Anatomy of the Peritoneum

Peritoneum

• The peritoneum is a membrane formed of two layers: parietal peritoneum (lining the abdominal wall) and visceral peritoneum (enveloping most abdominal viscera).
• Omenta and mesenteries are double layers of visceral peritoneum.

Divisions and Relations

• The peritoneum lining the diaphragm sends two layers to surround the liver, which stop at the porta hepatis.
• The two layers descend as the lesser omentum to surround the stomach.
• At the greater curvature, the two layers descend as the anterior two layers of the greater omentum, which return to form the posterior two layers of the greater omentum.
• The posterior two layers of the greater omentum ascend to surround the transverse colon and then ascend to the anterior border of the pancreas, forming the transverse mesocolon.

Greater and Lesser Sacs

• The peritoneum is divided into the greater sac and the lesser sac.
• The greater sac is behind the anterior abdominal wall and in front of the stomach, continuing below with the pelvic cavity.
• The lesser sac lies behind the stomach, extending upward as far as the diaphragm and downward between the layers of the greater omentum.
• The lesser sac communicates with the greater sac via the epiploic foramen.

Peritoneal Cavity

• The peritoneal cavity is a potential space between the parietal peritoneum lining the abdominal wall and the visceral peritoneum enveloping the abdominal organs.
• The peritoneal cavity contains a serous fluid called peritoneal fluid, which allows motion.
• Normally, about 50-75 ml of fluid is present in the peritoneal cavity.

Omenta

• Omenta are peritoneal folds formed of two layers of visceral peritoneum that connect the stomach to another viscus.
• There are four types of omenta: lesser omentum, greater omentum, gastro-splenic ligament, and lienorenal ligament.

Blood Supply and Innervation

• The parietal peritoneum and the area of the abdominal wall it lines are supplied by the same blood vessels, lymphatics, and somatic nerve supply.
• The visceral peritoneum and the organs it envelops have the same blood vessels, lymphatics, and visceral nerve supply.
• The total peritoneal blood flow ranges from 50-150 ml/min.

Clinical Importance

• The peritoneum is important in abdominal pain, which can be classified into three types: somatic, visceral, and referred.
• Visceral pain is caused by distension of a hollow viscus, stretching of a viscus or mesentery, ischemia to a viscus, or damage to a viscus or its covering visceral peritoneum by chemicals.
• Referred pain is a feeling of pain at a place other than the site of origin of the stimulus, supplied by the same spinal segments.
• Blumberg's sign (rebound tenderness) is indicative of peritonitis.