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1. PHYSIOLOGY OF DIGESTION

2. Digestion is a complex of physical and chemical processes, as a result of which specific nutrients are split up to non-specific substances suitable for absorption into the blood and lymph.

3. The essence of digestion consists in splitting (hydrolysis) of specific nutrients to non-specific monomers: proteins to amino acids, fats to fatty acids and glycerin, carbohydrates to monosaccharides (mainly glucose). In addition to nutrients with food, the body receives the necessary substances that are absorbed without processing. These are mineral salts, microelements, vitamins (water - and fat-soluble), water, and also alimentary fibers (fiber and pectins which are almost not assimilated). Alimentary fibers are very important for the body. They perform the detoxifying function - absorb radionuclides , stimulate the motility of the gastrointestinal tract, provide a more complete digestion and absorption.

4. Value of digestion. Digestion provides : 1. Energy needs of the body-the inflow of energy with nutrients (the most energy-intensive-fats); 2. Plastic needs of the body - nutrients are the building material for growth, development and renewal of all cellular structures. 3. Digestion is the initial stage of metabolism.

5. PRINCIPLES OF THE GASTROINTESTINAL TRACT 1 . Complex principle of food processing: * physical processing-grinding, dissolving, shaking, malaise, thermal stabilization; * chemical processing-hydrolysis of nutrients due to enzymes of digestive juices. 2. The conveyor nature of the activity of the digestive tract . Each department of GIT performs a certain function. If the function fails, the food is returned. For example, in the oral cavity occurs mainly mechanical food processing, in the stomach-rupture of cell membranes of food cells, in the small intestine - the final hydrolysis of nutrients to monomers and their absorption into the blood and lymph. 3. Adaptive nature of the activity of the gastrointestinal tract . Food for the digestive tract is an external irritant. The gastrointestinal tract can be represented as a part of the external environment, placed deep into the body. A feature of the action of food as an irritant is that it acts for a long time on the excitable tissue of the gastrointestinal tract (glandular and muscular). Given nature of the interaction of excitable structures with the stimulus always pronounced adaptive response.

6. Digestive tract adapts: * to the amount of food by changing the amount of juice produced. * to the quality of food-on every kind of food is generated specific set of enzymes. Monotonous nutrition leads to the disappearance of individual enzymes of the digestive tract. The quality of food determines the specificity of digestion in different people and animals. In the selection of therapeutic diets can not be assigned monotonous food. This impoverished the composition of the juice, which leads to the disruption of the adaptive capabilities of the gastrointestinal tract and disoder of its activities. * to the diet - the digestive tract works in time intervals. By a certain time of eating the activity of the gastrointestinal tract is increased. Violation of the diet leads to diseases such as gastritis, ulcers, etc.

7. The main processes occurring in the digestive tract (gastrointestinal functions ). The functions of the digestive tract include: secretion, motility, absorption , excretion , and protective function. Secretion is the release of digestive juices with enzymes into the digestive tract. Features of enzymes : 1. Specificity , implying differences of enzymes * by type of action - each enzyme acts on a specific type of nutrients. There are: proteolytic enzymes (proteases, splitting proteins through intermediates to amino acids), lipolytic enzymes (lipases, causing the hydrolysis of fats to fatty acids and monoglycerides ) and glucolytic enzymes (amylases or carbohydrates, causing the hydrolysis of carbohydrates to monosaccharides );

8. by the nature of action : initial action (rough processing of food, rupture of cell membranes); continuing action (separation of side radicals from protein molecules); final action (hydrolysis of di - and tripeptides to amino acids). 2 . The conveyor principle of enzymes activity-consistent in the course of the digestive tract the inclusion of enzymes. In most cases, each subsequent enzyme continues the effect of the previous one. 3 . Termination of enzyme activity during the transition from one department to another. This is facilitated by a sharp change in the pH of the environment in different departments of GIT. So, in the oral cavity environment is often slightly alkaline, in the stomach acidic (especially at the height of digestion) and intestinal is alkaline again. 4. The increase in the number of enzymes from the oral cavity to the small intestine, where their number reaches a maximum. The nature and mechanism of release of enzymes depends on the type of digestion.

9. Types of digestion 1 . Intracellular digestion , typical for unicellular. Nutrients enter the cell by phagocytosis and pinocytosis. Inside the cell, they are hydrolyzed in digestive vacuoles lysosomal enzymes. Undigested residues with enzymes and digestive vacuole elements are actively released into the environment. A lot of energy is spent on all the processes. In the human body, intracellular digestion is preserved in leukocytes and cells of the lympho -reticular- histiocytic system. 2 . Extracellular digestion is divided into 3 types: cavitary (distant), parietal (membrane, contact) and inorganic. In the digestive tract of a person is the place of cavitary and parietal digestion.

10. The distinctive features of cavitary and parietal digestion № Cavitary digestion Parietal digestion 1 Initial stage The final stage, which ends with the absorption of monomers into the blood and lymph. 2 Food juices are released into the gastrointestinal cavity, hydrolysis of nutrients occurs in the food lump in the process of chaotic movement of enzymes when mixed with food. Hydrolysis of nutrients occurs on the surface of the plasma membranes of enterocytes , enzymes are rigidly fixed, their active centers are strictly oriented in space. 3 Occurs in all cavities of gastrointestinal tract Partly in the duodenum, as well as in the jejunum and ilium , that is in the small intestine.

11. 4 It spends a lot of juice, enzymes and energy, as the juice with food masses goes to the next Department. Economical consumption of enzymes and energy, as enzymes are fixed and can repeatedly react into hydrolysis reaction. 5 There is a rough breakdown of molecules of nutrients to oligomers . There is a final hydrolysis of nutrients to monomers, which ends with absorption into the blood and lymph. 6 A small surface of contact with food. The huge contact area due to folds, villi (outgrowths of the mucosa) and microvilli (growths membrane of enterocytes ), up to 10 thousand m 2 . **

12. The motility of the gastrointestinal tract is a diverse forms of the motor activity of the gastrointestinal tract. Motility also contributes to the conveyor principle of the digestive tract. Motor skills are carried out: 1 . Due to the contraction of skeletal muscle , located in the oral cavity (tongue, larynx, pharynx), the upper third of the esophagus and at the end of the digestive tube (external anal sphincter). They give arbitrary, tetanic contractions, with large expenditure of energy. 2 . Due to the contraction of smooth muscles throughout the digestive tract. They are involuntary and give 3 types of contractions: tonic (for better contact with the food masses), peristaltic (for the progressive motion of the food mass in the oral-anal direction) and periodic (for mixing with food).

13. Functions of motor processes in the gastrointestinal tract: 1 . The capture of food and its grinding. 2 . Progressive movement of food through the digestive tract, where sphincters play a large role. 3 . Mixing with juices to dissolve substances and better contact with enzymes. 4 . Close contact with the mucosa. 5 . The creation of a hydrostatic pressure gradient for suction. 6. Excreation of undigested residues from the body.

14. Types of motor activity of the GIT -oral cavity- suking ( in newborns), chewing, swalloving -esophagus- tonic, peristaltic -stomach- tonic, peristaltic, systolic - intestines- tonic, peristaltic, pendular , rhythmic segmentation Violations of motor activity : atony (stasis of food), reflux (reverse throw food in the previous division). Suction - transport or transfer of the final products of digestion, non-specific monomers from the gastrointestinal cavity through a semi-permeable membrane into the internal environment of the body (blood and lymph).

15. Conditions necessary for suction. 1 . The presence of the final non-specific substances (monomers) - glucose, amino acids, fatty acids, glycerol. 2 . The presence of a large surface area for absorption. 3 . The permeability of the membranes of the gastrointestinal tract to substances. 4 . The presence of specific proteins-carriers. 5 . The presence of ATP energy for active transport. 6 . Presence of gradients for passive transport (concentration, osmotic, hydrostatic , chemical , electrical) 7 . A certain time of food stay in the digestive tract.

