Imagine taking a bite of a burrito. Follow the beans in the burrito through the process of digestion. Explain what type of changes take place and where each change happens.
Digestion begins in the mouth with mechanical digestion (via chewing). Chemical digestion also begins in the mouth as the enzyme amylase begins the breakdown of simple sugars.
Peristalsis (involuntary movement) of the esophagus pushes the chewed food (bolus) into the stomach. The stomach mixes food with digestive juices (such as HCl). Proteins are largely digested in the stomach.
Peristalsis moves food along the small intestine. Here, starches, proteins, and carbohydrates are digested. The cells of the small intestine contain many cilia that increase their surface area for greater absorption of nutrients. Some of these nutrients are picked up and delivered by the blood.
From the small intestine, the food enters the large intestine. Here, water is absorbed from the remaining indigestible food matter.
The food next enters the colon. Finally, the waste is eliminated from the body.
The pancreas and liver also aid in digestion. The pancreas produces pancreatic juices that help to break down starch, fat, and protein. The liver produces bile that helps to break down fats.