Fig. 287.—Primitive dorsal and ventral mesogastrium with course of hepatic artery.

It now becomes necessary to regard the development of the great omentum from the primitive dorsal mesogastrium in relation to this course of the hepatic artery. We have seen that the great omentum and the cavity of the omental bursa is produced by the extension of the dorsal mesogastrium to the left and caudad, subsequent to the rotation of the stomach. The splenic artery and the left gastro-epiploic branch pass from the cœliac axis to the left between the layers of the mesogastrium, as previously seen ([Figs. 291] and [292]).

The hepatic artery, however, is so to speak placed on the border line between the portion of the primitive mesentery which, as dorsal mesogastrium, is to turn to the left and caudad to form the great omentum, and the portion which, as mesoduodenum, turns to the right and passes to the duodenal loop (Fig. 287).

In the further course of development the dorsal mesogastrium grows more and more, forming the omental bag, while the mesoduodenum on the other hand becomes anchored early and obliterated as a free membrane by adhesion of its original right layer to the primitive parietal peritoneum. The hepatic artery runs on the line dividing these two different mesenteric segments. We can imagine, so to speak, that the redundant growth of the omentum to the left and caudad, takes place over the hepatic artery as a resistant support (Figs. 288 and 289). Cephalad of the hepatic artery is the developing omentum, caudad of the vessel the mesoduodenum. The artery follows the cephalic limit of the mesoduodenum and becomes, as stated, adherent to the abdominal background in the segment between its origin from the cœliac axis and the point where, after having crossed the dorsal surface of the duodenum, it enters the right edge of the lesser omentum on its way to the liver.

Fig. 288.—The liver divides the ventral mesogastrium into a dorsal segment, the gastro-hepatic or lesser omentum, and a ventral segment, the suspensory or falciform ligament of the liver.   Fig. 289.—Stages in the development of the dorsal mesogastrium (omental bursa) and mesoduodenum to show relation of hepatic artery to these two segments of the primitive common dorsal mesentery.

Pancreatico-gastric Folds.—If we open the lesser peritoneal cavity by dividing the gastro-hepatic omentum and look into the background of the retro-omental space, we will see a fold of the secondary lining parietal peritoneum (derived from the mesogastrium), which can be traced from the cephalic border of the pancreas to the pyloric extremity of the stomach. This fold carries the hepatic artery to the lesser omentum behind the first portion of the duodenum, and is called the right or main pancreatico-gastric fold. A similar fold, further to the left, carries in a like manner the coronary artery of the stomach to the cardiac end of the lesser curvature. This fold forms the left or secondary pancreatico-gastric fold. Between the two folds the caudal margin of the Spigelian lobe projects into the lesser cavity.

The appearance of the two pancreatico-gastric folds in the adult human subject is well seen in [Fig. 284].

Fig. 290.—Abdominal viscera of Nasua rufa, brown coaiti, with stomach turned up and great omentum divided. (From a fresh dissection.)