104 Anatomy Quick Revision Part 2 (MOST IMPORTANT TOPICS)

追加: 2026-05-11

[00:00:07]So today we'll continue the topics that we left yesterday.

[00:00:13]The first for today's coronary arteries.

[00:00:20]First we'll do right coronary artery and then left coronary artery.

[00:00:26]Okay.

[00:00:28]The story starts from the coronary sinus. What's coronary sinus?

[00:00:33]Aortic coronary sinus.

[00:00:38]Here this is the aortic coronary sinus.

[00:00:40]It's actually situated here at the wall of of the aortic wall. It's right here like these are the cusps of the wall.

[00:00:50]Wall.

[00:00:52]There are three types of sinuses.

[00:00:58]The right posterior, left posterior, and anterior. The right coronary artery starts from anterior coronary sinus uh sinus. Anterior aortic sinus.

[00:01:14]Anterior aortic sinus.

[00:01:19]This is the wall of the aorta.

[00:01:23]Okay, these are the cusps. Just behind the cusps there are posterior bulges called aortic sinuses. These are called aortic sinuses, these bulges.

[00:01:35]This one is called uh right posterior, left posterior, and anterior.

[00:01:43]The anterior one is the one starts right coronary artery, and the left posterior one is the right left coronary artery. Okay?

[00:01:54]Let's start.

[00:01:56]So we'll understand its course, its branches, and its distribution.

[00:02:02]Okay?

[00:02:04]First, it's course.

[00:02:07]So, it starts at your anterior aortic sinus.

[00:02:14]Anterior aortic sinus goes like this.

[00:02:17]Above, between between right auricle.

[00:02:22]I've made a small A so that you don't get confused between right atrium. It's right auricle.

[00:02:28]Right auricle and pulmonary trunk.

[00:02:32]It's between pulmonary trunk and right auricle of the right atrium.

[00:02:38]Goes between that, squeezes itself between them, and it comes out from the coronary sulcus. We did this in the last video, coronary sulcus from left third intercostal to right sixth intercostal cartilage.

[00:02:54]So, it runs along this way.

[00:02:57]It runs along this way, and while it's towards the coronary sinus, and it's passing right atrium and right right ventricle, it gives out its branches. What are its branches?

[00:03:18]We'll see here.

[00:03:20]The first branch is right.

[00:03:22]If you notice so that it gets the diagram gets engraved in your brain as exactly as I've made it, the right ones are here, just in case.

[00:03:31]So, right conus artery. One artery goes out from the um right coronary artery.

[00:03:42]It's called right conus artery.

[00:03:46]It provides to conus arteriosus.

[00:03:49]Let's actively call what's um conus arteriosus.

[00:03:54]It's the smooth area that provides the easy blood flow, smooth blood flow from right ventricle to the aorta.

[00:04:03]So, this is the artery, this right conus artery that offshoots itself from the right coronary artery provides the conus arteriosus and pulmonary trunk. The second one is to SA node. We all know SA node, the pacemaker of the heart, that part of pacemaker. Here, SA node.

[00:04:29]60% of the people in 60% of the people, that's what 60% actually means, that in 60% of people SA node is provided by the right coronary artery, an offshoot, a small branch from the coronary artery, right coronary artery.

[00:04:49]Then, there is right marginal artery that provides to right ventricle, margins of the heart, the edge of the heart.

[00:04:59]We've seen the um right border of the heart is covered by right ventricle. That's why right ventricle margin provided by the right marginal artery. Margin, margin.

[00:05:13]So, edge of heart, marginal artery. And then, we have very very most asked uh artery, very clinically significant, as well as such an anatomically important landmark.

[00:05:29]Posterior interventricular artery, aka PDA.

[00:05:35]This is the one also that provides to AV node in 80% of the people.

[00:05:39]How will you remember that this is 60% and this is 80%? Simply by S 60, A 80 That's it.

[00:05:50]That's how you remember. So, 60% SA node to 60% and AV node 80%.

[00:05:58]Now, this grow this goes posteriorly within the groove posterior interventricular groove. Very easy to identify posterior side. This is the left atrium. This is the left ventricle. And here, this is the green marked artery is inside the postinterventricular groove. This artery, PD artery, okay?

[00:06:27]Now, then it anastomoses. This symbol, when I say it means anastomosis. Anastomosis means uh connection between two arteries. When two arteries connect to each other, it's anastomosis.

[00:06:39]Okay? So, what two arteries are getting connected here?

[00:06:43]This coming from the coronary sinus, it goes posteriorly goes posteriorly at the back of the heart and joins to the circumflex artery. What is circumflex artery? This is a branch of the left coronary artery.

[00:06:59]We'll see here in the left coronary artery. Look.

[00:07:04]Circumflex artery.

[00:07:06]Okay? So, right coronary artery one of the branch terminates into anastomoses with circumflex artery. Very important.

[00:07:20]Extremely important. I hope you can visualize this. So, how does it start?

[00:07:26]It starts from the aortic arch walls anterior aortic sinus then right atrium, right auricle, not atrium.

[00:07:40]Then runs through the coronary sulcus and terminates itself with anastomosis with circumflex artery. While its journey, it divides into branches providing blood to this part of the heart.

