Hello, everyone. This is Joao from Kenhub and welcome to another anatomy tutorial where this time we’re going to be talking about the different nerves of the esophagus.
And to do so, we’re going to be looking at this image that you see now on your screen. What we have here is your thorax.
We just opened it, took all of the organs or the major organs that you find on the thorax.
You see here the diaphragm, the esophagus, bit of the stomach. You also see here ... this is the thoracic aorta, the aortic arch.
Then you see some of the scalene muscles and, of course, the yellow structures are representing the nerves that we’re going to be discussing on this tutorial.
Now, the esophagus as you probably know is a long fibromuscular tube that connects the pharynx with the stomach.
Now, we’re going to be seeing here on this image all these yellow structures consists of different nerves, trunks, and also plexuses that we’re going to be talking about.
And before I do so, I'm going to list them. They include the intercostal nerves, also the right and left vagus nerves, the anterior vagal trunk, the right and left recurrent laryngeal nerves, the greater splanchnic nerve, the anterior gastric plexus, the esophageal plexus, and the right and left sympathetic trunks.
We’re going to start off with the very first ones on the list that you see here highlighted in green. Again, we’re looking at the anterior view of your thorax where you can see the intercostal nerves.
Now, the intercostal nerves are part of the somatic nervous system. They arise from the anterior roots of the thoracic spinal nerves from T1 to T11.
Eleven of them are located between the ribs and are therefore termed as intercostal.
The twelfth one will be lying below the last rib. That’s why we call it then the subcostal nerve.
Now, these nerves will be controlling contraction of the intercostal muscles as well as providing specific sensory information regarding the skin and parietal pleura.
The next structures that we’re going to be talking about, and right now, I'm showing you a different image here where you can see where they come from, these are the vagus nerves.
So as you can see here, the right vagus nerve and the left vagus nerve, and keep in mind that we’re looking at an anterior view of the neck.
You see here, a bit of the mandible, the larynx, bit of the trachea and two clavicles. So you see what is happening here. So we can see where the two vagus nerves come from.
These are also known as the tenth cranial nerves.
The right and left vagus nerves, they will be descending from the cranial vault through the jugular foramina and then trading the carotid sheet between the internal and external carotid arteries.
We’re now going to go back to this image of the open thorax where you see highlighted the right vagus nerve.
The right vagus nerve will be giving off the right recurrent laryngeal nerve which as you can see here on this image, it will be hooking around the subclavian artery and descends into the neck between trachea and the esophagus.
And on this image you can see here the trachea and the esophagus.
The right vagus nerve will be contributing to the cardiac, pulmonary, and esophageal plexuses. It also forms the posterior vagal trunk at the lower part of the esophagus and enters your diaphragm through the esophageal hiatus.
Now, we’re going to be highlighting what you see on the image, the left vagus nerve. This one will be giving off the left recurrent laryngeal nerve.
Now, the left recurrent laryngeal nerve as you can see here on the image is then hooking or hooks around on this structure here which is the aortic arch. Now, to the left of the ligamentum arteriosum and ascend between the trachea and esophagus.
This nerve will further give off the thoracic cardiac branches and contributes to the pulmonary and esophageal plexuses. The left vagus nerve will be also forming the anterior vagal trunk in the esophageal hiatus of the diaphragm.
And speaking of the anterior vagal trunk, I'm now highlighting it, so this is the anterior vagal trunk highlighted in green which is a branch of the left vagus nerve as I talked about on the previous slide. This one will be contributing to the esophageal plexus.
The anterior vagal trunk will be giving off different branches. So hepatic branch which will be supplying then the liver, cilia branch which are small branches which provide parasympathetic innervation to the celiac plexus.
Finally, the anterior gastric branches which supply the stomach.
The posterior vagal trunk is very similar to the anterior one. But you cannot see it here very well here on this image because as I mentioned before, we’re looking at an anterior view.
So I would like to add here that the posterior vagal trunk is also a branch of the vagus nerve which contributes to the esophageal plexus.
