Hello, hello, everyone! This is Joao from Kenhub, and welcome to another tutorial. This time, I’m going to be talking about one of everyone’s favorites—organs, I’m talking about—and especially during Valentine’s Day. This is the heart. And we’re going to be talking about the structures that you can find on the anterior view of this organ, of the heart.
Now, before I go into any more detail on this tutorial, I want to just explain a little bit of what you’re seeing here on the screen. We’re looking at the thorax, the open thorax. If we were to strip everything you have on your chest from skin, to fat, and other tissues, and expose a little bit of the organs that you find within your chest or within the thorax, you would find, then, the heart. And we’re looking at the subject face to face so you would see, then, the anterior, his/hers, anterior view of his/her heart.
Now, keep in mind that this is the subject perspective, the anterior view, and for that reason, his/her left side… or right side (sorry). It’s going to be our left side when we’re looking at this. And now, on your right side here, you’re looking at the subject’s left side. Keep that in mind throughout the rest of the tutorial.
Now, before we go into more details about the heart, about the structures that we find on the anterior view of this organ, I want to briefly give you a little intro to the cardiovascular system to make a little bit of sense of where the heart comes from and why it’s important. Now, the cardiovascular system is comprised mainly by the heart, which is the main organ of this system, and blood vessels, and also the blood, of course. This is known as, also, the circulatory system or cardiovascular system as you see on the screen, and it consists of two circuits or two circulatory systems.
So we can subdivide this cardiovascular system into two subsystems let’s say. And this consists of the pulmonary circulation which runs between the heart and the lungs, and then the other one is the systemic circulation, which runs between the heart and the peripheral tissues—so the rest of your body.
Now, the pulmonary circulation carries deoxygenated blood to the lungs, where the exchange of oxygen and carbon dioxide that the body has produced occurs. The oxygenated blood is then returned to the heart where it is bound for this second one, the systemic circulation.
Now that we covered briefly the cardiovascular system, I want to pay a little bit more attention to the heart, the structure that we’re going to be talking through the rest of this tutorial. And the heart is a muscle that acts to pump the blood throughout the cardiovascular system. It is located in a structure known as the mediastinum, just behind your sternum. It is also located within a saclike structure known as the pericardium which is attached to the diaphragm, and you can clearly see here the pericardium, which is now cut, and we just removed it so we could expose the anterior view of the heart.
Now, also important to mention that due to the asymmetric position of the heart with the apex, we can see here the tip of the heart, right here, known as the apex, which is pointing downward to the left. Not all the great vessels and structures are visible from the anterior view, but on the following slides, we will definitely look at the structures visible on the anterior aspect of this organ.
Now, the first structure that is worth mentioning seen on the anterior view, I already talked about it. This is known as the apex of the heart, highlighted here in green. Now, the apex of the heart is found on the left ventricle and is the lowest part of the heart. It is found at the position of the fifth intercostal space on the or close to the left midclavicular line. If you want to locate precisely the apex of your heart within or on your chest, this is the guidelines or the coordinates you would use. Now, the apex points downward, protruding forward and to the left. This is due to the asymmetric positioning of the heart.
From the anterior view of the heart, there is a structure you cannot neglect, and this is the aorta. Now, the aorta is the largest blood vessel in your body, and you can clearly see here on this image. This is the aorta right about here. Now, it arises directly from the heart, as you can also see here on this image, and then goes all the way to descend through the thorax into the abdomen. Now, all arteries except the pulmonary arteries stem from the aorta or one of its branches.
Now, the aorta can be broken down into segments or portions, and the first one is this seen here highlighted in green. This is known as the ascending aorta, and you can clearly see it from the anterior view. And the ascending aorta is about five centimeters in length, and it also starts at the aortic valve and ends at the level of the second right sternocostal joint.
Now, the other portion of the aorta that you can also see from the anterior view, seen also here, highlighted in green, this is known as the aortic arch. You can see that it has the shape of an arch, so it’s easy to remember that this is the aortic arch that starts at the point where the ascending aorta ends and then goes all the way to finish at the level of the fourth thoracic vertebra, also known as the T4.
