In mammals, it is common for the lesser sac to contain considerable amounts of fat.

If any of the marginal structures rupture their contents could leak into the lesser sac.

If the stomach were to rupture on its anterior side though the leak would collect in the greater sac.

[citation needed] The lesser sac is formed during embryogenesis from an infolding of the greater omentum.

The open end of the infolding, known as the omental foramen is usually close to the stomach.