The greater omentum (omentum majus; great omentum; gastrocolic omentum) is the largest peritoneal fold.
It consists of a double sheet of peritoneum, folded on itself so that it is made up of four layers.
The two layers which descend from the stomach and commencement of the duodenum pass in front of the small intestines, sometimes as low down as the pelvis; they then turn upon themselves, and ascend again as far as the transverse colon, where they separate and enclose that part of the intestine.
These individual layers may be easily demonstrated in the young subject, but in the adult they are more or less inseparably blended. The left border of the greater omentum is continuous with the Gastrosplenic ligament (gastrolienal ligament) ; its right border extends as far as the commencement of the duodenum.
The greater omentum is usually thin, presents a cribriform appearance, and always contains some adipose tissue, which in fat people accumulates in considerable quantity. Between its two anterior layers, a short distance from the greater curvature of the stomach, is the anastomosis between the right and left gastroepiploic vessels.