Motor and secretory function of the gastrointestinal tract. The structure of the intestinal villi, intestinal epithelium, brush border. properties of hydrochloric acid. secretory function of the stomach

DIGESTION

For normal life, the body needs plastic and energy material. These substances enter the body with food. But only mineral salts, water and vitamins are absorbed by a person in the form in which they are in food. Proteins, fats and carbohydrates enter the body in the form of complex complexes, and in order to be absorbed and digested, complex physical and chemical processing of food is required. At the same time, food components must lose their species specificity, otherwise they will be accepted by the immune system as foreign substances. For these purposes, the digestive system serves.

Digestion - a set of physical, chemical and physiological processes that ensure the processing and transformation of food into simple chemical compounds that can be absorbed by the cells of the body. These processes occur in a certain sequence in all parts of the digestive tract (oral cavity, pharynx, esophagus, stomach, small and large intestines with the participation of the liver and gallbladder, pancreas), which is ensured by regulatory mechanisms of various levels. Sequential chain of processes leading to splitting nutrients to monomers that can be absorbed is called digestive conveyor.

Depending on the origin of hydrolytic enzymes, digestion is divided into 3 types: proper, symbiotic and autolytic.

own digestion carried out by enzymes synthesized by the glands of a person or animal.

Symbiotic digestion occurs under the influence of enzymes synthesized by the symbionts of the macroorganism (microorganisms) of the digestive tract. This is how fiber is digested in the large intestine.

Autolytic digestion carried out under the influence of enzymes contained in the composition of the food taken. Mother's milk contains the enzymes needed to curdle it.

Depending on the localization of the process of hydrolysis of nutrients, intracellular and extracellular digestion are distinguished. intracellular digestion is a process of hydrolysis of substances inside the cell by cellular (lysosomal) enzymes. Substances enter the cell by phagocytosis and pinocytosis. Intracellular digestion is characteristic of protozoa. In humans, intracellular digestion occurs in leukocytes and cells of the lymphoreticulohistiocytic system. In higher animals and humans, digestion is carried out extracellularly. extracellular digestion divided into distant (cavitary) and contact (parietal, or membrane). Distant (cavitary) digestion carried out with the help of enzymes of digestive secrets in the cavities of the gastrointestinal tract at a distance from the place of formation of these enzymes. Contact (parietal, or membrane) digestion(A.M. Ugolev) occurs in the small intestine in the glycocalyx zone, on the surface of microvilli with the participation of enzymes fixed on the cell membrane and ends suction - transport of nutrients through the enterocyte into the blood or lymph,

1. Functions of the gastrointestinal tract

secretory function associated with the production of digestive juices by glandular cells: saliva, gastric, pancreatic, intestinal juices and bile.

Motor or motor function carried out by the muscles of the digestive apparatus at all stages of the digestive process and consists in chewing, swallowing, mixing and moving food along the digestive tract and removing undigested residues from the body. Motility also includes the movements of villi and microvilli.

suction function carried out by the mucous membrane of the gastrointestinal tract. From the organ cavity, the breakdown products of proteins, fats, carbohydrates (amino acids, glycerol and fatty acids, monosaccharides), water, salts, medicinal substances,

Endocrine, or intrasecretory, function consists in the production of a number of hormones that have a regulatory effect on the motor, secretory and absorption functions of the gastrointestinal tract. These are gastrin, secretin, cholecystokinin-pancreozymin, motilin, etc.

excretory function It is provided by the release of metabolic products (urea, ammonia, bile pigments), water, salts of heavy metals, medicinal substances into the cavity of the gastrointestinal tract by the digestive glands, which are then removed from the body.

The organs of the gastrointestinal tract also perform a number of other non-digestive functions, for example, participation in water-salt metabolism, local immunity reactions, hematopoiesis, fibrinolysis, etc.

1. General principles of regulation of digestion processes

The functioning of the digestive system, the conjugation of motility, secretion and absorption are regulated by a complex system of nervous and humoral mechanisms. There are three main mechanisms of regulation of the digestive apparatus: central reflex, humoral and local, i.e. local. The significance of these mechanisms in various departments digestive tract is not the same. Central reflex influences (conditioned reflex and unconditioned reflex) are more pronounced in the upper part of the digestive tract. As you move away from oral cavity their participation decreases, but the role of humoral mechanisms increases. This effect is especially pronounced on the activity of the stomach, duodenum, pancreas, bile formation and bile excretion. In the small and especially the large intestine, predominantly local regulatory mechanisms (mechanical and chemical irritations) are manifested.

Food has an activating effect on the secretion and motility of the digestive apparatus directly at the site of action and in the caudal direction. In the cranial direction, on the contrary, it causes inhibition.

Afferent impulses come from mechano-, chemo-, osmo- and thermoreceptors located in the wall of the digestive tract to the neurons of the intra- and extramural ganglia, spinal cord and brain. From these neurons, along efferent vegetative fibers, impulses follow to the organs of the digestive system to effector cells: glandulocytes, myocytes, enterocytes. The regulation of digestion processes is carried out by the sympathetic, parasympathetic and intraorgan divisions of the autonomic nervous system. The intraorgan division is represented by a number of nerve plexuses, of which the most important in the regulation of the functions of the gastrointestinal tract are the intermuscular (Auerbach) and submucosal (Meissner) plexuses. With their help, local reflexes are carried out, closing at the level of the intramural ganglia.

