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If you need to have any questions, just unmute yourself and ask questions, I think they are able to do that. Um So I will go ahead and get started. My understanding is that you're all maybe sitting the MRC as part a either May or September. So if you're setting it in May, then hopefully, this is all very brief overview just to highlight areas that you might not be 100% on yet. And if you're sitting in September, this is just a broad overview of the topics that may come up. Now, the word of caution is that for the purposes of MRC S thorax is actually not that th thoracic anatomy isn't that big in terms of all the questions that they could ask. So there is an MRC S syllabus floating out there on the web somewhere. I couldn't find the most recent version. But the one I did find said that in your uh paper, one which is your applied basic sciences that contains a lot of the surgical anatomy of the 63 questions on regional anatomy, you will only get six on the thorax. You might get at least one embryology or developmental question on the thorax. And when it comes to surface and imaging anatomy, they only have four questions and thorax isn't even on there. So they might ask it, but it might not be there. Whereas if you look at your paper too, um if say, for example, you only look at the trauma section because thoracic trauma is quite a big topic as well. Then there are 30 questions. If you know your at os backwards and forwards, then you'll be grand for those 30 questions. So just think about it when you are planning your revision and sort of map what you're trying to do to the um um syllabus, but obviously part A is about breath, you need to know a lot of things. But thankfully, it's multiple choice questions. Now, today we're talking about surgical anatomy and the emphasis is they always say applied surgical anatomy and what that means is that it has to be surgically relevant. What does it mean when you actually apply it in practice? And just to mention, we're not covering any physiology or pathology today. And uh as you probably already know for part A, you must pass both paper one and paper two to get an overall pass. They don't just take an average. So thorax anatomy. So we'll cover regional anatomy, they surgically related to embryology and development and a little bit of imaging anatomy at the very end. And that is based on the syllabus but when it comes to thoracic anatomy, there are, there is a lot to cover. So you have the thorax, mediastinum, heart and lungs. But technically, the esophagus and breast are also within the thoracic area. So we'll talk very briefly about the esophagus, but just know that I would not be covering breast. I'm hoping that you have a endo and breast session later on. Um And in no particular order, we'll go through all of these items. So thoracic wall, chest drain angle of the mediastinum, great vessels, diaphragm, esophagus, et cetera, et cetera. And I have assumed some very, very basic understanding of anatomy. So, you know, I won't be telling you that there are four chambers to your heart, et cetera. So we'll get started first with a thoracic wall then. So the thoracic wall consists of 12 pairs of ribs. 1 to 7 is true, which means that they have direct attachment to the sternum via a costal cartilage, te 8 to 10 is false because they have an indirect attachment. And 11 and 12 are your floating ribs. The sternum is made out of three parts. You have the manubrium body. And as if we process at the very top, we have a jugular notch between the manubrium and the body. You have the sternum manubrial junction. And again, if somebody's asking, this is more part b related, but the thoracic will also consist of the thoracic vertebrae. The intercostal muscles are important there So you need to know that there are three layers of intercostal muscles. These being the external intercostal, internal intercostal and the innermost external runs forwards and downwards. Whereas the internal runs backwards and upwards and that's very much similar to your abdominal muscles as well. The clinical important bit is that the neurovascular bundle runs on the under surface of each rib. And the arrangement is in intercostal vein, artery and nerve, which means that when we're trying to do any procedures that needs to go through these ribs, then the intercostal nerve is at risk of damage. And what procedure would that be that would most commonly just be a chest strain which will come on to. And it's very unlikely that they'll ask you the art where um where the arteries come from based in part A. So arteries, 1 to 9 come from the internal mammary. They supply the anterior chest wall arteries, 1011 subcostal supply the anterior abdominal wall and the veins, the intercostal veins drain into the aus and the hem aha. And we'll talk about all of those as well. The important muscles that you need to really know about for the purposes of this exam around the chest wall. The big muscles are your pectoralis, major, lutitus, dorsi serrate anterior and trapezius. Now, for muscles that are important, you also then need to know the origin attachment, nerve supply and that goes for all muscles. And you know, especially in your orthopedic section as well. So the nerve supply to, we'll just go through a nurse supply really quickly as a recap pectoral is major as two supply. So you have the clavicular head which is supplied by the lateral pectoral nerve and the sternal costal head, which is supplied by the medial pectoral nerve, latissimus dorsi. Anybody is the thoraco dorsal nerve serrate anterior. This is the one that everybody gets right is the long thoracic nerve bell and trapezius is your accessory nerve. Now, these are all important clinically because you need to think about chest drain insertion. So when it comes to chest drain insertion, you have to know the triangle of safety, but it's not really a triangle. It's a trao sometimes. So you need to know that the borders of the triangle safety is first of all, the lateral edge of the pectoralis major, the lateral edge of the latissimus dorsi base of the axilla and the fifth intercostal space which is sometimes marked by the line from the nipple, excuse me. So, insertion of a chest strain is just at 1 to 2 centimeters anterior to the mid axillary line. And the reason for that is that you've got your serrous anterior and the long thoracic