[00:07:55]This part.

[00:07:57]What part? We have right atrium, we have right ventricle, we have AV node, we have SA node.

[00:08:03]Okay?

[00:08:04]Now, there's another concept that we've always learned about but we usually forget is inter vertic- inter- ventricular septum and interatrial septum.

[00:08:18]Now, this this part. This is interatrial between atrium. And this part is interventricular septum between ventricles.

[00:08:29]Okay? So, this interatrial is a thin as as compared you can see here. It's thinner than the interventricular septum.

[00:08:37]So, between this this this is between its right atrium, right ventricle, left atrium, left ventricle. This part of the heart is called the crux of the heart.

[00:08:48]Okay? Now, we'll talk about interventricular septum. If we divide this into three parts, okay? 1 2 3.

[00:08:57]The 1/3 part 1/3 part of interventricular septum is supplied by PDA.

[00:09:08]Posteriorly, this 1/3 part of the interventricular septum is provided by PDA. So, now you can imagine that when this goes posteriorly, when RC goes posteriorly and becomes posterior interventricular sep- interventricular artery within going to inside the posterior interventricular groove towards the apex of the heart. This is apex of the heart, right?

[00:09:38]During this journey, it provides 1/3 posterior part to PD. That's what's written here. Let's read.

[00:09:46]Arise from anterior aortic sinus.

[00:09:50]Between pulmonary trunk and right oracle. Goes through coronary sulcus, descends.

[00:09:57]Turns posteriorly. Turns posteriorly.

[00:10:01]Coronary sulcus posterior.

[00:10:04]Ends anastomosing with circumflex artery.

[00:10:07]Now, if you don't remember any of this, if you don't remember the course of right coronary artery, just remember that it covers right and posterior.

[00:10:18]Okay? If you don't remember anything.

[00:10:21]And then logically realize or come to this realization that wherever its course is, it's going to provide supply to that area.

[00:10:31]Let's read the branches.

[00:10:34]Right conus artery.

[00:10:36]Marginal artery. The margins the right ventricle. What is the margin of the heart? Right ventricle.

[00:10:43]Posterior interventricular artery, very important. Now, look here, it's written.

[00:10:48]Now, in our notes, in examiner's it's written in one line. So, I've explained to you what it really means. Septum. And AV node to 80% of the people.

[00:10:58]Then small branches to right atrium.

[00:11:02]Okay, this one. The small branches, as I told you.

[00:11:05]Exactly what I told you, it's written in words.

[00:11:10]Then we talk about its distribution.

[00:11:12]Whole right atrium. Whole right ventricle.

[00:11:17]Band.

[00:11:19]Left ventricle.

[00:11:21]Diaphragmatic surface.

[00:11:23]We'll do this.

[00:11:25]Posterior, we know this and we know this. So, if you don't remember any of this, just remember that RCA provides wraps the right part and goes posteriorly. What are the things that includes that RA, RV, SA node?

[00:11:39]60% SS 60 60 SA node 60% AV node 80% 1/3 of the interventricular septum Are we done with right coronary artery? This is actually a major PYQ.

[00:11:59]Major PYQ.

[00:12:01]Can be asked.

[00:12:03]The examiner loves this artery. Always usually asks this usually ask about this.

[00:12:11]But it either till now they have not asked about left coronary artery. So there is a chance they'll ask left coronary artery tomorrow. But if they don't they probably ask right coronary. They always do. They love this artery so much. Examiner's favorite topic.

[00:12:28]Let's do left coronary artery.

[00:12:31]Again, we've done this.

[00:12:33]I've said coronary sinus that's different. This is not coronary sinus.

[00:12:36]This is aortic sinus.

[00:12:38]In the start of the video.

[00:12:39]So this bulgy part posteriorly bulgy part This is called aortic sinus and one of them the left posterior one offshoots into left coronary artery.

[00:12:54]Okay? Left posterior aortic sinus.

[00:12:58]Okay, now let's read about this.

[00:13:00]What it does again, how the right coronary coronary artery begins or forms begins from between the pulmonary pulmonary trunk and right oracle this also does the same thing.

[00:13:15]Between pulmonary trunk and left oracle.

[00:13:21]Starts from the posterior left posterior aortic sinus.

[00:13:27]It goes like this.

[00:13:29]Now, what it does, it goes posteriorly.

[00:13:32]This is in a in such a hurry that it offshoots really quickly. It's too short.

[00:13:39]It's very short, so it divides really quickly. For example, the right takes its time. Along the course, it divides and as I told you before. But, this one divides quickly.

[00:13:50]So, it's short.

[00:13:52]It divides into two main branches.

[00:13:55]This is also a very important. You already know circumflex artery. We'll get to that. First, we'll understand LAD.

[00:14:06]Okay? Anterior interventricular artery.

[00:14:09]It's called LAD.

[00:14:13]Okay?

[00:14:16]In short, it's called LAD. Now, it has its own branches. LAD has its own branches. Look, this is LAD. It goes unlike posterior interventricular artery, goes inside the groove, goes not inside, along the side of the groove called posterior interventricular groove. This also does the same thing. Goes through anterior interventricular groove. If you ever see a diagram of heart anatomical diagram of heart, you will be very easily be able to recognize this groove. This is the first thing you'll notice.