16. Intensity of absorption in different parts of the gastrointestinal tract. 1 . Oral cavity . There are no conditions for the absorption of nutrients. Food is here for a short time, there are no final products of hydrolysis. In the oral cavity are absorbed medicinal substances (nitroglycerin, validol ), poisons (potassium cyanide). 2. Stomach. There are almost no end products of hydrolysis in the stomach. Absorbed water, mineral salts, drugs, alcohol, glycerin. 3. Intestine. In the small intestine, there are all conditions for absorption and therefore all are absorbed here: glucose, amino acids, glycerin, fatty acids, mineral salts, water (in the form of isotonic solutions) and vitamins. 4. Large intestine. In the large intestine, water is absorbed mainly up to 2 l/day.

17. Basic mechanisms of absorption 1. Passive transport without expenditure of energy by a gradient. 2. Active transport with ATP energy expenditure (the gradient does not matter), involved protein carriers. Passively absorbed: water (by osmotic gradient), organic acids and organic bases (concentration and hydrostatic gradients), mineral salts K+, CL- ( by concentration and electrical gradients), vitamins ( by concentration gradient). Actively absorbed : amino acids, glucose, fatty acids, Ca+, Na+.

18. Mechanisms of absorption of proteins, fats and carbohydrates. PROTEINS are absorbed in the form of amino acids in the small intestine (possibly in the form of di - and tripeptides ). Amino acids are absorbed actively, with the participation of Na+ and carriers (4 system of carriers). The amino acid and the carrier form a complex with Na + ions, which penetrates the enterocyte through the apical membrane along the sodium gradient. In the cell, this complex decays. Amino acid by concentration gradient through the basal membrane is absorbed into the blood and portal system enters the liver. The carrier returns to the intestinal cavity, with the help of Na+-K+ pump Na+ is also expels from the cell into the intestinal cavity actively with the cost of ATP. CARBOHYDRATES are absorbed in the form of monosaccharides (glucose, galactose , fructose). The mechanism of glucose absorption is similar to the absorption of the amino acids, only a private carrier. The energy is required on the K+ - Na+ pump. Through the basal membrane of enterocyte glucose absorbed by the mechanism of facilitated diffusion.

19. FATS are absorbed in the form of monoglycerides , glycerol and fatty acids. Glycerin is absorbed passively by the concentration gradient. Fatty acids and monoglycerides together with cholesterol, lecithin and bile acids form micelles, which are captured by the membrane of enterocytes and transferred into the cells without energy costs. In enterocytes from fatty acids and glycerol is the synthesis of neutral fat, specific to humans. The smallest droplets of neutral specific fat, with cholesterol and phospholipids, are covered with a lipoprotein membrane and form chylomicrons, which are actively absorbed into the lymph through the basal membrane and then transferred to the General blood stream into the fat depot. Bile acids are absorbed through the basal membrane into the blood, enter the liver and participate in the formation of bile. Part of the bile acids enter back into the lumen of the small intestine.

20. Incretion - production of gastrointestinal hormones in the blood. There are over 30 of these hormones present. Among them the most important are: * gastrin (produced by g-cells of the stomach, stimulates gastric secretion): * secretin (produced in the duodenum, stimulates pancreatic secretion); * cholecystokinin- pancreosimin (CCK-PS, produced in the duodenum, stimulates pancreatic secretion and bile secretion); * motilin (produced in the proximal small intestine, stimulates gastric secretion and motility); • willikin (produced in the duodenum, strengthens the contraction of the villi, increase absorption); * bombesin (produced in the duodenum, stimulates gastric secretion ); * somatostatin (produced in the stomach and in the proximal small intestine, inhibits digestion).

21. Excretion are the processes aimed to excrete from the blood into the cavity of the gastrointestinal tract unnecessary to the body substances. Through the digestive tract from the internal environment to the external output: - salts of heavy metals (lead, gold, mercury, silver); - alcohol; - medicinal substances (antibiotics, salicylates); - narcotics (morphine); - toxic substances (methane, ammonia, aromatic acids); - excess substance (water, salts); - metabolites (urea, uric acid, creatinine , bile pigments).

22. Protective or barrier function of the gastrointestinal tract-a barrier, bacteriocidal , bacteriostatic and detoxification functions. REGULATION OF THE GASTROINTESTINAL Basic principles : 1. Adaptation of the gastrointestinal tract to eating. 2. Interaction of the gastrointestinal tract with the state of the body (mood affects digestion, and vice versa, digestion affects mood). Mechanisms of regulation of the GIT. - local level of regulation - central level of regulation. Local regulation includes : peripheral reflexes formed by peripheral ganglia and plexuses (at this level, there are local reflex arcs with 3 types of Dogel cells), as well as local endocrine apparatus that produces gastrointestinal hormones in the blood (see above), tissue hormones in the interstitial fluid-paracrine function (GIP , VIP, substance P, somatostatin , serotonin, histamin ), which have a more local effect.

23. Features of the action of gastrointestinal hormones Hormones activate their and the underlying departments of the gastrointestinal tract, but inhibit the previous department (this is the basic law of the activity of the gastrointestinal tract ). 2. Humoral substances are released under the influence of local factors (nervous and humoral ), as well as under the influence of central reflex mechanisms (for example, gastrin is produced in the stomach and enters the blood under the influence of hydrochloric acid and is also released under the action of conditional and unconditional digestive reflexes ). 3. Humoral substances have an impact on the neural mechanisms of regulation of the gastrointestinal tract (receptor apparatus, local reflex arcs).

24. Central regulation is represented by neuro-humoral mechanisms. It is unconditional and conditioned reflexes that perform the starting function for the digestive tract, and humoral effects In the mouth the food is very short time, therefore, to regulate its functions are fast and accurate neuro -reflex mechanisms (+++). In the small intestine, having a very great length and the area it is advisable economical inclusion of local mechanisms of regulation of (+++). In the stomach, reflex mechanisms are included mainly in the cerebral phase of regulation (see below), but since the food is there for a long time, then have time to work and humoral , prolonged regulation mechanisms, and local mechanisms are still weak (+). In the duodenum, the role of reflex mechanisms falls sharply ( + ), and the value of local mechanisms increases (++), mechanisms of humoral regulation are significantly expressed.

25. Different types of regulation in the digestive system № Regulation Mouth Gastric Duodenum Small intestine Colon 1 Nervous-reflex +++ ++ + - - 2 Humoral - +++ +++ + - - 3 Only local regulation - + ++ +++ ++

26. METHODS OF RESEARCH OF THE GASTROINTESTINAL TRACT 1 . Experimental methods 2. Clinical methods of study of gastrointestinal tract. Experimental method . In acute experiments it is impossible to investigate the functions of the gastrointestinal tract, as for the normal functioning of the digestive system need a healthy, holistic body. For this reason, the study of the functions of the digestive system (in contrast to the structure) began relatively late. In 1842, the Russian scientist Basov suggested a fistula of the stomach. Fistula is a tube for communicating the hollow organ of the gastrointestinal tract or the glands duct with the external environment. However, Basov could not get pure gastric juice without the admixture of food. The founder of chronic experiments in the study of digestion is a Russian scientist I. P. Pavlov with his students

27. For experimental studies of the functions of the digestive organs and mechanisms of their regulation I. P. Pavlov was awarded the Nobel prize. Pavlov's merits are determined by the following: • Pavlov developed a series of surgeries on dogs (in the operating room a sterile environment with postoperative care until complete recovery); * In the course of chronic experiments Pavlov was able to get digestive juices in pure form and in natural conditions. The main experiments developed by Pavlov: fistula of the salivary gland, the experience of "imaginary" feeding, isolated ventricle according by Pavlov, the operation of the Tiri-Vell with a modification of Pavlov, fistula Ekka -Pavlov.

28. Clinical methods of research: 1. Mastico с iography - registration of movements of the low jaw; 2. Electromyography - the recording of the potentials of the chewing muscles; 3. Capsule of Leshly-Krasnogorsky for collecting saliva; 4. Probing different parts of the digestive tract; 5. Radiotelemetry ; 6. Electrogastrography - recording of the currents of the stomach; 7. Radioscopy or radiography; 8. Endoscopy, biopsy; 9. Ultrasound examination; 10. Blood and urine tests for the concentration of Pro-enzymes, hormones. 11. Immunological methods.

