Description

Anatomy of the Stomach

Topography of Gaster:

• Holotopy: Located in the Epigastric Region and Left Hypochondriac Region (Left Upper Quadrant).
• Extends from the Cardiac Orifice (Ostium Cardiacum) to the Pyloric Orifice (Ostium Pyloricum).

Syntopy (Relations to Neighboring Structures):

• Anterior Wall: Diaphragm, Liver, Anterior Abdominal Wall
• Posterior Wall: Left Kidney, Spleen, Pancreas, Transverse Colon

External Features of the Stomach:

• Lesser Curvature (Curvatura Minor)
  • Angular Notch (Incisura Angularis)
• Greater Curvature (Curvatura Major)
  • Cardiac Notch (Incisura Cardialis)

Parts of the Stomach:

• Cardiac Part (Pars Cardiaca)
• Fundus (Fundus Gastricus)
• Body (Corpus Gastricum)
• Pyloric Part (Pars Pylorica)
  • Pyloric Antrum (Antrum Pyloricum)
  • Pyloric Canal (Canalis Pyloricus)

Layers of the Gastric Wall:

• Tunica Mucosa (2-3 mm thick)
  • Gastric Folds (Plicae Gastricae)
  • Gastric Areas (Areae Gastricae)
  • Simple Columnar Epithelium
  • Gastric Pits (Foveolae Gastricae)
  • Lamina Propria
  • Muscularis Mucosae
• Tela Submucosa
  • Loose connective tissue
• Tunica Muscularis (Smooth Muscle Layers)
  • Inner: Oblique Muscle Layer
  • Middle: Circular Muscle Layer
    • Pyloric Sphincter (Musculus Sphincter Pyloricus)
  • Outer: Longitudinal Muscle Layer
• Tunica Serosa
  • Formed by the peritoneum