nerve in the mid axillary line. So you don't want to damage anything there. And that's why you go about 1 to 2 centimeters anterior to the mid axillary line. Now, MRC S loves layers. Um so for anything that you're putting into the patient chest strain being an example. And so you can also have any other kinds of line or if you're doing a lumbar uh puncture, for example, they'll always, always want to know the layers that you're going through. So for a chest drain insertion, what you're going through is skin, subcutaneous tissue and fat. So these are fairly common superficial fascia that you're gonna go through the three intercostal muscles. So, external intercostal, internal intercostal and innermost intercostal muscle, then your endothoracic fascia, then your pleura. So, endothoracic fascia is the bit that people sometimes forget about. So, just before the pleura, there is a little bit of endothoracic fascia that you do have to go through as well for a chest drink, sorry. So we'll shift gears a little bit and we'll talk now about the first rib. So, because in part A, it's MC Qs, it's very, it's not possible for them to give you a short rib and say here, please orientate that. But for part B, you do need to kind of not that, but first rib is shortest and flatt, you have the subclavian vein that is just anterior on the first rib, followed by the anterior scaly muscle, followed by the subclavian artery posteriorly. And then the brachial um plexus is be uh posterior to the subclavian artery as well. So the order of structures on the first rib is very, very important. Um and we'll come back to that when we also look at nerves around that area as well. So the sternal angle of lo I know sometimes it uh this talk might seem a bit haphazard, but hopefully we're covering all of the main areas. So, sternal angle of lo um I just lifted this off Google images. I thought it was a great um summary of it. So it's formed by the articulation of the manubrium and the sternum. So that's your manubrial sternal junction. It marks the level of the second costal cartilage. And that's the, you know, when you're palpating, you can always feel the bump on the sternum. And that is the point from which all costal cartilage and ribs are counted. So that's where you start, that's your second rib and then you count downwards from there, it lies opposite the intervert disc between T four and T five. And you can see that in this image, there's a section of a plane and that kind of corresponds with that disc uh between T four and T five. Now, this is in the thorax. This is probably if you have to learn anything, this is the structures at the sternal angle are what you will have to know. So for us, this is sort of the magical playing of, of where everything happens. So the first thing to know is that this plane divides your mediastinum into superior and inferior. It's, it's the intervertebral disc. But sometimes you can see it as the lower border of T four vertebra. So if you're looking at a CT image and you think, you know, you just count T four, then you know, you are at the sternal angle that plane. Now, the a lot of things happen here. So if you, if you think about your, all the structures in your thorax, something is bound to happen at the sternal angle. So the trachea bifurcates, the arch of aorta sits at. So the arch of aorta begins and ends at T four. The az vein empties into the superior vena cava here and the superior cava actually empties into the right atrium at the same level. The pulmonary trunk also bifurcates at this level. Thoracic duct crosses from the right to left and clinically the tip of the central line. If you're inserting, one should stop here. And the most, this is also the most common site of the trauma, any thoracic trauma such as aortic rupture. And the reason being that there is the ligamentum arterial that is sort of tethering the aorta. So in the trauma that will make it a common site of rupture. So this is a lot of structures. But if you just kind of think about the structures that you have within the thorax, something happens at T four, something happens at the sternal angle. So just just keep that in mind because unfortunately, this is a shopping list that you just have to know for anatomy. Now, talking a little bit more about the mediastinum. So the mediastinum is divided, as we said earlier, onto superior and inferior. Now the inferior mediastinum is then divided into anterior, middle and posterior. And that's demarcated by the pericardium. And you do unfortunately have to know the contents within each of the mediastinal sections. So in the superior, you can have a little bit of thymus, as we mentioned above. The T four is, you know where the, like I said, the aortic arch begins and ends, you have the brachiocephalic trunk esophagus, which also then goes into your posterior mediastinum and the trichia before it bifurcates, the vagus and the right recur right, recurrent laryngeal nerve in the sorry, both left and right. So you, you will have both recurrent laryngeal nerves in there. Sorry, in the anterior mediastinum, you have the thymus and the lymph nodes. If you just have those down, that's, that's the easiest mediastinum of them all. Really the middle one. You have the pericardium heart, the great vessels and the front nerve and the posterior is where everything else happens. You have the sympathetic trunk spine, nerve, descending thoracic aorta, you have the venous drainage, the aus hem az and accessory veins. Um then you have thoracic duct, esophagus and vagus nerves. Um It does feel a bit like a shopping list sometimes. So you just need to think of it in terms of what structures are there in the mediastinum in the thorax and where they might sit. So for example, the way I was always taught to think about the posterior structures is if you work backwards from the spine. So along the ver um thoracic vertebra, you have the sympathetic trunk and the splanchnic nerves and then you have the descending aorta, you have the esophagus, so you can work back backwards like that. But thankfully for part A, the answers will be in front of you. So you just have to choose the right one. Now, we'll move on a little bit to thoracic aorta. So the image here on the right shows you all the branches of the thoracic aorta. Now, the trick question is always which are the first branches of the ascending aorta or just the thoracic aorta. And even