The peritoneal cavity is the continuous area between the parietal peritoneum lining the abdominal wall and the visceral peritoneum surrounding the abdominal organs. It does not contain organs, but instead contains a thin film of peritoneal fluid.
Peritoneal fluid is comprised of water, electrolytes, and other substances coming from the interstitial fluid in adjacent tissues. It provides lubrication for the peritoneal surfaces, enabling the viscera to move freely over each other without any friction, and allowing movements of digestion. Moreover, the peritoneal fluid contains leukocytes and antibodies that fight off infections.
The peritoneal cavity is completely closed in males. However, in females, there is a communication pathway to the body’s exterior via the uterine tubes, uterine cavity and vagina. The peritoneal cavity in both males and females is subdivided into a main greater sac region, and a smaller omental bursa or lesser sac region.
The greater sac accounts for most of the space in the peritoneal cavity. It begins at the diaphragm superiorly, and continues to the pelvic cavity inferiorly. The transverse mesocolon divides it further into two compartments: the supracolic compartment and infracolic compartment.
The supracolic compartment lies above the transverse mesocolon, between the diaphragm and the transverse colon. It contains three major organs: the stomach, the liver and the spleen. The infracolic compartment lies below the transverse mesocolon and transverse colon. It is subdivided into two unequal spaces - the left and right infracolic spaces - by the mesentery of the small intestine. The infracolic compartment contains the small intestine, as well as the ascending and descending colon. The supracolic and infracolic compartments are interconnected by the paracolic gutters, a series of open spaces between the posterolateral abdominal wall, and the lateral aspect of the ascending and descending colon.
The omental bursa or lesser sac is the smaller subdivision of the peritoneal cavity. It lies posterior to the stomach, the lesser omentum and adjacent structures. The omental bursa has a superior recess that is limited by the diaphragm and the posterior layer of the coronary ligament of the liver; and an inferior recess that is present between the superior portions of the layers of the greater omentum.
The omental bursa allows free movement of the stomach against the structures posterior and inferior to it. The greater sac and omental bursa communicate with each other via the epiploic foramen, which is situated posterior to the free edge of the lesser omentum. The epiploic foramen is surrounded by several structures. Anteriorly, there is the portal vein, the hepatic artery proper, and the bile duct. Posteriorly, there is the inferior vena cava. Superiorly lies the caudate lobe of the liver, and inferiorly lies the first part of the duodenum.
Throughout the peritoneal cavity are numerous peritoneal folds that connect the organs with each other, or to the abdominal wall. These folds are the omenta, the mesenteries and the peritoneal ligaments. The omenta are double layered extensions or folds of peritoneum that pass from the stomach and proximal part of the duodenum to the adjacent organs in the abdominal cavity. The mesenteries are double peritoneal layers formed as a result of invaginations created by organs. They connect the intraperitoneal organs with the body wall. The peritoneal ligaments consist of double layers of peritoneum that connect an organ with another organ or to the abdominal wall. Some of the folds contain vessels and nerves to supply the viscera, others function to maintain the proper position of the viscera in the abdominal cavity.