Structures seen on the medial views of the right and left lungs.
Hello, everyone! This is Joao from Kenhub, and welcome to another tutorial. This time, I'm going to be talking about the medial views of your right and left lungs. Now, keep in mind that I did, on a previous tutorial that you can find here on Kenhub, a tutorial where I just dedicated to the lateral views of the lungs. So if we’re looking now at the anterior view of the thorax, now exposing here the lungs, your heart, what I did was I did a tutorial where I covered all the structures that you can see on the lateral views of your lungs. But on this tutorial, I'm going to do or cover the lungs from medial views. So we’re going to look at all the structures that can be seen on the medial views of the lungs.
Now, if you ask me why I decided to do this, well, when you are in an anatomy lab or when you’re in an exam, usually, your professor will show the lungs in different positions, in different views, and you need to be able to identify all these structures that are found within the medial views and also the lateral views, and anterior, and posterior, and so on of every organ, every structure there is. So I think it’s important to dedicate an entire tutorial where we’re just going to dive into the structures that we find on the medial views of these organs.
Now, one important thing to mention is that the lungs are located on the chest cavity as you probably guessed by not only knowing from common knowledge or from the first grade that you learn that your lungs are located within your chest, but also from this image that you can see that they’re located in the chest cavity occupying the left and right pleural cavities on either side of the, more fancy word here, the mediastinum which is where they’re located and are covered by visceral pleura known as the pulmonary pleura, which is covering the lungs basically. And then this structure will reflect at the mediastinum and continue as this other type of pleura known as the parietal pleura, and you can clearly see here. So visceral pleura is basically covering the lungs, while the visceral pleura… or the parietal pleura is this one here that is covering the thoracic cavity.
Now, another thing that I want to mention is that the lungs differ from the right. So in terms of size, the right lung has a different size from the left lung. And it’s due to this organ here, the heart, that is a bit projected forward, and also to the left side, and occupies a bit more of the left side of your thoracic cavity, making the left lung a bit smaller than the right lung for spatial reasons. Now, then we can say that the lungs are paired and also asymmetrical organs, so they have different sizes. They’re not… they are two lungs, but they’re not exactly the same. There are few differences that we’re going to look at on this tutorial, of course.
Keep in mind that even though they are different from one another, there are some structures that are similar or found within both lungs. And we’re also going to see that here on this tutorial.
Now, another thing that I want to do before I move on is to make a note here, a reminder, very important and is usually object of confusion. And I have to make a note before we can continue, so on the next exam, you won’t miss this. So visceral pleura covers the lungs, while the parietal pleura is covering the thoracic cavity. Remember that distinction I made in the beginning, and this is something that is worth making a note before we continue.
Now, moving on to the next slide where you can see now the medial views of your lungs, and without any further ado, I want to show you that this one, here, on your left side is the right lung, while the one that you see on the right side is the left lung. My intention is clearly not to confuse you here. So this is the subject’s perspective. So you’re looking at someone, and he/she is looking at you. And this is the direction of their right lung, so it would be on your left side, and the direction of their left lung, that would be on your right side. But either way, this is how your right lung and left lung looks like. Now, knowing this, I want to continue by saying that the lungs have three surfaces that we’re going to look at right now.
The first one is seen here highlighted in green. This surface is known as the vertebral part of the costal surface. Now, the costal surface, which from the medial side of the lungs, can be seen as the vertebral part of the costal surface. So this… on the medial side of the lungs, you can see a part of the costal surface which is known as the vertebral part basically. Now, this is the portion of the costal surface which relates to the ribs laterally and posteriorly as well as to your vertebral column.
The next surface is seen here, highlighted in green. This surface is known as the mediastinal surface. And then this surface is located medially to the structure known, this cavity known as the mediastinum. The third surface that we need to remember here on the medial views of the lungs is this one located inferiorly. This is known as the diaphragmatic surface of the lung. And this structure, this surface, relates to the diaphragm inferiorly, hence the name. Now, also important to add here that here is where you find the base of the lungs.
Now that we covered the surfaces of the lungs, I want to move on and talk about the different borders of these structures that can be seen on the medial views. Now, the first one is seen here highlighted in both lungs, both the right and left lungs, and is known as the anterior margin or border of the lungs. Now, the anterior border of the lungs inserts into the costal mediastinal recess and is located at the junction between the costal surface and the mediastinal surface of the lungs.
