Peritoneum and peritoneal cavity (2024)

Peritoneum

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.

Test yourself on the peritoneal relations of organs.

Peritoneal cavity

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 in our study unit, then test yourself to consolidate your knowledge:

Divisions

There are two divisions of the peritoneal cavity: lesser sac (omental bursa) and greater sac.

Mesentery

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.

Omentum

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 study unit and custom quiz:

Peritoneal ligaments

Peritoneal ligaments are duplicatures 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.

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.

Peritoneal relations

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 study units. 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.

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• Abdominal wall
• Anterior abdominal muscles
• Clinical case: Giant inguinal hernia
• External abdominal oblique muscle
• Iliohypogastric nerve
• Inguinal canal
• Inguinal ligament
• Internal abdominal oblique muscle
• Pyramidalis muscle
• Quadratus lumborum muscle
• Spermatic cord
• Subcostal nerve
• Transversus abdominis muscle