After being stored and mixed with hydrochloric acid in the stomach for about 30 to 60 minutes, chyme slowly enters the duodenum through the pyloric sphincter. Next, Brunner’s glands in the mucosa of the duodenum secrete alkaline mucus containing a high concentration of bicarbonate ions to neutralize the hydrochloric acid present in the chyme. This alkaline mucus both protects the walls of the duodenum and helps the chyme to reach a pH conducive to chemical digestion in the small intestine.