The mediastinum is a space that some authors consider simply a cavity that is located within the thoracic cavity. In my video on body cavities I more or less addressed what the mediastinum and the rest of the body cavities were, but this video It was necessary because it is more specific in what are the exact divisions of the mediastinum and what are the structures that we find in each of them; This is Dr Juan José Sánchez and this is an anatomical video of easy anatomy by Juan José Sánchez. Let's start then talking about the large divisions in the thoracic cavity, in this view it is an anterior view we are seeing the thoracic cavity as if we were seeing it from the front, a frontal cut while here we are seeing it in a left lateral view, Basically what we did was remove the left lung, remove the shoulder first of course, the left upper limb, then the lung and we are looking inside the thoracic cavity but without seeing the lung.
So speaking clearly about the thoracic cavity, you have to know that the thoracic cavity is divided into three large cavities: first, two lateral cavities called pleural cavities, which are responsible for housing the lungs, they are the so-called sacs or pleural cavities, the two are large. lateral cavities of the three that make up the thoracic cavity, but it turns out that there is a space that I am putting here in blue that is between both pleural cavities, that space that is between both pleural cavities is what we call the mediastinal cavity or simply mediastinum, in Greek mediastinum literally means to be in the middle, so what would mediastinum be? It is nothing more than the space found between both pleural cavities where the heart is mainly located, but we are going to see that it is not the only organ found here, some authors say that the mediastinum is a space as such because it really is a virtual cavity due to the fact that it is always occupied by organs, the way of becoming spaces that I took out of the organs, but since anatomy is really studied with people, with corpses that are supposed to have the organs there, I cannot call it a cavity, then there is this debate with certain authors of whether it is a real cavity or if it is a virtual cavity, let's say the diatribe, however, we already know that it is the space so to speak, not to call it a cavity, which is between the two.
pleural arches and we are going to divide it, which is the most used division, a fairly old division, now there are other new divisions, but well the oldest one divides it into a simpler mediastinum; an upper mediastinum and an inferior mediastinum, now the dividing line, which is imaginary by the way, which divides the upper mediastinum and the lower mediastinum, is just going to pass in front of the sternal manubrium joint, that actually corresponds to the Lewis angle and in the posteriorly we speak of the lower edge of the fourth dorsal vertebra , then that vertical line that remains there between the sternal manubrium joint and that fourth dorsal vertebra throws me, let's say, the imaginary line that divides the superior mediastinum, above that line and the mediastinum inferior mediastinum below that line, but to further complicate the study of the mediastinum it turns out that the inferior mediastinum is subdivided into three portions: we will talk about a middle mediastinum which is the most important because it is where the heart is housed, in an anterior mediastinum which is in front of it and in a posterior mediastinum that is behind this middle mediastinum, so that then the largest mediastinum is the inferior one and within the inferior one there are three subdivisions; We are going to talk then about the general limits of the mediastinum and what structures are found in each of these divisions of the mediastinum and what are the dividing structures, from where to where I say that the mediastinum is called in one way or another; So don't miss out on the video [Music] I invite you to subscribe here in the lower right corner click [Music] and don't forget to like the video, it is vitally important that you subscribe to the channel here At the bottom in the corner where it says subscribe, click on it and you will automatically be subscribed to the channel and can have access to the more than 150 videos that are found there. You can write to me if there is any video that you can't find or that you prefer that I always make for you. When it is within the anatomical limits and thus you help the channel to grow more, we already have more than 55 thousand subscribers, until this moment the realization of this has really been quite expansive, the growth of the channel is quite rapid.