this diagram has it wrong because the first branches are not actually shown and they are the coronary arteries, both left and right that arise from the aortic sinus. So if, if one of the questions ask you, what are the first branch of the thoracic aorta then go oh I totally know this. It's the brachiocephalic artery. No, it's probably a trick question. It's the coronary arteries. So, coronary arteries arise in the ascending aorta and then you have the aortic arch. So you have the three branches, your brachiocephalic, your um common carotid and the left subclavian artery. Um Sometimes you do get the thyroid IMA which supplies the inferior thyroid that is also a branch there. Um This one does show you the, the ligamentum arteriosum as well and then coming down into the descending thoracic aorta, you have the left and right bronchial arteries that supply the bronchus, a branch to the esophagus there. The mediastinal branches as well as all the posterior intercostals following with a subcostal artery that will supply ulcer in the lower spaces of your thorax. S VC. Again, fairly straightforward, you have your right brachiocephalic joining the left brachiocephalic to form your S VC. And just remember the Aus Veno so drains into the S VC at the magic level angle of Louis sternal angle, hep two pulmonary artery. So I write that this is often the foregone structure because we are always taught to think artery vein and the or sorry artery vein, nerves in medical school. But then sometimes in the great vessels, people forget that we do also have an extra pulmonary artery there besides the aorta. Um And uh I think for the purposes of the exam, you really just need to know that it divides into the pulmonary trunk, divides into the left and right pulmonary artery and then goes branches off into the lungs, pulmonary vein. So the artery, there are two arteries, two main arteries that we talked about. Now, there are four pulmonary veins and that's divided into left and right and the superior and inferior. So the right superior goes to right upper lobe, right middle lobe and the right inferior goes to right lower lobe. Whereas on the left side, you have the left upper lobe and lingula and the inferior goes into left lower lobe, you just, it's fairly straightforward. No. Um it's very unlikely that they'll ask you uh beyond that, that said pulmonary vein, just keep in mind is the one in clinically and surgically speaking, it has the most number of variants and there's a lot of variant anatomy when it comes to pulmonary vein. But for purposes of exam, stick to the four branches. Now, aus vein we have kind of mentioned, but they drain the intercostal um vein, venous, they, it is the intercostal venous drainage to the chest wall. So on the right hand side, you have your azu vein that drains into the S VC at the level of T four. And on the left hand side, it's divided into accessory hemiazygous which supplies the upper part and the hemiazygous vein that supplies the lower part. Now, both the accessory hemiarius and the hemiazygos then drains into azo vein, then S VC, then right atrium, thoracic duct is another structure that sometimes you forget to read about and then some suddenly comes up on an exam, but it starts off as a sterna kly in the abdomen. It passes through the aortic hiatus at the diaphragm and rises posterior to the esophagus until level of T 45. And again, this is your sternal angle where then the thoracic duct actually crosses from the right to the left to run behind the nominate or the subclavian vein and it then drains into the left subclavian internal jugular vein confluence. So it's right. Yeah, I don't know if you guys can actually see my mouse when I move it, but it's just up here where the subclavian and the internal jugular veins come together. Now, the nerves. So the biggest nerves that you have to know when it comes to thoracic anatomy are going to be your phrenic and vagus nerve. And you do need to know the course of them, how they enter the thorax, what they do in the thorax and how they exit really. So the front. So both of them have relation. So if we think about it as sort of top to down, um they are both related to your anterior scaling muscles. So vagus nerve kind of starts off in the medially in your carotid bundle and it comes down into and both of these nerves actually cross into the thorax at the plane between the subclavian vein and the subclavian artery. So we just think about what we talked about around the first rib. You have your subclavian vein, anterior scaly muscle, subclavian artery and the nerves cross at this plane in between the vein and the artery. Um And then on the right hand picture, you can see that the vagus nerve comes down on the right hand side, it loops around your subclavian artery to become the right recurrent laryngeal nerve. Whereas on the left hand side, it go, the vagus nerve goes further down, loops around your arter um art aort sorry, the arch of the aorta around ligamentum arteriosum and then becomes the left recurrent laryngeal nerve. Um This is I thought just a really nice schematic of the layers in between them. So as you, as you remember, vein, then there's the nerve in between the plane of the vein and the artery and the arteries in the back. So, diaphragmatic openings, I think this is a very common question on MC Qs I've seen before. So uh T eight, T 10 and T 12 are the three levels you need to know. Um the mnemonic that was always taught with um for Vena cava. Uh So that's your IVC. There are eight letters in that. So that's your T eight esophagus has 10 letters. So that's your T 10. And this th the third one is aortic hiatus that makes up 12 letters and that's your T 12, excuse me. So at T eight, you have your IVC and your right phrenic that goes through the um opening together at T 10, you have your esophagus and you have your vagal trunks. So that is both anterior and posterior trunks. And the trick that I always think about is eso esophagus and vagus nerves tend to go very close and together and vagus supplies a lot of the, the gut. So really uh traveling through the thorax with esophagus makes a lot of sense to me. And there is also a branch of arterial branch, which is the ascending esophageal branch of the left gastric artery that will go on to supply the esophagus. And that also crosses at T 10 along with the esophagus. Now, t 12 is your aortic hiatus. So you have the