Stomach & Duodenum Rotation
Let's start with the rotation of the stomach during weeks 5-11.
In week 5, the stomach appears as a spindle-shaped tube; we show the indicate the
ventral and dorsal mesenteries (the dorsal mesentery is more specifically called the dorsal mesogastrium).
We draw representative branches of the left and right vagus nerves (CN X); tracking their movement will help us visualize the rotation of the stomach.
Differential growth of the stomach and clockwise rotation along the longitudinal axis alters the course of the vagus nerve branches:
The left
vagus nerve now innervates the anterior (ventral) surface of the stomach, and the right vagus nerve lies on the posterior (dorsal) surface. (know that this is a simplification, as fibers from the right and left vagal plexuses intermix with each other and the celiac plexus, to some degree).
Notice that the cephalic and caudal ends remain in the midline.
However, as the stomach rotates along the antero-posterior axis, the pyloric (caudal) end moves superiorly and to the right, while the cardiac (cephalic) end moves slightly inferiorly and to the left.
Now, the ventral and dorsal mesenteries are also displaced to the right and left, respectively. The ventral mesentery attaches to the lesser curvature, and the dorsal mesentery attaches to the greater curvature.
The ventral mesentery gives rise to the falciform ligament, which secures the liver ventrally, and, the lesser omentum, which connects the liver and stomach and proximal duodenum. The dorsal mesentery gives rise to the greater omentum, the apron-like fold of mesentery that attaches to the greater curvature of the stomach and drapes over the small intestine.