Sympathetic preganglionic neurons secrete Acetylcholine, enkephalin, neurotensin; in postsynaptic - joradrenaline, acetylcholine, VIP, in parasympathetic preganglionic neurons - acetylcholine and enkephalin; postganglio-&

drug - acetylcholine, enkephalin, VIP. Gastrin, somatostatin, substance P, cholecystokinin also act as mediators in the stomach and intestines. The main neurons that excite motility and secretion of the gastrointestinal tract are cholinergic, inhibitory - adrenergic.

big role in humoral regulation play digestive functions gastrointestinal hormones. These substances are produced by endocrine cells of the mucous membrane of the stomach, duodenum, pancreas and are peptides and amines. According to the property common to all these cells to absorb the amine precursor and carboxylate it, these cells are combined into APUD system. Gastrointestinal hormones exert regulatory influences on target cells in various ways: endocrine(delivered to target organs by general and regional blood flow) and paracrine(diffuse through the interstitial tissue to a nearby or closely located cell). Some of these substances are produced by nerve cells and act as neurotransmitters. Gastrointestinal hormones are involved in the regulation of secretion, motility, absorption, trophism, the release of other regulatory peptides, and also have general effects: changes in metabolism, the activity of the cardiovascular and endocrine systems, eating behavior(Table 2).

Table 2 Main effects of gastrointestinal hormones

Secretion of various juices - essential function gastrointestinal tract (GIT). There are many glandular cells that are located in the thickness of the mucous membrane of the oral cavity, stomach, small and large intestines, in which secretion is carried out, the products of which are released into the gastrointestinal tract through special small excretory ducts. These are large and small salivary glands, gastric glands, Brunner's glands of the 12th duodenum, Lieberkruhn's crypts of the small intestine, goblet cells of the small and large intestine. The liver occupies a separate place: its hepatocytes, performing many other functions, produce bile, which is necessary for the digestion of fats as an activator and emulsifier.

Secretion processes proceed in three phases: 1) receipt of raw material(water, amino acids, monosaccharides, fatty acids); 2) synthesis of the primary secretory product and its transport for secretion. According to G.F. Korotko (1987), in pancreatic cells in this phase, from the amino acids that entered the cell on the ribosomes of the endoplasmic reticulum, the protein-enzyme is synthesized within 3-5 minutes. Then this protein in the composition of the vesicles is transferred to the Golgi apparatus (7 - 17 minutes), where it is packed into vacuoles, in which the proenzyme granules are transported to the apical part of the secretory cell, where the next phase takes place; 3) secretion (exocytosis). From the beginning of the synthesis to the release of the secret, an average of 40-90 minutes passes.

Regulation of all three phases of secretion is carried out in two ways: 1) humoral- mainly due to intestinal hormones and parahormones. Hormones act through the blood, parahormones through the intersticium. They are produced by cells scattered in various parts of the gastrointestinal tract (stomach, duodenum, jejunum and ileum) and belong to the APUD system. They are called gastrointestinal hormones, regulatory peptides, hormones. Of these, they act as hormones. gastrin, secretin, cholecystokinin-pancreozymin, gastric peptidase inhibitor(GIP) , enteroglucagon, enterogastrin, enterogastron, motilin. Parahormones or paracrine hormones are pancreatic polypeptide(PP), somatostatin, VIP(vasoactive intestinal polypeptide), substance P, endorphins.

Gastrin enhances the secretion of gastric juice with a high content of enzymes. Histamine also enhances gastric secretion with a high content of hydrochloric acid. Secretin It is formed in the duodenum in an inactive form of prosecretin, which is activated by hydrochloric acid. This hormone inhibits the function of the parietal cells of the stomach (the production of hydrochloric acid stops) and stimulates the secretion of the pancreas due to the secretion of bicarbonates. Chocystokinin-pancreozymin enhances cholekinesis (bile secretion), increases the secretion of pancreatic enzymes and inhibits the formation of hydrochloric acid in the stomach. GUI inhibits gastric secretion by inhibiting the release of gastrin. VIP inhibits the secretion of the stomach, enhances the production of bicarbonates by the pancreas and intestinal secretion. PP is a cholecystokinin antagonist. FROM substance R enhances salivation and secretion of pancreatic juice.

The humoral mechanism is carried out by mediators (cAMP or cGMP) or by changing the intracellular calcium concentration. It should be noted that the hormones of the gastrointestinal tract play an important role in the regulation of the activity of the central nervous system. Ugolev A.M. showed that the removal of the duodenum in rats, despite the preservation of the processes of digestion, leads to the death of the animal; 2) nervous- by local reflex arcs, localized in the Meissener plexus (metasympathetic nervous system) and influences from the central nervous system, which are realized through the vagus and sympathetic fibers. The secretory cell responds to nerve influences by changing the membrane potential. Factors that enhance secretion cause depolarization cells, and inhibiting secretion - hyperpolarization. Depolarization is due to an increase in sodium and a decrease in potassium permeability of the secretory cell membrane, and hyperpolarization is due to an increase in chloride or potassium permeability. The average membrane potential of a secretory cell outside the period of secretion is –50 mV. It should be noted that the MPP of the apical and basement membranes is different, which is important for the direction of diffusion flows.

