MUCOUS MEMBRANE OF STOMACH The reddish-gray mucous membrane of the stomach, composed of a surface layer of epithelial cells, the lamina propria, and the muscularis mucosae, commences at the cardia along an irregular or zigzag line (referred to as the Z line). Deep to the mucosa is the submucosa and three external muscle layers of the stomach. When the stomach is empty, the mucosa appears to be formed of folds (rugae), which flatten considerably when the stomach is distended. In the region of...