Peritoneal Membranes
Peritoneum
- The continuous double-layered membrane that lines the abdominopelvic body walls and the viscera within.
- The two layers of the peritoneum arise from embryonic mesoderm, and their complex arrangement reflects the developmental rotation of the gut.
Parietal peritoneum
Lines the internal surface of the body wall; it comprises the outer layer of the peritoneum.
Visceral peritoneum
Adheres to the organs; thus, it comprises the outermost covering of some organs in the abdominopelvic cavity and contributes to the serosa of the GI tract.
Peritoneal cavity
The (potential) space between the parietal and visceral layers.
Mesenteries
Folds of peritoneum that suspend organs in the abdominal cavity and provide protected neurovascular and lymphatic pathways.
- The greater omentum is an apron-like fold that overlies the small intestine; it attaches to the greater curvature of the stomach and transverse colon.
- The lesser omentum spans from the liver to the stomach and duodenum of the small intestine;
- The mesocolon anchors the colon to the posterior body wall;
- The mesentery proper (aka, mesentery) anchors the small intestine to the posterior body wall.
Intraperitonal vs Retroperitoneal:
Intraperitoneal organs
Enveloped in visceral peritoneum:
- Liver, stomach, jejunum and ileum (of the small intestine), and the transverse colon (of the large intestine)
Retroperitoneal organs
Lie between the body wall and the parietal peritoneum.
- Most of the pancreas and duodenum, the rectum, urinary bladder, uterus, and kidneys (not shown) (some of these are technically secondarily retro-peritoneal, which refers to their embryological origins).
Clinical correlation:
- Retroperitoneal hemorrhage refers to bleeding in the retroperitoneal space and commonly occurs from trauma.
- Peritonitis, aka, inflammation of the peritoneum, occurs when the GI tract is ruptured and gas, fecal matter, and bacteria enter the peritoneal cavity. Widespread infection can be fatal.
- Adhesions, aka, scar tissue, form if the peritoneum itself is damaged. Adhesions can inhibit movement of the viscera and cause chronic pain.