Chapter 81. The Foregut: The Omental Bursa and Duodenum - Review of Medical Embryology Book

CLEFTS develop between the cells of the dorsal mesogastrium which coalesce and eventually form a single cavity, the omental bursa

The cavity expands in all directions and comes to lie behind the stomach and to the right of the esophagus
The upper portion of the cranial extension of the sac is limited by the developing diaphragm, to form closed space or sac called the infracardiac bursa
The lower portion of the cranial extension of the sac persists as the superior recess of the lesser sac
As the stomach enlarges, the lesser sac expands into an inferior recess which forms between the layers of the elongating dorsal mesogastrium (greater omentum)

The 4-layer greater omentum overhangs the developing small intestines
Most of the inferior recess of the lesser sac disappears as the layers of the greater omentum fuse

The omental bursa communicates with the main peritoneal cavity or greater peritoneal sac by way of the epiploic foramen or foramen of Winslow

The duodenum forms from the terminal portion of the foregut and the cephalic or cranial portion of the midgut

The junction of the foregut and midgut is at the apex of this embryonic loop, just distal to the origin of the liver bud

AS A RESULT OF ITS DUAL ORIGIN, the duodenum is supplied by branches of both the celiac and superior mesenteric arteries
AS THE STOMACH ROTATES, the duodenum rotates to the right and comes to lie retroperitoneally
DURING WEEKS 5 AND 6, the duodenal lumen is reduced and temporarily may even be obliterated by epithelial cells. However, under normal conditions, the lumen recanalizes by the end of the embryonic period
A GREAT PORTION OF THE VENTRAL MESENTERY of the duodenum disappears. The free border of this mesentery which does remain lies between the duodenum and the liver and forms the ventral border of the epiploic foramen and the duodenohepatic ligament. This mesentery is also a portion of the so-called lesser omentum