Final answer:
The mucosa is the stomach layer with gastric pits that secrete protective mucus, acid, and digestive enzymes, protecting against self-digestion.
Step-by-step explanation:
The layer of the stomach that contains the gastric pits, which in turn lead to the gastric glands secreting mucus, acid, and digestive enzymes, is the mucosa. The mucosal layer is the innermost lining of the stomach and it consists mainly of the epithelium. This epithelium is vital as it not only secretes a protective coat of alkaline mucus but also forms the mucosal barrier that protects the stomach from self-digestion by blocking gastric juice and quickly replacing damaged epithelial mucosal cells.