Video: Coronary arteries and cardiac veins

Ahh, the heart. Like a tireless DJ, it pumps the rhythm of life with a lively beat. Now you might be familiar with how the heart delivers blood to the other major organs in the body, but have you ever wondered exactly which vessels are responsible for delivering oxygen and nutrients and disposing of waste products from the heart itself?

Enter the coronary arteries and cardiac veins, collaborating on a behind-the-scenes remix, supplying and draining the heart, ensuring it keeps on spinning the beats of life. So without further ado, let's delve deeper into the vasculature of the heart and investigate the coronary arteries and cardiac veins.

So in this tutorial, we'll first be looking at the coronary arteries and their main branches, which nourish the heart muscle, also known as the myocardium, followed by the main cardiac veins, which drain deoxygenated blood and remove wastes from the myocardium. So let's get into the heart of the matter and begin by looking at the coronary arteries first.

There are two major parent coronary arteries – the left coronary artery and the right coronary artery. These two arteries arise from aortic sinuses of the aortic root, which are dilations of the aortic wall found just above the cusps of the aortic valve and they give off several major branches that supply the myocardium which we will discuss in this tutorial. So let's have a look at the left coronary artery and its branches first.

The left coronary artery arises from the left coronary aortic sinus and runs between the auricle of the left atrium and the root of the pulmonary trunk, which we can just about see the base of here. After about two centimeters, the left coronary artery bifurcates into two main branches. We have the circumflex artery, which we can see a small segment of here, as well as the anterior interventricular artery.

Looking at the circumflex artery first, we can see that it runs on the left side of the heart coursing within the coronary sulcus, also known as the atrioventricular groove. We can get a better appreciation of its course from this superior view, where we can see it curving around the left border of the heart onto its inferior surface.

The circumflex artery itself gives of several branches including the left marginal artery, several atrial branches like this one seen here, and an inferior left ventricular branch as well. Together, these branches supply the inferolateral parts of the left ventricle and the left atrium.

The other main branch of the left coronary artery is the anterior interventricular artery, also commonly referred to by clinicians as the left anterior descending artery, or the LAD. This branch runs along the anterior interventricular sulcus to the apex of the heart, where it often anastomoses with the inferior interventricular artery, situated on the inferior surface of the heart.

The anterior interventricular artery gives off several anterior ventricular branches which are mostly unnamed, except for the largest example which supplies the left ventricle, sometimes called the diagonal branch, whilst there are also septal branches, which are not visible here, and occasionally a small conal branch. Together, the anterior interventricular artery and its branches supply the anterior, lateral, and apical walls of the left ventricle, a small part of the right ventricle adjacent to the anterior interventricular sulcus, as well as the anterior two-thirds of the interventricular septum.

The anterior interventricular artery is the most commonly occluded artery of the heart, and as it supplies such a large part of the myocardium, occlusion of this vessel can lead to severe infarction.

Next we're going to look at the right coronary artery. This artery arises from the right coronary aortic sinus and travels through the coronary sulcus, continuing around to the inferior surface of the heart. During its course, it gives off several branches, including the sinuatrial nodal artery, conal branch, atrial branches, ventricular branches, right marginal artery, and inferior interventricular artery.

Phew, that sounds like a lot! Fortunately, their names give us insight into their location and supply to make it a bit easier to learn. So let's go and take a closer look at each of these branches.

The conal branch is first to arise from the right coronary artery. It runs between the base of the conus arteriosus and the superior part of the right ventricle. This branch, as the name suggests, supplies the region of the conus arteriosus of the right ventricle. Within millimeters after emerging from the aorta, the right coronary artery also gives off the sinuatrial nodal branch which extends to and supplies – yep, you guessed it – the sinuatrial node. However, it should be noted that in about 40 percent of the population, it has been known to arise from the circumflex branch of the left coronary artery instead. Also arising from the right coronary artery are a series of atrial branches which are commonly grouped into anterior, lateral, and inferior branches. These branches supply the right atrium of the heart.

The next prominent branch of the right coronary artery is the right marginal branch which runs close to the inferior border of the heart along the right ventricle. This branch, in addition to several smaller anterior ventricular branches, supply the right ventricle of the heart.

Finally, the inferior interventricular branch, also commonly known as the posterior descending artery, or PDA, runs along the inferior interventricular sulcus and is the terminal branch of the right coronary artery. It supplies blood to the inferior part of the interventricular septum and adjacent surfaces of both ventricles.

Now it should be noted that the inferior interventricular artery arises from the right coronary artery only in individuals considered to be right-heart dominant. But, what does this mean and what is coronary dominance? Well, it definitely does not mean that we have a heart on each side of our body. Instead, anatomists and clinicians alike refer to right or left dominance with respects to which coronary artery gives rise to the inferior interventricular artery.

