The dorsal mesentery becomes thinner and suspends the gut from the dorsal body wall. It attaches to the gut from the caudal part of the esophagus to the caudal part of the hindgut near the rectum.
The dorsal mesogastrium attached to the greater curvature of the stomach moves to the left with the greater curvature. As a result, part of the peritoneal cavity called the lesser sac or omental bursa is isolated dorsal to the stomach. The rest of the peritoneal cavity is known as the greater sac. Part of the lesser sac extends toward the right lung bud as the pneumatoenteric recess.
The dorsal mesoduodenum is pulled to the right of the midline when the duodenum moves to the right. It receives the ventral pancreas.
The dorsal mesentery of the midgut loop twists in a counterclockwise direction along with the midgut but remains attached to the dorsal body wall.
The dorsal mesentery of the hindgut is short, broad and lies in the midline.
VENTRAL MESENTERY
A ventral mesentery attaches the terminal segment of the esophagus, lesser curvature of the stomach and adjacent part of the duodenum to the ventral body wall.
The liver grows at such a rapid rate that it expands into the ventral mesentery subdividing it into two portions; the portion between the gut and the liver is called the lesser omentum, the portion between the liver and the ventral body wall is called the falciform ligament. As the liver expands into the ventral mesentery, it is covered by a thin layer called the serosa. That part of the liver adjacent to the septum transversum has no such covering and is called the bare area.
Blood vessels course through the caudal edge of both subdivisions of the ventral mesentery; the portal vein, hepatic artery and bile duct course through the edge of the lesser omentum, the umbilical vein passes through the edge of the falciform ligament.
As a result of the stomach moving to the left and the duodenum to the right, the lesser sac opens to the right into the greater sac through a narrow opening called the epiploic foramen. This passageway lies dorsal to the portal vein.
Source: Atlas of Human Embryos.