We’re going to move on and talk about a pair of structures that I already briefly mentioned before. This one that you see here highlighted in green is known as the right recurrent laryngeal nerve, while this one here that is also highlighted in green, if you remember, this is the left recurrent laryngeal nerve.
Now, these are, as I mentioned also before, they are branches of the vagus nerves. They emerge from the vagus nerve at the level of the aortic arch. Then they travel up to the side of the trachea to then the larynx.
There are two recurrent laryngeal nerves, right and left in the human body. The right and left laryngeal nerves they are not symmetrical.
The left nerve loops under the arch as I mentioned and as you can see here on this image. While the right nerve will be travelling directly upwards looping around the subclavian artery as you can see here on this image.
The recurrent laryngeal nerves will be controlling all intrinsic muscles of the larynx except for the cricothyroid muscle.
These muscles act to open and close your vocal cords and include the posterior cricoarytenoid muscles, the only muscle to open the vocal cords.
And the nerves will be supplying the muscles on the same side of the body with the exception of the interarytenoid muscle which is innervated from both sides.
These nerves will be also carrying sensory information from the mucus membranes of the larynx just below the lower surface of the vocal fold as well as sensory, secretory, and motor fibers to the cervical segment of the esophagus and the trachea.
Next on our list, we’re going to see these nerves, these nerves highlighted in green. These are known as the greater splanchnic nerves. They travel through the diaphragm and enter the abdominal cavity where its fibrous synapse at the celiac ganglia.
They arise from T5 to T9 or T6 to T10 of the sympathetic ganglia.
Now, these nerves will be contributing to the celiac plexus which is a network of nerves that is located in the vicinity of where the celiac trunk branches from the abdominal aorta. And the fibers in this nerve will be modulating the activity of the enteric nervous system of the foregut.
They also provide the sympathetic innervation to the adrenal medulla which stimulates the release of catecholamine.
Next structure that we’re going to be seeing here highlighted in green, this is known as the anterior gastric plexus. Now the anterior gastric plexus is formed by the left vagus nerve and in the same way the right vagus nerve will be forming the posterior gastric plexus. As you would probably guess, the anterior gastric plexus will be innervating the stomach.
Moving on to the next structures that you see here highlighted in green, all around the esophagus as you can see on this image, these are then the esophageal plexus.
The esophageal plexus is formed by nerve fibers from two sources. One is from the branches of the vagus nerves and another one from visceral lower branches of the sympathetic trunk.
Now, what happens is that the vagus nerve will be delivering two types of fibers to the esophageal plexus. One is known as the preganglionic parasympathetic fibers. And these fibers have their cell bodies in the dorsum motor nucleus of the vagus, and they will be synapsing in the terminal ganglia in the walls of the esophagus.
The other types of fibers coming from the vagus nerve are known as afferent fibers. These are primarily concerned with autonomic reflexes, and they have their cell bodies in the inferior ganglion of the vagus.
Also the visceral branches of the sympathetic trunk will be delivering two types of fibers to the esophageal plexus.
One is the sympathetic post ganglionic fibers which the cell bodies of these fibers are located in the sympathetic chain ganglia. You’ll also going to be seeing afferent fibers and these fibers are primarily concerned with pain and have their cell bodies located in the dorsal root ganglion.
Knowing that, we’re ready to move on to the next structures. The first one is also ... these are also a pair.
And the first one that you see here highlighted in green is known as the right sympathetic trunk. While on the right side, you can see, right image, you can see highlighted in green the left sympathetic trunk.
Now, the sympathetic trunks are paired bundle of fibers. And they run from the base of the skull to the coccyx just lateral to the vertebral bodies, and they will be interacting with the spinal nerves on their ventral rami.
Now, the superior ends of the right and left sympathetic trunks, they are continued upwards to the carotid canal into the skull and form a plexus on the internal carotid artery.
The right and left sympathetic trunks will also allow nerve fibers to travel to the spinal nerves that are superior and inferior to the one from which they originated from.
Also a number of nerves such as most of the splanchnic nerves arise directly from these trunks.