29. DIGESTION IN THE ORAL CAVITY

30. Features of digestion in the oral cavity: 1. The food is a short time-15-20 seconds. 2. The taste of food is analyzed. 3. Cavitary digestion . 4. The environment is often weakly alkaline. 5. Occurs mainly physical-mechanical processing of food.

31. Functions of the oral cavity I. Digestive functions: 1. Capture of food. 2. Analysis of the suitability of food (edible, inedible ). 3. Analysis of the taste of food (sour, sweet, bitter, salty). 4. Analysis of the food consistency of food (soft, solid, liquid). 5. The temperature analysis (cold, warm, hot ).

32. All types of analysis occur with the participation of various receptors in the oral cavity. These are taste, tactile, temperature and pain receptors. 6. Physical and mechanical processing of food-grinding, wetting, dissolving, forming a food lump (this involves the types of movement: chewing, sucking, swallowing). 7. Initial chemical processing of food. 8. The oral cavity is a powerful reflexogenic zone for the regulation of digestion and metabolism.

33. II. Not-digestive functions. 1. Participation in breathing (anatomical dead space). 2. Participation in phonation (speech function, wetting of vocal cords). 3. Protective function ( lysozyme of saliva has bactericidal action, immunoglobulins involved in the immunity, the animals bite in self-defense) 4. Means of special communication between people (love, sex)

34. Research methods of the oral cavity Experimental (fistula of the salivary gland). 2 . Clinical (capsule Leshly-Krasnogorsky , probing the ducts of the salivary glands, sialography - x - ray study of the salivary glands)

35. Salivary glands There are 3 pairs of large salivary glands. 1. Parotid (serous). 2. Submandibular (mucous-serous). 3. The sublingual (mucous-serous). In addition, saliva is produced by glass-like mucous cells scattered on the mucous membrane of the tongue, cheeks, palate and lips. Saliva-transparent, viscous liquid, often slightly alkaline reaction, sometimes neutral. 1.5–2 liters of saliva is produced per day. It consists of 99% water and 1% dry residue. The dry residue includes organic substances (enzymes, non - enzymes) and inorganic substances (Na+ , K+ , Ca ++, HCO3 -, Cl -)

36. The enzymes of saliva: Amylase - splits starch to maltose. Maltase - splits maltose disaccharide to monosaccharides (glucose, fructose). But, since the food is in the oral cavity for a short time, the action of saliva enzymes continues in the stomach until the food lump is impregnated with acidic gastric juice. Lysozyme is a bactericidal enzyme. Non-ferments include: • mucin (licks food lump, easier to swallow and protects oral mucosa against mechanical damage); * metabolites (lactic acid, uric acid, urea, creatinine , oth .).

37. Functions of saliva: * wets, dissolves, licks food; * promotes the formation of food lump; * splits carbohydrates; * promotes the perception of taste sensations; * performs mineralizing, protective and trophic functions for hard tooth tissues • a person stands out constantly in a small amount, since it moistens the vocal cords. Some animals in the composition of saliva contains special substances: for example, the hirudin of the leeches has an anticoagulant effect, spiders have sticky stuff for weaving the web

38. Regulation of salivation In the regulation of salivation is dominated neuro - reflex mechanisms, as the food is in the mouth is a short time. Distinguish unconditional and conditional reflexes. Unconditional reflexes - congenitale , species, constants. It begin immediately after getting food into the mouth. At the same time taste, tactile, temperature, and sometimes pain receptors are excited. Afferent signals go in the composition of the facial, trigeminal, lingual and wandering nerves in the main center of digestion, which is located in the medulla oblongata (diamond-shaped fossa at the bottom of the fourth ventricle). Efferent pathways approach the salivary glands in the facial and lingual nerves.

39. Parasympathetic nerves stimulate the release of liquid and abundant saliva containing a small amount of organic matter ("washing saliva"). With irritation of the sympathetic nerves, a small amount of saliva is released, which contains enzymes and mucin making it thick and viscous. The sympathetic innervation begins from the upper thoracic segments of the spinal cord (lateral horns) and switches through the upper cervical ganglia.

40. Conditional reflexes – acquired, individual, variable-are developed on the basis of unconditional reflexes. Begin befor getting food into the mouth at the sight of it, the smell, talking about food, the ringing of plates, spoons. The olfactory, visual, auditory receptors are excited. Afferent signals go in the composition of the optic, olfactory and auditory nerves to the central nervous system and reach the cerebral cortex, exciting the cortical centers of vision, smell and hearing. If a person perceives familiar food (by smell, appearance and sound manifestations), it is means between the centers of vision, smell and hearing in the cortex, and also the highest cortical center of digestion are temporary connections

41. In the mechanism of their formation is of great importance dominant digestive center, which attracts signals from other centers. Then impulses from the higher digestive center enter to the main center of digestion of the medulla oblongata, and from there by the efferent nerves to the salivary glands. Thus, the reflex arc is closed using the temporary connections of the cerebral cortex. Salivation is also associated with the participation of the hypothalamus of the intermediate brain . The nature of saliva depends on the amount and consistency of the food. If the food is liquid, then there is viscous saliva and a small amount. If the food is dry, then produced saliva liquid more abundant.

42. The scheme of regulation of salivation: A – unconditioned reflex, B – conditional reflex. 1 – receptors of the oral cavity; 2 – visual, auditory, obnajennye receptors; 3 – afferent path; 4 – the main center of digestion of the medulla (sensory and preganglionic parasympathetic neurons); 5 – the Supreme center of digestion in the cerebral cortex (along with direct and feedback to the main center of digestion); 6 centers of vision, hearing and smell to the cerebral cortex; 7 – temporal relationships of conditional visual, auditory and olfactory reflexes in the cerebral cortex; 8 – the sympathetic center of the spinal cord (preganglionic neurons); 9 – postganglionic sympathetic neuron; 10-sympathetic nerve; 11-parasympathetic nerve; 12 – intramural parasympathetic ganglion neuron; 13 – salivary gland.

43. DIGESTION IN THE STOMACH. PANCREAS. LIVER.

44. Features of digestion in the stomach . 1. С avitary digestion. 2. Enviro n ment is acidic. 3. Food in stomach is a long time (3-10 hours) and often in large numbers, so stomach is not only organ digestion, but also a food depot. 4. Digestion in the stomach is mainly exposed proteins before polypeptides, with the destruction of all cell membranes and shells in foods, as a result from a food lump formed a homogeneous semi - liquid mass of acidic consistency- chyme .

45. Functions of the stomach . 1. Digestive: * secretory - production of gastric juice with enzymes; * motor - grinding, mixing and moving food; * suction - due to the lack of necessary conditions in the stomach absorbed only water, mineral salts, alcohol, glycerin, drugs (antibiotics, narcotic, potassium iodide), toxins; * endocrine - in the pyloric part of the stomach hormones are produced: gastrin , motilin , as well as bioactive substances histamine, serotonin; * excretory - stomach removes toxins, heavy metal salts (lead, mercury, gold), medicinal substances, metabolic products from the internal environment into external; * protective - bacteriocidal and bacteriostatic action of gastric juice.

46. 2. Not digestive : participation in maintaining the pH of the internal environment; participation in erythropoiesis. The stomach produces internal anti-anemic factor of Castle, which promotes the absorption of vitamin B12 (external factor of Castle). Vitamin B12 is involved in the formation of erythropoietins , necessary for the maturation of red blood cells; production of lipotropic substances that prevent fatty degeneration of the liver.

47. The stomach consists of: * cardiac part - is the place where the esophagus enters the stomach where is cardiac sphincter located; • the bottom of the stomach - a dome or vault; * the body of the stomach-the expanded part; * pyloric par t - narrowed part, which ends with a pyloric sphincter. The lower, left, convex edge of the stomach forms a large curvature, and the upper, concave, right - a small curvature.

