Peritoneum

What is the Peritoneum?

The peritoneum is a thin serous membrane lining the abdominal and the pelvic cavity and its organs. The peritoneum acts as a protective barrier against micro-organisms and is additionally a support to the abdominal and pelvic organs.

How can we describe the Peritoneum?
The peritoneum is a thin membranous structure, pale yellow in color, that is thrown into numerous folds. Peritoneum is of two types visceral and parietal.

Visceral peritoneum is firmly adherent to the respective organ and cannot be peeled off from the organ.

Parietal peritoneum is loosely thrown over the visceral peritoneum and forms a gap between the two layers of peritoneum. The space thus formed between the visceral and parietal peritoneum is called as the peritoneal cavity. The cavity contains viscid fluid called as the peritoneal fluid. The folds of the peritoneum divide the peritoneal cavity in two major sections; the greater sac and the lesser sac. The greater sac is present in front of the stomach and extends right up to the pelvis. The lesser sac is present behind the greater sac and opens through a small window like opening near the stomach called as the epiploic foramen.

The peritoneum covers most of the abdominal and pelvic organs. The organs lying behind the peritoneum are called as retroperitoneal organs and include the kidneys, ureters, inferior vena cava, pancreas, duodenum, ascending colon and descending colon.

There are some specialized areas of the peritoneum which need to be understood :

• Mesentery : This is a double-layered fold of peritoneum that attaches a part of the intestines to the posterior abdominal wall.
• Omentum : This is also a double-layered fold of peritoneum that attaches the stomach to another abdominal organ. The omentum is also called as the soldier of the abdomen. It is attached to the greater curvature of the stomach and hangs in front of the stomach like an apron. It seals off any bacterial infection likely to occur in the intestines.
• Peritoneal ligaments : These are double layered folds of peritoneum that attach the less mobile organs to the abdominal walls. E.g. liver is attached to the abdominal wall by the falciform ligament.

What are the functions of the Peritoneum?

• The peritoneal fluid in the peritoneal cavity ensures that the movement of organs over each other in the abdomen is smooth and there is no friction between them.
• The peritoneum is also useful in the absorption of lymph from the intestines and sending it to the lymphatic system due to its large surface area.
• The peritoneum seals off infection in the peritoneal cavity and prevent them from spreading.
• The peritoneal folds help to suspend the abdominal and pelvic organs within the peritoneal cavity and form a channel for the blood and nerve supply of the intra-peritoneal organs.
• Storage of fat in the mesenteries and ligaments is also a major function of the peritoneum.