thoracic aorta that crosses T 12 thoracic duct as well as the aus vein. OK. So this is the one slide I have about the esophagus. Um MRC S loves esophagus. Uh There is a lot of things that they can test you on about the esophagus. There is a lot of pathology physiology all involved in the structure. So I would say it, it actually came up on my part b exam as an entire station as well. So if you need to know some structures in the thorax, uh surprisingly, you have to know about the esophagus. So it is kind of the organ of three, there are a lot of three things. So you know that there are three types of muscles at the proximal and it starts gyrated and then at the distal one third is a smooth muscle, whereas in between is mixed. Um there are actually three physiological constrictions to the esophagus that is sometimes asked about as well. So the first one is your pharyngoesophageal constriction which starts really by um uh actually around the level where the trachea starts as well. Um And that constriction is caused by the muscle cricopharyngeus. The second constriction, which is the thoracic constriction. I'm sorry, this image had it spelled incorrectly. Um is caused by, actually, you can say either the left main bronchus or the arch of the aorta. So both of these cause constrictions. But for, in, for, you know, p exam purposes, usually the two of them get merged into one constriction. And then the third one is your diaphragmatic constriction, which is caused by the right cross of the diaphragm. And that also forms your physiological sphincter for the esophagus. So that is your sphincter for the food to go into your stomach. So those three constrictions are important to know because as you're passing an endoscope for an example, those are what you expect to see at the levels. Um Mucosa is actually all squamous. It changes from stratified squamous eventually to non stratified squamous. Just remember for your pathology, columnar epithelium in of the esophagus is only in pathological conditions, which is barrett's now for your blood supply. Again, they love the blood out of the esophagus. Um So again, divide into an upper middle and lower. So the upper is supplied by the inferior thyroid artery drained by the inferior thyroid vein. The middle will be supplied by the branches of the descending thoracic aorta and it's drained by the Azac vein, which is I think it's straightforward enough um and then the lower is actually the esophageal branch of the gastric artery that again, we talked about also crosses at 10 and it's drained as such by the left gastric vein. And the clinical significance is that between the middle and the lower portion, this is where portosystemic anastomosis happens. And this is where you can get your esophageal varices that can bleed and cause a lot of um the severe hematemesis as an example. So that I would say if you have to know about thoracic anatomy, please, please, please don't forget about the esophagus because the emeria loves it. Ok. Now, we actually shift gears to talk about the heart and lung. Now. So it's the lung sys the respiratory system really for us, starts at the trachea, which begins at the lower border of the cricoid cartilage at the level of C six, it terminates. So it bifurcates into your left and right main bronchus at you guessed it t four or five, the sternal angle of Lewy. And the trachea is actually a series of sort of u shaped cartilages um that are held posteriorly together by a little muscle called trachealis. It's not very likely that they're going to ask you about the blood supply or the venous drainage to the trachea. But if you need to know, think about, you know, the anatomically speaking, it's sort of in the area of the inferior thyroid just as how the esophagus had the inferior thyroid, um artery and veins. So that's probably the way I would approach this. It then you've got the main bronchus, which then is split into left and right main bronchus and they will continue to divide into lobar bronchi and then segmental bronchi until eventually reaching the alveoli, the right main bronchus is wider, shorter and more vertical. And this comes out again and again, because this is where foreign body is most likely to be stuck in. Um And the way we know about that is because actually, we'll show you an image a little bit, but the right upper lobe bronchus is very, very quick to branch off and I'll show you a nice picture of it. But just because the the first bronchus is so quick to branch that makes the main bronchus shorter and why um more vertical as well. Um As you know, there are three lobes on the right and two lobes on the left. So on the right, you have upper, middle and lower lobes on the left, upper and lower lobes. And these are divided by the oblique fissures. And on the right hand side, there is also the horizontal fissure as well. Now, this is sort of kind of the mediastinal area that we're approaching and it gets very, very complicated when it comes to anatomy. But anatomy, uh anatomies love planes. So the easiest way to think about all the structures in the grave vessels is by the plane So the first most anterior plane you're going to come across is your venous plane. So you, that's thinking about your brachiocephalic, your superior vena cava. Then the next plane you have is your arterial plane. So you can see the, the aorta, the ascending and the arch of the aorta with the branches. The next one is the pulmonary trunk. And then behind that. So posterior to that is the bifurcation of trachea. And these are the four planes that we sort of try to keep in mind. And when we're talking about the right main bronchus, you can see that perhaps probably best in this pulmonary trunk image. Here, you can see the a vein arches over the right main bronchus to reach the superior vena cava. Um And that on the left main bronchus, the left um pulmonary artery sort of spirals over the bronchus and then anteriorly then above. So there are names for these, the way that the relation of the right and left main bronchus to the pulmonary arteries. So the right main bronchus is called arterial. And that's because it lies above the pulmonary artery. So you can see this is the first branch. So this is your right upper lobe bronchi, that is the first branch of your right main bronchus. And this is why we say that this is a shorter bronchus on the right than the left and the art the pulmonary artery is