Abdominal Foregut & Peritoneum Development - Transverse View
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Key Concepts
- The peritoneum is a continuous serous membrane that covers the abdominal wall and viscera.
- Parietal layer of the peritoneum lines the body wall
- Visceral layer envelops the viscera, aka, the organs
- In some places, the visceral layer extends from the organs as folds that form ligaments, omenta, and mesenteries.
- Viscera is categorized by their relationship to the peritoneum:
- Intraperitoneal organs are covered by visceral peritoneum; as we'll see, the stomach is an example of this.
- Retroperitoneal organs lie between the body wall and the parietal peritoneum (the kidneys, for example, are retroperitoneal).
- Some organs are said to be secondarily retroperitoneal, because during their early embryologic stages, they are enveloped in visceral peritoneum, but later fuse to the body wall and are covered only by parietal peritoneum.
Week 5
Just prior to rotation of the stomach.
Diagram instructions: draw the outer surface and body wall, and indicate that the body wall is lined by parietal peritoneum.
- Organs at the midline, from dorsal to ventral:
- Abdominal aorta
- Stomach; branches of the right and left vagus nerves extend along the sides of the stomach
- Liver
- Peritoneal coverings and ligaments:
- Dorsal mesogastrium anchors the stomach to the posterior body wall
- Visceral peritoneum covers the stomach
- Ventral mesogastrium connects the stomach to the liver
- Falciform ligament anchors the liver to the ventral body wall
As you may recall, the dorsal mesogastrium is a portion of the dorsal mesentery, and the ventral mesogastrium and falciform ligament arose from the ventral mesentery. It's helpful to remember that "gastric," as in mesogastrium, = refers to the stomach.
Elongation and Rotation
The stomach elongates and expands asymmetrically as it rotates within the abdominal cavity. As it does so, other organs and their connecting ligaments are also rearranged.
- Organs
Mature Form
- The majority of the pancreas is fused to the body wall, and its ventral surface is covered by parietal peritoneum; thus, it is secondarily retroperitoneal.
- Spleen and stomach are to the left; liver is to the right.
- The dorsal mesogastrium gives rise to:
- The lienorenal (aka, splenorenal) ligament, which attaches to the spleen
- The gastrolienal (aka, gastrosplenic) ligament connects the spleen to the stomach
- When the stomach rotated on its longitudinal axis, it took the vagal branches with it:
- Right vagal branches are on the dorsal surface of the stomach
- Left vagal branches on the ventral surface (be aware that fibers of each intermix with each other to some degree).
- The ventral mesogastrium gives rise to two ligaments that connect the liver to the stomach and proximal duodenum:
- Only the hepatogastric ligament, which extends between the stomach and liver, can be seen in our diagram; notice that the tissue envelops the liver as visceral peritoneum. It's helpful to remember that hepatic, as in hepatogastric, refers to the liver.
- The falciform ligament connects the liver to the anterior body wall.
Lesser and Greater Omenta
- The lesser omentum extends between the liver and the stomach and duodenum; can be subdivided according to its specific attachments:
- The hepatogastric ligament connects the liver and the stomach.
- The hepatoduodenal ligament connects the liver and the duodenum.
- The greater omentum is a single fold of peritoneum that comprises two double-layered sheets of peritoneum.
- More specifically, it arises anteriorly from the greater curvature of the stomach, and posteriorly from the abdominal wall above the small intestine; thus, as it grows, it drapes over the transverse colon and small intestine.