Here well, as a diagram I show you this dividing line that passes through the lower edge of the D4 vertebra and here in the sternal manubrium with its union, with the body in the famous Lewis angle or sternal angle, what would be in red would be then the superior mediastinum and everything below it is the inferior mediastinum, the inferior mediastinum being then divided into the anterior mediastinum, a middle mediastinum, posterior mediastinum; Let's quickly see what the limits of the mediastinal cavity are as such: we continue with this lateral division, the anterior limit will be given by the posterior face of the sternum, as well as the insertion of the costal cartilages of the ribs on those lateral edges. of the sternum, then both the posterior part of the sternum and the posterior part of those costal cartilages would become the anterior limit of the mediastinum, the posterior limit of the mediastinum is going to be, listen well, maybe some books only say that they are the vertebral bodies These are not left in doubt to the student that the vertebral bodies part, it is more specifically this posterior limit says that it happens in the area where the famous vertebral pedicle is located, which is the posterior edge of the vertebral bodies when this body is uniting With the arches, to make it easier, the theory says that you have to pass a tangential line that touches the posterior common vertebral ligament, which is also called the posterior common longitudinal ligament because in this way you do not exclude, for example, the intercostal veins, to the intercostal artery, the intercostal nerves, to the descending aorta itself that would be the content of the posterior mediastinum, that is why this posterior limit has to go so far, anyway, right now I am going to show you an image of a cross section so that you understand what implications it has for me to delimit the posterior border of this mediastinum or the posterior limit; The upper limit will be given by the upper thoracic opening which is or more or less will be, it will go from the upper edge of the first dorsal vertebra to the upper edge of the sternal manubrium where the jugular notch would be found, the lower limit It would then become the upper face which is the let's say thoracic face that looks towards the thorax of the thoracoabdominal diaphragm muscle, then I have more or less a square surface that seen from the side, but if you are quite active let's say you will realize that There should also be lateral limits and in fact it is like that, when I see the mediastinal cavity seen from a frontal view I would also find that there are lateral limits that in fact are the limits that would stop me in theory of the pleural cavities, in fact These lateral limits would become the mediastinal parietal pleura, which is part of the pleura as such but is what delimits the lateral limits of this mediastinum, so that for you to imagine the mediastinum, imagine a cube that would be a surface with approximately 6 sides. Very well , in this section I wanted to show you more or less at this level is the pedicle, here would be the posterior common longitudinal ligament and here I would pass my my horizontal line that would then include me to the structures that are at this level more or less, that is why the importance of taking that posterior limit well is so important, because it tells me that I must take here as the anterior edge of the vertebra of the vertebral body, I would simply exclude part of the aorta, I would exclude the trunks sympathetic, to the azygos veins would exclude many many structures that are studied within the contents of the posterior mediastinum.
Let's talk of the content of each of them, let's take advantage and talk about the limits of each of them: we start with the superior mediastinum here see, remember that the second rib reaches the Lewis angle so more or less this would be the level of the Lewis angle In the upper mediastinum, we first find arterial structures. We try to separate them into groups so that it is easier to study. We first find the callus of the aorta, a large part of the callus of the aorta, also called the aortic arch, and its branches.
What are they? your branch? the brachiocephalic trunk that we see here, the common carotid artery on the left side and this would be the subclavian artery on the left side, generally there may also be a middle thyroid artery and they also call it the imo thyroid artery, which generally leaves the atrium-cephalic trunk when it exists and ascends towards the thyroid gland, then when it exists it is also content of the superior mediastinum; venous structures that we will find, here well the superior vena cava and its formers, remembering that the formers of the superior vena cava would be the brachiocephalic veins, both brachiocephalic veins previously called innominate veins, we would also find at this level the inferior thyroid veins that would be draining to The thyroid gland, specifically, those veins drain into the brachiocephalic gland itself and that is why we can find it at this level.
What structures do we also find important here? We find inside the nervous part, we find the vagus nerves, both here we actually see the left vagus nerve descending, the phrenic nerve, which well here is cut, not here, but you know that it descends along the superior mediastinum and branches of the vagus nerve as is the recurrent laryngeal nerve, here we see the left one as it turns around here, ascends here and in the middle you can see the left recurrent laryngeal nerve; It is important that you also know that there are structures that are because they are long structures that are in various parts of the mediastinum, as happens with the trachea, as happens with the esophagus, as happens with the same vagus nerves that, since they are so long that you see them in the superior mediastinum but you also see it tucked inside the inferior mediastinum, we are also going to find the thoracic duct here, in fact look at it here, in the posterior mediastinum part of the inferior one is hidden but it makes a curvature behind the trachea and the esophagus and see it here again, then it would also be found within the upper mediastinum, other structures that we find there would be a large part of the cervical, let's say thoracic, more superior portion of the thymus, we would find part of the esophagus and we would find the trachea deeper , this would be good In this image here you can see the recurrent nerve a little better and this so that you can see what the superior mediastinum would look like also seen from anterior, here the phrenic nerve is not seen cut, you can see it along its entire length and it is also one of the structures, for example, this phrenic, which in addition to being found in the superior mediastinum is also located in the middle mediastinum. The structures found here are quite different.
