Physiology of digestion

Digestion begins in the mouth, where it is crushed and moistened with saliva to form a pasty mass. Not enough shredded food may be released from the body in maloizmenennom form of, resulting in the malabsorption of nutrients. Besides, enough shredded food causes increased gastric motility, which can lead to diarrhea and development of endogenous malnutrition.

Saliva - Colorless, slightly opalescent liquid slightly alkaline reaction. It consists of various salts from the water, certain organic substances, ptyalin (amilazы) and small amounts of maltose

Amylase It breaks down starch food Eritrea- and ahrodekstriny, which are then converted (under the action of the enzyme) in the disaccharide maltose, cleavable by the enzyme maltose to glucose. The action of amylase in the stomach and continues until, while the food is not saturated acidic stomach contents. After 20-30 min after exposure to the stomach of food effect pytalin terminates in an acidic medium. By this time almost completely converted starch into dextrins and maltose.

In the stomach, food is further machining and effects gastric enzymes.

Hydrochloric acid gastric juice colloidal state alters protein and fiber, preparing them for further digestion. Due to this under the influence of pepsin digest fibrin, collagen and connective tissue. Muscle fibers are released in the stomach by layers of connective tissue and sarcolemma, whereby the first cross-fading, and then the longitudinal striations, and the edges are rounded fibers. In this state, most of the muscle fibers enters the duodenum.

Under the action of hydrochloric acid of the stomach tissue, forming the shell of plant cells, swells and macerated.

The duration of digestion in the stomach depends on the quantity and quality of food. Food, rich in carbohydrates, It enters the intestine quickly, protein foods - slowly, and fat lingers long in the stomach.

The fastest way to pass through the alimentary canal dairy foods, which contains lactose, increases peristalsis. Liquids can come directly from the stomach into the intestine, and heat is conducted faster, than cold. On average, the food is in the stomach by 1,5 to 5 no, when a large amount of it - up to 6-8 hours.

In the duodenum food finally cleaved by enzymes pancreatic and intestinal juices, with the participation of bile. Enzymes, contained secret duodenum, are able to cleave various nutrients, even if, if they are not prepared for digestion in the previous steps (mouth and stomach). Therefore, the conversion of nutrients in the duodenum are essential for digestion and absorption.

Trypsin pancreatic juice is easy to digest the muscle fibers, and on collagen and dense connective tissue (Tendon, ligaments, cartilage, etc.) It has little effect. Alpha-chymotrypsin, karʙoksipeptidazы, A- and B- elastase are involved in the hydrolysis of proteins to amino acids, which are absorbed.

Lipase in the presence of bile acid cleaves triglycerides (neutral fats) into glycerol and fatty acids (palmytynovuyu, oleic, stearic). The fatty acid content in the alkaline environment of the duodenum under the influence of bile acids are converted mainly in dissociated unstable soaps, which are then dissolved and absorbed. Under the action of pancreatic juice amylase hydrolyse polysaccharides to form maltose.

Bile It enhances the action of amylase, trypsin, and especially lipases (to 15 20 time) pancreatic juice. Besides, provides education bile resistant fat emulsions, creating optimal conditions for the action of lipase. Bile acids help dissolve fatty acids and absorption of products of digestion of fats. Bile is depressing to pepsin gastric juice, as well as with pancreatic and intestinal juices neutralize acidic food chyme, from the stomach, and it prevents the destruction of trypsin under the influence of pepsin.

Secretion of intestinal mucosa during digestion continues until 8 no. One of the key enzymes of the intestinal juice are peptidase, which split polypeptides and peptones to amino acid. These include enzymes leucine aminopeptidase, отщепляющая NH2-terminal amino acid residues. Thus, in the bowels of proteins completely hydrolysed to free amino acids, which are easily absorbed. The intestinal juice also contains nuclease, cleaving nucleic acid and polynucleic:

  • b-фруктофуранозидаза (invertase, sucrase), расщепляющая b-D-фруктофуранозиды, including sucrose, glucose and D-fructose;
  • b-галактозидаза (lactase), splits lactase into glucose and galactose;
  • intestinal maltase, splits maltose.

The intestinal juice contains a large amount of lipase, and enterokinase - Enzymes. It converts inactive enzyme pancreatic trypsinogen to active trypsin.

Of great importance in the process of digestion is slime, which is part of the intestinal juice. Adsorbed on the surface enzymes, It contributes to their mucus action. Digestion continues in the small intestine 4-5 hours. During this time all the nutrients fully digested intestinal juice and the resulting hydrolysis products are absorbed slowly. To a small extent the absorption occurs in the stomach, where water can be absorbed, alcohol, glucose and mineral salts.

At the junction of the small intestine to the large located mışeçnıy pulp, which is constantly in a state of moderate contraction. His periodic relaxation promotes entry of chyme in small portions into the colon, wherein during the movement of the food mass is being stirred in the formation of faeces. The secret of the colonic mucosa contains peptidase, nucleases, amylase, b-фруктофуранозидаза (sucrase) maltase, b-галактозидаза (lactase) and other enzymes.

Absorption of nutrients in the colon occurs in small amounts, and in the distal intestine is almost completely absent. The cecum and ascending part of the transverse colon sucked up 90 % water.

Decorated normal feces It has a neutral or slightly alkaline reaction, It contains stercobilin (gidroʙiliruʙin), heavily modified muscle fibers, vegetable fiber, soap; possible presence of trace amounts of fatty acids. Neutral fat is absent. Besides, in the feces are skatole, phenol, indole, leucine, koproeterin (of cholesterol), purine bases (guanin, adenine, et.), insoluble sodium salt, Calcium, magnesium and iron phosphate, elements and intestinal mucosa (epithelium, mucin) bacteria and, which are dominated by E. coli and enterococci.


Fecal most advantageously carried out after a pre-assigned patient trial diet. The most common are diet Schmidt and Pevzner.

Diet Schmidt: 11.5 liters of milk, 2-3 Soft-boiled eggs, 125 Mr. poorly roasted minced meat, 200-250 G mashed kartofelynogo, slimy broth (40 Mr. oatmeal), 100 g of white bread or crackers. 50 g oil. Energy value - 10467 kJ. During normal digestion residues write not found in the stool.

Diet Pevzner: 400 g bread, on them 200 g black; 250 g meat, fried piece; 100 g oil, 40 g sugar, buckwheat and rice porridge, fried potatoes, carrot, salad, sauerkraut, stewed fruit, Fresh apples. Energy value - 13607 kJ.

Diet in each case is selected based on the state of the digestive system of the patient and his usual food. Diet Pevsner provides a greater load on the digestive system and thus helps to identify the dysfunction of the digestive system, even a small degree. Diet Schmidt - sparing, It is used in cases, Pevsner when the diet is too annoying. Simultaneously provide the patient with a diet any indifferent colorant (Carbolite, carmine) and watching his appearance in the feces.

Collect feces should be in a clean container, desirable glass, or waxed cups. It is unacceptable to send feces for analysis to Matchbox and cartons, as this from feces in the paper absorbs the liquid, and its consistency can vary. Explore cal must be no later than 8-12 hours after his release, since under the action of microorganisms and enzymes in the there may occur changes. It is best to examine the feces, the resulting self-defecation, without impurities (Urine, barium chloride, fat, water enema and after t. d.). Put feces in a fume hood or well-ventilated room, where he prepared for the study.

Kal examined macroscopically, microscopically, chemical and bacteriological.

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