if you may remember is the longest vein in the body and the small saphenous vein. Then we moved on to talk about the veins of the abdomen and the pelvis which included the external iliac vein which drains most of the lower limb and the internal iliac vein which drains most of the pelvis. The common iliac vein is formed out of the external and internal iliac veins and drains into the inferior vena cava which is the major vein which empties into the right atrium as we saw before. We also looked at the gonadal veins and in women, this is known as the ovarian vein whereas in men, we have the testicular vein, and then there was also the renal vein which drains the kidneys.

We also looked at the hepatic portal venous system in the abdomen in this area which includes the splenic vein which drains the spleen as well as the stomach, the superior mesenteric vein which drains a large part of the abdomen, the inferior mesenteric vein and its counterpart, the inferior mesenteric vein. We talked about the hepatic portal vein which drains directly into the liver itself. And, of course, we talked about the hepatic vein which drains the liver towards the heart.

We talked about the veins of the upper limbs starting with the deep veins which include the ulnar vein which runs along the medial side of the forearm, the radial vein which runs along the lateral side of the forearm, the brachial vein, which is formed by the ulnar and the radial veins, the axillary vein which drains into the subclavian vein and then we had a look at the superficial veins which included the basilic vein, the median cubital vein which is the primary vein for taking blood followed by the cephalic vein which is also useful in venipuncture. And then we moved on to talk about the veins of the head and the neck which include the internal jugular vein and the external jugular vein, both of which are important in draining the head and the neck.

Lastly, we talked about the veins of the thorax which included the internal thoracic vein which is a venae comitantes that eventually joins together to become one, the brachiocephalic vein which drains into the superior vena cava which drains into the heart. And we also talked about deep vein thrombosis which is when a clot gets lodged in the vein.

That's all we have time for today. Thanks for watching and don't forget to check out our other tutorials at kenhub.com.

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