Peritoneum

The peritoneum can be categorized as:

1. Parietal peritoneum - this lines the abdominal cavity and receives somatic innervation and is therefore sensitive to localized pain in the region.

2. Visceral peritoneum - this lines the visceral in this region and receives autonomic innervation and therefore discomfort may arise due to reflex visceral motor activity.

The peritoneal cavity is a potential space between the visceral and parietal peritoneum. It is divided into the lesser peritoneal sac and the greater peritoneal sac.

1. The lesser peritoneal sac is an irregular-shaped sac that communicates with the greater peritoneal sac via the omental foramen (Foramen of Winslow). The lesser peritoneal sac forms due to the 90-degree clockwise rotation of the stomach during embryologic development. The boundaries of the lesser peritoneal sac are:

   • Anterior - liver, stomach, and lesser omentum

   • Posterior - diaphragm

   • Right side - liver

   • Left side - gastrosplenic and splenorenal ligaments.

2. The greater peritoneal sac is the remainder of the peritoneal cavity and extends from the diaphragm to the pelvis. The greater peritoneal sac contains a number of pouches, recesses, and paracolic gutters through which peritoneal fluid circulates.

Paracolic gutters are channels that run along the ascending and descending colon. Normally, peritoneal fluid flows upward through the paracolic gutters to the subphrenic recess, where it enters the lymphatics associated with the diaphragm.

Omental foramen (Foramen of Winslow) is the opening or connection between the lesser peritoneal sac and greater peritoneal sac. It is located posterior to the free edge of the lesser omentum (also contains portal triad). The following structures are related to the omental foramen:

1. Superiorly - liver

2. Inferiorly - first part of the duodenum

3. Anteriorly - hepatoduodenal ligament which contains the portal vein, bile duct, and hepatic artery.

4. Posteriorly - inferior vena cava, right crus of the diaphragm.