The foods we eat are chemically complex. They must be broken down by the body into simpler chemical forms which can be absorbed through the intestinal walls and transported by the blood to the body cells. In the cells, these nutrients provide energy and the correct building materials to sustain life.
Digestion is a series of physical and chemical changes by which food, taken into the body, is broken down in preparation for absorption from the intestinal tract into the bloodstream. These changes take place in the digestive tract, which includes the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
Beginning in the mouth, chewing breaks large food pieces into smaller. Food that is masticated well allows for more complete enzymatic action. If left in chunks, food that passes into the stomach and intestine will likely remain undigested as enzymes are only able to work on the surface of these larger particles. The enzyme that is secreted in the mouth from the salivary glands is ptyalin. Ptyalin is necessary for the breakdown of carbohydrates.