Central mechanisms of regulation carried out by neurons KBP(there are many conditioned food reflexes), limbic system, reticular formation, hypothalamus(anterior and posterior nuclei), medulla oblongata. In the medulla oblongata, among the parasympathetic neurons of the vagus, there is a cluster of neurons that respond to afferent and efferent (from the CBP, RF, limbic system and hypothalamus) impulse flows and send efferent impulses to sympathetic neurons (located in the spinal cord) and to the secretory cells of the gastrointestinal tract. It should be noted that most of the vagus fibers interact with secretory cells. indirectly, through interaction with efferent neurons metasympathetic nervous system. A smaller part of the vagus fibers interacts - directly With secretory cells.

All types of regulation are based on signals from the receptors of the digestive canal. Mechano-, chemo-, thermo- and osmoreceptors along the afferent fibers of the vagus, glossopharyngeal nerve, as well as along local reflex arcs, they send impulses to the central nervous system and the metasympathetic nervous system about volume, consistency, degree of filling, pressure, pH, osmotic pressure, temperature, concentration intermediate and end products of nutrient hydrolysis, as well as concentration some enzymes.

It was found that in the process of regulation of the secretory activity of the gastrointestinal tract central nervous influences are most characteristic of the salivary glands, to a lesser extent - for the stomach, and to an even lesser extent - for the intestines.

Humoral influences expressed quite well in relation to the glands of the stomach and especially the intestines, and local, or local, mechanisms play an essential role in the small and large intestines.

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secretory function kidney

What is the secretory function of the kidneys responsible for and its implementation

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The secretory function of the kidneys is the final step metabolic processes in the body, due to which the normal composition of the environment is maintained. This removes compounds that are not able to subsequently be metabolized, foreign compounds and excess other components.

The blood purification process

Approximately one hundred liters of blood passes through the kidneys daily. The kidneys filter this blood and remove toxins from it by placing them in the urine. Filtration is carried out by nephrons - these are cells. Which are located inside the kidneys. In each of the nephrons, the smallest glomerular vessel is combined with a tubule, which is a collection of urine.

It is important! In the nephron, the process of chemical metabolism begins, so harmful and toxic substances are removed from the body. Initially, primary urine is formed - a mixture of decay products, containing components that are still necessary for the body.

Implementation of secretion in the renal tubules

Filtration is carried out due to arterial pressure, and subsequent processes require additional energy costs in order to actively supply blood to the renal tubules. There, electrolytes are excreted from the primary urine and are released back into the bloodstream. The kidneys excrete only the amount of electrolytes that the body needs, which are able to maintain balance in the body.

For the human body, the most important is the acid-base balance, and the kidneys help to regulate it. Depending on the side of the balance shift, the kidneys secrete bases or acids. The shift must remain negligible, otherwise protein folding occurs.

The ability of them to perform their work depends on the rate of blood flow into the tubules. If the rate of transfer of substances is too low, then the functionality of the nephron is reduced, therefore, problems appear in the processes of excretion of urine by purifying the blood.

It is important! To establish the secretory function of the kidneys, a method for diagnosing maximum secretion in the tubules is used. With a decrease in indicators, it is said that the work of the proximal parts of the nephron is disrupted. In the distal section, the secretion of potassium, hydrogen and ammonia ions is carried out. These substances are also needed to restore the water-salt and acid-base balance.

The kidneys are able to separate from the primary urine and return sucrose and some vitamins to the body. The urine then passes into the bladder and ureters. With the participation of the kidneys in protein metabolism, if necessary, the filtered proteins enter the blood again, and the excess ones, on the contrary, are excreted.

Secretion processes of biologically active substances

The kidneys are involved in the production of the following hormones: calcitriol, erythroepin and renin, each of which is responsible for the functions of a particular system in the body.

Erythroepin is a hormone that can stimulate the activity of red blood cells in human body. This is necessary for large blood loss or high physical exertion. In such a situation, the need for oxygen increases, which is satisfied due to the activation of the production of red blood cells. Due to the fact that it is the kidneys that are responsible for the volume of blood cells, anemia is often manifested in their pathology.

Calcitriol is a hormone that is the end product of the breakdown of active vitamin D. This process begins in the skin under the influence of the rays of the sun, continues already in the liver, and then it penetrates the kidneys for the purpose of final processing. Thanks to calcitriol, calcium from the intestines enters the bones and increases their strength.

Renin is a hormone produced by cells near the glomeruli to increase blood pressure. Renin promotes vasoconstriction and the secretion of aldosterone, which retains salt and water. Under normal pressure, renin production does not occur.

It turns out that the kidneys are the most complex system of the body, taking part in a variety of processes, and all of the functions correlate with each other.

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The secretory function of the kidneys helps to regulate many processes in the body.

The kidneys are an organ that belongs to the excretory system of the body. However, excretion is not the only function of this organ. The kidneys filter the blood, return the necessary substances to the body, regulate blood pressure, and produce biologically active substances. The production of these substances is possible due to the secretory function of the kidneys. The kidney is a homeostatic organ, it ensures the constancy of the internal environment of the body, the stability of the metabolic indicators of various organic substances.

What does the secretory function of the kidneys mean?