48. Shells of the stomach. 1. The mucous membrane has a folded surface, 4-5 longitudinal folds go in the direction from the cardiac opening to the pylorus. Folds are clearly visible from a living person by endoscopy in empty stomach and straightened when it is filling. On the surface of the fields are gastric fossa - deepening each of which opens 2-3 glands that produce gastric juice. 2. Submucous - loose, movable, has many blood vessels and nerve plexuses. 3. Muscle - the most powerful, formed by a smooth muscle tissue, which forms 3 layers: the outer longitudinal, middle circular and inner oblique. In the muscle membrane located intermuscular nerve plexuses. 4. Serous - formed visceral leaf of peritoneum (under the serous membrane are subserosal nerve plexuses).

49. Glands of the stomach. The mucosa of the stomach forms cardiac, fundic and pyloric glands. There are 4 types of glandular cells of the stomach mucosa: • main ( glandulosytes ) - produce enzymes, located in the fundic glands; • parietal - produce HCL and also the internal anti-anemic factor of the Castle. They are located in a small number in the cardiac glands and mainly in the fundic glands; * additional ( mucocytes ) - produce mucus, located in all glands of the stomach; • endocrine ( endocrinocytes ) - mainly located in the pyloric glands of the stomach. These include argentophilic cells (produce serotonin), G-cells (produce gastrin ), mast cells (produce histamine) and other endocrine cells that produce BAS.  

50. Methods of studying the stomach . I . Experimental methods (operations on dogs): • a fistula of the stomach . It was proposed by V. A. Basov in 1842. It's a tube with two extensions. One end is inserted into the stomach, and the other is outside. Fistula of Basov does not allow to get gastric juice in its pure form; experience of imaginary feeding was developed under the leadership of I. P. Pavlov in 1899. To fistula of Basov is added operation esophagotomy – transection of the esophagus. Animal with gastroesophagostomy can consume food without saturation, as nutrients fall out of the holes of the esophagus. At the same time pure gastric juice is realeased through the fistula, but the condition is different from natural.

51. • Isolated ventricle by P. Heidenh ine – in this operation the small ventricle is formed from the flap of the large curvature of the stomach. This ventricle through the fistula connects with the external environment, gastric juice is released in its pure form. However, in such an operation, the allocation of juice by a small ventricle does not correspond to the dynamics of the production of gastric juice by large ventricle, since the innervation of the small ventricle is completely disrupted and only humoral regulation is preserved. * Isolated ventricle by I. P. Pavlov . A small ventricle is also formed from a large curvature, but with the leaving of the serous-muscular "bridge" from the side of the cardia (only the mucous membrane is cut). In this bridge are preserved branches of the vagus nerve, innervating the isolated ventricle, which adequately reflects the dynamics of the secretory process, including the initial reflex phases.

52. II. Clinical methods: * Probing the stomach and getting gastric juice in humans after a test breakfast or histamine stimulation. * Gastroendoscopy allows you to see and photograph the mucous membrane of the stomach. * Electrogastrography -registration of biopotentials of the muscle shell of the stomach. * Fluoroscopy, radiography of the stomach. • Ultrasounography and other methods.

53. Gastric juice, composition, functions of the components of gastric juice . Gastric juice is a colorless, slightly opalescent liquid acidic reaction. The amount of gastric juice 1.5-2 liters per day, pH at the height of the secretion is very acidic (up to 1-1,5), on an empty stomach is less acidic (4-6). Gastric juice consists of 99% water and 1% dry residue. The dry residue includes organic (enzymes and non-enzymes) and inorganic substances.

54. They excreted by the main cells in the form of inactive pepsinogens and activated in the cavity of the digestive tract by hydrochloric acid. Each enzyme is active in the acidic environment, but at different pH values. Pepsin belongs to proteolytic enzymes of the stomach. More than 7 species of pepsin were found. The main ones: * Pepsin A, active at PH 1,5-2, splits proteins to polypeptides. * Pepsin B , active at PH 3 - 4,splits proteins of connective tissue to polypeptides. The enzymes of the gastric juice is mostly proteases .

55. Pepsin C ( gastrixin ), the optimum activity at PH 3,2-3,5. Splits proteins to polypeptides, but acts on other relations than pepsin A. P epsin D (rennin or chymosin ), splits milk protein (casein) to polypeptides. In addition to proteolytic enzymes, the juice contains gastric lipase . This enzyme splits emulsified fats of milk to glycerol and fatty acids. The composition of gastric juice includes antibacterial enzyme lysozyme . Non-enzymes of gastric juice include mucin , mucopolysaccharides and metabolites (uric acid, lactic acid, urea, creatinine , oth .). Inorganic substances of gastric juice are HCL (0,5 % ), ions K+, Na+, Ca2+, Mg2+, chlorides, sulfates, phosphates, bicarbonates.

56. Functions of HCL: 1. Activates pepsinogens into pepsins. 2. Creates an optimum PH for enzyme activity. 3. Causes swelling, loosening and denaturation of proteins, which facilitates the action of enzymes. 4. Stimulates the motility of the stomach and intestines, promotes the evacuation of the chyme from the stomach into the duodenum. 5. Participate in the autoregulation of the gastric secretion. In the beginning, it stimulates the secretion of endocrine cells in the blood of gastrin and histamine, which contribute to the production of gastric juice. The excess of HC1 at the height of secretion inhibits the production of gastrin and histamine, and the secretion of gastric juice and the HC1 itself. 6. It has a bactericidal effect, provides sterility of gastric juice. 7. Stimulates the production of hormones of the duodenum ( secretin , cholecystokinin-pancreozymin ).

57. Functions of mucous: 1. Creates a protective layer (2 mm), which protects the gastric mucous from self-digestion. 2. Neutralizes excess HC1. 3. Adsorbs on the surface enzymes, vitamins, an internal factor of the Castle, contributes the absorption of vitamin B12. 4. It has bacteriostatic action. 5. Participates in the lipotropic metabolism of the liver, prevents its fatty degeneration.

58. REGULATION OF GASTRIC SECRETION . There are 3 phases in regulation of gastric secretion: 1. Cephalic phase , mechanism – complex reflex. Gastric juice begins to stand out in this phase before food enters the stomach. The latent period for the first phase is 5-10 min. In the experiment to obtain this phase in a pure form allows the experience of imaginary feeding, when the dog sees food, smell feels , hears the sound of manifestation, feels the taste, but the food does not enters the stomach. Despite this, gastric juice continues to stand out for 2-4 hours. The cephalic phase is based on conditional and unconditional reflexes.

59. • Conditioned reflexs . At the sight, smell, and talk about food are excited visual, auditory, olfactory exteroreceptors . Signals by the afferent sensitive nerves enter the Central nervous system and reach the cerebral cortex, stimulating the centers of vision, hearing and smell in the cortex. From these centers, the excitation pulses by temporal relations arrive in the higher cortical center of digestion (it dominates). The highest digestive center sends impulses to the same main center of the medulla oblongata, from where signals by the wandering nerve enter the stomach and stimulate the secretion of gastric juice by all types of secretory cells, as well as the activity of endocrine cells.

60. : Unconditioned reflex. After ingestion of food into the oral cavity, taste, tactile, temperature, and sometimes painful receptors of the oral mucosa are excited. The signals by the afferent nerves arrive in the main center of digestion of the medulla oblongata and by the vagus nerve go to the stomach, exciting all 4 types of cells (main, parietal, additional, and endocrine). Despite the fact that the cephalic phase is complexreflex , it includes mechanisms of humoral regulation due to reflex excitation of gastric endocrine cells.

61. Cephalic phase stimulators . All factors that increase the appetite of a person are stimulators of the cephalic phase. These include: hunger, pleasant smell, neat appearance, good taste of food (ritual meal, table setting), good mood, etc. Cephalic phase inhibitors. These include environmental factors that reduce the appetite of a person: the absence of hunger, untidy appearance, unpleasant odor, bad taste of food, distracting stimuli (news, etc.), bad mood.