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 stomach.
0:04
So in the last video, we went through the anatomy of the Esophagus. Now the step after
0:09
the Esophagus is the Stomach, as you see here. So in this video, we’re first going to go through
0:14
the topography of the stomach, basically where it is related to surrounding structures. After that,
0:21
we’re going to look at the external features of the stomach and the different parts of it. Then
0:26
we’ll go through the layers of the gastric wall. Now. Let’s go ahead and start with the topography.
Topography of the Stomach
0:31
So the stomach lies in the epigastric region and the left hypochondriac region, as you see here.
0:36
Or, if you’re studying using the 4 quadrant division,
0:38
you’ll find it in the left upper quadrant. If we expose the stomach a little more,
0:44
you’ll see that it starts from the abdominal part of the Esophagus,
0:48
and then it curves to the left and then reaches out to the small intestine.
0:53
And these two openings that go towards the Esophagus and the small intestine has unique names
0:59
The opening by which the Esophagus communicates with the stomach is known as the cardiac orifice
1:06
at the level of the 10th to 11th thoracic vertebrae. And the opening by which the
1:11
stomach communicates with the duodenum of the small intestine is known as the pyloric orifice
1:16
at the level of the 1st lumbar vertebra So if we look at the stomach from this
1:21
perspective, laterally, you’ll see this. The stomach has an Anterior wall and a
1:27
Posterior wall. So from this position, we can look at the
1:30
Syntopy, meaning the position of the Stomach To other organs. Anteriorly
1:36
We can find the Diaphragm being very close to the anterior wall; we’ll find the liver,
1:41
and we’ll also find the stomach facing the anterior abdominal wall aswell. And the
1:46
Posterior wall of the Stomach is close to the left kidney. You’ll also see the spleen,
1:51
the pancreas, and the transverse colon facing the posterior surface of the stomach as well.
External Features of the Stomach
1:56
So that was the Syntopy. Now, let’s go back and look at the external structures of the stomach.
2:01
We can see two distinct curvatures; we have the lesser curvature
2:06
Here. And since we have a lesser curvature, we also have a greater curvature here. On the
2:11
lesser curvature, we can find a slight depression Called the angular notch, or incisura angularis.
2:17
And on the greater curvature, we can also find a depression called
2:20
The cardiac notch of the Stomach, or incisura cardialis in Latin. Now, you should already
2:26
have a sense of where the Stomach is and the different external structures. Now let’s divide
Parts of the Stomach
2:32
the stomach into its parts. First, we have This part right here, the cardiac
2:36
Part. Then we have this portion right here
2:39
The fundus that’s the top elevation of the Stomach.
2:42
Then in the blue area, here is the body of the gaster.
2:46
And then the last portion is The pyloric part, which we divide
2:50
into two regions. We have the Pyloric antrum, which is
2:53
closest to the body of the gaster Then we have the pyloric canal,
2:57
which communicates with the duodenum of the small intestine. So already now, you can get a sense of
3:02
where the Stomach is and the different portions. But now we need to look at the walls of the
3:07
stomach because the stomach has some distinct features that are different from the rest of
3:12
the digestive system. And if you’re already familiar with the functions of the Stomach,
3:16
you’ll get a sense of why it’s built up like this. So let’s try to break this down together.
3:20
So first, we remove the outer layer of the Stomach, and then, we need to take a small
3:25
piece of it and look at it from a histological view. Keep in mind that the stomach does look
3:30
slightly different along the fundus, the body, and the pylorus. This is a slide from the body
3:36
of the stomach or corpus. But the layers are the same, and I’ll try to highlight the difference.
3:41
The innermost layer is called the Tunica mucosa, highlighted here in yellow.
3:46
And it’s usually 2-3cm thick. And if we look Closely into the lumen of the Stomach, you can
3:52
see that the tunica mucosa forms folds called the Gastric folds. And this slide I’m showing you is
Layers of the Gastric Wall
3:58
a section of one fold… Let me repeat that. Here are bumps, the large gastric folds.
4:05
They have some veeeery small bumps on them, called area gastricae,
4:09
which is essentially what we’re seeing here. So, the tunica mucosa is generally built up like this
4:14
It’s lined by simple columnar epithelium. Between them, there are gastric pits. And
4:20
you’ll find these mainly in the body and fundus of the stomach. They contain cells that produce HCL
4:27
and cells that produce digestive enzymes. There are many different cells in the stomach with
4:32
unique functions you’ll learn in histology and physiology.
4:35
Then underneath the epithelial tissue, you’ll find connective tissue with many blood vessels
4:40
and small lymphoid nodules, called lamina propria. Then there’s a muscle layer called
4:46
muscularis mucosa, which is a thin layer of smooth muscle cells at the base of the mucusoa
4:51
that support the tunica mucosa. So that is tunica mucosa.
4:55
And under it, you’ll always find Tela submucosa containing loose CT, along with
5:01
associated structures like BV. So next we have Tunica muscularis, and here is where this gets
5:07
interesting. Usually, in the digestive system, we only have two muscle layers in the tunica
5:13
muscularis. But this time we have 3. And also, keep in mind that these are all smooth muscles,
5:18
so you’re not really in control of them. Now let’s zoom in and look
5:21
at the layers in a little more detail. First, the inner layer is the oblique
5:25
muscle layer. This one consists of oblique muscle fibers that go from the cardiac notch
5:31
to the anterior and posterior walls. And then, the middle layer consists of circular muscle fibers,
5:37
and they form this sphincter between the stomach and the duodenum in the pyloric region called
5:42
the pyloric sphincter muscle. And just so you don’t confuse it with the sphincter between the
5:47
stomach and the Esophagus. The lower esophageal sphincter is formed by the smooth muscle of the
5:52
Esophagus, and it’s crucial to restrict the amount of acid going up to the Esophagus. There’s this
5:54
Gastroesophageal reflux disease where some people have this LES being very weak, so they get acid
6:01
reflux a lot, which in the long run can be very damaging to the mucosa of the Esophagus. But
6:07
that’s that one. And then The last layer is the The outer layer consisting of longitudinal
6:12
muscle fibers that are arranged along the lesser and the greater curvature.
6:17
So that is the tunica muscularis. And then lastly We have the tunica serosa,
6:22
which is formed by the peritoneum, now ill talk more about the peritoneum in a separate video,
6:26
but the peritoneum comes and grabs the Stomach along with all the other abdominal organs forming
6:32
a serous slippery surface called tunica serosa. So that was everything I had about the anatomy
6:39
of the Stomach. If you found this video helpful; Please put a like, share, comment. Whatever you
6:44
find convenient to you. Now the next video
6:46
In the digestive system is going to be about the small intestine,
6:49
which consists of the Duodenum, Jejunum and the Ileum