Video: Stomach in situ

Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, we're going to be talking about the stomach in situ. So what we're going to be doing here on this tutorial is mainly exploring this image that you see now on the screen which shows the anterior view of the abdomen. If we were to then cut all the muscles of the anterior wall – so the anterior trunk wall muscles are all removed here – and a few other structures then expose the stomach here, you can see that we're just moving back the liver so we can then show a bit more or expose the stomach. You can also see here a bit of the colon, or the large intestine, the gallbladder, and a few other structures that we're going to be talking about here. So, we're going to look at all these structures that are found nearby the stomach.

As you probably know, the stomach is the most dilated part of the gastrointestinal tract and takes on a short J-shape. You can also see a bit of the stomach here on this image highlighted in green. Now, the stomach is positioned between the esophagus which you see here on this image and also the small intestine. The stomach is found in the epigastric, umbilical and left hypochondriac regions of the abdomen. Now, it can be subdivided into four parts: the cardiac part, the fundus, the gastric body, and also the pyloric part which we will be looking at on the next slides.

In this tutorial, we will not be going into great detail about histology of the stomach mucosa, however, I would like to mention that though there are four divisions of the stomach, only three are histological distinct. I would like to also give you a quick overview of the types of glands that are found on the lamina propria of the stomach and they are: First, the alkaline mucous-producing mucous neck cells. Now, this alkaline mucous protects the epithelium from self-digestion through gastric juices. Hydrogen and chloride ion secreting parietal cells. The hydrogen and chloride ions bound to then form hydrogen chloride or HCl that keeps the pH level of the stomach around 1 to 1.5. Pepsinogen and gastric lipase secreting chief cells. Pepsinogen, the inactive precursor of pepsin enzyme. There are also enteroendocrine cells. These cells secrete the hormones histamine, serotonin, cholecystokinin, somatostatin, gastrin, and endorphins.

Now, that we had a quick glance on the histology of the stomach, we're going to start talking about the parts. Starting with this one that you see here highlighted in green, this is the cardiac part of the stomach – notice here – this is the highlight, the cardiac part of the stomach. Now, this is a portion of the stomach near the lower esophageal sphincter where the contents from the esophagus are emptied into the stomach. And, at its terminal end, the esophagus joins the cardiac part of the stomach forming then the esophageal-stomach junction. This specific part of the gastrointestinal tract, the stratified squamous epithelium of the esophagus abruptly changes into the simple columnar mucus secreting epithelium of the cardiac part of the stomach.

The next structure we're going to be highlighting here is known as the fundus. This is the cranially located dome-like part formed by the upper curvature of the stomach. It lies in the left hypochondriac region of the abdomen just beneath the diaphragm which you see a little bit here on this image – notice the diaphragm. This part is usually filled with air and is separated by the cardia – by the cardiac incisura – which is also known as the cardiac notch.

The next structure we're going to be highlighting is known as – next part of the stomach to be more specific – the gastric body, or the body of the stomach. Now, this is the largest part of this organ. It forms the lesser curvature cranially which you can see here – this is the lesser curvature of the stomach – and also forms then the greater curvature caudally. Now, this central portion of the stomach is located between the cardia or fundus and the pyloric part.

The next part of the stomach we're going to be highlighting is then known as the pyloric part. It's located just after or below the gastric body. This distal segment of the stomach lined with mucosa that contains mucous secreting cells or mucous neck cells and enteroendocrine cells.

The next structure we're going to be highlighting now that you see here is the pylorus. The pylorus sphincter marks the lower end of the stomach and the entrance to the duodenum which you see a little bit here, the duodenum. It is the most distal part of the stomach. It is marked on the surface by the pyloric constriction that contains a thickened ring of gastric circular muscle known as the pyloric sphincter.

The next structure I would like to highlight here – one that I mentioned before – this is known as the greater curvature of the stomach. This is a large convex curvature of the stomach directed right and downward and is about 4 to 5 times longer than the lesser curvature. So, as you can see, it starts at the cardiac notch of the cardiac orifice and then goes all the way to end at the pyloric part of the stomach. In terms of blood supply, the short gastric arteries and also gastric branches of the left gastroepiploic artery and gastric branches of the right gastroepiploic artery provide then blood supply to the greater curvature of the stomach. Now, please note that you may also come across the left and right gastro-omental arteries being referred to as the gastroepiploic artery. Now, these terms are used interchangeably.

