Digestion and absorption of ingested food

Digestion is the process of breaking down large, complex molecules and compounds that are found in ingested food into smaller, simpler molecules and compounds that the body can absorb and use as fuel and nutrients. This process begins in the mouth and is completed in the small intestine. The first stage of digestion begins in the mouth, where food is broken down by the mechanical action of chewing and the chemical action of saliva. Saliva contains enzymes that help break down some of the carbohydrates in the food. The food is then swallowed and enters the esophagus. Here, the food moves through a muscular tube and is pushed down to the stomach. In the stomach, the food is mixed with gastric juices, which contain enzymes and acid. This mixture helps to further break down the food. The stomach muscles also help to churn the food, which aids in the digestion process. Once the food has been digested in the stomach, it passes into the small intestine. Here, enzymes from the pancreas and bile from the liver help to further break down the food. The small intestine has a large surface area that is lined with tiny finger-like structures called villi.