Disorders of digestion and absorption of carbohydrates

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Carbohydrate absorption occurs primarily in the duodenum and jejunum with intestinal epithelial microvilli only in the form of monosaccharides. Hydrolysis of starch and glycogen food begins in the mouth under effect salivary α-amylase. Monosaccharides can be absorbed already in the mouth. In the stomach, no enzymes, performing the hydrolysis of carbohydrates. The intestinal cavity under the influence of α-amylase pancreatic juice before they hydrolyze dextrins and maltose (cavitary digestion). On the surface of the microvilli of enterocytes enzymes are localized: sucrase, maltase, isomaltase and lactase other, splitting and disaharaidy dextrins to monosaccharides (parietal digestion).

Monosaccharide absorption in the small intestine - mentioned active transport process of molecules through the membrane of epithelial cells, which requires energy. The driving force of glucose transport into the epithelial cell is an ATP-dependent sodium pump, and the transport occurs by means of specific transporter, physically independent of the sodium pump. This is an example of secondary active transport, in which to transfer a single connection (glucose) using the energy of the electrochemical gradient generated by another substance (sodium ions). Considered glucose transport mechanism also operates in epithelial cells of renal tubules. Receipt of the glucose into the red blood cells is carried out by a different mechanism.

The process of absorption of the individual monosaccharides occurs at different rates. The highest speed of the process is characterized by glucose. Apparently, this is due to the difference in specific monosaccharide transport mechanisms through the mucosa of the small intestine.

Violation of the breakdown of carbohydrates. Among the most common problems include the lack of enzymes - disaccharidases: sucrase and isomaltase manifested always a combination. As a result of this disaccharide sucrose and isomaltose are not split and not absorbed by the body. Accumulating with intestinal lumen disaccharides osmotically bind significant amounts of water, causing diarrhea (diarrhea). Under these conditions, it is also possible absorption of a certain amount of epithelial cells disaccharides. However, they are metabolically inactive and unaltered rather quickly excreted in the urine. When defects activity disaccharidases disaccharides load does not cause hyperglycaemia in the range of 30-90 minutes, as is the case in healthy people.

Monosaccharides (galactose, glucose, fructose, and pentose) from food or vacated by hydrolysis and poly disaccharides absorbed microvilli of epithelial cells of the small intestine.

Causes of disorders of the process of absorption of carbohydrates are:

1) The inflammation of the small intestine mucosa.

2) The action of toxins that block the process of phosphorylation and dephosphorylation (phloridzin, monoyodatsetat).

3) Lack of ions Na +, for example, when adrenocortical hypofunction.

4) Violation of the blood supply to the intestinal wall.

In addition, in neonates and infants insufficiency active as digestive enzymes and enzymatic systems phosphorylation and dephosphorylation of carbohydrates, whereby their absorption is slowed down.

Lactose intolerance syndrome without deficiency of lactase enzyme. Malignant syndrome manifests in the first days after birth as severe diarrhea, vomiting, acidosis, lactosuria often and proteinuria. Also revealed atrophy of the adrenal glands and liver, renal tubular degeneration.

Congenital lactase deficiency. The enzyme hydrolyses the disaccharide lactose into glucose and galactose. Newborn babies usually get 50-60 grams of lactose (milk) a day "The most characteristic expression of lactase deficiency - diarrhea after taking milk. Undigested lactose enters the lower parts of the small intestine, which is fermented by intestinal microflora to produce gases (which causes flatulence) and acid "Their osmotic action in the gut lumen attracts a large amount of water that causes diarrhea. Here Cal has acidic pH and contains lactose laktosuria sometimes observed. Over time, the child develops malnutrition. This syndrome should be distinguished from the acquired lactase deficiency (enteritis, inflammatory diseases of the colon, sprue) and intestinal lactase deficiency from occurring in adults.