[00:14:56]Okay? This groove is called anterior ventricular groove. Why is this so noticeable? Because it divides right ventricle to left ventricle. It divides exterior exteriorly if we appeared from outside.

[00:15:16]Then, what are the branches?

[00:15:20]Left conus artery, exactly like right right conus artery.

[00:15:25]Okay, left conus artery, then some septal branches and diagonal branches.

[00:15:33]Okay.

[00:15:36]Anterior groove, inferior border. Left ventricle, sternocostal plus anterior septum. What does this mean?

[00:15:47]Usually now it goes here. Now if it's going like this and this, it usually mainly provides blood supply to the left ventricle.

[00:15:59]Okay, mainly divides to provide supply blood supply to the left to the left ventricle.

[00:16:11]Okay.

[00:16:12]Left ventricle is the main part. Now what does this mean?

[00:16:16]Let's go here again.

[00:16:18]The other two third anterior part of the interventricular septum is provided by LAD.

[00:16:28]Okay.

[00:16:35]It's provided by anterior interventricular artery.

[00:16:39]Now we know the branches of LAD.

[00:16:44]We know branches of left We know we know branches of posterior interventricular uh and all the RCA and now we're done with this. So what's left? Circumflex so circumflex artery.

[00:17:02]Okay.

[00:17:09]LAD LAD The meaning of LAD is lateral anterior descending.

[00:17:18]I think so, as far as I remember. It's short form is LAD. The same thing. If you Usually it's so a little confusing because in books it's written anterior interventricular artery and just randomly they write LAD. It's both are the same things. Okay?

[00:17:34]Circumflex artery. Now, circumflex artery is quite different. Why? Because as soon as it gets as soon as it divides, it sees its brother uh the anterior interventricular artery going towards the apex of the heart. It says, "Who's going to provide blood to the posterior part of the heart? To the left posterior part of the heart." So, it goes back.

[00:17:56]Okay? It goes it curves and left it curves towards the left part of the heart. Okay?

[00:18:03]Look.

[00:18:04]Curves towards the left part of the heart. One of the small branches of the circumflex artery goes towards the apex.

[00:18:11]Okay? Some of them is the this one.

[00:18:15]The small branches that go towards the apex is called left marginal artery, exactly like RCA.

[00:18:21]Okay?

[00:18:23]Goes towards here.

[00:18:26]Then, another SA node and AV node. Okay?

[00:18:30]SA node. Now, you'll realize that SA node are not two things, no? So, in 40% of people, there's only one SA node. So, there has to be some connection between circumflex artery and RCA. That's the connection. This is the anastomosis that I talked about. So, two SA node in 40%.

[00:18:49]It's easy to understand. Make a table the corner of your answer paper, make a table.

[00:18:55]SA node SA node, AV node, AV node. Okay?

[00:19:00]RCA, LCA.

[00:19:03]So, just remember one part, which is your 60. Okay? SA node 60%. So, now you'll know 40% 80% here.

[00:19:12]So, the remaining will be your 20% and 40%.

[00:19:17]Simple.

[00:19:18]Okay? So, if if anybody asks about SA node, AV node, make this table.

[00:19:24]If this is 60%, this is 80%, and this has to be an LCA, or if you be precise, circumflex artery has to be 20 40% and 20%.

[00:19:38]That's how it is. Okay? So, we are done with circumflex artery, also. Let's read what's written, so that we don't miss any point.

[00:19:45]Between pulmonary trunk and left oracle, anterior interventricular groove divides into anterior interventricular artery and circumflex artery.

[00:19:55]Descends in anterior groove and inferior border.

[00:20:01]Left ventricle.

[00:20:04]Sternal costal anterior 2/3 septum and gives left conus artery. Circumflex artery turns left.

[00:20:11]Coronary sulcus posteriorly.

[00:20:13]It goes within the coronary sulcus, by the way. What How look.

[00:20:17]I've made here. Goes towards this coronary sulcus. So, now you can imagine it covers left part and posterior part.

[00:20:25]Right?

[00:20:28]No, it it provides anterior part and left part, not posterior.

[00:20:34]Posterior just this, in which it's already anastomosing with the RCA. So, posteriorly is more dominated by the RCA, not the LCA. Okay?

[00:20:44]Yes. So, SA node, this is very important topic, that's why I'm taking so long to make you understand. SA node, 40%, 20%, and these these are the distribution of the LCA. Let's read this.

[00:20:58]Circumflex artery, left marginal artery, we've done SA node and AV node.

[00:21:03]Distribution.

[00:21:06]Whole left atrium. Look.

[00:21:10]because left oracle is a whole left atrium whole left atrium, left ventricle, SA node, AV node, and 2/3 part of the anterior interventricular septum.

[00:21:22]SA node, AV node and 2/3 part of the interventricular septum.

[00:21:28]Okay?

[00:21:29]Now, distribution.

[00:21:33]whole left atrium and left ventricle Now, band right ventricle sternocostal surface right ventricle sternocostal surface.