beneath it, which makes the bronchus above the artery and therefore up arterial, on the left hand side, it goes the other way. So the bronchus lies beneath the art the pulmonary artery. And therefore, it's called hypo arterial. And the reason I'm mentioning this is because this helps a lot when you're thinking about your mediastinal relations and the orientation at the hila, which is also a but I don't know when I was a medical student, I really struggled with this. But there are ways to think about this. You can try to memorize it by, you know, brute memory or you can try to work it out logically as well. So if we just the rule of thumb in the both hila is that the most anterior structure is going to be your superior pulmonary vein. So remember pulmonary vein, there are two branches on in each side. There is your superior and the inferior and they will have divided at the point of Hyla as well. Ok. So your superior pulmonary vein is the most anterior, the inferior pulmonary vein is the most inferior. So on this picture, just note that on this picture, though the veins are red, which because they're oxygenated blood and the artery is blue on here. So you've got your superior pulmonary vein, most anterior here on the right lung and most anterior here on the left lung, then you have your inferior pulmonary vein, which is the most inferior structure here. And the most inferior structure here. Now, that's fine cause that's your pulmonary vein done. Now, you just have to work out how your pulmonary artery and the bronchi sit with one another and that's where we go back to this picture again. So on the right hand side, the bronchus is a arterial, meaning that it's above the artery. So it's likely that on the right hand side, then your um lobar bronchus is going to either be superior or anterior to your pulmonary artery. Ok. And in this picture, you can see that it's just anterior to it. And similarly, on the left hand side, you know that the bronchus is going to be hypo arterial. So it's going to be inferior to your artery, isn't it? So I hope that makes sense and I hope that helps and rather than confuse you all. But if you just remember vein, most anterior and inferior, then you have your artery and the pulmonary artery and the bronchus arranged depending left or right, depending on whether they're a arterial or hypo arterial. Now, rela uh sorry, this is the next slide, same picture, but just now showing you the impressions on the mediastinum. So on the lung impressions, on the right hand side, you're going to have generally venous structures. Whereas on the left hand side, it's going to be generally arterial common to the both sides are your first rib, subclavian and the esophagus. So if you look at the picture a little bit closely. So this is the, uh the one on the top is your right lung. So you're gonna see the sorry, the superior vena cava here. Um And then you're going to see the az vein that drains into this, drains into the superior vena cava. And there will also be a groove for the inferior vena cava as well on the right hand side because it's mostly arterial, you can see a nice groove for your aorta here and you can actually see a very big groove of your cardiac impression. And that's going to be generally your left ventricle, which is arterial as well. And common to both, you can see the groove for esophagus just around there and then the superior structures of your subclavian artery and vein on the top here. So we're coming back to the framing and Vegas again because we only talked about its course at the thoracic inlet. So looking at this picture, they've reversed. So this is anterior, they've labeled it anterior in the middle. And on this is the right hand side and the left hand side and the posterior kind of on the both lateral edges of the picture if that makes sense. So we start with Phren cause that's nice and easy. So phrenic passes anterior to both hyos lying on the pericardium. Ok. So it goes anterior to both hilum and that is sort of the anatomical relations that they look for eye exams and also clinically we look for the phrenic nerve at anterior to hilum, making sure that we don't damage it in the process. Um Similarly, then you have the um oh sorry, the vagus nerves. So the vagus nerves are going to be um posterior. It's going to travel posteriorly because it travels with the esophagus. Esophagus is in your posterior mediastinum. It's going to head in that direction so that it can cross the diaphragm. And therefore, it's probably quite easy to just uh remember that the vagus nerve travels posteriorly within this area at the hilum. Ok. And I've just provided sort of the overview of how it actually goes. So the phrenic nerve is your c 345 that provides motor and sensory innervation to the diaphragm. It descends over the anterior scaling enters the thoracic islet between the subclavian artery and the brachiocephalic vein passes anterior to the hilum to run on the surface of the pericardium vagus nerve. On the other hand, so that we mentioned, it runs posterior to the hilum. Again, it enters the thoracic inlet in the same plane between the subclavian vein and the artery. There is the recurrent laryngeal nerves. On the left hand side, it runs around the ligamentum arteriosum. And then on the right hand side, it runs around the subclavian artery and they both ascend along the tracheoesophageal groove. The vagus nerve also then becomes the anterior and posterior trunk at the diaphragm along with your esophagus coming back to the lungs. So the right main bronchus, we have reiterated, this is wider, shorter and more vertical. And you can see in the image here before it joins the lung fully, it gives up your right upper lobe branch, which will happen within 2.5 centimeter of the cara which is the bifurcation of your trachea. The then it on the right hand side, it becomes bronchus, medi intermedius that gives off your right middle lobe and the right lower lobe, bronchi, I wouldn't worry about the third point because I don't think Mr CF is going to ask you about this. So sort of how the bronchus are arranged, but just know that right upper lobe, first branch gives off really quickly, doesn't, doesn't quite reach the lung yet. Whereas the left main bronchus, it doesn't give off any bra branches until it enters the hi limb of the lung. And it gives off the left, upper lobe anteriorly and left lower lobe posteriorly. Now, the