Description

Esophagus:

• Length: ~25 cm
• Located between the pharynx and the stomach
• Divided into three parts:
  • Cervical Part (Pars Cervicalis)
  • Thoracic Part (Pars Thoracica)
  • Abdominal Part (Pars Abdominalis)

Parts of the Esophagus:

Cervical Part:

• Begins at the Pharyngeal Opening into Esophagus (Ostium Oesophageum)
• Ends at the Superior Thoracic Aperture (Apertura Thoracica Superior)

Thoracic Part:

• Starts at the Superior Thoracic Aperture (Apertura Thoracica Superior)
• Ends at the Esophageal Hiatus (Hiatus Oesophageus Diaphragmatis)

Abdominal Part:

• Begins at the Esophageal Hiatus (Hiatus Oesophageus Diaphragmatis)
• Ends at the Cardiac Orifice (Ostium Cardiacum Gastrici)

Curvatures of the Esophagus:

• Curves to the left at the beginning (Cervical Part)
• Curves to the right at the middle (Thoracic Part)
• Curves to the left above the diaphragm

Constrictions of the Esophagus:

Anatomical Constrictions:

• Pharyngoesophageal Constriction
• Bronchoaortic Constriction
• Diaphragmatic Constriction

Physiological Constrictions:

• At the level of T8-T9
• At the level of T11 (Lower Esophageal Sphincter)

Layers of the Esophageal Wall:

Tunica Mucosa:

• Stratified Squamous Non-Keratinized Epithelium
• Contains mucous glands and vasculature
• Includes Lamina Muscularis Mucosa

Tela Submucosa:

• Loose connective tissue
• Contains esophageal glands and esophageal cardiac glands

Tunica Muscularis:

• Inner circular muscle fibers
• Outer longitudinal muscle fibers
• Muscle composition:
  • Upper 1/3: Skeletal muscle
  • Middle 1/3: Mixed skeletal and smooth muscle
  • Lower 1/3: Smooth muscle

Tunica Adventitia & Tunica Serosa:

• Tunica Adventitia: Covers the esophagus in the thoracic part
• Tunica Serosa: Present in the abdominal part

Sources:

• Memorix Anatomy, 2nd Edition by Hudák Radovan, Kachlík David, and Volný Ondřej
• Biorender
• University Notes and Lectures

