Gastric secretion refers to the production of digestive fluids in the stomach, primarily composed of hydrochloric acid, pepsinogen, and mucus. These substances help break down food, kill harmful bacteria, and protect the stomach lining from acid damage. The secretion process is regulated by neural and hormonal signals, responding to the presence of food. The main cells involved in gastric secretion include parietal cells, which produce hydrochloric acid, and chief cells, which secrete pepsinogen. When food enters the stomach, these cells are stimulated, leading to an increase in gastric juices that aid in digestion and prepare the food for further processing in the small intestine.