important concept to understand is that there are bronchopulmonary segments within the lung and these are self-contained sections of lung that have their own dedicated bronchial and vascular supply. So they are functionally and anatomically distinct. And you'll find 10 on the right. And depending on the book you read, sometimes you see either 89 or 10 on the left. So just know that if you see numbers 10 is always on the right left hand is a bit more variable, it can be anywhere 8 to 10. And this is just an image of what bronchopulmonary segments look like. You don't need to know the specific, you know, segments within each lobe. Um unless you want to become a thoracic surgeon. But for exams, just know that these exist, they are functionally anatomically distinct and they have their own bronchial and vascular supply. OK. So we're going to now shift gears and look into the heart now. So the first thing that we're gonna look at is the aortic sinus. So this is, and so this is actually an image of the fibrous and skeleton of the heart. But you can see that this is where the aor ascending aorta starts. And, and this is at the root of the aorta, you have the aortic sinus of vala and you can see the aortic valve here. Now, there are two sinuses. So you have the right coronary sinus and the left coronary sinus. And those are the ones that give you your coronary arteries. And then there is a posterior sinus here, which is noncoronary because it doesn't give off any arterial supply, coronary artery supply, um sorry, the s the circulatory system. So you have to know that at the sinus, you get your left coronary and the right coronary, the left coronary here, I know they say left coronary. But in um cardiac surgery, we also sometimes refer to that as left main stem, it then gives off two main branches that is your L ad. So left anterior descending artery here and your circumflex artery there that kind of wraps around your AV groove kind of towards the back of the heart. Now, you also need to know there are branches off of these. Um So off your L ad, the first branch that is coming off is going to be your diagonal branch and off your circumflex. So there's a branch there that you can see that is going to be your left marginal artery. On the right hand side, you have your right coronary artery. And again, there is a right marginal branch there as well. And you need to know that the right coronary ulcers supply your nodal branches and towards the back, you can see there is a posterior interventricular branch, the posterior interventricular branch or sometimes we call it the PDA, posterior descending artery is what determines whether somebody is left or right dominant when it comes to their circulation in the heart. So if it arises from your right coronary artery, that is known as right dominance if for some reason. So that occurs in about 90% of the population. If your PDA is supplied by the left, then you would say that that is left dominant and in a very, very small proportion of the population around 3% you have mixed. So codominance in that instance. But yeah, just know that these are the branches of the left and right coronaries. And these would be the key ones that you need to know for exams, coronary veins. So they pretty much correspond in a way to the coronary arteries. So you have the small cardiac vein, which is over here and that corresponds to the right marginal artery. You have the middle cardiac vein that corresponds to the posterior interventricular artery or the PDA. You have the great cardiac vein here, which sort of corresponds to the left anterior descending. So your L ad and all of these drain in all of these drain into the coronary sinus, which then drains into the right atrium. There are some other minor cardiac veins. So you can also have the cardiac anterior cardiac veins that drain directly the anterior right ventricle directly into the right atrium. And then you have the thian veins which drain the myocardium and directly into the cardiac chambers itself. And these are very, very small vein. Sos very unlikely that you get asked about them, but then they are there and this is just an image of the coronary sinus. And you can best visualize it sort of from the posterior aspect. Um and coronary sinus drains into the right atrium in between the tricuspid valve and the inferior vena cava. Ok. So we're gonna move a little bit onto sort of the embryology side of things. And these are sort of the embryological remnants that you will kind of see and so sorry, from the internal surface um of the, of the heart. So you have the first of all the pectinate muscles which are both present in the atria. However, you get more of it on the right atria than the left atria. And these arise from a structure called Crista terminalis. And you can see the pectinate muscles are these sort of stringy bits. Um I guess they're not stringy, but they're kind of parallel muscles that are within the wall of the right atrium here. And they arise from the Crista terminalis which is a lateral ridge of the sinus miosis in the embryonic heart. So you can see again in this picture, the your pectina muscles, but this is sort of the ridge that the pectina muscles arise from. And these are derived from the sinus spinosus. And you also sometimes hear the term sulcus terminalis and really what that is is just the external part of your crystal terminalis. So you you're looking at the crystal terminalis from the internal aspect of the heart. The sulcus terminalis is from the external aspect and it runs sort of in this area between. So this picture is also grossly mislabeled. I lifted it from Google images because I thought it's a good image to show you the sulcus terminalis. But the, the labels don't make any sense, but this is your S VC and this is your IVC and the sulcus terminalis sort of runs in between the two and you will. This is important because you'll find your essay note at the s the plane for the essay note at the superior border of the sulcus terminalis. Whereas the A V note is at the inferior border. Now, looking at the internal structures within the ventricles, you have the cordite tendinea. So these are the little fibrous structures. You can see that these little cords that hold the papillary muscles to your atrioventricular valve cusps. And that could either be your tricuspid or your mitral valves. And the function of the Coria tendinea is to