[00:21:43]We've done this in the surfaces when we talked about heart surfaces.

[00:21:50]I've made this with the use of AI, I've made a small mnemonic, vampire mnemonic to make you understand the coronary arteries. For example, this vampire guy is the heart.

[00:22:01]Okay, this part is open.

[00:22:04]So, the cape Just focus on the cape. The cape of this vampire is the coronary arteries, okay?

[00:22:13]This part is at the back, posterior, not anterior, right? His hand is showing, so it's not present there.

[00:22:21]Hides behind right posterior side, right? posterior side. But here, he's covering.

[00:22:28]He's covering it, so left and anterior side. So, these coronary arteries are If you want to take a screenshot, or it's like a revision of the previous slide.

[00:22:42]So, LAD like front, circumflex in the left side marginal and RCA, it's not covering the in front part of that and the front part of the heart, usually the back.

[00:22:56]If you don't remember anything LA, LV. Now, I've written widow maker.

[00:23:01]Why widow maker?

[00:23:02]It's actually a very very important clinically important fact.

[00:23:10]That the blockage of left coronary artery can cause major major paralysis.

[00:23:23]Can cause major diseases or fatal consequences.

[00:23:30]Why? Because if it if LV the supply to LV gets blocked it's called a widowmaker. It's the it's fatal.

[00:23:37]So this is important.

[00:23:39]LCA is important because it provides blood to LV that the the ventricle that provides blood that pumps blood to whole system all the systems of the body, right? Systemic circulation.

[00:23:53]So this feed left and the anterior side.

[00:23:57]While here if RCA gets blocked or anything happens to RCA because it's providing 60% and 60% of the people it's providing supply to SA node it causes arrhythmia.

[00:24:10]Okay?

[00:24:13]That's the clinical importance.

[00:24:16]So I think we are completely done with coronary arteries. If anybody asks you they probably don't ask like this.

[00:24:24]They're going to ask you in specific things. Like just tell me the branches or tell me the distribution of coronary arteries.

[00:24:36]Let's come to coronary sinus.

[00:24:41]Okay?

[00:24:43]This is what I talked about.

[00:24:46]Coronary sinus have been asked so many times. It's a very important question.

[00:24:50]Because it sounds so tough but it's not.

[00:24:52]It's not so tough.

[00:24:53]Okay?

[00:24:54]So we'll read about it.

[00:24:57]How is it formed?

[00:24:58]It's formed from the great cardiac vein.

[00:25:02]It also bulges posterior and gives rise to coronary sinus.

[00:25:09]Coronary Coronary sinus is like um the after coronary arteries provide blood to the heart, the heart leaves or drains the deoxygenated blood into a different small small channels, okay?

[00:25:30]And they all channel the all these channels, these wide short channels, which are few small branches, they all drain in one channel system called coronary sinus.

[00:25:41]Okay?

[00:25:43]This way. So, it usually comes from the apex.

[00:25:49]Comes from the apex.

[00:25:52]The great cardiac vein just beside what? Anterior ventricular coronary artery. The offshoot of the LCA. In the same groove, we have cardiac vein.

[00:26:07]That bulges and causes um forms coronary sinus. It's a very short coronary It's a very short vein.

[00:26:16]Very short drainage system, you can say.

[00:26:18]It's 3 to 4 cm long.

[00:26:21]And it opens, if you remember, it opens in the right atrium. If you don't remember, I'll tell you it. Look.

[00:26:30]Opening of the coronary sinus.

[00:26:32]Right?

[00:26:34]We studied this yesterday.

[00:26:36]So, this is how it's formed.

[00:26:43]It opens here between IVC and tricuspid over here. It opens somewhere here.

[00:26:48]Okay? In the right atrium.

[00:26:55]It also follows coronary sulcus. The left posterior part of the coronary sulcus, not the anterior part. Okay?

[00:27:03]That's how it's situated. This is where it's situated. Look, I've made this. This is LAD anterior interventricular artery. This is the groove in which this also rests and just with that, we have cardiac vein. That's what's written here. Let's read. Right short, 3 to 4 coronary sulcus posterior part.

[00:27:25]Begins as great cardiac vein continuation.

[00:27:29]Ends in right atrium between IVC and tricuspid orifices.

[00:27:34]Guarded by semilunar valves.

[00:27:38]Now, this is important.

[00:27:40]Tributary of coronary sinus. I think this might come tomorrow. Honestly, not going to lie.

[00:27:45]Tributaries of coronary sinus. We have great cardiac, small cardiac, middle cardiac, oblique vein. It's very difficult to learn or memorize because we already have so much to memorize. So, we'll make a diagram.

[00:28:00]This is the great cardiac vein. We've already done one. For sure.

[00:28:05]Another one is the middle cardiac vein.

[00:28:08]That rests in the posterior interventricular groove.

[00:28:13]Then we have a small cardiac vein and then oblique vein comes from the left atrium. That's all you need to remember.

[00:28:20]If you write just word this diagram out in the exam paper. Don't make the diagram. Word this out. That okay, from the apex of the heart, the great cardiac vein that rests or that goes just beside the anterior interventricular artery in the groove in the anterior interventricular groove and then our 3 to 4 cm or as well as coronary sinus starts from this and it it drains to what? Right atrium. All these things.

