In HA17, the stomach is on the left and the esophagus takes up 3/4 of the right side of the image. The muscularis externa, especially the inner circular layer, is enlarged considerably to form the cardiac (lower esophageal) sphincter (HA17 cs). At the end of the esophagus, the epithelium changes abruptly where the cardiac region of the stomach begins (HA17L arrow). The submucosa contains adipose tissue, which is uncommon.