Peritoneum: Definitions

by James Pickering, PhD

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    00:00 So let's start off with some important definitions and there is lots of definitions that needs to be described in relation to this peritoneum.

    00:07 So let's start off with visceral peritoneum. This is a portion of the peritoneal membrane that is tightly adhered to a viscera. So tightly adhere to say the small intestine.

    00:18 If you are familiar with the thorax then this is the same as visceral pleura that was tightly adhered to the lungs. So we have visceral peritoneum. And in this diagram we can see this region around here would be visceral peritoneum.

    00:36 This tightly adhered to the small intestine.

    00:40 Parietal peritoneum, so visceral peritoneum, parietal peritoneum is what is adhered to the inside of the abdominopelvic wall.

    00:49 So this is the layer of peritoneum that lines the body wall that lines the anterior abdominal wall, the lateral abdominal wall and forms a sheet over the posterior abdominal wall.

    01:00 So this here is parietal peritoneum and parietal peritoneum can actually just run over an organ. It can just run over an organ like this and we can say this like is the kidney or the pancreas. And the parietal peritoneum just runs over the top of it.

    01:18 Now visceral peritoneum and parietal peritoneum. We also have definitions to define the relationship of an organ to the peritoneum.

    01:31 And these can be even intraperitoneal organ or retroperitoneal organ.

    01:35 We mentioned retroperitoneal organs before when we spoke about the duodenum that is retroperitoneal organ; well, the vast majority of it is.

    01:46 The kidneys are retroperitoneal organ. The pancreas is a retroperitoneal organ.

    01:52 And what I mean is by retroperitoneal organ is that this organ is positioned between the body wall and the peritoneum.

    02:01 Just like in this example we have the kidneys Here we have got the body wall in black and here is the body wall in black and red is our parietal peritoneum.

    02:09 This organ the kidney is between the body wall and the peritoneum. So it's retroperitoneal.

    02:17 And intraperitoneal organ is an organ that is completely surrounded by the peritoneum. And we have a series of these organs like the stomach, the spleen, the small intestine was surrounded by peritoneum. So here we could have the stomach, lets say, or the spleen.

    02:38 And this is where it is completely surrounded.

    02:42 Typically it will all be suspended via the mesentery.

    02:47 And here we can have mesentery.

    02:51 Now mesentery is a double layer of peritoneum.

    02:55 We can imagine the parietal peritoneum coming in this direction. And the parietal peritoneum coming in this direction.

    03:02 And where these two converge they then adhere and they move upwards where they can then surround the organ. So they converge, they move upwards and then they surround the organs.

    03:15 And this mesentery is really, really important because running through the mesentery are going to be various blood vessels, are going to be nerves, are going to be lymph allowing that organ to function.

    03:31 But the advantage of having the mesentery is it gives the organ mobility.

    03:38 Allows it to move around within the abdominal cavity, it's not restricted.

    03:43 And this is an intraperitoneal organ suspended by this mesentery.

    03:50 So that's a series of definitions to start off with.

    03:52 We spoke about retoperitoneal organs like the kidneys.

    03:59 But we also have organs which are known as being secondarily retroperitoneal.

    04:05 And these organs were initially intraperitoneal and suspended by a mesentery, just like we have here.

    04:13 So if for example we say this is a piece of colon then that piece of colon is suspended from the body wall via this mesentery via this mesentery.

    04:28 And during development, the small intestine grow a lot faster and to a greater extent than the large intestine.

    04:37 Now we know the position of the small intestine is right in the middle of the abdomen.

    04:44 And the large intestine is being pushed to one side.

    04:46 Now the consequence of that massive increase in growth of the small intestine is that it actually push the ascending and descending colons to their lateral margins.

    04:59 So what happened is that originally the large intestine was all suspended by this mesentery.

    05:08 But as the small intestine increased in size, so it pushed and it pushed the large intestine. Its ascending, descending portion to one side. It pushed it to one side so the mesentery actually collapsed. Which is what we can see here.