[00:28:49]Okay?

[00:28:51]Just word the diagram out.

[00:28:55]Near apex, also near apex.

[00:28:58]Okay?

[00:28:59]You can write here near near apex just in case if you do engrave it in your head.

[00:29:05]Then runs along the inferior border.

[00:29:07]Middle diaphragmatic near posterior interventricular groove.

[00:29:11]Oblique vein of left atrium.

[00:29:16]Then other cardiac veins.

[00:29:18]Simple, you just need to remember this that anterior cardiac vein comes from the right atrium and venae cordis minimae also right atrium.

[00:29:27]Now, this is a glitch in our notes in the curriculum notes that venae cordis minimae was given in the left atrium before. Look here.

[00:29:49]Look.

[00:29:51]Venae cordis minimae.

[00:29:55]But it's actually in the right atrium, mainly. Not 100% one tube going towards right, no.

[00:30:03]Mainly, most of it. Okay?

[00:30:05]Venae cordis minimae.

[00:30:08]Mainly right atrium.

[00:30:10]Into heart chambers, mainly right atrium. It's written left atrium in the notes, so we'll go according to the notes, the main notes. But originally, it's in mainly right atrium. This is the right part. But if it comes then if they talk about coronary sinus, right right atrium.

[00:30:29]But if it comes in left atrium, then right and left atrium also. Okay?

[00:30:34]Minute veins in myocardium.

[00:30:37]Cardiac plexus, so many times, very important.

[00:30:41]Very important.

[00:30:43]Superficial cardiac. Two types of cardiac plexus. I'll tell you it's a very long topic.

[00:30:50]Has very variations and many small details.

[00:30:53]But I'll just do it in short as much as possible for first year students.

[00:30:59]So autonomic nervous system it's a part of autonomic nervous system, okay?

[00:31:03]Starts from medulla.

[00:31:05]Left part of medulla.

[00:31:07]Okay? To superior cervical ganglion of the sympathetic trunk.

[00:31:12]Just think this is a sympathetic trunk.

[00:31:15]The superior cervical ganglion of this brings what fibers? Sympathetic fibers.

[00:31:21]We know what is If you ever hear sympathetic, the first thing that comes is fight and flight, right?

[00:31:28]Since pre-med we know this.

[00:31:31]So therefore it increases HR, adrenaline, epinephrine, so many things.

[00:31:37]So sympathetic fibers to arch, this part. Above the right pulmonary artery and below the arch of aorta, we have this.

[00:31:48]Superficial cardiac plexus.

[00:31:51]Okay?

[00:31:57]We'll read this. In aortic arch concavity left superior cervical, very important.

[00:32:03]If they usually ask formation of superficial cardiac plexus. So learn this, memorize this if you can't remember from the diagram. The other part is this. From the vagus nerve.

[00:32:13]Again, left. Okay? Left cardiac branch of vagus nerve decreases. This brings parasympathetic fibers.

[00:32:23]That decreases heart rate. Okay?

[00:32:27]The both of them makes or forms superficial cardiac plexus.

[00:32:32]So we have written exactly what's written in the diagram. Left superior cervical cardiac plexus.

[00:32:38]A cardiac ganglion.

[00:32:40]And left inferior cardiac branch of the vagus nerve.

[00:32:46]This provides to what? Coronary arteries, atrium and ventricle. It provides to SA node and AV node, as well as deep cardiac actually goes and meet deep cardiac plexus.

[00:33:06]Deep to Now we will understand deep cardiac plexus. Probably won't ask. But let's read it. It's situated where it's site is. Usually they'll ask site if they ask if they ask.

[00:33:18]Aortic arch deep, like behind aortic arch, but above the carina, the bifurcation, tracheal bifurcation. This is the cardiac plexus.

[00:33:27]Okay, this is the location.

[00:33:29]Behind deep to aortic arch, front of tracheal lecture, plexus tracheal bifurcation, and all other cardiac branches sympathetically. So, except these everything everything is actually superficial. You can say superficial cardiac plexus is like a part of the whole mechanism that's providing impulse to this. Okay?

[00:33:53]And deep cardiac plexus is actually the bigger spectrum of it. And superficial is the offshoot spectrum of it. Okay?

[00:34:02]This is simple clinical coronary artery disease, angina pectoris. I've told you there's a shoulder pain because of the phrenic nerve that also provides sensation to the shoulder skin. That's why there's some tingling when if you are have if you're experiencing acute chest pain in angina pectoris, you'll also realize you'll also go through a some kind of shoulder pain. Usually like this, right? Here. So, it's an agonizing pain. It's written front of chest, radiating to left shoulder and arm middle side.

[00:34:37]So, if there is less blood supply, it's called ischemia. That's angina pectoris. Myocardial infarction, there's a blockage of coronary artery by thrombosis, by deposition, or atherosclerosis, so many things.

[00:34:53]Myocardial heart death. Then poor anastomosis between right and left coronary arteries could also cause this.

[00:35:00]Arrhythmia, we've done this, the SA node thing.