The next structure we're going to be highlighting – we mentioned before – this is then the lesser curvature of the stomach which is a small curvature of this organ going from the cardia to the pyloric orifice that is then directed to the right and also downwards. It provides attachment for the hepatogastric ligament and receives blood supply from both the left and right gastric arteries.

The next structure we're going to be highlighting here is known as the duodenum. Now, this is a continuation of the stomach, and the duodenum is a C-shaped loop that makes the initial portion of the small intestine. Now, this structure is located adjacent to the head of the pancreas and is retroperitoneal except for the first part. Now, this section of the small intestine connects to the stomach and the jejunum. The jejunum is also another continuation of the small intestine and the duodenum is comprised of four anatomical parts: the superior part which is the horizontal first part of the duodenum is known as the ampulla or duodenal cap and most duodenal ulcers occur in this part of the duodenum – just a reminder of a few things you need to know whenever we talk about the parts of the duodenum.

The other part of the duodenum is known as the descending part. So, the lateral descending part that starts at the superior duodenal flexure and ends at the inferior duodenal flexure. This part of the duodenum contains the major duodenal papilla which you can see here highlighted in green and this structure is the opening for the pancreatic duct. There is also a horizontal part – this horizontal segment – is located below the head of the pancreas and begins at the inferior duodenal flexure and passes in front of the inferior vena cava, the abdominal aorta and also the vertebral column. And, finally, where you can find also on the duodenum, the descending part that is located to the left of the head of the pancreas and this part passes upwards up to the duodenojejunal flexure.

Now, to have a better view and understanding of all of these parts, I suggest you look at another tutorial we have here at Kenhub where we explore the duodenum in greater detail. Now, the duodenum receives partially digested food from the stomach and plays a vital role in the chemical digestion of food in preparation for absorption in the small intestine. Now, the duodenum contains mucous secreting glands called the Brunner's (9:58) glands and these are found only in the duodenum. It is supplied by the superior pancreaticoduodenal artery, a branch of the gastroduodenal artery, and also supplied by the inferior pancreaticoduodenal artery which is a branch of the superior mesenteric artery – just a few reminders of the blood supply of the duodenum.

We're now ready to move on to another structure that we see here clearly now highlighted in green. This is known as the greater omentum. The greater omentum is a double-layered apron-like fold of peritoneum that is fixed to the greater curvature of the stomach hanging down and also reflecting back on itself to then ascend to attach inferiorly to the transverse colon. The greater omentum contains variable amounts of fat and contributes to immunity owing to its macrophage collection. In addition, it is known that the greater omentum isolates wounds and infections in the peritoneal cavity. Vascular supply to the greater omentum comes from the left and right gastroepiploic arteries which are branches from the celiac tract.

If there is a greater omentum, there should be then a lesser one – the lesser omentum. This one is also a double-layer peritoneal sheath that extends from the liver to the lesser curvature of the stomach and you can clearly see here on this image how it extends from the liver here all the way to the lesser curvature of the stomach. Just a reminder here that the omental foramen which we will see in the next slide is found at the right border of the lesser omentum. This double-layer of peritoneum also will be transmitting various structures including lymphatics, portal vein, hepatic artery, left gastric artery and gastric veins as well as the common bile duct and hepatic plexus.

Next, we're going to be seeing then one of the structures I mentioned before now highlighted in green – notice here – this is then the omental foramen. So, at the right border of the lesser omentum, the two layers are continuous and form a free margin which constitutes the anterior border of the omental foramen. Now, the omental foramen – also known as the epiploic foramen or foramen of Winslow – is found between the greater sac of the abdomen and the omental bursa also known as the lesser sac. Now, this foramen is an opening or a passage of communication that borders the lesser omentum, the peritoneal coverings of the inferior vena cava, the caudal lobe of the liver, and the first part of the duodenum and also the gastrointestinal and splenorenal ligaments.

Next, I would like to highlight one structure that I mentioned here so you can have a bit of understanding what is happening around the stomach. This highlighted structure is the diaphragm. And as I mentioned before, the fundus of the stomach is located beneath the thoracic diaphragm and, in this illustration, you can see a small portion of the skeletal muscle sheath in relation to the stomach. Now, the esophagus descends into the abdominal cavity through this orifice – I would say – or this hole in the diaphragm which is known as the esophageal hiatus to then attach to the cardia of the stomach.

The next thing I would like to highlight here on this image which you see here is the parietal peritoneum. It's very close to the diaphragm as you can see in the peritoneal cavity we see then the parietal peritoneum. Now, the parietal peritoneum is one of the two mesothelial layers that make up the peritoneum. The other layer being the visceral peritoneum. These two layers are inseparable. The parietal peritoneum covers the internal abdominal walls and is supplied by the regional vasculature whereas the visceral peritoneum encapsulates the individual abdominal organs.