Secretory function - this means that the kidneys produce the secretion of certain substances. The term "secretion" has several meanings:

• Transfer by nephron cells of substances from the blood into the lumen of the tubule for the excretion of this substance, that is, its excretion,
• Synthesis in the cells of the tubules of substances that need to be returned to the body,
• Synthesis by kidney cells biologically active substances and their delivery into the blood.

What happens in the kidneys?

Blood purification

About 100 liters of blood passes through the kidneys every day. They filter it, separating harmful toxic substances and moving them into the urine. The filtration process takes place in the nephrons - cells located inside the kidneys. In each nephron, a tiny glomerular vessel connects to a tubule that collects urine. In the nephron, the process of chemical metabolism takes place, as a result of which unnecessary and harmful substances. First, primary urine is formed. This is a mixture of decay products, which still contains the substances needed by the body.

tubular secretion

The filtration process occurs due to blood pressure, and further processes already require additional energy for the active transport of blood into the tubules. The following processes take place in them. From primary urine, the kidney extracts electrolytes (sodium, potassium, phosphate) and sends them back to the circulatory system. Kidneys are removed only required amount electrolytes, maintaining and regulating their correct balance.

Acid-base balance is very important for our body. The kidneys help in its regulation. Depending on which direction this balance shifts, the kidneys secrete acids or bases. The shift must be very small, otherwise the coagulation of certain proteins in the body may occur.

The speed at which blood enters the tubules “for processing” determines how they cope with their function. If the transfer rate of substances is insufficient, then the functional abilities of the nephron (and the entire kidney) will be low, which means that there may be problems with blood purification and urine excretion.

To determine this secretory function of the kidneys, a method is used to detect the maximum tubular secretion of substances such as para-aminohyppuric acid, hippuran and diodrast. With a decrease in these indicators, we are talking about a violation of the function of the proximal nephron.

In another section of the nephron, distal, the secretion of potassium, ammonia and hydrogen ions is carried out. These substances are also necessary to maintain acid-base balance, as well as water-salt balance.

In addition, the kidneys separate from the primary urine and return some vitamins, sucrose to the body.

Secretion of biologically active substances

The kidneys are involved in the production of hormones:

• erythroepin,
• Calcitriol
• Renin.

Each of these hormones is responsible for the operation of some system in the body.

Erythroepin

This hormone is able to stimulate the production of red blood cells in the body. This may be necessary for blood loss or increased physical exertion. In these cases, the body's need for oxygen increases, which is satisfied by increasing the production of red blood cells. Since it is the kidneys that are responsible for the number of these blood cells, anemia can develop if they are damaged.

Calcitriol

This hormone is the end product of the formation of the active form of vitamin D. This process begins in the skin under the influence of sunlight, continues in the liver, from where it enters the kidneys for final processing. Thanks to calcitriol, calcium is absorbed from the intestines and enters the bones, ensuring their strength.

Renin

Renin is produced by periglomerular cells when blood pressure needs to be raised. The fact is that renin stimulates the production of angiotensin II enzyme, which constricts blood vessels and causes the secretion of aldosterone. Aldosterone retains salt and water, which, like vasoconstriction, leads to an increase blood pressure. If the pressure is normal, then renin is not produced.

Thus, the kidneys are a very complex system of the body, which is involved in the regulation of many processes, and all their functions are closely related to each other.

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secretory function of the kidneys

In the kidneys, along with the processes of filtration and reabsorption, secretion also takes place simultaneously. In mammals, the ability to secrete in the kidneys is rudimentary, but, nevertheless, secretion plays an important role in the removal of certain substances from the blood. These include substances that are unable to be filtered through the kidney filter. Due to secretion, medicinal substances are excreted from the body: for example, antibiotics. Organic acids, antibiotics, and bases are secreted in the proximal tubule, and ions (especially potassium) are secreted in the distal nephron, especially in the collecting ducts. Secretion is an active process that takes a lot of energy and occurs as follows:

In the cell membrane facing the interstitial fluid, there is a substance (carrier A) that binds to the organic acid removed from the blood. This complex is transported across the membrane and onto it. inner surface breaks up. The carrier returns to the outer surface of the membrane and combines with new molecules. This process takes place with the expenditure of energy. The incoming organic matter moves in the cytoplasm to the apical membrane and through it, with the help of carrier B, is released into the lumen of the tubule. Secretion of K, for example, occurs in the distal tubule. At the 1st stage, potassium enters the cells from the intercellular fluid due to the K-a pump, which transfers potassium in exchange for sodium. Potassium exits the cell through a concentration gradient into the lumen of the tubule.

An important role in the secretion of many substances is played by the phenomenon of pinocytosis - this is the active transport of certain substances that are not filtered through the protoplasm of tubular epithelial cells.

The processed urine enters the collecting ducts. The movement is carried out due to the hydrostatic pressure gradient created by the work of the heart. After passing through the entire length of the nephron, the final urine from the collecting ducts enters the cups, which have automaticity (periodically contract and relax). From the calyx, urine enters the renal pelvis, and from them through the ureters - into the bladder. The valve apparatus, when the ureters flow into the bladder, prevents the return of urine into the ureters when the bladder is full.

Methods for examining the kidneys

Urinalysis allows you to establish kidney disease and violations of their functions, as well as some metabolic changes that are not associated with damage to other organs. There are general clinical analysis and a number of special urine tests.