[00:35:04]That if there's some differ uh obstruction and in the SA node supply of the RCA, it causes arrhythmias. So, right coronary artery supplies most part of the heart conducting system. Its blockage causes heartbeat irregularities.

[00:35:22]Done this.

[00:35:23]We've done this, too.

[00:35:25]So, conducting system can be hindered if you touch these one of these arteries that provides to SA node and AV node.

[00:35:31]The table. This is just the table that we understood.

[00:35:35]60%, 40%, 80%, 20%. Why 60? Because SA node of RCA.

[00:35:44]And why 80? Because AV node of RCA.

[00:35:49]So, if you know of RCA, then you know of LCA.

[00:35:56]LCA, or to be precise, circumflex artery.

[00:36:00]Patterns of posterior interventricular artery.

[00:36:05]We've already done this. How? When we were discussing posterior interventricular artery, the its dominance is towards the right in the It's an offshoot of the right coronary artery. So, it's usually present It's usually effect is on the right part of the heart.

[00:36:22]Left dominance has the left coronary artery. Okay? Balanced pattern, one branch from each coronary. We know this.

[00:36:30]Let's come to aorta, very important.

[00:36:32]Ascending aorta and aortic arch.

[00:36:35]So, before what's written, before reading what's written, let's first do a diagram, okay?

[00:36:44]The oxygenated blood from our LV, from left ventricle, goes from this is the must be coronary arteriosus, right? Smooth muscles and providing easy flow of the blood from LV to aorta.

[00:37:00]These are the cusps and the there is also what?

[00:37:03]If you remember, here is the aortic sinus and two carotid arteries comes out from here. I've written here, look, LCA, RCA RCA LCA, okay? Also comes from here.

[00:37:14]So, if you're visualizing this, visualize everything.

[00:37:19]Okay? Now, this part is ascending aorta.

[00:37:22]From what to what?

[00:37:23]From third intercostal space.

[00:37:27]Third intercostal space it starts.

[00:37:29]The ascending aorta starts to second intercostal junction.

[00:37:37]Second intercostal junction it ends. So, it starts from here, it ends here.

[00:37:41]The ascending aorta.

[00:37:43]Okay?

[00:37:44]What does it have? Just below it has pulmonary trunk crossing after bifurcation. Bifurcation happens here, but only one part of the pulmonary trunk, okay?

[00:37:54]This is ascending aorta.

[00:37:56]Let's read first ascending aorta, okay?

[00:37:59]Origin aortic orifice of left ventricle.

[00:38:03]Opposite to third intercostal behind the sternum.

[00:38:07]Ends behind the right second intercostal junction, becomes aortic arch.

[00:38:13]Relations, anterior ventricular in infundibulum, pulmonary trunk, right oracle, right lung. I think this is obvious. If you know two parts around your you'll be able to write. Then branches is right RCN LC.

[00:38:30]Anterior aortic sinus to posterior aortic sinus. We just did that.

[00:38:35]Okay?

[00:38:36]Let's come to arch.

[00:38:39]Okay, arch of aorta starts from second intercostal junction and ends at the T2 T5 vertebra.

[00:38:48]Okay? From here we then furthermore is descending aorta.

[00:38:54]That's what that is. Three branches BCS.

[00:38:57]Mnemonic is BCS. Very famous. Everybody knows this.

[00:39:01]Brachiocephalic carotid and subclavian. So BCS.

[00:39:08]What are the relations of arch of aorta? Left side. On its left side we have a we have phrenic nerve.

[00:39:16]We have vagus nerve.

[00:39:18]And cervical cardiac left nerve and intercostal.

[00:39:22]Intercostal nerve.

[00:39:24]This is what's present at the left. If you want to take a screenshot, take a screenshot. It's better.

[00:39:28]Right?

[00:39:32]Then below it is the bifurcation of the pulmonary trunk.

[00:39:41]Okay? Trachea comes from here and the left principal bronchus.

[00:39:46]Trachea is behind it. Okay? You can see it's going like this. So it's not below the arch of aorta. What is below the arch of aorta? Pulmonary trunk and left principal bronchus.

[00:39:57]There's an important fetal remnant called ligamentum arteriosum that connects from arch of aorta to pulmonary trunk.

[00:40:10]Okay?

[00:40:11]Now behind behind arch of aorta is trachea and esophagus. Okay?

[00:40:19]Just within just beside the ligamentum arteriosum the the left recurrent laryngeal nerve just loops.

[00:40:29]In case of aneurysm and all these things, it loops just beside it.

[00:40:34]This is very clinically important.

[00:40:37]Okay? Due to aneurysms.

[00:40:40]Left recurrent laryngeal nerve.

[00:40:43]RLN.

[00:40:45]Okay?

[00:40:47]Let's read this.

[00:40:48]Begins at and also also from T4 to T5 and descending aorta starts.

[00:40:58]So, arch of aorta starts from second intercostal to Remember this. This this can be asked.

[00:41:03]So, the examiner is going to give you mas- marks if he says this. T4 to T5, okay?

[00:41:10]Begins at second intercostal junction, passes upwards, backwards, and lateral.

