Several minutes later, the food is mixed with secretions and enzymes, which break down the food. In normal digestion, the stomach wall is coated with mucus to protect it from secretions and enzymes. If the mucus coating fails, acid secretions and the digestive enzyme pepsin can disrupt the lining of the stomach, resulting in an ulcer. The stomach then empties its contents into the first part of the intestines, called the duodenum . Meals are transported to the duodenum within a few hours.
Carbohydrates empty the fastest, with proteins emptying more slowly and fatty foods the slowest.
The intestine produces some of its own secretions and obtains secretions from outside organs to assist in the process of digestion. The broken-down food continues to move through the twisting and turning intestines with the aid of wavelike muscular contractions. During the journey, nutrients are absorbed into the blood vessels or lymph vessels. Finally, waste material is expelled after travelling through the colon, where water is reabsorbed.