The Physics Factbook
Edited by Glenn Elert -- Written by his students
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|Van De Graaf, Kent. Human Anatomy. McGraw-Hill. 2000.||"The GI tract extends from the mouth to the anus, is a continuous tube about 30 ft long."||9 m|
|"Alimentary Canal." Encyclopedia of Family Health. Volume 1. Marshall Cavendish, 1998.||"The body's food-processing plant is the alimentary canal, a muscular tube about 33 ft (10 m) long that starts at the mouth and ends at the anus."||10 m|
|National Geographic Society. Exploring the Human Body. Washington, DC: National Geographic Society, 1998.||"Basically an extended and convoluted tube, the 30-ft-long digestive tract packs itself efficiently into the abdominal cavity."||9 m|
|Gray, Henry F.R.S. Gray's Anatomy. Pennsylvania: Running Press, 1974.||"The alimentary canal is a musculo-membrane tube, about 30 ft in length, extending from the mouth to the anus."||9 m|
|Dubois, Andre. "Alimentary Canal." World Book Online America's Edition, 2001.||"Alimentary canal is a long tube through which food is taken into the body and digested.In human beings, this passage is about 30 ft (9 m) long."||9 m|
The alimentary canal, or the digestive tract as it is most commonly known, is 9 meters from the esophagus to the anus. Digestion begins at the mouth, where food is chewed and mixed with saliva, which adds moisture and contains the enzyme amylase that begins to break down starches. The tongue molds the food into a ball mass, known as the bolus. The bolus travels down the esophagus, through the pharynx by a muscular contraction called the peristaltic movement. Once the bolus enters the stomach, the hormone gastrin arouses the secretion of acidic juices, which further aid in the digestion of the food mass. After the stomach carries out its role in the digestion process, the food is no longer in a solid state form; rather its now a liquid called chyme. The chyme travels into the small intestine, into a section called the duodenum. This is where most of the digestion occurs because different enzymes, released by the pancreas and by glands in the intestinal wall, affect each food molecule in the chyme. At the end of this laborious process, each complex molecule has been broken down into its simple states. For example, carbohydrates are broken down into simple sugars, the protein into amino acids, and the fats into glycerol and fatty acids. These substances are absorbed by cells and various systems for the proper functioning of the organism. Substances that cannot be broken down by the body pass through the large intestine, or the colon, where the last of the water, ions, and salts are reabsorbed, and the remaining solid material, called feces, exits through the anus. Thus, the alimentary canal is a passageway for food to be transported, absorbed, and released.
Anna Taran -- 2001
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