[00:41:15]Yeah, so upwards, lateral, and left. Okay? Upward, laterally, and left.

[00:41:23]This is the direction of the arch of aorta.

[00:41:26]Ends at the T2 to T5 disc.

[00:41:30]Disc in between these. It ends here.

[00:41:32]The disc disc.

[00:41:34]Above Okay, structures crossing arch.

[00:41:37]Left phrenic nerve, vagus nerve, left superior cervical cardiac branch, and left superior intercostal nerve. So, this this thing.

[00:41:47]Left phrenic nerve, left vagus nerve, left cervical branch, cardiac branch, and left intercostal nerve.

[00:41:55]Above arch, we have three things.

[00:41:58]Brachiocephalic.

[00:42:00]Uh BCS.

[00:42:02]Brachiocephalic.

[00:42:04]Carotid and subclavian.

[00:42:07]Below arch is the pulmonary trunk bifurcation, left principal bronchus, and ligamentum arteriosum.

[00:42:15]Right posterior and behind is trachea, deep cardiac plexus also there, esophagus is there and R L N.

[00:42:24]Left anterior side left pleura and lung mediastinal surfaces.

[00:42:36]Branches from upper convex brachiocephalic artery, it becomes common carotid artery and left subclavian artery.

[00:42:45]Just that carotid subclavian.

[00:42:49]Clinical importance coarctation, any the arch of aorta.

[00:42:55]Narrowing proximal distal to ductus arteriosus, not so important, don't remember this. Different collateral patterns.

[00:43:07]Aneurysm.

[00:43:09]Just four slides more.

[00:43:12]Two to three, four slides.

[00:43:17]Aneurysm.

[00:43:20]The arch of aorta dilates.

[00:43:22]That's what it means.

[00:43:24]Okay, it dilates and it pushes the structures around it causing fatal hemorrhage or consequences.

[00:43:33]Okay, complications. So, we have trachea that can be esophagus or R L N, no.

[00:43:41]That's what it means by aneurysm.

[00:43:43]Clinical importance, aneurysm and coarctation.

[00:43:45]So, compresses superior mediastinum also can cause mediastinal syndrome.

[00:43:52]Its rupture causes fatal hemorrhage.

[00:43:55]Okay.

[00:43:56]Descending thoracic aorta and its large veins. So, we all know, starts from the T4 T5 uh disk.

[00:44:06]Okay, and it goes till T12.

[00:44:10]Descending aorta ends at T12 and from there abdominal aorta starts. This is the diaphragm.

[00:44:17]Okay?

[00:44:18]And right here it's it's one branch called subcostal artery.

[00:44:23]Of descending aorta, subcostal artery.

[00:44:25]So, remember this.

[00:44:27]Three, four points at the end of the descending aorta.

[00:44:31]Just three, four points. Subcostal artery, T12, diaphragm, and abdominal aorta.

[00:44:38]Descending thoracic aorta, let's start.

[00:44:48]Begins at this, ends at T12, passes through aortic opening, abdominal aorta.

[00:44:55]Descends on left side, T5 to T7 vertebrae.

[00:45:00]In front of lower five thoracic vertebrae.

[00:45:05]Then, branches. There are nine pairs of posterior intercostal arteries, from third to 11th. Look.

[00:45:23]Okay? From third to 11th.

[00:45:26]Three to 11 intercostal arteries coming out from here.

[00:45:30]Okay? Posterior intercostal arteries.

[00:45:34]So, there are nine pairs of it. One.

[00:45:38]From both sides.

[00:45:41]Then, subcostal artery we already did.

[00:45:44]Then we have bronchial arteries that provide supply to the lung tissue.

[00:45:52]And esophageal branches to esophagus.

[00:45:55]That's it.

[00:45:58]These are the branches of aortic.

[00:46:00]Now, what are the tributaries? Actually, the tributaries is what comes or drains into it.

[00:46:11]So, we'll start from here.

[00:46:13]SVC.

[00:46:15]Start from right.

[00:46:17]SVC is situated at the right first costal cartilage.

[00:46:21]Okay?

[00:46:26]And then, how is SVC formed?

[00:46:29]By brachiocephalic vein.

[00:46:32]Superior vena cava is formed by right brachiocephalic vein and left brachiocephalic vein. And how right brachiocephalic vein is formed? By subclavian right subclavian vein and internal jugular vein.

[00:46:46]This forms brachio- which is a very small part of this is right brachiocephalic, while a long part is left brachiocephalic vein.

[00:46:56]This part is under above the aortic just above the aortic arch.

[00:47:01]Okay?

[00:47:02]Two parts drain here. Which ones? Let's see.

[00:47:07]Brachiocephalic veins. Right brachiocephalic vein and left brachiocephalic vein. Already done. This is short, this is longer. Descends vertically behind manubrium, joins laterally to form SVC. We just did.

[00:47:20]Longer oblique course above aortic arch, we just did. Ends behind first costal cartilage. Also, we just did. Look, first costal cartilage. First costal cartilage.

[00:47:33]Now, it's tributaries. You just This is what you need to remember. This is one, internal thoracic vein.

[00:47:39]Two, left first posterior posterior intercostal vein, left superior intercostal vein, thoracic duct.