62. Gastric phase is neuro-humoral . Under normal conditions, it begins on the background of the first phase after ingestion of food in the stomach. In the absence of the cepfalic phase, the gastric phase begins after a long latent period (1 hour) and lasts about 6-8 hours. In the stomach food is irritating mechano -, chemo - and osmoreceptors . Signals by the afferent branches of the vagus nerve enter the medulla oblangata (the main digestive center) and further along the vagus to the stomach, stimulating all 4 types of secretory cells. In natural conditions on the basis of this unconditional reflex conditional reflexes are not usually formed.

63. In the gastric phase, the most gastric juice is produced by the humoral regulation mechanism. Reflex and under the influence of HCL G-cells of the pyloric part of the stomach produce hormone gastrin , and mast cells of the stomach-histamine, entering to the blood and tissue fluid. These humoral factors act on secretory cells and stimulate the production of enzymes, HCL and mucus. When the environment of gastric juice becomes very acidic (pH 1-1.5), the HCL begins to slow down the production of gastrin , histamine and respectively gastric juice ( autoregulation ).

64. In the gastric phase , there is a local regulation of secretion. In the thickness of the stomach wall are nerve plexuses ( submucous , subserous , and intermuscular ), composed of nerve cells Dogel 1, 2 and 3-type. They form local reflex arcs, which stimulate gastric secretion under the influence of food ingredients and chemical irritants of gastric juice. Dogel cells of the 1-th type at the same time are the postganglionic neurons of the vagus nerve. The sympathetic innervation of the stomach is obtained by the branches of the celiac nerve, which go into the stomach and branch in its walls. The sympathetic nervous system has a trophic effect on the glands of the stomach and inhibits gastric secretion.

65. Stimulants of gastric phase: Food stimulants: * protein extracts-meat, vegetable broths; • meat food; * salting, bitterness, condiments in small quantities; • vegetable salads from (fresh cabbage salad and fresh cucumbers, tomatoes); • acidic foods in a small amount; * alcohol in small quantities. Regulatory stimulators: • HC1 in a small amount; • acetylcholine; • gastrin ; • histamine.

66. Inhibitors of the gastric phase. Food inhibitors: • sweet food; • fatty food; salting, bitterness, condiments in large quantities; alcohol in large quantities; Regulatory inhibitors: • HC1 in a large number; • adrenaline; • noradrenaline .

67. 3 . Intestinal phase . The intestinal phase begins after the entrance of the chyme in the duodenum. In regulation 2 mechanism involved. 1. Neuro -reflex mechanism . Presented by unconditional reflexes. They start with the mechano - and chemoreceptors of the duodenum. Impulses from receptors go in the composition of afferent branches of the vagus nerve into the digestive center of the medulla oblongata and further be the vagus to the stomach, stimulating the activity of secretory cells. It is also possible to regulate with the help of local reflex arcs through the Dogel cells of three types - signals from the receptors of the duodenum pass to the gastric plexus.

68. 2 . Humoral mechanism is mostly has a inhibitory value. On gastric secretion affected the following hormones and bioactive substances; * Secretin -produced by the endocrine cells of the duodenum under the influence of HCL incoming chyme . It is released into the blood and with it enters in the stomach, inhibiting its secretory activity; • HCK-PS . It is produced in the duodenum under the influence of HC1 and hydrolysis products of proteins. Through the blood enters the stomach, inhibiting its secretion;

69. * VIP ( vasoactive intestinal peptide). It is produced in the duodenum, inhibits gastric secretion; * GIP (gastric inhibitory peptide). It is produced in the duodenum, inhibits gastric secretion; * fatty food substances, which also inhibit gastric secretion; * bombesin -is produced in the duodenum at the entrance of the chyme , initially stimulates gastric secretion.

70. GASTRIC MOTILITY . In the stomach distinguish 3 types of contractions of smooth muscles. 1.Tonic contraction of the stomach without fatigue: * basal tone of the empty stomach. Creates a slight pressure of the gastric contents; • plastic tone ( food relaxation) - stretching of the stomach when its filled, depending on the quantity of food taken. Plastic tone ensures close contact of the gastric mucosa with the food mass. Swallowed portion of food gets into the cardiac part of the stomach-on the bottom layer by layer. Contraction of the stomach starts near the esophagus where is the pacemaker located - cardiac pacemeker . Then a wave of contractions spreads through the body of the stomach.

71. 2. Peristaltic contractions are undulating contractions involving the circular and oblique muscles of the stomach. They ensure the movement of the chyme from the cardiac to the pyloric part. The chyme in the food mass of the stomach forms a parietal and the peristaltic wave is removed as a glove. If the undigested mass falls into the pyloric part, it is thrown back to the bottom of the stomach due to antiperistaltic contractions. 3. Systolic contractions (propulsive wave) are powerful contractions of the muscles of the pyloric part of the stomach, proving the evacuation of a portion of the chyme from the stomach to the duodenum.

72. Regulation of gastric motility. 1 . Neuro reflex mechanism are central reflexes and local reflex arcs. Excitation of the parasympathetic nervous system increases the motility of the stomach, and the sympathetic - inhibits. 2 . Humoral mechanism: * increases the motility acetylcholine, gastrin , histamine, insulin, motilin , HC1 and bile acids; • inhibit the motility of epinephrine, norepinephrine , serotonin, HCK- PS, secretin , glucagon, GIP, VIP.

73. Evacuation of the chyme from the stomach to the duodenum. The transition of the chyme from the stomach to the duodenum is fractional, in separate portions. When a portion of the chyme accumulates in the pyloric part of the stomach, mechano , chemo and osmoreceptors are excited. Impulses enter to the center of the digestion by the afferent branches of the vagus nerve, and from there by the efferent to the muscles of the stomach. The powerful systolic contraction begins, the hydrostatic pressure increases sharply in the pyloric part of the stomach. At this time, the pyloric sphincter is relaxed, but covered by the fold of the mucous membrane as a valve.

74. Under pressure, the fold is raised and the portion of the chyme passes from the high-pressure zone of the stomach to the low-pressure zone of the duodenum. After that, the systole of the stomach is replaced by relaxation, and the pyloric sphincter closes. For this reason, the chyme can not return to the stomach. As the chyme is removed from the pyloric sphincter into the intestine, the sphincter relaxes, although its opening remains closed. In the pyloric part of the stomach at this time there is the accumulation of a new portion of the chyme . Liquid food by the small curvature of the stomach easily gets into the pyloric department and evacuated without delay.

75. The following factors influence the rate of evacuation of chyme : * HCL. The influence of HCL on the stomach side relaxes the sphincter and promotes the evacuation of the chyme , and the influence of HCL on the side of the duodenum leads to the closure of the sphincter; * volume of the chyme : its increase leads to acceleration of evacuation; * chyme consistency: evacuates only the chyme semi-liquid consistency, well mixed with gastric juice; * temperature: cold food evacuates faster than hot; • the qualitative composition of food: the first evacuate are carbohydrates, then proteins and slower fats; * osmotic pressures gradient between the stomach and the duodenum: the higher the gradient, the faster the evacuation; * the condition of the duodenum and especially its initial department: increasing the acidity, accumulation of fats inhibits evacuation.

76. Features of digestion of proteins, fats and carbohydrates in the stomach . . 1. Proteins split in the acidic environment of the stomach under the action of pepsin to the state of polypeptides. 2. In the stomach, only emulsified fats of milk under the action of gastric lipase undergo hydrolysis 3. Own enzymes, acting on carbohydrates, in the composition of gastric juice there is no. However, the enzymes amylase and maltase enter the stomach from the oral cavity with a food lump. Their effect on carbohydrates continues in the center of the food lump until it is completely impregnated with acidic gastric juice. These enzymes are inactivated in acidic medium

77. PANCREAS

78. Pancreas is the second largest gland of the digestive tract weighing 60-100 grams. Located behind the stomach in close contact with the duodenum, has a head, body and tail. Is innervated by the vagus nerve and sympathetic branches from the celiac nerve. Consists of 2 parts: exocrine part secretes pancreatic juice, endocrine (islets of Langerhans ) secretes hormones in the blood: insulin, glucagon, somatostatin. Pancreatic juice is produced by exocrine acinar cells and released through the duct into the duodenum.

