primary digestion

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Related to primary digestion: respiratory system, Human digestive system


1. the subjection of a substance to prolonged heat and moisture, so as to soften and disintegrate it.
2. the act or process of converting food into chemical substances that can be absorbed into the blood and utilized by the body tissue.
 Digestion. 1. Carbohydrates: principally starches, lactose, and sucrose. Starches are acted on by the enzyme ptyalin (alpha-amylase) secreted in saliva, by hydrochloric acid (HCl) in the stomach, and by pancreatic amylase and intestinal amylase in the small intestine, which split the starches into maltose and isomaltose. These, in turn, are acted on by maltase and isomaltase and split into two molecules of glucose. Lactose is split by the enzyme lactase into a molecule of galactose and a molecule of glucose. The monosaccharides glucose, galactose, and fructose are absorbed from the small intestine into the blood. 2. Fats: emulsified by bile salts and agitation. The emulsified fats are acted upon by pancreatic and enteric lipase to form fatty acids, glycerol, and monoglycerides, which are absorbed through the intestinal walls. Small quantities of diglycerides and triglycerides are also absorbed. 3. Proteins: acted on chiefly in the stomach by pepsin, which splits proteins into proteoses, peptones, and polypeptides. In the small intestine they are acted on by the pancreatic enzymes trypsin, chymotrypsin, and carboxypeptidase to form polypeptides and amino acids. In the small intestine the peptidases complete the breakdown of the peptides into dipeptides and amino acids. Almost all proteins are eventually digested and absorbed either as amino acids or as dipeptides or tripeptides.
See illustration. Digestion is accomplished by physically breaking down, churning, diluting, and dissolving the food substances, and also by splitting them chemically into simpler compounds. Carbohydrates are eventually broken down to monosaccharides (simple sugars); proteins are broken down into amino acids; and fats are absorbed as fatty acids and glycerol (glycerin). The digestive process takes place in the alimentary canal or digestive system. The salivary glands, liver, gallbladder, and pancreas are located outside the alimentary canal, but they are considered accessory organs of digestion because their secretions provide essential enzymes.
gastric digestion digestion by the action of gastric juice.
digestion/hydration in the omaha system, a client problem defined as converting food into substances suitable for absorption and assimilation into the body and supplying water to maintain adequate body fluids.
intestinal digestion digestion by the action of intestinal juices.
pancreatic digestion digestion by the action of pancreatic juice.
peptic digestion gastric digestion.
primary digestion digestion occurring in the gastrointestinal tract.
salivary digestion the change of starch into maltose by the saliva.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

pri·mar·y di·ges·tion

digestion in the alimentary tract.
Farlex Partner Medical Dictionary © Farlex 2012

pri·mar·y di·ges·tion

(prī'mar-ē di-jes'chŭn)
Digestion in the alimentary tract.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012