Now, as a continuation, this is basically a continuation of the aorta as you see—so ascending aorta, then you have the aortic arch. And you notice here that it descends into an arch and goes to the left mediastinum. It is found in front of the right… so in front of the right pulmonary artery that is hidden right about here and goes all the way to, then, cross or in front of the bifurcation of the trachea. Then, it surpasses the base of the right lung and goes and finishes at the level of T4, as you see here also on the slide already.
Now, there are a few branches that come out of the aortic arch. The first one that we’re going to be seeing on the anterior view is known as the brachiocephalic trunk. Now, the brachiocephalic trunk is also known as the brachiocephalic artery, and this is the first branch of the aortic arch because the blood is coming from here. So the blood is coming from the left ventricle and then is pumped into the ascending aorta. “Ascending” means “going up,” therefore, the blood goes up, and it goes all the way to, then, descend on the descending aorta that should be seen on the posterior view a bit more clearly. And here, this is the aortic arch.
Now, the first branch that we’re going to find, then, is going to be this one here: the brachiocephalic trunk, and that’s why we say this is the first branch of the aortic arch. Now, the brachiocephalic trunk and its branches supply blood to the right arm, head, and neck. You can also see here on the image on the right side, you can see the highlighted brachiocephalic trunk within the thorax.
Now, the other one, the second branch, this one seen highlighted in green, this is known as the left common carotid artery. Like I mentioned, this is the second branch of the aortic arch. And this artery supplies blood to the head and to the neck and can also be seen here on the right side.
The next branch is this one seen here. This is known as the left subclavian artery. This is the third branch of the aortic arch whose function is to supply blood to the left arm. And you can clearly see here on this image, where it’s highlighted in green, that this branch, the left subclavian artery is going towards your left arm.
The next structure that we’re going to be covering on this tutorial seen on the anterior view, it is the pulmonary trunk. And the pulmonary trunk emerges from the right ventricle and carries deoxygenated blood from the heart to the lungs. Do not confuse here with this image where we have these structures highlighted in green, but originally, they’re red, because their names are actually arteries, but they do carry deoxygenated blood. So keep that in mind. And you can also see here on this different image on the right side.
Now, from the pulmonary trunk, there are two arteries that are going to branch off this trunk. The first one is seen here highlighted in green. This is known as the left pulmonary artery. And like I mentioned before, the left pulmonary artery is a horizontal branch of the pulmonary trunk that goes to the root of the lungs, and it carries deoxygenated blood to the left lung.
And if I zoom in here on the left pulmonary artery, you can see that two arteries should stem off the trunk or the pulmonary trunk. One is the left pulmonary artery that we just looked at, and the other one is hidden here behind the aorta and also this structure here that we’re going to look at later on, the superior vena cava, and you can see that the pulmonary… or the right pulmonary artery is hidden behind these two. So it’s really hard to see them from an anterior view of the heart.
Now, let’s move on to another structure: this one seen here, also highlighted in green, known as the arterial ligament—a ligament, yes—that is found connecting the previous structure that we talked about, the left pulmonary artery and the aorta. And this structure is known to be an embryological remnant of the ductus arteriosus. This is something that we’re going to cover in a little bit more detail once we go into embryology. Now, if I zoom in here, you can clearly see that the arterial ligament is connecting the… or attached between the left pulmonary artery and the aorta.
The next structure, if I swoosh here out of… or swoosh this image out of here and show you the next one, this is the left pulmonary veins. The left pulmonary veins carry oxygenated blood from the lungs and drain into the left atrium. So here’s something not to confuse, that the left pulmonary veins carry oxygenated blood and not deoxygenated blood. So write this on your notes. This is very important. And you can also see it on this image right here, on the right side, these structures highlighted in green.
