|C O N T R I B U T E : D I G E S T I V E S Y S T E M|
THE DIGESTIVE SYSTEM
The digestive tract is a long tube extending through the body. It begins in the mouth and ends at the anus where solid waste material is discharged. The tube is about nine metres long. Digestion of food begins in the mouth. Saliva, produced by the salivary glands, contains an enzyme, which breaks down starch foods into simpler sugars. An enzyme is a chemical which speeds up chemical reactions without being changed itself. The food travels from the mouth to the oesophagus which is a soft flexible tube. Powerful muscular action, called peristalsis, pushes the food down into the stomach.
When the food reaches the stomach it is mixed with gastric juices and churned around by muscular action. Gastric juices are produced by the stomach wall and consist of hydrochloric acid, the enzymes renin and pepsin, and water. The hydrochloric acid helps to kill any microbes and helps the enzymes to work (they will only function in the presence of an acid). Pepsin and rennin break down the proteins in food into simpler substances called amino acids
THE SMALL INTESTINE
The process of peristalsis pushes the partly digested food from the stomach into the small intestine. Digestive juices from the liver and pancreas, as well as from the wall of the small intestine, assist in completing digestion. One of the digestive juices, bile, is made in the liver and helps to change fats and oils into minute droplets. It also contains sodium hydrogen carbonate, an alkali that helps neutralise stomach acid. The pancreas produces enzymes which further digest proteins, starch, fats and oils. The walls of the small intestine are covered with small, protruding, finger like structures called villi. Digested food molecules pass through the walls of the villi into blood vessels
THE LARGE INTESTINE
The substances in food that cant be digested pass into the large intestine.
Water and salt are absorbed from the large intestine into the bloodstream
but any remaining matter collects in the rectum and then passes out of
the body through the anus. This mainly solid mass is called faeces.
Contributed by: Lara Lawler <email@example.com>
BEGINNING OF THE DIGESTIVE SYSTEM
Contributed by: panda <firstname.lastname@example.org>
The average time tkaen to totally digest the food you have taken in
Contributed by: jessie <email@example.com>
Sunday, September 05, 1999 at 17:51:41 (EDT)
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