Peritoneum and peritoneal cavity
On a scale from lesser omentum to mesentery, how difficult do anatomy students find the peritoneum? We guess that your answer comes out of all the hard-to-imagine pouches, layers and sacs.
So let’s start with the basics; the Peritoneum is a serous membrane which lines the walls of the abdominal cavity and lies on abdominal and pelvic organs. Between its two layers – parietal and visceral – is the peritoneal cavity. The peritoneum functions to support and protect abdominopelvic organs.
|Definition||Serous membrane lining viscera and abdominal cavity wall|
Mesentery: mesentery proper, transverse mesocolon, sigmoid mesocolon, mesoappendix
Omenta: greater omentum, lesser omentum
Peritoneal ligaments: hepatogastric, hepatoduodenal, gastrophrenic, gastrosplenic, splenorenal, gastrocolic ligament
|Peritoneal divisions||Lesser sac (omental bursa)
Greater sac (supracolic and infracolic compartments)
|Function||Protection of the abdominopelvic organs
Connect organs with each other
Maintain the position of organs by suspending them with ligaments
Prevent friction while organs move
|Clinical relations||Ascites, peritonitis|
This article will discuss the anatomy of the peritoneum, including key related topics; peritoneal cavity, omenta, mesentery, ligaments, and peritoneal relations.
The peritoneum consists of two layers:
- Parietal peritoneum – an outer layer which adheres to the anterior and posterior abdominal walls.
- Visceral peritoneum – an inner layer which lines the abdominal organs. It's made when parietal peritoneum reflects from the abdominal wall to the viscera.
Although in adults the peritoneum looks like it’s scattered all over the place, there is a (embryo)logic reason behind it. During intrauterine development, the parietal peritoneum forms a closed sac occupying most of the abdominal cavity. At this time, abdominal organs are small and pressed against the posterior abdominal wall.
As organs develop and grow, they push into the peritoneum without entering the peritoneal cavity. The cavity squeezes through any available space that exists between the abdominal organs forming peritoneal folds and pouches. It is the same idea as pressing your hand into a balloon filled with water; the balloon changes shape around your hand but your hand doesn’t go inside the balloon. Likewise, no organs lie within this potential space.
The peritoneal cavity is a potential space found between the parietal and visceral layers of the peritoneum. The cavity is filled with a small amount of serous peritoneal fluid secreted by the mesothelial cells which line the peritoneum. Peritoneal fluid enables the peritoneal layers to slide against each other with little friction while following the subtle movements of the abdominopelvic organs.
When the peritoneum folds while following the lining of the organs, it forms pouches (recesses) which can be filled with fluid if there is an ongoing inflammation of adjacent organs. Examples of such recesses are the inferior recess of the lesser sac formed by the folding of the greater omentum, and the recto-uterine pouch (of Douglas) found between the uterus and rectum in females.
Learn more about the layers of the peritoneum and peritoneal cavity anatomy here.
There are two divisions of the peritoneal cavity: lesser sac (omental bursa) and greater sac.
Lesser sac (omental bursa)
The omental bursa or lesser sac is found posterior to the stomach and liver, and anterior to the pancreas and duodenum. The function of the lesser sac is to provide space for unhindered movement of the stomach. It has an irregular shape with one superior and one inferior recess. The superior recess is bordered by the diaphragm and the coronary ligament of the liver, while the inferior recess is found between the folding layers of the greater omentum.
The lesser sac communicates with the greater sac via the epiploic foramen (omental foramen) found posterior to the free edge of the lesser omentum. This foramen has clear borders:
- Anterior – hepatoduodenal ligament
- Posterior – inferior vena cava and the right crus of the diaphragm
- Superior – caudate lobe of the liver
- Inferior – superior part of the duodenum
Learn more about the omental bursa with these resources.
Greater sacThe greater sac extends from the diaphragm to the pelvic cavity. It is divided into the supracolic and infracolic compartments by the transverse mesocolon. The supracolic compartment is found anterior and superior to the transverse mesocolon, and contains the liver, stomach and spleen.
Learn more about the anatomy of the digestive system with our quizzes and free learning tools.
The infracolic compartment is posterior and inferior to the transverse mesocolon. Looking from the anterior aspect, it is divided by the root of the mesentery of the small intestine into the right and left infracolic spaces. The infracolic compartment contains the small intestine, ascending colon and descending colon.
Master the anatomy of the greater sac with these articles.
The mesentery is the folds of peritoneum that suspend organs from the posterior abdominal wall.