79. Composition of pancreatic juice, functions of its components . Pancreatic juice is a clear, colorless liquid slightly alkaline reaction (PH = 7.8 - 8.4). Contains 99% water and 1% dry residue. The latter includes organic enzymes, non-enzymes and inorganic substances. The alkalinity of the juice due to the presence of bicarbonates. The juice also contains sodium and potassium chlorides, as well as other cations and anions.

80. Enzymes of pancreatic juice . Pancreatic juice has almost all kinds of enzymes. These include the following groups: 1. Proteolytic enzymes . Are allocated in an inactive form. They are divided into 2 types: acting on whole protein molecules and acting on polypeptides. • The following enzymes act on whole protein moleculs . Trypsinogen -the main proteolytic enzyme. Under the influence of enterokinase intestinal juice (which is strengthened by bile) passes into the duodenum in the active trypsin . Trypsin splits proteins to amino acids. Chymotrypsinogen is activated by trypsin and turns into chymotrypsin . It also breaks down proteins to amino acids, but affects other connections than trypsin . Pancreopeptidase ( elastase ) is activated by trypsin , splits collagen proteins to amino acids.

81. Polypeptide enzymes: carboxypeptidase A and B are activated by trypsin , break down polypeptides to amino acids. Aminopeptidases act on polypeptides, splits them to amino acids. 2. Amylolytic enzymes are released in the active form, their activity increases in the presence of bile. Amylolytic enzymes include: amylase, maltase, lactase. They split the corresponding sugars to monosaccharides . 3. Lipolytic enzymes . Lipase and phospholipase are allocated in an inactive form. Activated by trypsin and bile acids of the duodenum. Effect on emulsified bile fats and split them to glycerol and fatty acids. 4. Nucleases is a ribonuclease and deoxyribonuclease . Effect on polynucleotides , splits them to mononucleotid es.

82. Regulation and the adaptive nature the secretion of pancreatic juice. To study the pancreatic secretion, the methodology used for fistula ductless according to I. P. Pavlov. In the clinic, to assess the excretory function of the pancreas, the concentration of proenzymes in the blood (diastasis) is determined. The ultrasound method is widely used. Secretion of pancreatic juice begins 2-3 minutes after a meal and lasts 6-14 hours. In the regulation of pancreatic secretion also conditionally distinguish 3 phases: cephalic, gastric and intestinal. They have the same mechanisms as in the regulation of gastric secretion, but their significance is different.

83. 1.Cephalic phase . Found in the experience of imaginary feeding. Pancreatic juice begins to stand out in 2-3 minutes and lasts for 10 minutes, if the food does not get into the stomach. The mechanism this phase is neural-reflex (conditional and unconditional reflexes). Its purpose is the alkalinity of the duodenum. 2.Gastric phase. The the mechanism it is neuro-humoral . The nervous mechanism is dominated by unconditional reflexes from mechano -and chemoreceptors of the stomach, as well as local reflex arcs (intramural nerve plexuses of the stomach are in contact with the pancreas). Humoral mechanism is the influence of the hormone gastrin , which also stimulates pancreatic secretion. 3.Intestinal phase - is the main phase, in which the most amount of pancreatic juice is released. Local and humoral mechanisms are included in the regulation.

84. Local reflex arcs begin with hemo -and mechanoreceptors of the small intestine. Under the influence of HCL of the gastric contents in the duodenum hormone secretin is formed. It, gets into the blood, stimulates the secretion of pancreatic juice rich in bicarbonate but poor in enzymes. Another hormone - HCK-PZ. Its release by endocrine cells of the duodenum are promoted HCL, products of the hydrolysis of proteins, fats, some carbohydrates and amino acids. HCK-PZ stimulates the secretion of pancreatic juice rich in enzymes. Secretion of pancreatic juice strengthen: insulin, bombesine , salts of bile acids, inhibit: glucagon, GIP, calcitonin , somatostatin and some others.

85. LIVER

86. LIVER AND ITS MAIN FUNCTIONS The liver is the largest gland of the human, which weighs more than 1.5 kg. It is located in the abdominal cavity under the diaphragm on the right. It consists of two lobes (right more than left), on three sides covered with peritoneum, except the diaphragm surface. Under the peritoneum, the liver is covered with a fibrous membrane ( glisson capsule), which is tightly fused with the liver parenchyma. In the area of liver gate glisson capsule enters the liver and divides it into liver lobules. Each such lobule consists of hepatocytes , which are located in the form of beams - radially (from the center to the periphery).

87. The hepatocytes synthesize bile. On the periphery of them are bile and blood capillaries. The walls of blood capillaries include Kupfer cells, which perform a phagocytic function in relation to microorganisms and fragments of foreign substances. Bile capillaries, merging into larger ducts, form the hepatic duct. In the longitudinal furrow of the liver, the gallbladder and gallbladder duct are located. The bladder duct merges with the hepatic duct, forming a common bile duct that flows into the 12 duodenum. The sphincter Oddi regulates the flow of bile into the duodenum. The wall of the gallbladder consists of mucous, muscular and serous membranes. The gallbladder serves as a reservoir for bile, in which it concentrates due to the absorption of water by the mucosa.

88. Features blood supply of the liver. Unlike other organs, the liver receives blood from two sources: arterial – from the hepatic artery and venous –from the portal vein. The portal vein collects blood from all unpaired organs of the abdominal cavity. Entering the gates of the liver, portal vein and hepatic artery disintegrate into lobes, segmental, interlobular, intra- lobular arteries and veins, from which begin intralobular capillaries (sinusoidal vessels). In sinusoidal blood capillaries, mixed blood flows to the center of the lobule, from where the hepatic veins originate. 3-4 hepatic veins flow into the system of the inferior vena cava.

89. Liver functions . The liver is a multifunctional organ, which is a real biochemical laboratory of our organism. First of all, it is involved in all types of metabolism. 1.Carbohydrate metabolism . In the liver, glycogen is synthesized from glucose ( glycogenesis ), and also the formation of glycogen from proteins and fats ( glyconeogenesis ). The liver is a depot of glycogen, with hypoglycemia glycogen can turn into glucose ( glycogenolysis ). 2. Fat metabolism . In the liver are the synthesis and breakdown of cholesterol, the formation of fats from carbohydrates, the formation of steroid hormones, phospholipids, the fat breakdown with the formation of ketone bodies. It can deposit fats and actively participates in their absorption.

90. 3.Protein metabolism . In the liver there is a synthesis of blood proteins (albumins, globulins, fibrinogen, prothrombin , etc.), and also deamination and transamination of amino acids with the formation of urea. 4.Mineral metabolism . The liver is a depot of mineral salts (potassium, iron). 5.Water exchange . The liver serves as a water depot. 6. Pigment metabolism. Bile pigments are formed in the liver. 7. Vitamin metabolism . The liver is a depot of vitamins groups A, B, C, D, K, PP and is also involved in the activation of vitamins. 8. Metabolism of enzymes and hormones . In the liver inactivation of catecholamines , serotonin, steroid hormones occurs. 9 . Fetal liver is a hematopoietic organ , and after the birth is the place of the destruction of red blood cells .

91. 10. The liver is involved in blood circulation - regulates blood distribution in the body, as a depot of blood (20% of the blood can be deposited in the liver). 11. Involved in blood coagulation , forms coagulation factors and anticoagulation. 12. Involved in maintaining the pH of the internal environment of the body. 13. Performs excretory function (removes with bile pigments, salts of heavy metals, medicinal substances). 14. Participates in digestion , produces digestive juice-bile. 15. Performs the barrier and detoxification function : * participation of Kupfer cells in phagocytosis ; • neutralization of protein metabolism products ( indole , skatole , phenol); * inactivation of toxins and some drugs; * toxic ammonia in the liver is turns into urea, which is then excreted from the body by the excretory organs.

