Henry J. Binder
The stomach plays several important roles in human nutrition and has secretory, motor, and humoral functions. These activities are not separate and distinct, but rather represent integrated functions that are required to initiate the normal digestive process.
The stomach has several specific secretory products. In addition to the stomach's best-known product, acid, these products include pepsinogen, mucus, bicarbonate, intrinsic factor, and water. These substances continue the food digestion that was initiated by mastication and the action of salivary enzymes in the mouth. In addition, they help protect the stomach from injury. The stomach also has several important motor functions that regulate the intake of food, its mixing with gastric secretions and reduction in particle size, and the exit of partially digested material into the duodenum. Moreover, the stomach produces two important humoral agents—gastrin and somatostatin—that have both endocrine and paracrine actions. These peptides are primarily important in the regulation of gastric secretion.
Although these functions are important in the maintenance of good health, the stomach is nevertheless not required for survival. Individuals who have had their entire stomach removed (i.e., total gastrectomy) for non-neoplastic reasons can maintain adequate nutrition and achieve excellent longevity.