[00:47:47]Let's come to superior vena cava.

[00:47:49]Behind, of course, by union of two brachiocephalic vein.

[00:47:53]Upper half in superior mediastinum, lower in middle mediastinum. This upper half is superior mediastinum and lower half is inferior mediastinum.

[00:48:05]Okay?

[00:48:07]Then ends in right atrium behind right third costal cartilage.

[00:48:14]Tributary, we did this in the azygos vein with a slide. Azygos vein enters to second costal cartilage just before piercing pericardium.

[00:48:23]Now, let's come to phrenic nerve.

[00:48:28]Phrenic nerve is very very very important, very famous nerve. Why?

[00:48:32]Because it originates from C3, C4, C5.

[00:48:36]And there's a famous mnemonic for this that C3, C4, C5 keeps the diaphragm alive.

[00:48:42]Okay?

[00:48:43]Both of them, left and right, starts the same way, C3, C4, C5.

[00:48:49]This is the nerve of the diaphragm.

[00:48:52]It's It's usual common uh course is from the neck to thorax to mediastinum and then to diaphragm.

[00:49:02]So, it's a mixed nerve. It also has motor part and sensory part. Motor part provides to diaphragm and sensory is to three serous membranes, fibrous pericardium, parietal pericardium, and mediastinal pleura.

[00:49:18]Okay?

[00:49:20]Now, let's do this with the help of a diagram.

[00:49:23]Okay?

[00:49:24]Starts in front of subclavian artery here.

[00:49:30]It goes to the level of brachiocephalic.

[00:49:37]Brachiocephalic when it joins or forms SVC.

[00:49:40]Okay?

[00:49:42]So, subclavian artery, superior vena cava.

[00:49:46]Goes around like Look here. Goes around the right atrium. This is the right atrium. Goes like this.

[00:49:54]And it ends at the diaphragm, dome-shaped diaphragm.

[00:49:58]This is longer, why?

[00:50:00]As compared to this one, the left one, left phrenic nerve. This is longer because the liver pushes the diaphragm a little bit up.

[00:50:09]So, you can see that this is vertical and straight. This is important to mention. Two Two keywords, vertical and straight.

[00:50:18]It goes all through that and ends in the IVC.

[00:50:22]At the T8 vertebral level.

[00:50:25]Thoracic level.

[00:50:26]Okay?

[00:50:28]In front of subclavian starts to SVC, goes straight with the margin of right atrium and ends in the IVC and deflects. Look, that's what's written.

[00:50:44]So, enters thorax in front in front of subclavian artery. Crosses internal internal thoracic artery laterally.

[00:50:51]Here, internal thoracic artery laterally.

[00:50:57]Okay? If you don't remember this, it's okay.

[00:51:01]Descends mediastinum, venous side venous side, okay? Again, we have heard this mnemonic before, right? Right is veins and left is atrium arteries.

[00:51:14]Not atrium arteries.

[00:51:16]So, this Usually, all the veins are going to be on its spot.

[00:51:21]Right brachiocephalic vein, superior vena cava, and inferior vena cava.

[00:51:27]Okay?

[00:51:28]Also, pericardium.

[00:51:29]Because it's going to on the right atrium, so the pericardium that covers right atrium is also included.

[00:51:38]It terminates through diaphragm, vena caval opening.

[00:51:42]So, right phrenic is shorter, it's more straight and nearly vertical. Why is it shorter?

[00:51:49]Because of liver, it pushes the liver pushes the diaphragm a little bit up.

[00:51:55]Let's do left phrenic. Similarly, C3, C4, C5. And then arterial side, little bit has arteries in it. So, how?

[00:52:05]First of all, left subclavian artery.

[00:52:08]Also goes through the carotid artery.

[00:52:12]I think so.

[00:52:13]Yes, left common carotid artery. So, that's also included. Left common carotid artery, your then aorta, aortic arch.

[00:52:27]Look, aortic arch.

[00:52:29]Then straight and curves. It is a little convex. It curves here.

[00:52:36]So, the pericardium of the left ventricle and the left ventricle, it curves and it also has the same termination just like right terminates in the diaphragm.

[00:52:49]This is the mediastinal arterial side.

[00:52:52]Where there are mostly arteries uh on its path.

[00:52:57]Let's do this. Left common carotid artery and subclavian artery. Aortic arch and pericardium of the left ventricle. Terminates, diaphragm.

[00:53:07]Left cupola. Cupola means dome-shaped.

[00:53:11]Left phrenic curves with heart convexity. Look, this is what they're saying. That here if if it's there's a comp- comparison, here it's straight, short, and vertical, while here it's convex.

[00:53:24]With the Why is it convex? Because left ventricle is more towards uh the left l- the left lung in the mediastinum.

[00:53:34]Right? So, the pericardium is also there, so it's everything.

[00:53:39]Then sensory, it also has a fibers, parietal series. We done this before, right?

[00:53:44]Motor to diaphragm abdominal surface.

[00:53:49]Sensory part to three series membranes similarly. And motor part to diaphragm.

[00:53:56]So, I think these were the most important parts for today's video.

[00:54:02]Rest I'll do later.