The next border that we need to cover is this one seen, also, highlighted in green. And as you probably guessed from the location, this is the inferior margin or border of your lungs. And this border makes a sharp border at the junction of the diaphragmatic and costal surface of the lungs and at the junction of the diaphragmatic and mediastinal surfaces. It inserts into the costal diaphragmatic recess at the junction of the diaphragmatic and costal surfaces.
Now, that we covered the different borders that can be seen clearly from the medial views, I want to just cover here one of the first structures that we’re also going to cover on this tutorial known as the apex of the lungs. The apex of the lung extends toward the thoracic inlet or the root of your neck and has some clinical importance, because as it extends to the root of your neck or the base of your neck, it is important for different physical exams including percussion and auscultation.
We just covered the apex of the lungs. Let’s move on to another structure now known as the hilum of the lung. The hilar region of the lungs is a triangular depressed area of these organs. And in this region, we can see the structures that make up the root of the lungs. And definitely facilitates the neurovascular supply and also gaseous exchange to and from the lungs.
Now, let’s take a closer look here and using the right lung where we can see the root of the lungs. Now, in terms of the root of the lungs, there are structures, different structures that make up this area here. And we’re going to look… first, list them and then look at them in more detail.
The first one, first list is going to be blood vessels, then we’re going to cover nerves that are also found here, lymphatic vessels, and finally, bronchi that enter and leave the lungs to facilitate the proper function of these organs.
Let’s start off here with the first topic: the blood vessels. And there are various important blood vessels found at the root of the lungs that carry blood to and from the lung tissue. The first blood vessel that we’re going to cover is an artery known as the pulmonary or the right pulmonary artery. And we’re looking, yes, at the right lung. And the right pulmonary artery carries deoxygenated blood to the right lung, as you can see here on this image.
And this might be subject of confusion because usually or most of your arteries are supposed to carry oxygenated blood, but this is an exception. The right pulmonary artery actually carries deoxygenated blood. So this artery has three branches with each branch carrying blood to one of the three lobes of the right lung. This deoxygenated blood is then destined for the alveoli where gaseous exchange occurs. So CO2 in the blood is exchanged for oxygen, and the CO2 is then exhaled.
If we look at the hilum, here, of the left lung, we can also find a pulmonary artery known as then the left pulmonary artery. And the left pulmonary artery is in the same way carrying deoxygenated blood to the left lung, as we’ve seen with that other exception, the right pulmonary artery.
The other structures that we can find on the hilum, and we’re looking now at the right lung, this is known… these structures are known as the bronchial arteries. The bronchial arteries carry oxygenated blood to the bronchi and to the connective tissue of both the left and right lungs. As you can see here, I'm showing you both lungs with bronchial arteries highlighted in green.
The other structure that we’re going to find on the hilum is this one seen here on the right lung, and this is known as the right superior pulmonary vein. Now, the superior right pulmonary vein carries oxygenated blood from the lungs to the heart, and this is also an exception here, because usually, veins carry deoxygenated blood. But in this case, the right superior pulmonary vein will be carrying oxygenated blood from the lungs to the heart. From which, now, from this right superior pulmonary veins, from this point, the oxygenated blood is destined for systemic circulation.
The next structure found now, also here on the right lung is known as the right inferior pulmonary vein. And the right inferior pulmonary vein also carries oxygenated blood from the lungs to the heart. Also, here an exception that we’re used to listening all our lives that veins do carry deoxygenated blood. But in this case, this is an exception where oxygenated blood will go from the lungs all the way to your heart through this vessel here.
The next one is the… seen here on the left lung is known as the left superior pulmonary vein. And the left superior pulmonary vein carries oxygenated blood from the left lung to the heart as well.
The next structure seen on the hilum is also highlighted here in green, and we’re also looking at the left lung now. And this is known as the left inferior pulmonary vein. And the left inferior pulmonary vein, in the same way as the other pulmonary veins, carries oxygenated blood from the lungs to the heart.
Now, let’s go back to the list of structures that make up the root of your lungs. And I just wanted to say that I'm going to continue talking and focus on the bronchi, because they are relatively large structures when compared to the lymphatic vessels and the nerves.
Now, in terms of the bronchi, it is important to know that, at the root of each lung, enter a secondary bronchi or also known as the lobar bronchi. The first one is seen on the right lung—this highlight here. This is known as the middle and inferior lobar bronchi. As you can see, if I zoom in, you can clearly see here the middle and inferior lobar bronchi.