prevent valvular regurgitation. So sometimes you can have um these can rupture and you can end up with valvular dysfunction as a result. Then you also have the trabecula carnine, which are these irregular muscular ridges that are within the ventricles and they work to increase the contractility of the heart. And they also give rise to the papillary muscles on which the um corda tendinea are attached to as well. Now, this is somewhat physiology, somewhat anatomy, but you do need to know sort of the location of the cardiac conduction system. So we start off with the essay note, which sometimes people say is at the junction of um S VC and the right atrium. And you have these in internodal tracts that lead you to the A V node. Um and the Aveno becomes the bundle of his dividing into left and right bundle branch and then branching out at the apex into the purkinje fibers. There is also this um branch that goes from the right atrium to the left atrium, which is called Bachmann's bundle, which sometimes people we get asked about in cardiac surgery, but I've not seen that in um MRC S exams personally. So, conduction system is important to remember. But chances are you're going to get asked a lot more about the physiology of it, to be honest, cardiac embryology. So there are some pathology that are associated with cardiac embryology. I wouldn't go into the, you know, nitty gritty detail of knowing every single thing uh about it, but I'll give you a couple of examples. So the first one which is quite common is your talking about your um patent Foramen ovale. So what happen in the sort of the division between the atria of the right and the left is that first you get the septum premium that forms and there's a gap in embryology, the blood flows, you know, sort of the right to the left direction, there's a gap that's known as ostium premium and then you have septum secundum, a second septum that starts forming. Um And as such, you get a second ostium as well. And at birth, you know, with your first breath, the reversal, the reversal of blood flow forces the septum primum to close on septum secundum. OK. And that is how you end up with where initially is the foramen ovale. But because if it's closed, then it becomes a fossa ovalis. But if it doesn't close, which is what happens in this picture, blood can then still go from the right to the left. And that is the what happens when you have a patent for Foramen ovale? Then the other big um I guess pathology from embryology is tautology of and these are the four, you just need to remember these four or I always find it a bit easier to remember from the anatomical side of things. So you get, first of all, you have because there's a VSD like things just don't fuse properly like they're supposed to. There is a big VSD here which means that you have an aorta that is overriding both ventricles. So it's getting blood supply from both the right and the left ventricles. You also have a pulmonary valve stenosis and just remember your right ventricle is usually, well, it's the ventricle that pumps blood into your pulmonary valve and the pulmonary trunk. But because of the stenosis is having to work a lot harder and you end up with a thickened right ventricle. So that's your right ventricular hypertrophy. So these are the four characteristics of a tetralogy of that you do need to remember. Now, the last slide I do have before we go on to some practice questions is the surface anatomy of um of the thorax and really the surface anatomy. So we've already discussed the angle of Louie. You need to know the structures. Um uh what happens to the structures at that angle. But the surface markings from the lung perspective, you need to know the markings for the pleura and the lung. So this is where you start sort of the above the medial third of the clavicle comes down to the midline. And then this is where your 2468, 1012 comes in. So eight at the mid um clavicular line 10 at the mid axillary line and 12 posteriorly. And the lung marking is just two below the pleura the heart marking. So the heart borders, you do need to know the surface marking as well. So you will commonly see the second intercostal space on the left third, intercostal space on the right sixth intercostal space on uh right as well. And then your apex which is the fifth um intercostal space. And these form the heart borders, which are also clinically important, especially for imaging because you know that the border that is formed between the second and the sorry, the third and the sixth costal cartilage is your right atrium. The base is going to be your right ventricle and the border that is sort of the apex to the second costal cartilage is going to be your left ventricle here as shown on the chest X ray. So we have a few minutes left. So I just thought I put together some N UQ questions just to see how much of that made sense or how much of that didn't make sense. So the first question, what muscle attaches at the red and blue lines and red is the origin and blue is the attachment? OK. And the answer to this question is going to be external. So a external intercostal muscle. Next question, a 35 year old man is brought to the emergency department following a road traffic accident. He demonstrates signs and symptoms of a simple pneumothorax which is confirmed on chest radiography, which of the following anatomical landmarks is not useful for delineating the safe triangle for chest drain insertion in this patient. So you have a apex of the axilla b inferolateral border of pectoralis, major anterior border of the latissimus dorsi nipple or the midclavicular lines. The answer to this question is e midclavicular line because it's the mid axillary line. That's important. Midclavicular line is sort of your anterior chest and you really shouldn't be going anywhere near that for a chest drain insertion. Um And I don't know if you guys have had a chance to take ATL S as a course yet, but it used to be that when I was in medical school, they said for tension pneumothorax and a needle decompression, you should be going for the second intercostal space in the midclavicular line, but that has changed on the recent additions of ATL S. So really the for attention pneumothorax, you should be doing needle decompression in the safety triangle as well. OK. And I think the reason for that is that the population is becoming more and more obese. So actually the needles are not going all the way into the correct space. But if you're doing it in the safety triangle, then the needle, the needle that you inserted can then be converted into a chest strain which a patient will eventually need as well. The next question, which of the following is not true about coronary blood supply. So a this essay node is usually supplied by the right coronary artery. 