If it is via the right coronary artery, then the heart would be described as being right dominant, which is actually the case for about 60 to 80 percent of the population. In about 5 to 10 percent of individuals, the opposite is true, where it arises from the circumflex branch of the left coronary artery, therefore resulting in a left-dominant heart. In 10 to 20 percent of cases, both coronary arteries give rise to the inferior interventricular branch which is termed codominance.

And that takes care of the arterial supply of the heart. Now let's move on to the venous drainage of the heart which is performed by the cardiac veins.

The veins of the coronary circulation can be organized into two groups – the greater and smaller cardiac venous systems. The greater cardiac venous system comprises the large veins found in the subepicardiac, or outer, myocardium and their tributaries. The smaller cardiac venous system refers to the small veins in the subendocardiac, or inner, myocardium which empty directly into the atria and ventricles. So let's take a look at the major veins of these systems, starting with the greater cardiac venous system first.

Drainage through the greater cardiac venous system is primarily governed by the coronary sinus. As we can see here, the coronary sinus is located on the inferior aspect of the left atrium, coursing within the left inferior part of the coronary sulcus. Its function is to drain the majority of deoxygenated blood of the heart into the right atrium. It is a particularly wide, channel-like vein that is initially formed by the confluence of two veins. However, it also receives a number of other tributaries, all of which we will discuss in a moment.

The great cardiac vein is the larger of the two major veins that form the coronary sinus. It originates at the apex of the heart and runs through the anterior interventricular sulcus next to the anterior interventricular artery. As it reaches the coronary sulcus, it passes to the left, accompanying the circumflex artery, before eventually draining into the coronary sinus. The great cardiac vein drains the anterior surface of both ventricles and the left atrium.

Now the great cardiac vein itself commonly receives the left marginal vein as a tributary, which courses the left side of the heart, and it also drains part of the left ventricular myocardium.

Now the vein which joins the great cardiac vein in forming the coronary sinus is the oblique vein of the left atrium. As the name suggests, this vein takes an inferior oblique course along the back of the left atrium to join the great cardiac vein in forming the coronary sinus. Unsurprisingly, this vein drains the left atrium.

The next tributary is the inferior vein of the left ventricle, also known as the posterior vein of the left ventricle. This cardiac vein can be found on the inferior surface of the left ventricle. This vein drains the inferior and lateral walls of the left ventricle into the coronary sinus.

One of the large tributaries to the coronary sinus is the middle cardiac vein, also known as the inferior interventricular vein. This vein ascends in the inferior interventricular groove and enters the coronary sinus on the opposite end to the great cardiac vein. It drains the inferior wall of both ventricles and the interventricular septum.

The next tributary to the coronary sinus is the small cardiac vein. It can be found in the coronary sulcus between the right atrium and the right ventricle and it drains the inferior part of the right atrium and right ventricle into the coronary sinus. It should be noted that the small cardiac vein sometimes receives the right marginal vein as a tributary, which we can see here on the inferior margin of the anterior surface of the heart. However, in approximately two-thirds of individuals, the right marginal vein drains deoxygenated blood from the lateral part of the right ventricle directly into the right atrium, rather than via the coronary sinus.

Phew! Well, that takes care of all the tributaries of the coronary sinus. I'm sure all of your time spent there won't be in vain.

Now you might have noticed that we haven't yet mentioned these veins on the anterior view of the heart, which are the anterior cardiac veins, also known as the anterior veins of the right ventricle. That's because these veins do not drain into the coronary sinus. Instead, they collect deoxygenated blood from the anterior part of the right ventricle and drain directly into the right atrium.

And those were the last of the veins of the greater cardiac venous system that we're covering in this tutorial. Now let's move on to discuss the smaller cardiac venous system.

Fortunately, the only veins to discuss within the smaller cardiac venous system are called the smallest cardiac veins or Thebesian veins. They are a complex network of small vascular channels and sinusoids located within the subendocardial part of the myocardium of all four chambers of the heart. They drain the inner third of the myocardium and empty directly into the four cardiac chambers, however, are the most prevalent in the right atrium and right ventricle.

And that concludes our tutorial on the coronary arteries and cardiac veins. To revise this content and ensure your time spent here was not in vain, check out our quiz and other learning materials in our study unit on this topic.
And on this image of the left side here, you can see then the diaphragmatic surface of the heart, where you can also see the different coronary arteries and cardiac veins that we’re going to be talking about on this tutorial. And just to show you what’s happening here on this image, you can see here the ascending aorta, the pulmonary arteries here, the right one and the left one. You can also see here the superior vena cava and the inferior vena cava, both cut, and the pulmonary veins. Notice here a bit of the right atrium and also the left atrium and below you then going to find the left ventricle and the right ventricle.