The projection of an organ into the peritoneum creates a peritoneal fold which extends from the abdominal wall, wraps around that organ, and extends back to the abdominal wall. These double layers of peritoneum are the mesentery. Mesenteries carry neurovascular bundles through the fat between peritoneal layers to supply organs.
The mesentery of the small intestine is simply called the mesentery or mesentery proper, while the other parts of the digestive system have their mesenteries named more specifically: transverse mesocolon, sigmoid mesocolon, and mesoappendix. You’ll notice the prefix “meso-” before the corresponding part of the intestines.
Dive further into mesentery anatomy with these study materials.
The omenta are two layers of peritoneum which have fused, and extend from the stomach and proximal duodenum to neighbouring organs. There are two subdivisions of the omentum depending on whether they extend from the greater or lesser curvature of the stomach.
Have you been making any of these common learning mistakes?
The greater omentum hangs like a curtain covering the anterior surface of the small intestine. It hangs from the proximal duodenum and greater curvature of the stomach and then folds to attaches superiorly to the anterior surface of the transverse colon and its mesentery on the inferior edge. The lesser omentum extends superiorly from the lesser curvature of the stomach and proximal duodenum to the liver.
Solidify your knowledge about the omentum with this great video tutorial and quiz.
Peritoneal ligaments are dupl icatures of the peritoneum and can make up parts of the omenta. They have two main functions:
- To attach organs to the abdominal wall and/or to other abdominal organs and hold them in position
- To carry neurovascular structures which supply abdominal organs
Based on from which they originate, peritoneal ligaments are classified as splenic, gastric or hepatic ligaments.
|Splenic ligaments||Phrenicocolic ligament (sustentaculum lienis)
Splenorenal (lienorenal) ligament
|Gastric ligaments||Gastrophrenic ligament
|Hepatic ligaments||Falciform ligament
Notable ligaments include the hepatogastric ligament and hepatoduodenal ligament which make up the lesser omentum. The hepatoduodenal ligament carries the portal triad – hepatic portal vein, hepatic artery proper, common bile duct. The gastrophrenic ligament, gastrosplenic ligament, gastrocolic ligament and splenorenal ligament form part of the greater omentum.
Want to learn more about the peritoneal ligaments? Check out this content we have prepared for you, including the quiz we specially designed for testing your knowledge.
Depending on how deep the abdominal organs dive into the peritoneum during development, they can be classified as:
- Intraperitoneal organs
- Retroperitoneal organs (primarily and secondarily retroperitoneal)
Intraperitoneal organs are completely wrapped by visceral peritoneum. These organs are the liver, spleen, stomach, superior part of the duodenum, jejunum, ileum, transverse colon, sigmoid colon and superior part of the rectum.
Retroperitoneal organs are found posterior to the peritoneum in the retroperitoneal space with only their anterior wall covered by the parietal peritoneum. If they develop and remain outside the peritoneum, they are primarily retroperitoneal organs: kidney, adrenal glands and ureter. Other retroperitoneal organs develop inside the peritoneum, but then move beneath it: pancreas, distal duodenum, ascending and descending colons.
Master peritoneal relations with our video tutorials and quizzes. Also, take the chance to go further with clinical anatomy of the abdomen by reviewing our clinical case of necrotizing fasciitis of anterior abdominal wall.
Ascites by definition is accumulation of more than 20 milliliters of fluid within the peritoneal cavity. The most common cause is increased pressure in the hepatic portal vein, portal hypertension. Portal hypertension is most often seen in people with liver cirrhosis. Ascites clinically presents as a bulging belly showing waves of moving fluid when gently struck – this is not the case for fat tissue.
The diagnosis of ascites is by physical examination and medical imaging. The ideal treatment of ascites is directed towards its cause together with dietary restrictions of sodium because sodium promotes fluid retention. In any case, it is important to treat ascites as a potential complication of this state is peritonitis – inflammation of the peritoneum.
Peritonitis is an inflammation of the peritoneum. In most cases it emerges as a complication of ascites. Peritonitis is usually caused by intestinal bacteria which find their way to the peritoneum via lymph (lymphatic dissemination) or ruptured bowel. Patients usually experience fever, mental confusion, abdominal pain and notable ascites. So any patient with diagnosed ascites and sudden onset of these symptoms should be examined for peritonitis.
The easiest way to diagnose peritonitis is to extract a small amount of peritoneal fluid and perform microbiological analysis to confirm the presence of bacteria and inflammatory cells. Peritonitis is treated with antibiotics.