Digestion

Digestion the process by which the body breaks down food and extracts nutrients from it. The word was first used by medieval alchemists to describe a chemical reaction which dissolved materials. When the French scientist Denis Papin invented the first pressure cooker (see pressure cooking) in 1679, he called it a digesteur.

The digestion of food takes place in stages. It begins in the mouth where the enzyme ptyalin, present in saliva, begins to break down starch in food to sugars. Chewing food, by breaking it into small pieces, exposes a large surface area for digestive enzymes to work on.