The lesser sac, also known as the omental bursa, is the cavity in the abdomen that is formed by the lesser and greater omentum. Usually found in mammals, it is connected with the greater sac via the omental foramen (previously known as the Foramen of Winslow). In mammals, it is not uncommon for the lesser sac to contain considerable amounts of fat.
It is demarcated anteriorly by the quadrate lobe of the liver, the stomach, lesser omentum and gastrocolic ligament. Posteriorly it is marked by the pancreas. Its left lateral margin is made by the left kidney and adrenal gland. Its boundary on the right is made by the omental foramen and lesser omentum. If these structures rupture they may leak into the lesser sac. For the stomach, which lies anterior to the lesser sac, the rupture must be on the posterior side; if it were anteriorly located, the leak would collect in the greater sac.
The lesser sac is embryologically formed from an infolding of the greater omentum. The open end of the infolding, known as the omental foramen, is usually close to the stomach.
- Shahani RB, Bijlani RS, Dalvi AN, Shah HK, Samsi AB. Massive upper gastrointestinal haemorrhage due to direct visceral erosion of splenic artery aneurysm. J Postgrad Med 1994;40:220–2. Full Text.
- "Lesser sac". Medcyclopaedia. GE. Archived from the original on 2012-02-05.
- Anatomy photo:37:09-0100 at the SUNY Downstate Medical Center – "Abdominal Cavity: The Lesser Peritoneal Sac"
- Anatomy image:8070 at the SUNY Downstate Medical Center