Now, that we understand what’s happening here on this image is that it is time for us to move on and start talking about the different coronary arteries. There are two major coronary arteries, the left coronary artery and the right coronary artery that I talked about. So, here you see the right coronary artery and here you see then the left coronary artery. Now, these two arteries arise from the aortic sinus as you can see also here on this image of the ascending aorta which is cut here on the image and they gave off several branches which we will discuss later in this tutorial.

Now, be aware that these two coronary arteries are sometimes referred to as the epicardial coronary arteries in some texts, so just to know that they are referring to the coronary arteries, if you do come across that name in your reading.

So let’s take a closer look here by highlighting it at the left coronary artery. The left coronary artery arises from the left aortic sinus runs between the left auricle – as you can see here – and also the trunk of the pulmonary artery which you cannot see here because we just removed here the pulmonary trunk where you could then see the two pulmonary arteries. Now, after about 2 cm, the left coronary artery will be bifurcating – as you can see here, a bifurcation – into two main branches – the circumflex branch which you see a little bit here, and the anterior interventricular branch which you see here highlighted in green clearly.

Now, let’s take a closer look at these branches that I just talked about. You now see this one here highlighted in green which I talked about before, this is then the circumflex branch. So, the circumflex branch of the left coronary artery which runs on the left side of the heart coursing within the atrioventricular groove. And you can see here on this image where we’re now looking at a superior view of the heart here where you see then the left coronary artery exiting the aorta and then splitting or bifurcating into the two branches that we talked about one of them highlighted here in green which is the one that we’re talking about, the circumflex branch. And notice here that it is then coursing through the atrioventricular groove, so, a groove between the left atrium and the left ventricle.

So as you can clearly see here also in this image that the circumflex branch of the left coronary artery encircles your heart. Now, this branch of the left coronary artery supplies the lateral surface of the left ventricle and the posterior surface of the heart as well.

We’re going to move on and talk about the next branch of the left coronary artery which you see now highlighted in green, this is the anterior interventricular artery, or you can also name it as I did before as the anterior interventricular branch of the left coronary artery but this is a bit longer if you want to write it down. So, let’s make things a bit easier and call it anterior interventricular artery.

Now, this one as you can see here on this image, it runs inferiorly down in the anterior interventricular groove to then the cardiac apex or the tip of the heart here. And as the word indicates, interventricular, meaning that extends in this groove that is just between the two ventricles, so the right ventricle and the left ventricle. On the apex of the heart, this artery is going to anastomose or form a connection with the posterior interventricular artery. This artery is also commonly referred to as the left anterior descending artery or LAD.

Still on the anterior interventricular artery, I am just changing here the image to talk about the function of the anterior interventricular artery. Now, notice here that we just added then the pulmonary trunk and the ascending aorta. On the previous image, we had these two structures cut but we’re still looking at the anterior view of the heart.

Now, as for the function, this artery is going to be supplying the anterior and the lateral walls of the left ventricle, the apical wall of the left ventricle. Now, as you can see, this branch supplies greater part of the myocardium. For that reason, it plays the most critical role in cardiac function and, in addition to that, it is the most commonly occluded of the coronary arteries causing then severe infarction.

We are going to move on and talk about this artery that we’re seeing here highlighted which I talked about before on a previous slide. This one is known as the right coronary artery. This artery arises from the right aortic sinus. It passes through the right atrioventricular groove as you can see here. Now, during its course, the right coronary artery will be giving off different branches, the sinoatrial nodal branch, the right marginal branch, the atrioventricular nodal branch, and the posterior interventricular branch.

Now, let’s take a look at a few of these branches that we see here on this image. This one that you see now highlighted in green is known as the sinoatrial nodal branch. So, within millimeters after emerging from the aorta, the right coronary artery will be giving off the sinoatrial nodal branch which then extends to and also will be supplying the sinoatrial node in about 60% of the population. However, it is important to note that in 40% of the population, the sinoatrial nodal branch has been known to arise from then the other coronary artery, the left coronary artery.

The next branch that we’re going to be highlighting here on this image of the anterior view is known as the right marginal branch. Now, this is the next prominent branch of the right coronary artery which will be running to the right outer margin of the heart inferiorly. This branch supplies then the right ventricle of the heart.

The next branch that we’re going to be highlighting here on this image is now from a diaphragmatic view of the heart or a posteroinferior view of the heart where you see then the posterior interventricular artery. Now, this one runs along the posterior interventricular groove which you see a bit here, this groove that exists between the two ventricles. So, as you can see, this is the last branch of the right coronary artery. So, this is also known as the terminal branch of the right coronary artery and will be supplying then blood to the posterior part of the interventricular septum and the posterior ventricular walls.

