Kaplan Nursing Entrance Practice Exam

Where does chemical digestion begin?

1. In the stomach

2. In the intestines

3. In the mouth

4. In the esophagus

The correct answer is: In the mouth

Chemical digestion begins in the mouth. This is primarily due to the action of enzymes found in saliva. When food is chewed and mixed with saliva, the enzyme amylase starts breaking down carbohydrates into simpler sugars. This initial phase of digestion prepares the food for further breakdown as it continues through the gastrointestinal tract. The stomach and intestines are also involved in chemical digestion, but the stomach primarily focuses on protein digestion with the help of gastric juices that contain hydrochloric acid and the enzyme pepsin, while the intestines continue the process using enzymes from the pancreas and bile from the liver. The esophagus, on the other hand, mainly functions as a passageway for food to travel from the mouth to the stomach and does not partake in chemical digestion.