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00:00We all understand the duty of police officers.
00:02Yes, I'm talking about those real-life superheroes who protect us, our property, and investigate crimes.
00:08I'm not talking about those friendly folk who you might bump into at a cops and robbers theme night at one of your local nightclubs.
00:14But did you know that you actually have a police officer in your abdomen?
00:17Well, today we're going to be learning about that officer, which is the greater omentum.
00:21Before we start talking about the greater omentum, it's important that we orientate ourselves.
00:25And in this illustration, which will feature heavily in this tutorial, we can see an anterior view of the abdominal cavity.
00:32The layers of the anterior abdominal wall, including the skin, the fat, and muscles, have been dissected away.
00:38And this has been done to reveal the membranes and organs within the abdomen.
00:41Here we can see the greater omentum and some associated structures, such as the small intestine, the large intestine, the stomach, and the liver.
00:49If I told you that the greater omentum is the largest fold of visceral peritoneum in the abdominal cavity, it might not mean that much to you.
00:57So, I think it's important that I give you some background information and define a few key terms.
01:01Let's start with the peritoneum.
01:03If we look at our image, we can see the peritoneum highlighted in green in the mid-sagittal plane.
01:08And this is the plane that effectively cuts the body into two equal halves.
01:12So, the peritoneum is a continuous serous membrane that lines the abdominal cavity and wraps around the abdominal organs.
01:19It can be divided into two parts, the parietal peritoneum and the visceral peritoneum.
01:23The parietal peritoneum is the portion of the peritoneum that lines the abdominal cavity, as you can see in our image here.
01:30Whereas the visceral peritoneum wraps around the abdominal organs or the viscera.
01:34And between these two layers, there's a potential space known as the peritoneal cavity, which contains a small amount of lubricating fluid.
01:41The peritoneum consists of many folds and ligaments, and the largest fold of visceral peritoneum in the abdominal cavity is the greater omentum.
01:49So, now you'll definitely know what I'm talking about.
01:52Now that we've oriented ourselves and I provided some background information, let me give you a quick overview of what we're going to be talking about in today's tutorial.
02:00We'll start with the structure and function of the greater omentum, followed by the blood supply, and then we'll go on to look at some associated structures.
02:07And finally, we'll conclude our tutorial with some clinical notes relating to the greater omentum.
02:13So, let's begin by talking about the structure of the greater omentum.
02:19The greater omentum is also known as the epiploon, which is derived from the Greek word epipleo, meaning floating on the surface of something, which in this case is the surface of the intestines.
02:30The greater omentum is usually thin and has a perforated appearance.
02:35It contains variable amounts of adipose tissue or fat and consists of an anterior sheet and a posterior sheet, each made up of two layers.
02:43Therefore, the greater omentum consists of four layers in total.
02:47So, if we go back to our image showing the abdominal cavity in the mid-sagittal plane, we can see the organisation of the greater omentum a lot more clearly.
02:55The anterior sheet descends from the greater curvature of the stomach, then folds under itself to become the posterior sheet.
03:02The posterior sheet then passes superiorly to attach to the structure here, which is the transverse colon.
03:08Okay, now that we're familiar with the structure of the greater omentum, let's move on to talk about its function.
03:13So, this is the section of the tutorial where we find out why it is called the policeman of the abdomen.
03:19So, one of the functions of the greater omentum is fat deposition, as it contains variable amounts of adipose tissue.
03:26Macrophages contained within milky spots of the greater omentum help fight infections of the peritoneum,
03:31and it also may physically limit the spread of intraperitoneal infections.
03:36The greater omentum often adheres to inflamed visceral organs within the abdomen, which is thought to limit the spread of infection.
03:43And the last two functions are why it's commonly called the police officer of the abdomen.
03:48Now for the blood supply.
03:50The blood supply of the greater omentum is derived from these arteries just here, the right and the left gastroepiploic arteries.
03:58And these arteries run along the greater curvature of the stomach to anastomose with one another within the anterior sheet of the greater omentum.
04:05They give off many omental branches, which we can see the start of just here, that travel the length of the greater omentum, supplying it with oxygenated blood.
04:13The venous drainage of the greater omentum varies that of the arterial supply, draining into the gastroepiploic veins.
04:20Let's move on now to look at some relations or associated structures of the greater omentum,
04:25because knowing the relations of the greater omentum is really important in clinical practice when palpating the abdomen, and even more so in abdominal surgery.
04:34So let's go back to our original image and start with the liver, specifically the right lobe of the liver.
04:40So superior to the greater omentum, we can see the right lobe of the liver.
04:44And the right lobe of the liver is located in the right upper quadrant of the abdomen, which is also known as the right upper hypochondrium.
04:51If we look at the liver on its own, we can clearly see that the right lobe is the larger of the two lobes.
04:58To the left-hand side of the right lobe is, of course, the left lobe of the liver.
05:02The left lobe is located in the epigastrium and towards the upper left hypochondrium.
05:07And as we just mentioned, the left lobe is the smaller of the two lobes.
05:11Note that there are two further accessory lobes of the liver, the chordate lobe and the quadrate lobe.
05:17These lobes arise from the right lobe and are located on the visceral surface of the liver.
05:22Therefore, we can't see them in these images.
05:25Let's have a look at some peritoneal ligaments associated with the liver, starting with the falciform ligament of the liver.
05:31And as you can see, this ligament separates the right and the left lobes of the liver and connects the liver to the anterior abdominal wall.
05:38To the right of the falciform ligament, we can see another peritoneal ligament, which is the round ligament of the liver.
