Stomach wall. Coloured Scanning Electron Micrograph (SEM) of the surface of the fundus region of the human stomach. Numerous dark red openings, known as a gastric pits are seen. These are the location of the secretory glands that produce digestive enzymes and acids which break down food. Around the gastric pits are epithelial cells (yellow). These cells produce a thick layer of mucus (not seen here) which lines and protects the wall of the stomach from self-digestion. The fundus is the uppermost section of the stomach which, together with the body of the stomach, contains such gastric glands. Magnification: x 200 at 5x7cm size.