In a clinical analysis of urine, it is studied physiochemical properties, produce microscopic examination of the sediment and bacteriological culture.

For the study of urine, the average portion is collected after the toilet of the external genital organs in a clean dish. The study begins with the study of physical properties. Normal urine is clear. Cloudy urine can be caused by salts, cellular elements, mucus, bacteria, etc. The color of normal urine depends on its concentration and ranges from straw yellow to amber yellow. The normal color of urine depends on the presence of pigments (urochrome and other substances) in it. Urine acquires a pale, almost colorless appearance with strong dilution, with chronic kidney failure, after infusion therapy or taking diuretics. The most striking changes in the color of urine are associated with the appearance in it of bilirubin (from greenish to greenish-brown in color), erythrocytes in large numbers (from the color of meat slops to red). Some medicines and foods can change color: turns red after taking amidopyrine and red beets; bright yellow - after taking ascorbic acid, riboflavin; greenish-yellow - when taking rhubarb; dark brown - when taking Trichopolum.

The smell of urine is usually unsharp, specific. When urine is decomposed by bacteria (usually inside Bladder) appears ammonia smell. In the presence of ketone bodies (diabetes mellitus), urine acquires the smell of acetone. At congenital disorders metabolism, the smell of urine can be very specific (mouse, maple syrup, hops, cat urine, rotting fish, etc.).

The reaction of urine is normally acidic or slightly acidic. It can be alkaline due to the predominance of a vegetable diet in the diet, the intake of alkaline mineral waters, after profuse vomiting, inflammation of the kidneys, with diseases of the urinary tract, and hypokalemia. Constantly alkaline reaction occurs in the presence of phosphate stones.

The relative density (specific gravity) of urine varies widely - from 1.001 to 1.040, which depends on the characteristics of metabolism, the presence of protein and salts in food, the amount of fluid drunk, the nature of sweating. The density of urine is determined using a urometer. Increase the relative density of urine containing sugars (glucosuria), proteins (proteinuria), intravenous administration radiopaque substances and some medicines. Diseases of the kidneys, in which their ability to concentrate urine is impaired, lead to a decrease in its density, and extrarenal fluid loss leads to its increase. Relative density of urine: below 1.008 - hypostenuria; 1.008-010 - isosthenuria; 1.010-1.030 - hyperstenuria.

Quantification of normal constituent parts urine - urea, uric and oxalic acids, sodium, potassium, chlorine, magnesium, phosphorus, etc. - is important for studying kidney function or detecting metabolic disorders. When examining a clinical analysis of urine, it is determined whether it contains pathological components (protein, glucose, bilirubin, urobilin, acetone, hemoglobin, indican).

The presence of protein in the urine is an important diagnostic sign of diseases of the kidneys and urinary tract. Physiological proteinuria (up to 0.033 g / l of protein in single portions of urine or 30-50 mg / day per day) can be with fever, stress, physical activity. Pathological proteinuria can range from mild (150-500 mg/day) to severe (more than 2000 mg/day) and depends on the form of the disease and its severity. big diagnostic value also has a definition of the qualitative composition of the protein in the urine with proteinuria. Most often, these are plasma proteins that have passed through a damaged glomerular filter.

The presence of sugar in the urine in the absence of excessive consumption of sugar and foods rich in it, infusion therapy with glucose solutions indicates a violation of its reabsorption in the proximal nephron (interstitial nephritis, etc.). When determining sugar in the urine (glucosuria), qualitative samples, if necessary, also count its amount.

Special samples in the urine determine the presence of bilirubin, acetone bodies, hemoglobin, indican, the presence of which in a number of diseases is of diagnostic value.

From cellular elements sediment in the urine is normally found leukocytes - up to 1-3 in the field of view. An increase in the number of leukocytes in the urine (over 20) is called leukocyturia and indicates inflammation in the urinary system (pyelonephritis, cystitis, urethritis). The type of urocytogram may indicate the cause of an inflammatory disease in the urinary system. So neutrophilic leukocyturia speaks in favor of urinary tract infection, pyelonephritis, kidney tuberculosis; mononuclear type - about glomerulonephritis, interstitial nephritis; monocytic type - about systemic lupus erythematosus; the presence of eosinophils is about allergy.

Erythrocytes are normally found in the urine in a single portion in the field of view from 1 to 3 erythrocytes. The appearance of red blood cells in the urine above normal is called erythrocyturia. The penetration of erythrocytes into the urine can occur from the kidneys or from the urinary tract. The degree of erythrocyturia (hematuria) can be mild (microhematuria) - up to 200 in the field of view and severe (macrohematuria) - more than 200 in the field of view; the latter is determined even by macroscopic examination of urine. From a practical point of view, it is important to distinguish between hematuria of glomerular or non-glomerular origin, that is, hematuria from the urinary tract associated with a traumatic effect on the wall of stones, with a tuberculous process and the decay of a malignant tumor.

Cylinders - protein or cellular formations of tubular origin (casts), having a cylindrical shape and various sizes.