Now, the next structure that we’re going to be talking about is a large vein known as the superior vena cava. And the superior vena cava carries deoxygenated blood from the upper extremities and then drains the blood into the right atrium. Notice here on this image that you have here this vessel here, this vein, known as the right brachiocephalic and this one, here, as the left brachiocephalic vein. They come together to form the superior vena cava. And this structure begins approximately at the level of the junction of the second and third thoracic vertebrae.
If you have a superior vena cava, well, I would say that everyone should have an inferior vena cava, as you can see here, highlighted in green. And this is also a large vein that ascends from the abdominal cavity through your diaphragm and then enters the chest cavity and drains the blood into the right atrium of your heart. Now, the inferior vena cava carries deoxygenated blood from the lower part of your body to the heart.
The next structure worth covering here on this tutorial is this one seen here highlighted in green. This is known as the right atrial appendage, and also, some people call it the right auricle. And the right auricle or the right atrial appendage is a muscular pouch attached to the outer wall of the right atrium. It occupies the space between the superior vena cava as you can see here on this image and also the root of the aorta.
Now, the contour of the right side of the heart is defined by your right atrium, and the right atrium collects deoxygenated blood from the superior vena cava and also the inferior vena cava, as we saw on the previous slides, which then open into the posterior wall of the atrium and the coronary sinus.
The next structure is, then, the left atrial appendage, which is then an appendage or a muscular pouch attached to, then, the wall of the left atrium, which makes up part of the base of the heart. The four pulmonary veins drain oxygenated blood from the lungs into the left atrium, and from the left atrium, the oxygenated blood is pumped into the left ventricle through the mitral valve, which is a bicuspid valve.
The next structure that we’re going to talk about is known as the right ventricle, and the right ventricle has a triangular shape, and a large part of the sternocostal surface of the heart is formed by its anterior and superior borders. Its inferior surface rests on the diaphragm, the right ventricle functions to, then, pump the deoxygenated blood to your lungs through, first, the pulmonary valve, then it goes into the pulmonary trunk that you can also see here on this image, and then goes into these arteries here that we talked about: the pulmonary arteries.
The walls of the right ventricle are not as thick as those on the left ventricle, and the reason is very simple—because the right ventricle, the blood that is going to be pumped out of the right ventricle is going to go to a shorter distance right next to the neighboring lungs, right about here, while the blood that is going to be pumped from the left ventricle is going to go to a longer distance, which is the rest of your body. Therefore, the walls of the left ventricle need to be thicker, have to have more muscle to pump the blood all the way to the rest of your body.
And speaking of which, we’re going to move on to, then, the left ventricle. And the left ventricle is also a conical, and its… or has a conical shape, and its apex forms the apex of the heart, the structure that we talked about on the previous slides. And it is slightly bigger than the right ventricle, like I mentioned also, and the walls are thicker, owing to the fact that the oxygenated blood pumped by the left ventricle goes to the systemic circulation via the aorta. And you can also see here on this image where the left ventricle and the heart is included within the thorax.
Now, moving on to the next structure, this one here, highlighted in green, known as the coronary sulcus, the coronary sulcus is also sometimes referred to as the atrioventricular groove. This sulcus or groove separates the right atrium from the right ventricle. And its anterior aspect of the heart, we see the coronary sulcus runs somewhat horizontally between the right atrium and the right ventricle. And you can clearly see here. I just removed here the wall of the right atrium, exposing it for you. And you can see here that it’s defining the border between the right ventricle and then the atrium which will be right about here.
Next structure on our list is this one here, also highlighted in green. This is known as the anterior interventricular sulcus—another sulcus. The anterior interventricular sulcus is a vertically running longitudinal groove that separates the right ventricle from the left ventricle anteriorly. Now, this is an important structure because two vessels are going to be running through this or upon this sulcus, and they’re known as—the one seen here highlighted in green—known as the anterior interventricular artery, which is a branch of the coronary artery. And another one is going to be the great cardiac vein that you can also see here on the right side, highlighted in green.