Hello all this is Dr.
Kathleen Alsup
And I'm going to provide a quick overview of the esophagus
Recall that we dissected portions of the esophagus in the respiratory sequence
Now we're really going to review the entirety of the esophagus to provide you as scaffolding to better prepare you for the anatomy dissection
experience, but more importantly really prepare you for this clinical and basic science lectures that you'll be getting throughout the gastrointestinal sequence.
So let's get started.
Now the esophagus is the proximal portion of the gastrointestinal tract and it's going to connect the pharynx
to the stomach and
conceptually, we often describe the esophagus in three to four different areas. However, it's important to note that of course
it's continuous.
So the most proximal area is what we consider the cervical portion
Then you'll have the thoracic portion
That's the portion that we dissected already, and then we get to the diaphragmatic and the abdominal portion
Sometimes those are considered separately, sometimes they're considered together.
The abdominal portion is really what's distal to that esophageal hiatus of the diaphragm. So remember the diaphragm would be located right about here
So you'd have your esophageal hiatus to allow the esophagus to enter into the abdomen and then you would have a very short
abdominal portion that will connect to the stomach.
Okay, before we get into the neurovasculature of the esophagus I want to talk about how there's different muscle associate with the esophagus and
That's quite different than what you have for the rest of the GI tract
The superior third of the esophagus is actually striated muscle
Which is similar to what we had with the pharynx and we know that all striated muscle you're going to have somatic innervation
So that's also different than what you have from the rest of the GI tract
The inferior third of the esophagus is smooth muscle just like you would expect with the autonomic innervation
But right around the middle portion or the thoracic portion, you're going to have both types of muscle cells
So you'll have striated muscle as well as smooth muscle
So this is a distinction that you have in the esophagus that you won't in the rest of the GI tract
There are three main constrictions in the esophagus caused by surrounding structures:
You will have the cervical, or the upper esophageal sphincter. This is caused by that cricopharyngeal muscle
of the pharynx
you will have a thoracic or a bronco-aortic
constriction, this is where that esophagus is crossed by the arch of the aorta as well as the left main bronchus
And this is often considered a compound constriction. So a very complicated region right there
And lastly you're going to have a diaphragmatic
constriction and this is where that esophagus is passing through the diaphragm through the esophageal hiatus
Now, why do we care about these constrictions?
awareness of these constrictions is important because when you're passing an instrument through the esophagus to the stomach you
Really need to be aware of where these constrictions occur
There is a robust arterial supply associated with the esophagus and there are various sources from very different areas
The cervical part of the esophagus is supplied by branches of the inferior thyroid artery. Remember that inferior
thyroid artery is a branch of the first part of the subclavian artery.
When we're talking about the thoracic part of the esophagus,
this is going to be supplied by visceral branches of the thoracic aorta such as the bronchial and obviously esophageal branches,
And when we're talking about the abdominal part of the aorta
This is ultimately supplied by branches of the celiac trunk
So esophageal branches from the left gastric artery
Which is one of the main branches of the celiac trunk as well as short gastric arteries from the splenic artery
Another one of the main branches of that silly act trunk
Venous drainage
Mostly follows the arterial supply so that cervical part is going to drain into the inferior thyroid vein
the thoracic part is going to drain into that complex Azygos system right next to the vertebral column,
And the abdominal part of the esophagus is a really important site
This is a site of portal caval and I should have an A-L here. So portal-caval
anastomoses.
Recall that portal caval anastomosis are sites where the portal venous system communicates with the systemic or the cable venous system
so the main veins draining the inferior esophageal part are the left gastric veins which are part of the portal system as
well as the
esophageal veins which are part of the systemic or the caval system.
As mentioned there is differential innervation of the esophagus based on the muscle type
the superior portions of the esophagus which are that striated muscle are going to be innervated by the
Recurrent laryngeal nerve which is a branch of the vagus nerve
This smooth muscle is innervated by the esophageal plexus and it's important to note that this is continuous with the more superior
cardiac and pulmonary plexuses.
They're going to be both sympathetic and parasympathetic
contributions. The sympathetics are mostly derived from about
T4-46 but the more inferior portions of the esophagus are going to have sources from that greater splanchnic thoracic nerve and
The parasympathetics are going to be derived from those vagal trunks. So from cranial nerve 10
This concludes the overview of the esophagus for additional information and images, please refer to the blue link website.