The next structure we're going to be highlighting here that you see is this is clearly the right lobe of the liver. One of the structures of the abdomen that borders the stomach is the right lobe of the liver which you see here. It's separated from the left lobe of the liver by the falciform ligament which we will talk about later on on this tutorial and also by the ligamentum venosum posteriorly which is continuous with the round ligament of the liver caudally. You can also see here then the left lobe of the liver – so this is the smaller left lobe of the liver – which is here bordering the superior part of the stomach near the fundus. It's located in the epigastric and hypochondriac regions and the left lobe is separated from the right lobe by the falciform venosum and round ligaments of the liver.

I'd like to show a couple of these ligaments – one of them that you can see here – this is the round ligament of the liver which we just saw that the left and right lobes of the liver are separated on their visceral surface by the round ligament of the liver. This ligament is a remnant of the fetal umbilical vein and it divides the left part of the liver into medial and lateral sections. It exits in the free edge of the falciform ligament and inserts around the umbilicus.

Speaking of which, we're going to also show you see here this ligament which is then the falciform ligament. Notice here on this image below we have the anterior view of the liver as we were to remove all these tools and just have the liver resting then on top of some of these structures but now seen from an anterior view. The other ligament that is then visible here highlighted in green is the falciform ligament of the liver that extends from the upper part or the upper convex surface of the liver to the diaphragm in the anterior abdominal wall allowing then the liver to be attached to the anterior abdominal wall.

Another structure you can see here, now this green structure that we just changed the highlight here, this is the gallbladder. This is another structure closely located to the stomach and the gallbladder serves as the reservoir for bile produced by the liver and is then comprised of a fundus, body and neck which we will look into on a separate tutorial but just to give you an idea of the structures that you find, or the structure of the gallbladder. Now, this pear-shaped organ receives blood supply from the cystic artery and receives sympathetic innervation from the celiac plexus, parasympathetic innervation from then the tenth cranial nerve – the vagus nerve – and also sensory innervation from the right phrenic nerve.

One structure you can see here on this image as well is known as the ascending colon and we have here just a bit of the large intestine on this image but I wanted to show you the large intestine here completely so you can see that this is the ascending colon which is the part that we see here of this image of the stomach in situ. So, this is the part of the large intestine that ascends retroperitoneally on the right side. It is the section of the large intestine between the cecum which is located inferior to it and the transverse colon superiorly – so, as a reminder here, the part between the cecum and the transverse colon, which is this portion. Now, it receives sympathetic innervation from the thoracic splanchnic nerves and parasympathetic innervation from the vagus nerve.

You can also see a little bit here now of the transverse colon and, so, immediately after the ascending colon, we see this part of the large intestine. Now, the transverse colon is the part of the large intestine between the right colic flexure and the left colic flexure – to be more specific, this is the right colic flexure and this is the left one. This transverse segment is the most movable part of the colon and is located intraperitoneally and here we can see a small portion of the transverse colon on this image of the stomach in situ. The transverse colon receives blood supply from the middle colic artery, a branch of the superior mesenteric artery.

If we look here also on this image of the stomach in situ, we see this structure – a little bit of this structure here – just to show you that we have a kidney – to be more specific, the right kidney here. So, posterior to the right colic flexure, we see this small part a very important organ which is then the right kidney. The kidneys, as you know, they play a very important role in the urinary system. Now, they are bean-shaped organs – the very famous bean-shaped organs – that are responsible for the removal of the byproducts of metabolism. The kidneys are located on the posterior wall of your abdomen in the retroperitoneal space.

The right kidney is located slightly lower than the left kidney due to the position of the liver in the abdominal cavity. In this illustration, you can see a portion of the right kidney in relation to the stomach. And here on this image, if I remove the stomach and the liver, you can see then the right kidney here highlighted in green and also the left one.

Finally, here on back to this image of the stomach in situ, we find this structure highlighted in green which is a very important one, the spleen. Found in the left side of the peritoneal cavity, we see then this organ. Now, the spleen is the largest immunological organ of the body. Here, you can see a portion of the spleen in relation to the stomach. It is located intraperitoneally inferior to the diaphragm on the left side of your abdomen. And if I remove here the stomach, you can then see the spleen highlighted in green on the left side of your abdomen. The main functions of the spleen include immune responses – involved in immune responses – also synthesis of antibodies, filtration of blood, also lymphopoiesis, phagocytosis.