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The lesser omentum, referred to as the small omentum or gastrohepatic omentum, is the double layer of peritoneum that extends from the liver to the lesser curvature of the stomach, and to the first part of the duodenum.
It is extremely thin, and is continuous with the two layers of peritoneum which cover the antero-superior and postero-inferior surfaces of the stomach and first part of the duodenum, respectively.
When these two layers reach the lesser curvature of the stomach and the upper border of the duodenum, they join together and ascend as a double fold to the porta hepatis.
To the left of the porta, the fold is attached to the bottom of the fossa for the ductus venosus, along which it is carried to the diaphragm, where the two layers separate to embrace the end of the esophagus.
At the right border of the lesser omentum, the two layers are continuous, and form a free margin which constitutes the anterior boundary of the omental foramen.
It is usually divided into these two connecting parts: the hepatogastric ligament, and the hepatoduodenal ligament.
Anatomically, the lesser omentum is divided into ligaments.
hepatogastric ligament: the portion connecting to the lesser curvature of the stomach.
hepatoduodenal ligament: the portion connecting to the duodenum.
Ligaments also considered part of the lesser omentum:
hepatophrenic ligament: the portion connecting to the thoracic diaphragm
hepatoesophageal ligament: the portion connecting to the esophagus
hepatocolic ligament: the portion connecting to the colon
Between the two layers of the lesser omentum, are the hepatic artery proper, the common bile duct, the portal vein, lymphatics, and the hepatic plexus of nerves.
All of these structures being enclosed in a fibrous capsule, the Glisson’s capsule.
Between the layers of the lesser omentum, at the stomach, are the right and left gastric arteries, as well as the gastric veins.