Here, for reference, I show you the thoracic duct seen from a left lateral thoracic view. As she searches for its mouth she has to swear to cross the upper mediastinum; talking about the anterior mediastinum so that they know the limits of it, which we do not talk about is everything that is in front of the pericardium, here you see the parietal pericardium, everything that is in front of it but behind the sternum is the anterior mediastinum There basically what we find are external pericardial ligaments that are part of the fibrous pericardium and the thymus, the thymus, the thymic cavity, it is also important for you to know that in the child as the thymus is as large, the anterior mediastinum is generally larger. , it is larger, the space in the adult is very small, it is very minimal, in fact, see there this would be the parietal pericardium and here see the thymus in front because it is an adult, so it is very small, this anterior mediastinum in the adult is very little developed, in addition to finding thymic structures, see here how we find the internal mammary artery and vein, which is a good old name, currently the payroll calls it the internal thoracic artery and the internal thoracic vein but they are the same internal mammary, here we see that this posterior view of the anterior wall of the thorax, that is, we are seeing the sternum but from behind it is as if it were tucked inside the thorax, so see how it contains the internal mammary vein and the internal mammary vein, as well as this muscle that is here.
Well, it wouldn't be such a muscle. because it is like part of the chest wall, but it is the triangular part of the sternum. We now pass the middle mediastinum, what is the middle mediastinum?
The middle mediastinum is everything that is anterior to make it easier for the tracheobronchial part, but posterior to the anterior part of the parietal pericardium, I don't know if I explain myself or less, we are going to see this from the side anyway, what do we find? in the middle mediastinum? First the parietal pericardium with everything it contains , which is the beginning of the great vessels, which is the heart itself that here gives the beginning of the great vessels, well, the superior vena cava, the ascending aorta, the trunk of the arteries.
lungs, is what he called the beginning of the great vessels, here at that level we also find, for example, the pericardiophrenic vein, the pericardiophrenic artery and the phrenic nerve, which is the one that accompanies these three structures, here we also find the mouth of the azygos vein that we are going to see them a little better, that it is located in the middle mediastinum, remembering that it has an elastic arch that empties into the posterior part of the superior vena cava and therefore, to the east, it will also be found partly in the middle mediastinum. that arch also of the azygos; nervous structures that we find here apart from the phrenic nerve that I already named, we are also going to find the cardiac plexus, pulmonary plexus which is a sympathetic plexus, really here we are seeing the middle mediastinum, look at it from the tracheobronchial part more or less and see that From then on all this would be the middle mediastinum, it contains the heart, the great vessels, see here the pericardial phrenic artery and the phrenic nerve itself, here in the azygos arch, this is a right lateral view of the thorax, well there you can see how then this arch of the azygos would theoretically be in that middle mediastinum, also here we find the vessels and large vessels that would be these pulmonary veins, this one that would be the pulmonary artery and even at this level. Now important structures of the mediastinum, a good part of the trachea that you see is then located in both the upper and middle mediastinum, we also find the main bronchi that end the trachea, that is, its bifurcation and well we find lymph nodes that are located at the level of the trachea and the bronchi, which would be the bronchial tracts, such as those we are seeing here, for example, they are going to be taken by some authors as the posterior limits of the middle mediastinum to be the esophagus, everything from the esophagus onwards is called as part of the middle mediastinum, however in fact you see that this classification that I am giving you is very similar because the tracheobronchial part, see that it is behind the esophagus and I am including the trachea within the middle, it means that from there to the back it would be the mediastinum posteriorly, here we are seeing the middle mediastinum, they removed it, the inferior vena cava is also part of the middle mediastinum that I forgot to mention right now, the arch of the azygos here you can see those large vessels like the trunk of the pulmonary artery, the pulmonary arteries , look at the pulmonary veins, in the trachea, main bronchi, everything that I have been telling you is at that level, there so that you can more or less see what the final route of the trachea is like.
Good posterior mediastinum is quite rich in structure, in that posterior mediastinum we find the descending aorta, notice that the aorta would then occupy several portions. The mediastinum, the arch is the superior mediastinum, the ascending one is the middle mediastinum and the descending one is the mediastinum. posteriorly, we also find the visceral and parietal branches of that descending aorta such as the posterior intercostal arteries, the esophageal branches, the middle thymic branches, the branches that also go to the pericardium and important structures of the posterior mediastinum, the esophagus that is kept enveloped by the more posterior phrenic nerve, there is still the azygous vein, the hemiazygous vein, the accessory hemiazygous vein, the thoracic duct is found, the sympathetic trunk is found , see here the azygous, here you see the accessory hemiazygous and here the hemizygous, all of that within the posterior mediastinum and you can also see the esophagus, in this other good image we see the sympathetic trunks, remember that the vagus nerve surrounds the esophagus, so if the esophagus is there, the vagus nerve must also be there and here we also find the famous nerves thoracic splanchnics, this entire structure has a separate name.
You can find it in the channel with an explanation of each of them separately. Remember that this is a video that is really a compendium of what it is or what structure is found at the level of the mediastinum. In general, this was the entire mediastino video.
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