Why does digestion start in the mouth?
The short answer
Teeth break food into smaller pieces, and saliva moistens it and begins breaking down some starch.
How it works
The tongue forms food into a swallowable shape, while enzymes in saliva begin chemical digestion. Other enzymes and bile work later in the stomach and small intestine.
A familiar example
Chewing makes pieces smaller and increases the area that digestive fluids can reach.