05:44And this is also commonly known as the ligamentum teres.
05:47The round ligament of the liver is a chord-like ligament that is actually the remnant of the fetal left umbilical vein, which normally deteriorates soon after birth.
05:58So if we take a look at the liver on its own, we can see the falciform ligament here.
06:02And at its base or free edge, we can see the round ligament.
06:06Tucked under the right lobe of the liver, we can see this little structure here, which is the gallbladder.
06:11If we reflect the liver upwards, we can see this pouch-like organ a little bit better.
06:16And the gallbladder stores bile, which is produced by the liver.
06:19The next structure we're going to talk about is the stomach.
06:22And the stomach is part of the GI tract and is involved in digestion.
06:26And as we mentioned earlier, it is also the site of attachment for the anterior sheet of the greater omentum.
06:31Let's move on to look at the large intestine, starting with the ascending colon.
06:36The ascending colon is the second part of the large intestine and it comes after the cecum, which we can see if we look at the large intestine in isolation.
06:45As we can see from our first image, it is located to the right of the greater omentum and ascends from the lower right quadrant of the abdomen to the upper right quadrant.
06:55If we dissect away the greater omentum and some of the abdominal organs, we can also see the right colic flexure.
07:02And the right colic flexure is the transition point between the ascending colon and the transverse colon.
07:08So, let's look at the transverse colon.
07:11The transverse colon is the third part of the large intestine and we can see it here highlighted in green.
07:17As we mentioned earlier, it is the site of attachment for the posterior sheet of the greater omentum.
07:22While we're here, let's talk about the blood supply of the transverse colon.
07:26And just so you know what we're looking at, in our image, the greater omentum has been reflected upwards so that we can see the structures we're about to talk about more clearly.
07:34And running within the transverse mesocolon, a fold of peritoneum that connects the transverse colon to the posterior wall of the abdomen, we can see the middle colic artery.
07:44And the middle colic artery is a branch of the superior mesenteric artery and it supplies the transverse colon.
07:50Immediately inferior to the middle colic artery is the middle colic vein, a tributary of the superior mesenteric vein.
07:57And the middle colic vein drains the transverse colon and follows the path of the middle colic artery.
08:03Now back to the large intestine.
08:05If we look to the left of the greater omentum, we can just about see a structure highlighted in green, which is in continuation with the transverse colon.
08:13This structure is named the left colic flexure.
08:16So in the following illustration, the greater omentum and several organs have been dissected away to give us a better view of the left colic flexure.
08:25And this is also known as the spleenic flexure, because as you can see, this flexure is in close proximity to the spleen.
08:32The left colic flexure is the point at which the transverse colon turns downwards to become the descending colon.
08:38So let's have a look at the descending colon.
08:42Again, we've reflected the omentum upwards so that we can see the descending colon, which is the fourth part of the large intestine.
08:48And it descends from the left upper quadrant of the abdomen to the left lower quadrant.
08:54And note that the large intestine consists of five parts.
08:56And the fifth part is known as the sigmoid colon, which we can see here.
09:01Now let's move on and talk about the small intestine, starting with the jejunum.
09:06So as we mentioned earlier, the greater omentum floats on the surface of the intestines.
09:11So we have to reflect it upwards to see this structure.
09:14The jejunum is continuous with the duodenum, which is the first part of the small intestine.
09:19Therefore, it is the second part of the small intestine.
09:22And as we can see, it occupies the central part of the abdominal cavity.
09:27Next, we can see the third and final part of the small intestine, which is the ileum.
09:31The ileum connects to the large intestine via the ileocecal junction.
09:37Inferior to the ileum and moving downwards towards the lower abdomen, we can see the urinary bladder.
09:43And the urinary bladder stores urine transported by the kidneys before it leaves the body via the urethra.
09:49So before we go on to our clinical notes, I have one more structure that I must mention.
09:54If we have a greater omentum, then we must, of course, have a lesser omentum.
09:58So the lesser omentum is a double layer of visceral peritoneum, and it attaches from the lesser curvature of the stomach and the proximal part of the duodenum to the liver.
10:07Okay, time for some clinical notes on the greater omentum.
10:15An omentectomy refers to the complete or partial surgical removal of the omentum.
10:21And this surgery is usually recommended to patients if cancerous cells have been invaded or metastasized to the greater omentum.
10:28Most commonly, these cancers have originated in the stomach, the ovaries, or in the large intestine.
10:34And as the metastases develop, the greater omentum becomes thickened.
10:37And in radiology, this is referred to as an omental cake.
10:41And that's definitely not something you'd want to serve up for dessert.
10:44Okay, thanks for sticking with me.
10:46We've now reached the end of our tutorial.
10:48Before we bring it to a close, however, let's, of course, quickly summarize what we've learned today.
10:52So today, we looked at the greater omentum.
10:54And we talked about its structure and how it attaches to the greater curvature of the stomach and to the transverse colon.
11:00We then talked about its function as the police officer of the abdomen.
11:04We talked about its blood supply, which is derived from the right and left gastroepiploic arteries.
11:09Then we talked about some associated structures, including the liver, the stomach, and the large and small intestine.
11:14And finally, we concluded our tutorial with some clinical notes on the greater omentum.
11:19So that brings us to the end of our tutorial on the greater omentum.
11:22I hope you enjoyed it.
11:23Thanks for watching.
11:24Happy studying.
11:39Happy ahain, thanks.
11:55Thank you very much.
11:56If you guys enjoyed it, we wanted to see you once in the next intencion.
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