92. The detoxification function of the liver is proved by the operation - fistula Ekka -Pavlov. The portal vein is cut, its central end is bind, and the peripheral is sewn into the system of the inferior Vena cava. As a result of this operation, the blood from the unpaired abdominal organs enters the system of the inferior Vena cava, bypassing the liver. Dogs after such an operation very quickly die with a protein diet due to intoxication and live much longer on a carbohydrate diet.

93. Bile

94. Participation of the liver in the digestive process involves 2 processes: • bile formation – a continuous process; bile secretion - intermittent process, occurring only during digestion. Bile, composition, functions of components . The formation of bile by hepatocytes occurs constantly (secretion). This process is active. Bile is formed from products that are already in the blood (extrahepatic components): water, inorganic substances, some enzymes (amylase, phosphatase, protease, catalase, oxidase), glucose, amino acids, cholesterol, vitamins A, B, C, fatty acids, neutral fats, lecithin, soaps, mucin, metabolites (urea, uric acid, creatinine).

95. Bile pigments and bile acids belong to the specific substances of bile. Bile pigments are products of destruction of hemoglobin ( bilirubin - red-brown color, biliverdin - green color, at the person in the form of traces). Bile acids are cholic and chenodeoxycholic acids. Several secondary bile acids are formed from these primary acids: taurocholic and glycocholic . Bile acids are liver components of bile, as they are synthesized in the liver. Cholesterol comes partly from the blood and is partially synthesized by hepatocytes. Bile pigments are removed from the body after getting into the intestine in the form of stercobilinogen with the subsequent transition in sterkobilin (excreted with feces) and urobilinogen , which goes to urobilin (excreted with urine).

96. Bile is a transparent liquid, golden-yellow color, weakly-alkaline reaction (PH=7,3 - 8). The day is produced 700 ml-1 liter bile. The bile consists of 97.5% water and 2.5% dry residue (organic and inorganic substances). Organic substances - see above. Inorganic ions include sodium, iron, magnesium, potassium, calcium, many bicarbonates, chlorides, phosphates. The study of the composition of bile is carried out using duodenal sounding , in which receive 3 portions of bile: * portion A- duodenal bile. This portion of bile is mixed with the contents of the duodenum; * portion B- gallbladder bile, dark brown color , concentrated, the most abundant . The norm should not contain deleted epithelium and leukocytes; * portion C- hepatic bile, golden yellow, transparent, normally does not contain leukocytes.

97. Composition of hepatic and gallbladder bile № Hepatic bile Bladder bile 1. Water 95-98 g/dl 92 g/dl 2. Bile salts 1,1 g/dl 3 - 10 g/dl 3. bilirubine 0,2 g/dl 0,5 – 2 g/dl 4. Cholesterine 0,1 g/dl 0,3 - 0,9 g/dl 5. Fatty acids 0,1 g/dl 0,3 -1,2 g/dl 6. Lecitine 0,04 g/dl 0,1 - 0,4 g/dl 7. Na + 145 mmol/l 130 mmol/l 8. К + 5 mmol/l 9 mmol/l 9. Са 2+ 2,5 mmol/l 6 mmol/l 10. CI 100 mmol/l 75 mmol/l 11. НСО 3 - 28 mmol/l 10 mmol /l

98. Functions of bile: 1. Emulsifies fats. 2. It promotes absorption of fatty acids, fat-soluble vitamins (A, D, E) and cholesterol. 3. Creates an alkaline reaction in the intestine. 4. Inactivates the pepsin of the gastric juice. 5. Activates lipases of pancreatic and intestinal juices. 6. Enhances the motility and secretion of the GIT. 7. It has bacteriostatic and bactericidal action, inhibits the growth of putrefactive microflora . 8. Stimulates bile formation and bile secretion. 9. Involved in the parietal digestion (provides closer contact of food with the microvilli of enterocytes ).

99. Choleresis . As noted above, bile formation in hepatocytes occurs continuously. In its regulation there are 2 mechanisms: neuro -reflex and humoral . In the neuro -reflex mechanism involving the digestive centers the main efferent nerves are the vagus and right diaphragmatic nerve. Both strengthen bile formation. The sympathetic nervous system, on the contrary, inhibits bile formation. Humoral stimulators of bile formation include fatty foods (especially egg yolk), bile itself (by type of autocatalysis), HCL, gastrin, secretin, cholecystokinin- pancreozymin , glucagon.

100. Bile secretion ( cholekinesis ). Occurs only during digestion. Regulatory mechanisms provide the opening and closing mainly the sphincter of Oddi . The vagus nerve increases the contraction of the gallbladder wall and relaxes the sphincter of Oddi , what promotes bile secretion. The sympathetic nerves, on the contrary, relax the gallbladder and close the sphincter of Oddi , preventing bile secretion. Conditionally the regulation of bile secretion is divided into 3 phases: 1. Cephalic phase - neuro -reflex, is provided by conditional and unconditional reflexes, with the participation of visual, auditory, olfactory receptors and receptors of the oral cavity. This phase is preparatory, lasts 7-10 minutes and prepares the intestine for the reception of chyme .

101. Gastric phase - starts after getting food into the stomach. Unlike other departments, this phase inhibits bile secretion. 3. Intestinal phase is the most important (due to the humoral mechanism). Its neuro -reflex mechanism is represented by unconditional reflexes, which begin with the mechano -, chemo-and osmoreceptors of the small intestine. Vagus increases bile secretion, and the sympathetic nerve inhibits it. Humoral effects are carried out with the participation of hormones cholecystokinin- pancreozymin , which stimulates the contraction of the gallbladder through the blood and relaxes the sphincter of Oddi . Contractions of the gallbladder (although weak) are also caused by hormones gastrin , secretin , bombesin . Inhibit gallbladder contractions glucagon, calcitonin , VIP, PP.

102. DIGESTION IN THE SMALL INTESTINE

103. Features the structure of the small intestine Its mucous membrane is folded, it has villi -mucosal outgrowths. In the center of each such villus is a lymphatic vessel, on the periphery from it – blood vessels. There are also smooth muscle elements. The villus can be reduced and works as a micro pump, strengthening the suction processes. The apical membrane of enterocytes has microvilli -outgrowths of biomembranes . The surface of the microvilli are covered with glycocalyx . Folds, villi , microvilli and glycocalyx dramatically increase the contact surface of the small intestine.

104. The intestinal mucosa has 2 types of glands: 1. Brunners glands-located in the duodenum , resemble pyloric glands of the stomach. Secre ted juice, rich in water, bicarbonates, mucin , with weak enzyme activity. Mucin protects the mucous membrane of the duodenum from the action of HC1 and enzymes of gastric juice. 2. Liberkuhns glands – located in the jejunum and ileum. It produces intestinal juice, rich in enzymes. Most of the enzymes of intestinal juice are fixed on the microvilli and involved in parietal digestion (see above).

105. The composition of the intestinal juice Intestinal juice is a muddy, whitish color liquid with a specific smell. When settling it forms 2 layers: the upper, transparent, contains mineral salts and a lot of bicarbonates. The lower layer is cloudy, contains enzymes, mucus, exfoliated epithelium, white blood cells. The reaction of alkaline juice-7.5 – 8.6, the amount – 1.5-2 liters/day. The composition of intestinal juice includes more than 20 different enzymes: 1. Peptidases: * Enterokinase - enzyme that activates trypsinogen into trypsin. • Aminopeptidases . • Carboxypeptidases .

106. Peptidases intestinal juice are a group of erypsin that break down polypeptides to amino acids. II. Amylolytic enzymes: amylase, maltase, sucrose, lactase. All these enzymes act on the corresponding carbohydrates and break them down to monosaccharides . III. Lipolytic enzymes: lipase, phospholipase -act on fats, pre-emulsified bile, splitting them to monoglycerides and fatty acids. IV. Nucleases: ribonuclease and deoxyribonuclease -split polynucleotides to mononucleotides.

