Peritoneal Cavity, Mesentery, Omentum, and Ligaments


  • Peritoneum
    • Membrane
    • Contents
    • Structures
  • Mesentery
  • Omentum
  • Peritoneal ligaments


  • Serous membrane with 2 layers
    • Parietal peritoneum – lines the abdominal wall
    • Visceral peritoneum  – lines the viscera
      • Intraperitoneal organs are simply organs that are covered with visceral peritoneum
        • Will be connected to the body wall/parietal peritoneum via ligaments, omentum, or mesentery (except liver which is kind of directly connected)
      • Extraperitoneal organs lie between the parietal peritoneum and the abdominal wall – therefore will usually have a surface covered in peritoneum
Key peritoneal features.
  • Certain aspects of the peritoneum also contain fat – this provides protection to the organs within
  • There are several types of peritoneal folds
    1. Mesenterybetween posterior abdominal wall and organ
    2. Ligamentbetween two organs
    3. Omentum between stomach and another organ
Abdominal structures are either intraperitoneal or extraperitoneal (retroperitoneal/subperitoneal). Table from Wikipedia


Subdivisions of the peritoneal cavity
  • There are two main divisions of the peritoneal cavity
    1. The Greater Sac
    2. The Lesser Sac (Omental Bursa
      • This is a potential space
      • Boundaries:
        • The lesser sac lies posterior to the hepatoduodenal ligament, lesser omentum, and stomach
        • Superiorly limited by the diaphragm
        • Inferiorly limited by the fused greater omentum/transverse mesocolon
      • Clinically relevant due to various pathologies that can affect it
  • Both of these communicate via the (omental) epiploic foramen 
    • The boundaries of this are clinically important in surgery
      • Anterior: portal triad/hepatoduodenal ligament
      • Posterior: peritoneum covering IVC and right crus of diaphragm
      • Superior: caudate lobe of liver
      • Inferiorly: Superior duodenum + portal triad

        The epiploic foramen and greater sac (red) vs lesser sac (blue)

The Mesentery

  • = ‘Middle Intestine’
    • This is a double layer of the peritoneum which connects the organ/visceral peritoneum to the posterior abdominal wall’s peritoneum. 
    • Developed when an (intraperitoneal) organ invaginates the peritoneum
      • Therefore it is essentially a kind of stalk.
  • Embryologically, all of the GIT is intraperitoneal when it first develops and suspended by the dorsal mesentery.
    • However, some parts (the descending/ascending colon) are pushed out of the peritoneum and become secondarily retroperitoneal
  • The mesentery communicates nerves and vessels
  • It is actually quite fragmented depending on the organs it contains
  • 2 main bits
    • Mesentery proper – Jejunum and ileum
      • This is what is usually referred to as ‘the mesentery’
    • Mesocolon – covers parts of the large intestine
      1. Transverse mesocolon
      2. Sigmoid mesocolon
      3. Mesoappendix – mesentery covers the ideal aspect of the appendix
      4. Mesorectum – attaches to upper third of rectum
      • NB the ascending and descending colon, and middle 1/3 of rectum are fixed to the body wall


  • This is a double layer of peritoneum extending from the stomach
  • Lesser omentum – lesser curvature of stomach to the liver
    • Also attaches to the greater curvature
  • Greater omentum – hangs down the greater curvature of the stomach.
    • This is the largest peritoneal fold
    • Folds back to become continuous with the transverse mesocolon
    • Contains the left and right gastroepiploic arteries (which anastamose to form the epiploic arterial arc)
  • The omenta can contain within them some ligaments as well
  • Fat contained within here provides protection from trauma (as does the peritoneum as a whole)

Peritoneal Ligaments

  • A peritoneal double layer/fold that connects an organ to another organ
    • 3 hepatic and 3 gastric ligaments + splenorenal ligament
    1. Hepatic ligaments:
      1. Falciform ligament : Connects liver -> anterior abdominal wall
        • Attaches from umbilicus to below the ribs
        • Divides the left and right hepatic lobes
      2. Gastrohepatic ligment:  Liver -> stomach (part of lesser omentum)
      3. Hepatoduodenal ligament: Liver -> duodenum (free edge of lesser omentum)
        • This conducts the portal triad and divides the greater and lesser sacs



  • Gastric ligaments:
    • Gastrophrenic ligament: Stomach -> Diaphragm
    • Gastrosplenic ligament: Stomach ->  Spleen
    • Gastrocolic ligament: Stomach -> Transverse Colon (part of greater omentum)
    • Gastrohepatic ligament – see above