 We have completely removed all the thoracic structures. This is the esophagus. The esophagus, as you know, has about three segments, a cervical segment, a thoracic segment, and a small abdominal segment. So the thoracic segment of the esophagus is from T1 to T10, where it passes through the esophageal hiatus in the diaphragm, and after that it becomes a small abdominal segment, shown here, which is from T10 to T11. So from T1 to T10 is the thoracic segment. Coming to the relations of the esophagus, it's in the posterior media center. On the right side of the esophagus, we have this structure here, which I have lifted up. This is the asiagus vein. And on the left of the esophagus, for the most of its length, is the descending thoracic aorta. As they descend down, in the lower part, the esophagus comes a little anterior to the aorta, and we can see that here. It moves a little to the left and anterior to the aorta. In front of the esophagus, we have the trachea. We have the bifurcation of the trachea into the left principal bronchus and the right principal bronchus. The posterior part of the trachea, which I have turned, contains a muscle. And that is known as the trachealis muscle. So therefore, that ensures that there is no compression of the esophagus by the trachea. The esophagus in this segment does not have any serosa, unlike the abdominal segment, which has got a serosa, which is the visceral peritoneum. So because of the lack of the serosa here, it is prone to perforation and rupture. It can produce a very serious condition known as mediastenitis. Or it can even produce air in the mediastenum, which is known as pneumomediastenum. That brings me to the next point. That is the constrictions of the esophagus. The esophagus actually has got three constrictions, but one of that is the neck. So we shall not mention about that. Let's talk about the constrictions of the esophagus in the thorax. Let's take a look at this. This is the arch of the aorta. And we can see that the arch of the aorta goes to the left and posteriorly, and then continues down as the descending thoracic aorta. So when the aorta is arching, it compresses the esophagus from the left lateral side, where my instrument is showing right now. And this compression of the esophagus is approximately 22.5 cm from the incisor teeth as recorded by esophagus scope. Next constriction that we can see is at the bifurcation of the trachea into the left principle and the right principle bronchi. This compression of the esophagus takes place from anterior aspect just below the compression produced by the arch of the aorta. And that is approximately at the level of 27.5 cm from the incisor teeth as recorded by an esophagus scope. So therefore these two constrictions of the esophagus are physiological constrictions but they can also be the sides of pathological narrowing or stricture of the esophagus especially if a person ingests corrosive substances. And when we are doing an endoscopy these are the places where we are likely to injure and perforate the esophagus. 22.5 cm and 27.5 cm collectively we generally rounded off to say about 25 cm from the incisor teeth. The lateral compression is best seen in an anterior posterior perium swallow. And the anterior compression is best seen in a lateral perium swallow. This is a perium swallow to show the constrictions of the esophagus and the three parts of the esophagus. So these are the constrictions of the esophagus with their respective clinical implications. Coming to the nerve supply of the esophagus. Upper one-third of the esophagus is supplied by the recurrent laryngeal nerve. This is the recurrent laryngeal nerve on the left side going under the arch of the aorta. The middle one-third of the esophagus nerve supply is somatic and autonomic. And the lower part of the esophagus nerve supply is by the vagus. The vagus supply of the esophagus is for pedestal sits. This is the vagus on the left side and this is the vagus on the right side. And I have held them up with this instrument here. Normally the vagus breaks up into plexus called the cardiac plexus, pulmonary plexus esophageal plexus just behind the pulmonary hyalum on either side. And then as it descends down it again forms a trunk. And this is the left vagus and this is the right vagus. The two vagae, they also enter from the thorax into the domain through the same hiatus as the esophageal hiatus. That is at the level of D10. And here what the vagus does is what is known as a lark. That means the left vagus comes anterior and the right vagus becomes posterior. However, here we see a small variation. We notice that this is the right vagus and this was located anterior to the esophagus. And this is the right vagus. And this is the left vagus. And this is located posterior to the esophagus. We notice that the left vagus has gone posterior to the esophagus. The posterior vagus is larger and it is a little away from the esophagus. And this is the one we supplies up to the junction between the mid-gut and the hind-gut. Anterior vagus is smaller and it supplies only the foregut structures. So this is the course of the vagus. Now I'll draw your attention to the lower end of the esophagus at the region where it goes through the esophageal hiatus. The esophageal hiatus is located at the level of T10 and the hiatus is produced by the splitting of the fibres of the right crust of the diaphragm. And therefore they act as a pitch-cock mechanism and that is what is known as the lower esophageal sphincter. Just above the esophageal hiatus, as seen in barium swallow, there may be a transient dilatation of the esophagus which is due to peristalsis of the esophagus. That transient dilatation which is seen only radiologically is referred to as the phrenic ampullum. Barium swallow to show the phrenic ampullum just above the diaphragm, the esophageal hiatus. The esophagus is held in place at the esophageal hiatus by means of a thin fascia and part of that we have written here and this is referred to as the phreno-esophageal ligament. The phreno-esophageal ligament actually has got two components. One is above the diaphragm and the other is the abdominal side of the diaphragm. They are respectively derived from the endothoracic fascia above and from the end abdominal fascia below and they go from the diaphragm and they merge with the esophageal musculature and that phreno-esophageal ligament superior and inferior holds the esophagus in place inside the esophageal hiatus and it is one of the mechanisms which is responsible for maintaining the integrity of the lower esophageal sphincter. When the integrity of the lower sphincter is lost then we get a condition known as hiatus hernia. Barium swallow to show a sliding esophageal gastric hiatus hernia. Esophageal cancer is well documented especially those who take thermally hot liquids for long duration of time and do take spicy food among other carcinogens. Cancer of the esophagus does not have a very good progress. First reason being it does not have any serosa therefore it spreads very rapidly and secondly because of its posterior merestinal position it quickly spreads to the media stannum and other places and therefore esophageal cancer resection does not carry a very good prognosis. There are many other conditions which affect the esophagus. Central underlying symptom of any esophageal pathology is difficulty in swallowing and that is referred to as dysphagia. In the lower end of the esophagus in a patient with cirrhosis with portal hypertension we can get something which is known as esophageal varicis. It is seen in the gastroesophageal junction because of portal hypertension there is dilatation of the esophageal branches of the less migraine which produce sub-mucosal dilatations of the portal systemic communications and that is known as esophageal varicis which can produce very serious blood vomiting known as hematomus. This is an esophagoscopic view to show esophageal varicis at the lower end of the esophagus. That brings me to some clinical congenital anomalies which affect the esophagus indirectly. Let's come back to this arch of aorta. In certain situations the patient has got a double aortic arch an anterior and a posterior. The posterior arch goes behind the esophagus. Therefore the esophagus gets trapped between the anterior arch and the posterior arch and that can produce constriction of the esophagus and can produce difficulty in swallowing. So that is one congenital anomaly. This is the right subclavian artery which comes from the brachial cephalic trunk. In another congenital anomaly which of course is not very common the right subclavian artery may come from the left side. It goes behind the esophagus and it comes to the right side and that is known as a retroesophageal right subclavian artery. That can also compress the esophagus and can produce dysphagia. Coming to a few basic investigations for the esophagus. I have already briefly mentioned that earlier. Variants swallow still remains a very useful investigation for the esophagus. Patient is made to swallow a thick variants surface solution and we can see the mucosur pattern and any lesions of the esophagus. Other important investigation is esophagoscopy which is combined with estoscopy. So these are some of the points which I want to mention about the thoracic part of the esophagus with a little bit of the abdominal segment. That's all for now. Thank you very much for watching. Dr. Sanjay Sanyal. Please like and subscribe if you have any questions or comments. Please put them in the comment section below.