107. Regulation of intestinal secretion Secretion of the intestinal glands increases during meals, with local mechanical or chemical irritation of the intestine and under the influence of some intestinal hormones. The leading role belongs to the local mechanisms of regulation. These include local peripheral reflexes involving Dogel cells of three types. In this case, intestinal juice is released only in the area where the chyme is located. Receptors of peripheral reflex arcs are mechano - and chemoreceptors . Reflex arcs form meisners submucosal and auerbach intermuscular nerve plexus. Stimulators of intestinal secretion are: * The products of digestion of proteins and fats, which have a local irritant effect on the mucous membrane. * HCL * Hormones VIP, motilin .

108. Inhibitor of intestinal secretion is somatostatin . To study the regulatory mechanisms of intestinal secretion, operations on dogs are proposed: operation of Tiri – Vella and Tiri – Vella in modification of I.P. Pavlov. One ( Tiri ) or two ( Tiri – Vella ) ends of the isolated segment of the small intestine are removed into the skin wound (Fig.85). To preserve motility, I. P. Pavlov proposed a modification that consisted in creating a closed ring from an isolated segment of the intestine with one fistula.

109. Motility of the small intestine In the small intestine, the following types of movement are distinguished: 1. Tonic contractions, which provide the best contact of the chyme with the mucosa. 2. Peristaltic contractions provides the movement of the chyme from small intestine to large intestine. 3. Pendulum-shaped contractions, carried out by consequent contractions of the longitudinal muscles within the individual compartments. In this case, the chyme can move in one direction, then in the other (as a pendulum). These reductions provide rubbing of the chyme in the mucosa and more complete contact with the microfibers. 4. Rhythmic segmentation. In various parts of the small intestine increases the tone of the circular muscles. As a result, the intestine is divided into separate segments, then the places of the constrictions change. This type of movement is used for better contact chyme with the wall of the intestine and enzymes.

110. Regulation of intestinal motility The vagus nerve increases all kinds of intestinal movements, and the sympathetic nerve, on the contrary, inhibits motility. Humoral stimulants of motor activity of the intestine are acids, bases, HC1, gastrin , serotonin, willikin , motilin , bile acids. In 1961, the Soviet scientist P. G. Bogach described the basic law of motor activity of the gastrointestinal tract: chyme activates motor skills in this department of the gastrointestinal tract and in the underlying, and the motor function of the overlying department has a braking effect.

111. Digestion in the large intestine From the small intestine, portions of the chemy through the ileocecal sphincter pass into the colon. The large intestine consists of the following sections: the cecum , transverse colon, sigmoid colon and rectum. In the large intestine, the following processes occur: 1.The utilization of substances necessary for the body continues. Dietary fibers (cellulose, pectins , lignin) are break down by the enzyme cellulase , that produce bacteria. Dietary fibers enhance intestinal motility and act as light laxatives.

112. 2. Water (2 – 2,5 l/day) and mineral salts are absorbed into the blood. 3. Metabolites and salts of heavy metals are excreted. 4. There is the formation of fecal masses and their removal from the body. The primary center of defecation is located in the sacral part of the spinal cord. 5. Enzymatic hydrolysis and absorption of nutrient residues from the small intestine is carried out. 6. With the help of bacterial flora of the large intestine, the synthesis and assimilation of vitamins E, K and group B occurs.

113. Under normal conditions, the level of activity of the large intestine is low. However, if there are digestive disorders in the small intestine, the large intestine partially compensates them. In the juice of the colon in a small amount there are peptidases, cathepsin ( protolytic enzyme), amylase, lipase, nuclease, alkaline phosphatase . The large intestine has its own microflora . These are mainly without spore obligate bacteria, as well as lactic acid bacteria, E. coli, streptococci and spore-bearing anaerobes. Microflora is involved in the creation of the immune barrier, inhibits the growth of pathogenic microorganisms, balancing the processes of decay and fermentation in the intestine, participates in the metabolism of proteins, phospholipids, bile and fatty acids, bilirubin and cholesterol.

114. Motility of the large intestine In the large intestine there are the same types of motor activity as in the small intestine, plus mass peristalsis: * Peristalsis- it involves circular muscles and muscles in the area of bands. As result a swelling ( g austra ) is formed, the wave propagation velocity is 0.5 cm/s. The mixing and movement of the contents and absorption of water occurs. * Rhythmic segmentation -expressed in the large intestine and provides mixing of the contents. * Pendulum-shaped reductions-also expressed and provide mixing and absorption of water. • Antiperistaltic – rarely occurs, in contrast to the small intestine. * Mass peristalsis-contraction of circular and longitudinal muscles over a significant length of the colon. It leads to the emptying of its large areas. This is a very rare reduction-3-4 times a day. Contribute to the formation of fecal masses and rectum filling.

115. Regulation of the colonic motility a) local-under the action of cellulose , undigested food, extractive substances; b) reflex-on the principle of unconditional reflex: when irritating the receptors of the upper departments of the gastrointestinal tract. First-short-term inhibition, and then – increased motility. Composition of the fecal mass: • undigested food; • inactivated enzymes; • products of protein metabolism; * bile acids and pigments; • bacteria; rejected epithelial cells of the small and large intestine; • leukocytes; * water and minerals.

116. Defecation Defecation - emptying the colon and evacuation of feces from the body. It occurs when the center of defecation located in the sacral segments (S1 – S4) of the spinal cord is excited. This takes place under the action of impulses from the cortex during the filling of the rectum and increasing the pressure in it to 45 mm Hg. Receptors of mucosal and muscular layers are excited, impulses come to the centre of defecation the sacral segments of the spinal cord. Efferent fibers – fibers of the pelvic nerve and somatic nerves. The pelvic nerve innervates the internal and external anal sphincters and reduces rectal muscles. The sympathetic nervous system is represented by the lower celiac nerve, provides closure of the smooth muscle sphincter. Somatic nerves perform contra ctions of skeletal muscles. The act of defecation is a complex reflex process.

117. Physiological basis of hunger and saturation (satiety) Hunger is a physiological state characterized by a complex of unpleasant sensations that reflect the body's needs for food. Manifestations of hunger-a sense of burning, sucking, pressure, and sometimes pain in the epigastric region, nausea, dizziness and even headache. Behavioral reactions in the sense of hunger - is the search for food (food motivation).

118. For hunger is responsible food center, this is a set of neurons located at different levels of the central nervous system and taking part in the formation of food behavior. The food center integrates the functions of all digestive organs. The leading department in the center of hunger are the hypothalamus nuclei, which are closely related to the reticular formation of the brain stem, the limbic system and the new cortex. In the food center of the hypothalamus, two departments are conditionally distinguished: the center of hunger and the center of saturation, connected with each other reciprocally.

119. The feeling of hunger is formed when the hunger center is excited. The latter can be excited reflexively from the receptors of the GIT during its hunger periodic activity (impulses from empty stomach and intestines). Periodic activity of the gastrointestinal tract is activated on an empty stomach every 1.5 hours for 30 minutes. The hunger center is also excited by humoral way through "hungry" blood. If a hungry animal is transfused the blood of a well-fed animal, the feeling of hunger disappears.

120. There are several theories explaining the formation of a feeling of hunger by humoral way: 1. Glucostatic theory – a decrease the content of glucose in the blood. 2. Aminoacidostatic theory – a decrease the concentration of amino acids in the blood. 3. Lipostatic theory-an irritant is the mobilization of fat from the depot. 4. Metabolic theory-hunger occurs when the concentration of intermediate products in the Krebs cycle decreases, in particular, citric acid.

121. After eating and filling the stomach reflexively inhibits the center of hunger. The secretion of digestive juices, the incretion of hormones in the blood (gastrin, secretin) contribute to a feeling of saturation. D uodenal hormones can change the water-salt balance in the body, reduce appetite, stimulate absorption in the gastrointestinal tract and saturation. Specific dynamic action of food, increasing metabolism and temperature in the body, also contributes to the inhibition of hunger center and the excitation of the center of saturation. There are sensory (primary) saturation and metabolic (true) saturation. Sensory saturation prevents excessive food intake, because it is accompanied by a reflex release of nutrients from the food depot (liver, skeletal muscles, fat). True metabolic saturation occurs in 1.5-2 hours after eating due to the absorption of nutrients from the gastrointestinal tract and food depot replenishment.

122. Thank you for your attention!