Transcript

Introduction
0:00
What’s up. Meditay here, and in this video, we’re gonna go through the anatomy of the Esophagus.
0:04
So in the last video, we went through the anatomy of the Pharynx. Now the step after
0:09
the Pharynx is the Esophagus, as you see here. So in this video, we’re first going to look at the
0:14
parts of the Esophagus. After that, look at the curvatures and the constrictions of the esophagus.
0:20
Then we’re gonna go through the layers of the esophageal wall through a histology slide.
0:24
Cool, let’s start by looking at an anterior view of the Esophagus. The esophagus lies between the
Parts of the Esophagus
0:31
Pharynx, and the stomach as you see here. The length of the esophagus varies a lot, but in
0:36
average It should be approximately 25 cm long. Now. The esophagus is divided into three parts
0:42
according to their anatomical location. First we have the cervical part, which lies in the neck.
0:48
Then we have the Thoracic Part, which lies in the thoracic cavity. And then we have the Abdominal
0:52
Part, which lies in the abdominal cavity. So these are the three parts of the esophagus,
0:58
let’s go through where each of them start and end. The cervical part starts from the pharynx.
1:03
So remember the Pharynx has two openings. There’s the Laryngeal Inlet, which leads into the Larynx.
1:08
And there’s the Pharyngeal Opening into the Esophagus, or Ostium esophageum, which is
1:13
going to be the start of the cervical part of the esophagus. And the cervical part ends just
1:18
before it enters the thoracic cavity through the superior thoracic aperture, or the upper opening
1:24
of the ribcage. So the cervical part starts at the Pharyngeal opening into he esophagus,
1:30
and ends at the Superiro thoracic aperture. After the cervical part is the thoracic part.
1:36
And this one is going to start at the superior thoracic aperture and go all the way down until
1:41
it pierces the diaphragm. And remember, the area at which the esophagus pierces the diaphragm
1:47
is called Esophageal Hiatus. So the thoracic part starts at the superior thoracic aperture
1:54
and ends at the esophageal histus. After the thoracic part has gone through the diaphragm,
2:00
it enters the abdominal cavity and becomes the abdominal part. Which is going to start at the
2:06
esophageal hiatus, and end at the Cardial Orifice. So that was all the three parts of the esophagus.
2:14
Now. The esophagus goes vertically down at the midline. However It’s easy to imagine that the
Curvatures of the Esophagus
2:20
esophagus goes down as a straight line, but it actually have some curvatures that’s important
2:25
anatomically. First, at the beginning, it curves slightly to the left, as you see here. Then in the
2:32
middle of the Thoracic part it curves slightly to the right, and then at the lower thoracic region,
2:38
it curves to the left again to then go thrgouh the diaphragm and into the stomach.
2:43
So that is the curvatures of the esophagus. Another thing we need to know about the esophagus
Constrictions of the Esophagus
2:47
is that it’s going to have some constrictions. Depending on the tone of the constrictions, we
2:53
can divide them into anatomical constrictors that are there by anatomical development. Therefore,
2:58
they will continue to be there even when there is no life in the organism. And then we got something
3:03
called physiological constrictions, which function only in a living body, and you’ll understand why
3:08
in a minute. And here to navigate, we’ll add a vertebral column to know at which level
3:14
the different constrictions are located. First, we got the pharyngoesophageal constrictor,
3:19
which lies at the border between the pharynx and the Esophagus at the opening called ostium
3:24
esophageum, remember this one? It’s at the level of the 6-7th cervical vertebrae. This
3:29
one consists of skeletal muscles, and this is what I want you to think of also, you have different
3:34
muscles along a different part of the Esophagus, The physiological constrictors are all smooth
3:40
muscle, so you kind of get a sense of why they’re called physiological constrictors.
3:44
They’re smooth muscle, so you’re not in control of them because they’re
3:48
controlled by the autonomic nervous system. And after the body has lost it’s functions,
3:53
the physiological constrictions are going to relgax and dissapprear with it. Alright, so the
3:58
pharyngoesophageal constriction is all skeletal muscles, and it closes off when breathing. Next
4:05
We have the bronchioaortic constriction situated behind the left principal bronchus
4:10
at the level of the 4th thoracic vertebra. Then we have the phrenic constrictor,
4:14
or the diaphragmatic constrictor. I want you to remember this word, “phrenic” because you’re going
4:19
to see this word a lot when you look at many structures associated with eh diaphragm. After
4:23
all, phrenic is a general anatomical term used to describe structures related to the diaphragm. So,
4:28
the phrenic contractor is at the Esophageal Hiatus at the level of the 10th thoracic vertebra.
4:34
So those are the anatomical constrictors, now let’s look at the physiological constrictions.
4:39
Remember those are made up of smooth muscle. The first physiological constriction is at the
4:44
level of the 8-9th thoracic vertebrae, I had to add the aorta here to show it better, because this
4:50
physiological constriction is situated right where the Esophagus crosses the aorta, as you see here.
4:56
So the last constrictor is where the Esophagus terminates into the stomach at the region of
5:01
the 11th thoracic vertebra. This one is called the lower esophageal sphincter. So that’s all for the
5:07
constrictions of the esophagus. The last thing we’re gonna look at in this video, is taking a
Layers of the Esophageal Wall
5:12
small section of the esophagus, and look at the layers of the esophageal wall, as you see here!
5:18
And just so you get the orientation right, remember the lumen Is here,
5:22
so this is the inner layer of the tube. The word Lumen just means a hollow space
5:28
inside a tube, so this side is the inner layer of the esophagus.
5:33
Alright so the First layer of the esophagus is the tunica mucosa, which is a layer of stratified
5:38
squamous non keratinized epithelium. And right under the epithelia, there’s gonna be mucus glands
5:44
to lubricate the surface, and blood vessels and nerves and lymphoid nodules, we’ll just
5:50
call them vasculature. And it’s all supported by lamina muscularis mucosa, as you see here in red.
5:56
Underneath the mucosa layer we have Tela submucosa, and keep in mind that tunica means
6:02
a layer a tissue, while tela means a web like or loose tissue, so all the layers are tunica,
6:09
except for tela submucosa, because in this layer you’ll find loose connective tissue together with
6:14
some esophageal glands which produce mucin for lubrication, and they also have esophageal cardiac
6:22
glands which produce neutral mucin that protects the Esophagus fromt the acidic gastric juice
6:28
because remember the contain hydrochloric acid, which might damage the tunica mucosa, so it’s
6:36
important to have somrthing to neutralize the hydrochloric acid in case there’s any condition
6:41
that causes reflux of gatric content.. SO that’s the tela submucosa. Tehn after that we have
6:50
Tunica muscularis which consisit of two layers. The inner layer is a circular layer muscle layer,
6:56
or circular muscle fibers because they’re arranged circularly, while the outer layer is longitudinal
7:02
muscle fibers. And remember what I said about the different types of muscle layers along
7:06
different part of the Esophagus. The upper third of the Esophagus is
7:10
normally straited skeletal muscle, and then it’s gradually replaced by smooth muscle tissue, and
7:17
then the lower third of the Esophagus is all smooth muscles. So that’s this layer
7:22
The last layer is a protective outer layer, and it consists of either fibrous tunica adventitia
7:29
or a serous tunica serosa. In the Cervical and Thoracic region, the esophagus is covered by a
7:35
thick connective tissue called tunica adventitia. But the moment the eosphagus goes through the
7:41
diaphragm and becomes the abdominal part, it meets something called the peritoneum which
7:47
we’ll talk about in a separate video. But the peritoneum is what protects the abdominal organs
7:52
from external pressure, but it also forms a serous coat around the organs so that organs can slide,
7:59
without friction. So what the peritoneum does is that it goes along and grabs the Esophagus
8:05
at the abdominal region and forms a serous coat called a tunica serosa. That’s why only the
8:11
abdominal part consists of tunica serosa around it, while the rest consist of tunica adventitia.
8:18
So that was all I had for the Anatomy of the Esophagus. If you found this video helpful,
8:22
please put a like, share, comment. Whatever you find convenient to you.
8:26
The next video in the digestive system is going to about is about the stomach