Final answer:
Surface mucus cells in the gastric glands secrete an alkaline mucus that forms a protective barrier to prevent the stomach from self-digestion.
Step-by-step explanation:
The cells in the gastric glands that release a viscous, alkaline secretion to protect the stomach from digesting itself are called surface mucus cells. These cells secrete a protective coat of alkaline mucus, which forms a barrier on the stomach wall. This mucus is bicarbonate-rich, and its bicarbonate ions neutralize acid, providing substantial protection against the corrosive acidity of gastric juice. The protective action is crucial because stomach enzymes capable of protein digestion can also damage the stomach's mucosal lining.