    05:28 So they actually; an organ like the ascending or the descending colon started off having a mesentery.

    05:36 But this mesentery actually then blended with the parietal peritoneum that was on the body wall.

    05:45 So originally it was an intraperitoneal organ suspended with mesentery.

    05:50 But during development it has assumed as the retroperitoneal position.

    05:54 And therefore we call it secondarily retroperitoneal.

    05:59 It is retroperitoneal due to a different process than the kidneys or the pancreas.

    06:06 Other secondarily retroperitoneal organs include the duodenum as well.

    06:09 These organs that are originally started intraperitoneal but got pushed laterally due to expansion of the small intestine, the jejunum and the ileum.

    06:18 So they then blended, their mesenteries blended with the posterior abdominal walls, parietal peritoneum and become secondarily retroperitoneal.

    06:30 So that's an another important definition. Some more definitions...

    06:34 Mesenteries, peritoneal ligaments and the omenta.

    06:39 These are double layers of peritoneum that support and suspend the abdominal viscera.

    06:44 Let's just look at the mesenteries first. I mentioned mesenteries in the previous slide.

    06:52 These are the important conduits for blood vessels, nerves and lymphatics.

    06:57 A real good example is the small intestine mesentery so called the mesentery. It's very extensive and runs only about 5 or 6 cm from the upper left quadrant to the lower right quadrant.

    07:10 And the mesentery fans out; it fans out and then attaches, its free edge attaches to the jejunum and the ileum.

    07:18 That gives the jejunum and the ileum great mobility to move freely.

    07:23 We have an another one which is the transverse mesocolon but we could have the sigmoid mesocolon as other example.

    07:33 The mesentey that was the most extensive and it allows the branches of the superior mesenteric artery to run up through it to supply the small intestine with its blood, its nutrients.

    07:43 We also have what are known as the peritoneal ligaments.

    07:47 And these are double layers of peritoneum again and they specifically attach an organ to another organ or attach the organ to the body wall.

    07:58 For example the liver is attached to the anterior abdominal wall via the falciform ligament and we will come to know more about the falciform ligament later on.

    08:08 The stomach is attached to the spleen via the gastro, stomach, splenic, spleen, ligament, the gastrosplenic ligament.

    08:17 So the falciform ligament is associated with the liver and then we have the gastrosplenic which is associated with the stomach.

    08:25 And the splenic which is associated with the spleen.

    08:28 And these two are in communication, the gastrosplenic ligament.

    08:34 Again allowing these organs to have their structure, to have their position retained within the abdomen. We also have an omenta.

    08:42 Now the omenta, a greater omentum and the lesser omentum are associated with the stomach and we have seen these before.

    08:50 We saw the greater omentum where it was dangling down from the stomach.

    08:52 And then it attaches to transverse colon; we will look at that in the next few slides.

    08:58 And we spoke about the lesser omentum before as well connecting the lesser curvature of the stomach to the liver.

    About the Lecture

    The lecture Peritoneum: Definitions by James Pickering, PhD is from the course Abdomen.

    Included Quiz Questions

    1. Spleen
    2. Duodenum
    3. Kidneys
    4. Pancreas
    5. Esophagus
    1. Liver
    2. Spleen
    3. Stomach
    4. Pancreas
    5. Gallbladder
    1. It contains nerves, blood vessels, and lymphatics.
    2. It is derived from visceral peritoneum and parietal peritoneum.
    3. It is derived from remnants of Rathke's pouch.
    4. It attaches one organ to another.
    5. It contains only blood vessels.
    1. Ascending and descending colon
    2. Bladder
    3. Suprarenal glands
    4. Ureters
    5. Kidney

    Author of lecture Peritoneum: Definitions

     James Pickering, PhD

    James Pickering, PhD

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    By Jared P. on 11. August 2021 for Peritoneum: Definitions

    Excellent explanation, the definitions are clear, concise and the representations in the slides are really good.