90% of the human hearts are right dominant. The left coronary artery is usually smaller than the right coronary artery. Coronary arteries arise from the sinus of valsalva and that 3% of the heart are codominant. Ok. And the answer to this question is c so the left coronary artery is actually much bigger than the right coronary just because of the greater territory that is supplied. Just think about it, supplying your left ventricle, which if you remember, cross sections of the heart in sort of categoric heart, you can see that there is a lot more muscle mass to the left. So the left coronary artery is going to be bigger as well. A 17 year old male is brought to A&E after having sustained blunt trauma to his chest. The registrar diagnoses a tension pneumothorax and prepares to perform needle decompression. He palpates for the manubrial sternal joint, which of the following anatomical structures does not lie at this level. So the hemiaulus vein passing from the left to the right to join the AUS vein between the T four and T five vertebral bodies. Bifurcation of the trachea, entry of the AZ vein into the superior vena cava, beginning and end of the aortic arch. The answer to this one is C oh sorry, this is not c it's a, it's um hem azs vein passing from left to right. That doesn't happen at that um T 45 level. And it would be the AZ vein drains into S VC at that level though. And then the last question, 5558 year old man on chemotherapy for metastatic cancer is brought into A&E with acute general deterioration. He is found to be confused with a BP of 80/45 and pulse rate of 110. Examination reviews elevated jugular venous pressure, normal breath sounds and muscle heart sounds with no cardiac murmurs. So they've also uh in that question, I'm just given you the signs for beck triad, which suggests that there is a cardiac tampon, not in this patient, which is secondary to this chemotherapy for metastatic cancer, which of the following procedures is likely to be most beneficial to the patient. So we've not discussed this, but I hope you guys can work out the answers because we've worked out that this patient has cardiac tamponade a insertion of a large bore needle in the second intercostal space along the midclavicular line, large bore needle between the zoid process and the left seventh costal cartilage, aiming towards the left shoulder tip, inserting a needle in the cricothyroid membrane attached to a back valve device, inserting a chest strain in the left fifth intercostal space or a large bore needle in the fourth intercostal space aiming towards right shoulder tip. So the answer to this question should be be the. Um so that is how you would do a pericardiocentesis. However, nobody does it these days without ultrasound guidance. OK. Um A here is telling is suggesting the old way of needle decompression in a tension pneumothorax. Uh C is just how you get emergency access. So a needle through the cricothyroid membrane if, if you have airway obstruction, D is describing your standard chest pain. And I wasn't sure what E was describing actually. So that is the end of everything I wanted to go through. Um just some practical exam tips or advice. Really, I feel like everybody has done enough exams to know everything but have to reiterate. There is no negative marking. So you will have at least 20 20% chance of getting it right. If you're real, if you're sitting this exam in may then have a good look at the MRC S syllabus and sort of identify where you need to focus your revision on. But if you're sat sitting in September still look at the syllabus because that'll help you plan out how you're going to tackle the revision and don't forget that, you know, this is just anatomy, but you're going to have all these other aspects and there will always be some what the f questions on your exams. I remember I got a few of those and I'm just going, I have no idea, but I have 20% chance of guessing. Um, And do for part A, my personal opinion is to do as many practice questions as you can because it's about the breath of knowledge. Part B is about the depth of knowledge, but part A is about breath. So you're gonna need to know a lot more. And I would suggest actually sitting part B not too long after you pass part A because I had an almost two year gap myself. So when I came to start part bi felt like I had to relearn a lot of what was on part A. So hopefully that is helpful things to know about and the very best of luck to you all visiting the exam. Thank you very much, Miss Chang for a great lecture today. Um If there's any questions, uh feel free to ask guys. Um I had a question myself, Miss Cheng, what's the clinical significance of when you say, oh, patients right, dominant or left dominant? Or was that just a, so it's more significant in surgery? Because when we do heart surgery, we stop the heart by giving um cardioplegia. So it's just a very high potassium containing solution that arrests the heart completely. And you just, we need it for surgeons. We need to know the left or right dominance to know how much to give down the left and right coronary sinus. Ok. So if you're right dominant, you want to give more on the right and if you're left dominant, for some reason, you need to give more on the right. So that's the only clinical significance really. But for some reason, this dominance question still comes up from time to time. OK. Um So I'll put the feedback link in the chat guys. Um Please provide your feedback. Um Lets us know how we can improve. Um And what we can do better for you. I hope you've enjoyed this session. Um Once you've got your feedback form, you should get a certificate as well. Um Are there any other questions for Miss Chang? OK. Well, if that's the case, then um once again, thank you for coming guys. Thank you very much, Miss Cheng for giving up her time and expertise. Um And we wish you the best of in your exams, whether it's May or September. Good luck, everyone. Enjoy your weekend, enjoy your weekend guys. Thank you. Thank you, Mister bye.