Difference between Peritoneum and Omentum

What is Peritoneum?

Peritoneum is a serous membrane that forms a lining in the abdominal cavity. It forms a closed cavity that houses all the organs in the abdominal cavity except for the kidneys and adrenal glands. It is composed of a layer of mesothelial cells supported by connective tissues. Though the peritoneum is a continuous layer, it is of two types:

  • Parietal Peritoneum: It is the portion that lines the abdominal and pelvic cavities.
  • Visceral Peritoneum: It covers the outer surfaces of the abdominal organs such as the intestinal tract.

The peritoneal membrane secretes surfactant proteins that provide lubrication, and prevents adhesion of the organs. The mesothelial cells are ciliated, which helps in trapping cellular products to maintain a gliding surface. They also have microvilli that increase the surface area of the membrane. The peritoneal layer is attached to the body by a glycosaminoglycan matrix containing vessels, macrophages, nerves, collagen fibres and fat cells.

The inflammation of the peritoneal layer causes peritonitis and tuberculosis of the layer is common in developing countries.

What is Omentum?

Omentum (plu: Omenta) is an abdominal structure that arises from the peritoneum. Omenta are folds that are formed by peritoneal layers that hang in front of the stomach and intestines. There are two types of omenta arising from the peritoneal layer:

  • Greater Omentum: The greater omentum is a large apron-like, thick fold of the visceral peritoneum that hangs from the stomach. It has a rich vascular supply. It arises from the greater curvature of the stomach, lines the intestine and converges into the parietal peritoneum.
  • The layer comprises macrophages, B-lymphocytes, T-lymphocytes and mast cells that help in fighting infection during abdominal sepsis or inflammation.

  • Lesser Omentum: The lesser omentum is formed from double layers of peritoneum that extends from the liver to the lesser curvature of the stomach and hepatoduodenal ligament. It is composed of two parts, the hepatogastric ligament and hepatoduodenal ligament. It is an extremely thin layer. The lesser omentum houses the portal vein, the hepatic artery, lymph glands, bile duct and lymph vessels.

Peritoneum vs. Omentum

Peritoneum

Omentum

Definition

Peritoneum is a serous membrane lining the abdominal cavity.

Omentum is a fold of the peritoneal layer.

Types

Parietal peritoneum and visceral peritoneum

Greater omentum and lesser omentum

Layers

It is composed of a layer of mesothelial cells supported by connective tissues

It may be two-layered or four-layered with patches that give it a lacy appearance.

Lining

The parietal peritoneum lines the pelvic and abdominal cavities.

The visceral peritoneum covers the outer abdominal surfaces such as the intestinal tract.

The greater omentum emerges from the greater curvature of the stomach and lines the intestine.

The lesser omentum extends from the liver to the lesser curvature of the stomach.

Function

The peritoneal layer provides lubrication and prevents the organs from adhesion. It also has microvilli that increase the surface area of the membrane.

The macrophages and lymphocytes present in the omentum help in fighting sepsis and inflammation of the abdomen.

Explore BYJU’S Biology for more information.

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Frequently Asked Questions

What is the difference between the omentum and mesentery?

Omenta are folds present on the peritoneal surface that connects the stomach to other abdominal organs, whereas mesentery is another fold that connects the intestine to the abdominal wall.

What is the difference between peritoneum and perineum?

The peritoneum is a serous membrane covering the abdominal cavity in mammals, whereas perineum is an anatomical region that is located between the thighs, representing the most inferior portion of the pelvic outlet.

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