Facts at a Glance

• The average person eats 3 pounds of food a day. That's 1,095 pounds a year!
• An adult stomach holds 5 cups.
• 35 million glands produce acid. The acid can dissolve a razor blade in one week.
• A new stomach lining is produced every 3 days.
• The small intestine is about 20 feet long.
• The body uses energy efficiently. (900 miles to the gallon!)

All living things need fuel to carry on their life's work. On earth there are two basic ways of getting fuel. One way is to create your own food internally using sunlight. Only plants have this ability. The other way is to eat living or formerly living things. Since all living things are made up of pretty much the same thing, any creature can serve on the menu of any other creature. If not directly, then indirectly.

Putting the food into your mouth is only the beginning. The rest of the process involves breaking up the food so that the body can use it. This process is called digestion.

Digestion is a mechanical process where food is broken down into smaller and smaller particles until it can be used by the body. Digestion is also a chemical process, which varies with the kind of substance that is being eaten.

Your teeth and tongue take the first steps in battering food into bits. As they are shredding and grinding, more saliva is squirted into the food to moisten and soften it. The saliva contains chemicals called enzymes, which break down the starches in food.

When you have finished chewing, you swallow, and the mouthful of food makes its way down the food canal, or esophagus, to the stomach. Food does not free fall down to the stomach but is squeezed along by the muscles in the esophagus. This squeezing/pushing action by the muscles is called peristalisis (perry-STAL-sis).

In the stomach, food is treated to a strong acid bath, as it is churned about by the stomach's muscular walls. These walls are protected by a mucus lining, which saves he stomach from its own gastric juices (made up of pepsin enzyme and acids.) Any break in the lining of the stomach and in a couple of hours, the stomach will "eat" a hole in itself.

The food is now a mashed-up milky liquid. Next it is squeezed into the small intestines. The small intestines is 20-foot lone, curly tube with a shaggy lining. Small in this instance means skinny, not short; your small intestines is at least four times as long as you are tall. It has its own set of digestive juices for the final breakdown of food. Peristalsis puts the squeeze on the food using the muscles in the internal wall. The muscles contract and relax in the same way that you might squeeze a tube of toothpaste. All this movement makes a lot of noise. This is the grumbling and growling that you can sometimes hear from your stomach. The walls of the small intestines are lined with millions of tiny finger-like projections called villi. The villi absorb the usable parts of the broken -down food into the bloodstream. Finally the food is going to the body.

In addition to the organs of the digestive tract, the pancreas and liver are also part of the digestive process. They produce chemicals that aid digestion in the small intestines. Bile, a product of the liver used in digestion is stored temporarily in the gall bladder.