There are hyaline, granular, waxy, epithelial, erythrocyte, leukocyte cylinders and cylindrical formations, consisting of amorphous salts. The presence of cylinders in the urine is noted with kidney damage: in particular, hyaline cylinders are found in nephrotic syndrome, granular - with severe degenerative lesions of the tubules, erythrocyte - with hematuria of renal origin. Normally, hyaline casts may appear during exercise, fever, orthostatic proteinuria.

Unorganized urine sediments consist of salts precipitated in the form of crystals and an amorphous mass. In acidic urine there are crystals of uric acid, oxalic acid lime - oxalaturia. This happens with urolithiasis.

Urates (uric acid salts) are also found in the norm - with fever, physical activity, large losses of water, and in pathology - with leukemia and nephrolithiasis. Single crystals of calcium phosphate and hippuric acid are also found in urolithiasis.

Tripel phosphates precipitate in alkaline urine, amorphous phosphates, ammonium urate (phosphaturia) - as a rule, these are the components urinary stones with nephrolithiasis.

The mixed precipitate of acidic and alkaline urine is calcium oxalate (calcium oxalate); it stands out with gout, uric acid diathesis, interstitial nephritis.

Cells may be found in the urine squamous epithelium(polygonal) and renal epithelium (round), not always distinguishable in their morphological features. In the urine sediment, typical epithelial cells characteristic of tumors of the urinary tract can also be found.

Normally, mucus does not occur in the urine. It is found at inflammatory diseases urinary tract and dysmetabolic disorders.

The presence of bacteria in fresh urine (bacteriuria) is observed in inflammatory diseases of the urinary tract and is assessed by the number (small, moderate, high) and the type of flora (cocci, rods). If necessary, a bacterioscopic examination of urine for Mycobacterium tuberculosis is performed. Urine culture makes it possible to identify the type of pathogen and its sensitivity to antibacterial drugs.

Determining the functional state of the kidneys is the most important stage in the examination of the patient. The main functional test is to determine the concentration function of the kidneys. Most often, the Zimnitsky test is used for these purposes. The Zimnitsky test includes the collection of 8 three-hour portions of urine during the day with voluntary urination and water regimen, not more than 1500 ml per day. The evaluation of the Zimnitsky test is carried out according to the ratio of daytime and nighttime diuresis. Normally, daytime diuresis significantly exceeds nighttime diuresis and is 2/3-3/4 of total daily urine. An increase in nocturnal urine portions (a tendency to nocturia) is characteristic of kidney disease, indicating chronic renal failure.

Determination of the relative density of urine in each of the 8 servings allows you to set the concentration ability of the kidneys. If in the Zimnitsky sample the maximum value of the relative density of urine is 1.012 or less, or there is a limitation of fluctuations in the relative density within 1.008-1.010, then this indicates a pronounced violation of the concentration function of the kidneys. This decrease in the concentration function of the kidneys usually corresponds to their irreversible wrinkling, which has always been considered characteristic of the gradual release of watery, colorless (pale) and odorless urine.

The most important indicators for assessing the urinary function of the kidneys in normal and pathological conditions are the volume of primary urine and renal blood flow. They can be calculated by determining the renal clearance.

Clearance (purification) is a conditional concept, characterized by the speed of blood purification. It is determined by the volume of plasma, which is completely cleared by the kidneys from a particular substance in 1 minute.

If a substance that has entered the primary urine from the blood is not reabsorbed back into the blood, then the plasma filtered into the primary urine and returned by reabsorption back to the blood will be completely cleared of this substance.

It is calculated by the formula: С = Uin. x Vurine/ Rin., ml/min

where C is the amount of primary urine; formed in 1 min (inulin clearance), U is the concentration of inulin in the final urine, V is the volume of the final urine in 1 min, P is the concentration of inulin in the blood plasma.

Determination of clearance in modern nephrology is the leading method for obtaining quantitative characteristics kidney activity - glomerular filtration rate. For these purposes, various substances are used in clinical practice (inulin, etc.), but the most widely used method is the determination of endogenous creatinine (Rehberg's test), which does not require additional introduction of a marker substance into the body.

The functional state of the kidneys can also be judged by determining the renal plasma flow, examining the function of the proximal and distal tubules, and performing functional stress tests. It is possible to identify and determine the degree of renal failure by studying the concentration in the blood of urea, indican, residual nitrogen, creatinine, potassium, sodium, magnesium and phosphate.

To diagnose diseases of the kidneys and urinary system, in some cases, a study of the acid-base state is carried out. The determination of lipoproteins in a biochemical blood test indicates the presence of nephrotic syndrome, and hyperlipidemia indicates cholesterolemia. Hyper-Cl2-globulinemia, as well as an increase in ESR, indicate the presence of an inflammatory process in the kidneys, and immunological blood parameters may indicate certain disease kidneys.

The electrolyte composition of the blood (hyperphosphatemia in combination with hypocalcemia) changes in the initial stage of chronic renal failure; hyperkalemia is the most important indicator of severe renal failure, often this indicator of severe renal failure is guided when deciding on hemodialysis.

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The secretory function of the kidneys ensures the constancy of the body

The kidneys perform several functions in our body. The main function of the kidneys is excretory. They purify the blood, collect toxic substances formed in the course of our life, and excrete them in the urine. Due to this, harmful substances do not have a negative effect on the body. However, the kidneys are also involved in metabolic processes, in the processes of regulation, including in the synthesis of certain substances, that is, they also perform a secretory function.