Now, that we covered the main coronary arteries, it is time for us to move on and talk about then the main cardiac veins. Now, these cardiac veins will be providing venous drainage for the heart muscle, namely, the coronary sinus, the anterior cardiac veins, the smallest cardiac veins, the great cardiac vein, the middle cardiac vein, small cardiac vein, left marginal vein, and, finally, we’re going to be talking about the left posterior ventricular veins. So, this is the list of cardiac veins – main cardiac veins – that we need to know.

Starting off with the very first one that we’re highlighting here from this view of the heart – the posteroinferior view of the heart – which is known as the coronary sinus. Now, the venous drainage of the heart is primarily governed by this structure here that you see highlighted – the coronary sinus. Now, the coronary sinus runs transversely across the posterior as you can see here – posterior surface of the heart – in this groove here which is known as the coronary groove. Now, I can also show you here this image of the superior view where you can then see the coronary sinus highlighted in green. And one note here that this part here – this is the posterior part of the heart – this is the anterior portion where you see then the aorta and the pulmonary trunk.

Now, the coronary sinus will be draining deoxygenated blood into the right atrium which you also see here on this image. It is a relatively wide vein as you can see here on this image and actually is, to be more specific, a collection of veins that will come together to then form this large vein, the coronary sinus. And for that reason, it will be receiving blood from many veins that we’re going to be covering in the next slides.

Let’s continue on and talk about the next highlighted structure here, the next cardiac vein, which is known as the great cardiac vein. It is great indeed as you can see here on this image. It is the first vein that returns blood to the coronary sinus and it is actually the major vein that forms then this structure – the coronary sinus. Now, this vein will be originating at the apex of the heart – as you can see here – and then runs along the anterior interventricular groove next to the anterior interventricular artery which we talked about before. Now, as you can see here on this illustration at the junction of the interventricular groove with the atrioventricular groove, this vein is going to be entering the latter and passing to the left accompanied by the circumflex artery and finally enters the coronary sinus. This cardiac vein returns deoxygenated blood – metabolic waste products to be more specific – from the anterior surfaces of the left ventricle.

For the next structure that we’re going to be highlighting now from a posteroinferior view of the heart, we’re seeing the middle cardiac vein. As you can see here, this is the next one that will be returning blood to the structure, the coronary sinus. It is also known as the posterior interventricular vein. Now, this vein ascends in the posterior interventricular groove as you can see here on this image and then enters the coronary sinus – as you notice here – just on the opposite side to the great cardiac vein which should be entering the coronary sinus right about here.

So, after the great and middle cardiac veins, the next vein that returns blood to the coronary sinus is the small cardiac vein which you see now a little bit here highlighted in green, especially from the anterior view of the heart, you see a little bit of the small cardiac vein. Now, it can be found in the coronary sulcus between the right atrium as – you can see – and the right ventricle. And it drains deoxygenated blood from the posterior part of the right atrium and the right ventricle into then the coronary sinus. And, if I turn the heart to then the posteroinferior view or the diaphragmatic surface of the heart, you can then see the small cardiac vein highlighted in green, and how it enters then the coronary sinus.

Now, the next structure we’re going to be highlighting still from the posteroinferior view of the heart, this one is known as the posterior vein of the left ventricle. This is also one of the tributaries of the coronary sinus for the venous drainage. This cardiac vein can be found on the posterior surface of the left ventricle – so this is the left ventricle if you remember well – jus found then to the left of the middle cardiac vein which you see here.

The next vein that we’re going to be talking about back to the anterior view of the heart, now, this is the left marginal vein. So, finally, this is the last vein that returns blood to the coronary sinus and this vein courses the left side of the heart and drains the left ventricular myocardium.

So, we described all the veins that drain the myocardium and they return deoxygenated blood to the coronary sinus and afterwards to the right atrium and just to review them, they are the great cardiac vein, the middle cardiac vein, the small cardiac vein, the posterior vein of the left ventricle, and the left marginal vein. There are also some smaller veins that drain the myocardium and they are not entering the coronary sinus like this one that you see here highlighted in green which is known as the anterior vein of the right ventricle or the anterior veins of the right ventricle.

Now, there are two groups of these veins. The first group is the anterior veins of the right ventricle and these veins collect deoxygenated blood from the right ventricle and will be draining into then the right atrium. Now, the second group and the final veins that we see or will talk about on this tutorial are the smallest cardiac veins or also known as the veins of Thebesius. Now, these tiny veins cannot be seen microscopically and that is the reason that we don’t have an image for these veins so no highlight. They drain directly into the cardiac chambers and they are numerous in the right atrium and ventricle and are occasionally found in the left atrium and ventricle.

Now that you just completed this video tutorial, then it’s time for you to continue your learning experience by testing and also applying your knowledge. There are three ways you can do so here at Kenhub. The first one is by clicking on our “start training” button, the second one is by browsing through our related articles library, and the third one is by checking out our atlas.

Now, good luck everyone, and I will see you next time.