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Digestion
You've probably never thought of the middle section of your body as being
a complex chemical factory, but that is precisely what it is. Its function
is to "process" the nutrients in food, getting the "goodness"
into the bloodstream and disposing of the "waste".
The first part of the process is known as digestion this is where
the fats, protein and carbohydrates are split into smaller and simpler
chemical pieces to the point where they are eventually "broken down"
into units small enough to cross the intestine wall and enter the bloodstream.
Vitamins and minerals are not digested. They remain in their original
form but they are essential to the process of metabolism where the simplified
proteins, fat and carbohydrates are changed into fuel (energy) used for
growth or repair.
Digestion is both a mechanical and chemical procedure. The teeth mechanically
break the food up into small pieces which can be swallowed and sent down
the food passage. The food continues to be "minced up" as it
is propelled down the food passage by a series of muscular squeezes until
it reaches the stomach.
The chemical part of digestion starts in the mouth where the digestive
juice, saliva, begins the "breaking down" process. More digestive
juices get to work when the food reaches the stomach. Food usually remains
in the stomach's processing plant for between ten and sixty minutes before
passing into the small intestine where it is "broken down" even
further by more digestive juices.
The digesting food is moved along through the small intestine by a series
of gentle contracting and expanding movements.
When all the food has been thoroughly processed (i.e. digested) into
very small chemical particles it is absorbed by the tiny blood vessels
in the walls of the small intestine. From there it flows into the main
part of the bloodstream to be carried to all parts of the body as "nourishment".
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