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.
Anterior margin, named from the top to bottom margin:
Medial margin, named from the most anterior to the most posterior margin:
If any of the marginal structures rupture their contents could leak into the lesser sac. If the stomach were to rupture on its posterior side though the leak would collect in the greater sac.
- 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.