Gastric gland. Transmission electron micrograph (TEM) of a section through the deep region of a gastric (fundus) gland, showing several enzyme-secreting chief cells with many secretory granules, and a single parietal cell, which produces stomach acid. Gastric glands are found in the body, the gastric mucosa, and fundus of the stomach. Chief cells secrete pepsinogen. Acid secretion by the parietal cells converts pepsinogen to pepsin for partial digestion of proteins within the stomach. Both cell types are stimulated by nearby cells, nerves, and local hormones. Magnification: x8300, when printed 10 centimetres wide.