The secretory function of the kidneys is to produce:

• prostaglandins,
• Renina,
• Erythropoietin.

The endocrine complex of the kidney is involved in the performance of the secretory function. It consists of various cells:

• Juxtaglomerular,
• Mesangial,
• Interstitial,
• Juxtavascular Gurmagtig cells,
• Cells of a dense spot,
• tubular,
• Peritubular.

Why do we need renin and prostaglandins?

Renin is an enzyme involved in the regulation and maintenance of blood pressure balance. When it enters the bloodstream, it acts on angiotensinogen, which is converted into the active form of angiotensin II, and it directly regulates blood pressure.

Action of angiotensin II:

• Increases tone small vessels,
• Increases the secretion of aldosterone in the adrenal cortex.

Both of these processes lead to an increase in blood pressure. In the first case, due to the fact that the vessels "stronger" push the blood. In the second, the process is somewhat more complicated: aldosterone stimulates the production antidiuretic hormone, and the volume of fluid in the body increases, which also leads to an increase in blood pressure.

Renin is produced by juxtaglomerular cells and, when depleted, by juxtavascular cells. The process of renin production is regulated by two factors: an increase in sodium concentration and a drop in blood pressure. As soon as one of these factors changes, there is a change in the production of renin, due to which the pressure rises or falls.

Prostaglandin hormones are fatty acids. There are several types of prostaglandins, one of which is produced by the kidneys in the interstitial cells of the renal medulla.

Prostaglandins produced by the kidneys are renin antagonists: they are responsible for lowering blood pressure. That is, with the help of the kidneys, there is a multi-level control and regulation of pressure.

Action of prostaglandins:

• Vasodilator,
• Increase in glomerular blood flow.

As prostaglandins increase, blood vessels dilate, and blood flow slows down, which helps to reduce pressure. Also, prostaglandins increase blood flow in the renal glomeruli, which leads to an increase in urine output and increased excretion of sodium with it. Reducing the volume of the liquid and the sodium content leads to a decrease in pressure.

Why is erythropoietin needed?

The hormone erythropoietin is secreted by the tubular and peritubular cells of the kidney. This hormone regulates the rate at which red blood cells are produced. Red blood cells are needed by our body in order to deliver oxygen to organs and tissues from the lungs. If the body needs more of them, then erythropoietin is released into the bloodstream, then, getting into Bone marrow, stimulates the formation of red blood cells from stem cells. As soon as the number of these blood cells returns to normal, the secretion of erythropoietin by the kidneys decreases.

What is a factor in increasing the production of erythropoietin? This is anemia (decrease in the number of red blood cells) or oxygen starvation.

Thus, the kidney not only frees us from unnecessary substances, but also helps to regulate the constancy various indicators in the body.

The essence and significance of the process of digestion

Functions of the gastrointestinal tract

Types of digestion

In the modern animal world, there are three different types of digestion: intracellular, extracellular, membrane.
During intracellular digestion, enzymatic hydrolysis of nutrients is carried out inside the cell.
Extracellular digestion is external, cavitary and distant.
In humans, cavitary digestion is well expressed.
Types of digestion are characterized not only by the site of action, but also by the sources of enzymes. Based on this criterion, digestion proper, symbiotic and autolytic are distinguished.
Man basically has his own digestion. With such digestion, the body itself is the source of enzymes.
With symbiotic digestion, it is realized due to microorganisms located in the gastrointestinal tract. This type of digestion is well represented in ruminants.
Autolytic digestion is understood as the digestion of food, due to the enzymes contained in it. In the digestion of newborns, hydrolytic enzymes contained in mother's milk are of great importance.

Physiological basis of hunger and satiety

Research methods of the gastrointestinal tract

Fistulas of various parts of the gastrointestinal tract. A fistula is an artificial communication of a flat organ or gland duct with the external environment (I.P. Pavlov).
Clean gastric juice obtained from animals with gastric fistula and esophagotomy (sham feeding experience) (I.P. Pavlov).
The operation of creating an isolated ventricle (according to Gendeigain, according to I.P. Pavlov) in order to obtain pure gastric juice while food is in the stomach.
Breeding in skin wound common bile duct, which allows you to collect bile (I.P. Pavlov).
The study of intestinal secretion is performed on isolated areas of the small intestine (Tiri-Vella fistula).
When studying absorption, the method of taking blood flowing from the digestive tract is used (angiostomy according to E.S. London).
With the help of Leshli-Krasnogorsky capsules, saliva can be collected separately from the parotid, submandibular and sublingual glands.
To study the secretory function of the human gastrointestinal tract, probe and probeless methods (rubber probes, radio pills) are used.
To study the state of the gastrointestinal tract ( motor activity and other functions) apply radiological methods.
The motor function of the stomach is studied by registering biopotentials that are generated by the smooth muscles of the stomach (electrogastrography).
The act of chewing in a person is examined by recording the movements of the lower jaw (masticography) and the electrical activity of the masticatory muscles (myoelectromasticography).
Gnotodynamometry - determination of the maximum pressure that can be developed on different teeth chewing muscles when clenching the jaws.
Endoscopy methods (fibroesophagogastroduodenoscopy (FEGDS), sigmoidoscopy, irrigoscopy).

Digestion in the mouth

Fig.38. Secretion of saliva.

