The Digestive system depends on the action on the things we eat of substances called ENZYMES.

These are produced by the organs attached to the ALIMENTARY CANAL and are responsible for many of the chemical reactions involved in digestion. These changes begin in the mouth. When the food is chewed, the salivary glands beneath the tongue step up secretion of saliva, which contains the enzyme ptyalin. This starts breaking down some of the carbohydrates into smaller molecules known as maltose and glucose.

Food then travels down the OESOPHAGUS and in to stomach where the mixture of chemicals-mucus, hydrochloric acid and the enzyme pepsin is poured on to it.

Ptyalin stops working, but a new series of chemical reactions begins.