The left gastric artery is the narrowest of the three branches of the celiac artery. It runs upward on the back of the diaphragm behind the lesser sac toward the esophagus. Near the esophagus, it leaves the diaphragm, curves forward over the upper border of the lesser sac, and runs downward between the two layers of the lesser omentum near the lesser curvature of the stomach; it ends by anastomosing with the right gastric artery about the middle of the lesser curvature. During its course it gives off (1) esophageal branches to the lower part of the esophagus (these may arise by a common trunk); and (2) gastric branches to both surfaces of the stomach.

The left gastric vein runs alongside its artery as far as the celiac artery, and then accompanies the hepatic artery to end in the portal vein. Its tributaries correspond to the branches of the artery; it communicates with systemic veins at the lower end of the esophagus. This is one of the sites where obstruction to the flow of portal blood through the liver may cause enlargement of portal-systemic anastomoses; and hemorrhage may occur from the swollen veins into the stomach with vomiting of blood (hematemesis).