 So this is the ascending aorta. We have to remove the heart from here. Then we have the arch of the aorta Then we have the descending thoracic aorta. Just to break up to speak, the very proximal portion of the aorta as it emerges from the heart That portion is enclosed inside the fibrous pericardium and we have removed the fibrous pericardium along with the heart So that portion of the aorta is considered as in the middle-media stena. The ascending portion is up to here This is the arch of the aorta. So therefore the end of the ascending, the beginning of the arch, end of the arch and the beginning of the descending aorta, all of them take place at the level of T5 Or at the level of bifurcation of the trachea. That is the sternal angle of Louie Now let's take a look at some of the branches from the arch of the aorta, which are basically located in the root of the neck Three important branches are this one here. This is the brachycephalic trunk, which divides into a right common carotid and a right subclavian Then we have the left common carotid and then we have the left subclavian. Rarely in about 10% of the population We can have what is known as a thyroidia ima artery, which if it is present it comes from the brachycephalic trunk But it can also come from the arch of the aorta. So these are the branches which are present from the arch and they are located in the root of the neck The descending thoracic aorta, the branches are divided into what are known as vascular plates We have one set of branches which come in the midline and they are known as the unpaired visceral branches We cannot see them because most of them have been removed and they are rather small They are the esophageal branches, which supply the esophagus Then we have the pericardial branches and we have the mediestinal branches Then we have a series of branches going posterior laterally on both the sides A are the posterior intercostal arteries and we shall show the posterior intercostal arteries just now I have retracted the aorta and I have retracted the esophagus and we can see the posterior intercostal arteries now We can see the numerous segmental arteries coming out and they are travelling from the left to the right And if you trace them further we can see they are coming to the posterior intercostal chest wall on the right side Likewise if you look on the left side they will learn on the left side also Though we have not dissected them out but we can see them clearly here These are the posterior intercostal arteries These are the paired parietal branches and then we have the paired visceral branch also Which we cannot see because they are rather small and they are the bronchial arteries Apart from that there is another paired set which comes out just above the diaphragm One on the left side, one on the right side that is known as the superior phrenic artery Which supplies the upper surface of the diaphragm So these are the vascular plane concept of the aorta The aorta initially is located to the left of the esophagus and we can see that And as it descends down it moves a little to the right and the esophagus moves a little to the left So therefore in the lower part it is located behind and to the right of the esophagus And it exits the thorax by passing through the aortic hiatus in the diaphragm Which is the level of T12 And at this hiatus it is accompanied also by the aegis vein which I have lifted up here And the thoracic duct So therefore going from right to left passing through the aortic hiatus We have aegis vein, thoracic duct and aorta Let's mention a few clinical correlations pertaining to the aorta The aorta is a very useful root for aotogram Not only for coronary angiogram but also to study the great vessels at the root of the neck Namely the sprakercephalic, left common carotid and the left subclavian This is a digital subtraction angiogram showing the arch of aorta and the great vessels This is an MR angiogram showing the arch of aorta and the descending thoracic aorta In the earlier days when syphilis was rather common and penicillin had not been discovered Tertiary syphilitic aortic hiatus and aortic aneurysm was very common And many known celebrities had expired from rupture of a syphilitic aneurysm But nowadays it is not so common However nowadays atherosclerotic aneurysm of the aorta is quite common As demonstrated in this MR angiogram Dissecting aneurysm of the thoracic aorta is very well documented Especially in hypotensives In dissecting aneurysm there is an intimal tear and blood tracks between the intima and the tunica media And it tracks through the aortic wall and it produces a tearing, cutting pain Especially on the posterior aspect of the chest wall which can mimic myocardial infarction And that is run as dissecting aneurysm The posterior intercostal arteries supply the chest wall from the posterior to the angi aspect And they anastomose with the paired anti-intercostal arteries Which arise from the internal thoracic artery There is a congenital condition called coactation of aorta There are two kinds of coactation of aorta which is a congenital narrowing of the aorta One of them is called the pre-ductal What is this pre-ductal? Take a look at this pulmonary trunk here Which we have got, this was the portion attached to the heart The pulmonary trunk is located under the arch of aorta This is the right pulmonary artery which is located under the arch And this is the left pulmonary artery which is free from the arch Connecting the pulmonary trunk to the under surface of the arch of aorta We have this fibrous structure here This is the ligamentum arteriosum which is the fibrous remnant of the ductus arteriosus So to come back to the pre-ductal coactation of aorta before the ductus arteriosus That is usually seen in infants The more common variety is the post-ductal which is seen in adults And that occurs after the left subclavian artery has been given off So it occurs somewhere in this region In the post-ductal coactation of aorta As we can imagine, blood supply to the aorta is seriously hampered In such a situation, by default, the anterior supply to the chest wall becomes prominent And that is by means of internauthoracic arteries This is one internauthoracic artery coming from the subclavian artery And this is the other internauthoracic artery coming from the left subclavian artery Then the blood supply to the internauthoracic arteries become prominent And the blood supply then gets reversed They flow from the anterior intercostal arteries to the posterior intercostal arteries In the third to the ninth space And then they flow back to the aorta So the blood flow gets reversed In such a situation, the posterior intercostal arteries also become dilated and tortuous And they can produce notching of the inferior margin of the ribs And that is seen in X-ray and it is called notching of the ribs Which is the sign of coactation of aorta, the post ductal variety These intercostal arteries also communicate with the dorsal scapular artery on the scapula Which participates in the scapula and ostomosis And therefore these patients also have what is known as the dancing scapula Where when we put our hand on the back of the chest, we can feel pulsations And when we do a plain X-ray, the arch of aorta which is normally visible as an aortic knuckle Because of the coactation, there is a dent in the knuckle And that dent is referred to as number 3 sign This is the plain chest X-ray to show the number 3 sign And the notching of the ribs seen in coactation of aorta So these are some findings pertaining to coactation of aorta I would draw your attention to this post of the arch here This is the left vagus nerve descending down And the vagus as it descends in front of the arch It is giving this branch here This is the left recurrent laryngeal nerve This hooks under the arch of aorta Just distal to the ligamentum arteriosum and then it climbs up on the neck As the recurrent laryngeal nerve This hooking of the recurrent laryngeal nerve on the left side Occurs at the level of T4, T5 vertebra This happens only on the left side If there is an aneurysm of the arch of aorta Then it can compress the recurrent laryngeal nerve on the left side And that can lead to vocal cord paralysis on the left side And can lead to forceness Just to complete the story, on the right side This hooking occurs under the right subclavian arch So I will draw your attention to the right side This is the vagus nerve on the right side As it is travelling in front of the right subclavian artery We can see it is giving this nerve here This is the right recurrent laryngeal nerve Which hooks under the right subclavian artery This occurs at the level of approximately T1 and T2 So therefore this pathology pertaining to the aorta Does not apply to the right side However, this can be involved in yet another condition When we have a tumor of the apex of the lung on the right side Which is referred to as a pancos tumor That can compress the right recurrent laryngeal nerve That can produce a forceness of voice Because of paralysis of the right vocal cord So these are all some of the salient points Which I wanted to mention about the arch of the aorta And the descending thoracic aorta