Stomach, illustration. Stomach is opened longitudinally. The cut stub of the esophagus leads to the cardiac orifice. To the left the cut stub of the duodenum is adjacent to the pyloric orifice. The layers of the stomach wall from outer to inner are the peritoneum, the smooth muscle wall and the gastric mucosa. The latter is seen as irregular folds and ridges (rugae) forming the inner lining of the stomach. From Lizars, J. 1823 A system of anatomical plates of the human body. W. H.Lizars, Edinburgh.