We have a middle and an inferior lobar bronchi. Now, it is time to look at also another bronchus that we find on the right lung known as the superior lobar bronchus. And it’s important to remember here that each bronchus is an airway for an individual lobe. So the superior lobar bronchus is going to be the airway for the lobe here, the superior lobe of the right lung. And the middle and inferior lobar bronchi that we just looked at in the previous slide is going to be the airway to the inferior and also the middle lobes of the right lung.
Now, let’s look at the left lung, and we have also here two lobar bronchi, and these are known as the superior and inferior lobar bronchi, as you can see here, also airway entrances for the superior and inferior lobes of the left lungs.
Let’s move on to other structures that we find on the root of the lungs. And now, I'm looking at the right lung and we’re looking at pulmonary lymph nodes that you can find within the root of the lungs. And you can also find these on the left lung as you can see here on both images showing the pulmonary lymph nodes.
The other structure that we need to cover here on this tutorial and seen on the medial views of the lungs is this one seen highlighted in green. This is known as the pulmonary ligament. And this is a section of parietal pleura that extends downwards from the root of the lung, ending in a free falciform border. This basically functions to keep the inferior part of the lung in its place.
The next structures that we’re going to be talking about are impressions, impressions left by organs. And the first one that we’re looking at is known as the cardiac impression. And due to the asymmetric position of the heart in the mediastinum, sitting in between the two lungs, impressions the heart leaves on the lungs can be seen, and you see now them, highlighted in green. On the right lung, the cardiac impression is visible as a deep concave depression on the mediastinal surface inferior to the hilum. And you can clearly see on this image.
The other structure worth noting, seeing here is the cardiac notch of the left lung, and the cardiac notch of the left lung is an impression left by the pericardium on the superior lobe of the lung.
Inferior to the cardiac notch, we find the structure here highlighted in green. This is known as the lingula of the left lung. Now, the human left lung, unlike the right, contains no middle lobe. However, the term lingula is used to denote a projection of the upper lobe of the left lung that serves as the homologue. Some sources define the lingula as a distinct lobe, but in this case, we’re not going to define it as a distinct lobe but just as an important structure that needs to be denoted here on the medial views of the lungs.
On the medial views of the lungs, we can clearly see the next structures that we’re going to be talking about: the pulmonary fissures. Now, if we’re going to be talking about pulmonary fissures, we’re going to, also, be talking about the structures that they break or they separate, and these are known as lobes of the lungs. And we’re going to clearly see how these structures separate the lobes of the lungs on the medial views.
Starting off with a view, now looking at medial views of both the right and left lungs, and you can clearly see here that each lobe is separated by a fissure. Now, starting off with the left lung here, as you can see, you can notice here that the left lung has one and two lobes that are separated by one fissure. And we’re going to look at all these structures and how they connect to one another.
Let’s start off with the first lobe here. This is known as the superior lobe of the left lung, and then you also have to have an inferior lobe. And these two lobes are separated by this fissure that you can see here highlighted in green. This is known as the oblique fissure. And the oblique fissure is now seen on the left lung, but is also found on the right lung. And we’re going to look at it later on on this tutorial.
Let’s move on then to the right lung, and also, the right lung has different fissures due specifically, and each lobe is separated by a fissure. Now, the right lung doesn’t have two lobes but instead one, two, three lobes, specifically. And these three lobes are separated by two fissures that we’re going to talk about right about next.
Now, moving on, the first lobe that you find within the right lung is known as the superior lobe of the right lung. Then you also have this one here that is exclusive to the right lung and is known as the middle lobe of the right lung. So you do not find a middle lobe on the left lung. The middle lobe is only found on the right lung. And you can also see here on this image of the anterior view of the thorax, anterior view of the lungs, you can notice the highlight of the middle lobe of the right lung.
Now, the other lobe that you find within the right lung is known as the inferior lobe of the lung and seen here highlighted in green and is also found, as we’ve seen previously, on the left lung. Now, these lobes are separated by two fissures. The first one is seen here, highlighted in green, and also exclusive to the right lung. So you do not find this fissure on the right… on the left lung (sorry), and this one is known as the horizontal fissure of the right lung—so exclusive to this particular lung.
Important to notice here that this fissure is breaking down or separating the superior and middle lobes of the lungs, as you can see here also written.
The next fissure that we’re going to be seeing here on the medial views of the lungs or the right lung is known as the oblique fissure. And oblique fissure is also… was also seen on the left lung if you remember well from the previous slides. And it’s important to mention that the oblique fissure is going to separate the middle lobe from the inferior lobe and also, as you can see here, the superior lobe from the inferior lobe.