Parietal peritoneumLines the inside of the abdominal wall. It is one layer of a single sheet.
Visceral peritoneumCovers the organs inside the abdomen. It is the same sheet, folded in over them.
Peritoneal cavityThe thin space between the two layers. It holds a little slippery fluid.
Greater omentumHangs like an apron from the stomach. It folds back up to the transverse colon.
Lesser omentumJoins the liver to the stomach. It is a double layer of peritoneum.
MesenteryFastens the small intestine to the back wall. Its vessels and nerves run inside it.
Transverse mesocolonHolds the transverse colon to the back wall. It is that part of the mesentery.
Lesser sac (omental bursa)A pocket of the cavity behind the stomach. Its older name is omental bursa.
PancreasLies behind the peritoneum, against the back wall. Such organs are called retroperitoneal.
DuodenumMost of it lies behind the peritoneum. It is the small intestine's first part.
How this list was compiled: Every name checked on 2026-10-01 and kept only where two of these three use it. (1) Wikipedia, text only: Peritoneum, Greater omentum, Lesser omentum, Mesentery, Peritoneal cavity and Retroperitoneal space, https://en.wikipedia.org/wiki/Peritoneum and https://en.wikipedia.org/wiki/Mesentery . (2) TeachMeAnatomy, The Peritoneum and The Peritoneal Cavity, https://teachmeanatomy.info/abdomen/areas/peritoneum/ and https://teachmeanatomy.info/abdomen/areas/peritoneal-cavity/ : parietal and visceral layers, the greater and lesser sacs, the omenta and mesenteries, and which organs are retroperitoneal. (3) Gray, Anatomy of the Human Body, 20th edition, 1918 (public domain), The Abdomen, read as text at https://www.bartleby.com/lit-hub/anatomy-of-the-human-body/2e-the-abdomen/ : the peritoneal cavity and the omental bursa, the apron-like greater omentum, the lesser omentum, the mesentery and the transverse mesocolon. No OpenStax page was read. Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work
How it works
The peritoneum is one thin sheet that lines the abdomen and wraps most of its organs. This drawing cuts the abdomen from front to back so you can correctly label the parts of the peritoneum a lab figure asks for.
Read the full guide
Two layers, one sheet
The parietal peritoneum lines the wall. Where the sheet turns in to cover an organ it is called visceral peritoneum. The peritoneal cavity is the space between them, drawn wide here; in life the layers touch.
The folds, and what lies behind
Where the sheet doubles on its way to an organ it makes a fold. The lesser omentum joins the liver to the stomach, the greater omentum hangs from the stomach like an apron, and the mesentery and the transverse mesocolon hold the intestine to the back wall. The pancreas and most of the duodenum lie behind the peritoneum, against the back wall. The pocket in front of them, behind the stomach, is the lesser sac.
The cavity is drawn open so you can tap it; it really holds only a film of fluid.
The quiz accepts omental bursa for the lesser sac and greater sac for the peritoneal cavity.
Questions and answers
What are the parts of the peritoneum?
Two layers and the folds between them. The parietal layer lines the wall and the visceral layer covers the organs. The folds are the greater and lesser omentum, the mesentery and the mesocolons. The space between the layers is the peritoneal cavity.
Where does the mesentery label go on a peritoneum figure?
When a figure asks you to drag the appropriate labels to their respective targets, mesentery belongs on the fold that runs from the back wall of the abdomen to the loops of small intestine.
What is the difference between the greater and lesser omentum?
The lesser omentum is a short fold from the liver to the stomach. The greater omentum is a long fold that hangs from the lower edge of the stomach in front of the intestines and folds back up to the transverse colon.
Which organs are behind the peritoneum?
Organs that lie against the back wall with peritoneum only on their front are called retroperitoneal. This drawing shows two of them, the pancreas and the duodenum. The kidneys are another example.