Around the longitudinal axis the stomach undergoes a 90° clockwise rotation, causing its left surface to face anteriorly and its right surface posteriorly. Also the greater curvature of the stomach comes to lie on the left side and the lesser curvature is now on the right side. Rotation around the longitudinal axis explains why the left vagus nerve, originally innervating the left wall of the primitive stomach now innervates the anterior wall of the stomach. Similarly, the right vagus initially innervating the right wall of the stomach now supplies its posterior wall.