Digestion in the stomach

Composition and properties of gastric juice. In addition to the cells of the gastric mucosa that secrete mucus, there are two types of glands: gastric and pyloric.
The gastric glands secrete an acidic juice (due to the presence of hydrochloric acid in it) containing seven inactive pepsinogens, intrinsic factor and mucus. The pyloric glands secrete mainly mucus, which protects the mucous membrane, as well as a small amount of pepsinogen. The gastric glands are located in the inner surface of the body and fundus of the stomach and make up 80% of all glands. The pyloric glands are located in the antrum of the stomach.
Secretion of the gastric glands. The gastric glands are made up of 3 different types of cells: the main ones, which secrete pepsinogens; additional - secrete mucus; parietal (parietal) - secrete hydrochloric acid and intrinsic factor.
Thus, the composition of gastric juice includes proteolytic enzymes that take part in the initial stage of protein digestion. These include pepsin, gastrixin, rennin. All these enzymes are endopeptidases (i.e., in the active state, they cleave internal bonds in the protein molecule). As a result of their action, peptides and oligopeptides are formed. Note that all these enzymes are secreted in an inactive state (pepsinogen, gastrixinogen, reninogen). The process of their activation is triggered by hydrochloric acid, then proceeds autocatalytically under the action of the first portions of active pepsin. Actually pepsins are usually called those forms that hydrolyze proteins at pH 1.5-2.2. Those fractions whose activity is maximum at pH 3.2-3.5 are called gastrixins. Thanks to hydrochloric acid, the pH of gastric juice is 1.2-2.0. If the pH increases to 5, pepsin activity disappears. The composition of gastric juice also includes Ca 2+ , Na + , Mg 2+ , K + , Zn , HCO 3 - .
Hydrochloric acid. When stimulated, the parietal cells secrete hydrochloric acid, the osmotic pressure of which is almost exactly equal to that of the interstitial fluid. The mechanism of secretion of hydrochloric acid can be imagined as follows (Fig. 39).

Fig.39. Mechanism of secretion of hydrochloric acid

Fig.40. Regulation of gastric acid secretion by parietal cells

(W.F. Ganong, 1977)

The nature of gastric secretion to various foods

Outside of digestion, the glands of the stomach secrete a small amount of juice. Stimulating and inhibitory regulatory factors ensure the dependence of gastric juice secretion on the type of food taken (I.P. Pavlov). According to I.T. Kurtsin, the indicators of secretion for meat, bread, milk are arranged in magnitude as follows:
The volume of juice - meat, bread, milk.
Duration of secretion - bread, meat, milk.
Acidity of juice - meat, milk, bread.
The digestive power of juice is bread, meat, milk.
In addition, it should be noted that:
1) for all these irritants, pepsin is released more at the beginning of secretion and less at its completion;
2) food stimuli that cause secretion with a large participation of the vagus nerves (bread) stimulate the secretion of juice with a higher content of pepsin in it than stimuli with a mild reflex effect (milk);
3) the correspondence of secretion to the characteristics of food ensures efficient digestion.
Therefore, if a person eats any one type of food for a long time, then the nature of the secreted juice can change significantly. When taking plant foods, secretory activity decreases in the second and third phases, slightly increasing in the first. Protein food, on the contrary, stimulates the secretion of juice mainly in the second and third phases. Moreover, the composition of the juice can also be transformed.

Gastric ulcer. The appearance of a stomach or duodenal ulcer in humans is associated with a violation of the barrier function of the mucous membrane and exposure to aggressive factors of gastric juice. Important in breaking this barrier are

Microorganisms Helicobacter pylori;
medications, such as aspirin or non-steroidal anti-inflammatory drugs widely used as pain relievers and anti-inflammatory drugs in the treatment of arthritis;
prolonged hypersecretion of hydrochloric acid in the stomach.
An example is the appearance of an ulcer in the prepyloric stomach or duodenum in Zollinger-Ellison syndrome. This syndrome is observed in patients with gastrinomas. These tumors can appear in the stomach or duodenum, but as a rule, most of them are in the pancreas. Gastrin causes prolonged hypersecretion of hydrochloric acid, resulting in severe ulcers.
Treatment of such ulcers consists in surgical removal of gastrinoma.

Exocrine activity of the pancreas

The pancreas is a large, complex gland similar in structure to the salivary gland. In addition to the fact that the pancreas secretes insulin, its acinar cells produce digestive enzymes, and the cells of small and large ducts emerging from the acini form a bicarbonate solution. Then the product of complex composition through a long duct that flows into the common bile duct enters the duodenum 12. Pancreatic juice is almost entirely secreted in response to the entry of chyme into the upper part small intestine, and the composition of this juice depends entirely on the nature of the food taken.
Composition of pancreatic juice. The juice contains enzymes of all types: proteases, carbohydrases, lipases and nucleases.
Proteolytic Enzymes: trypsin, chymotrypsin, carboxypeptidase, elastase. The most important of these is trypsin. All proteolytic enzymes are secreted in an inactive form. The conversion of trypsinogen to trypsin occurs under the influence of an enzyme located on the brush border of enterokinase (enteropeptidase), when pancreatic juice enters the duodenum. The secretion of enterokinase is enhanced under the influence of cholecystokinin. It contains 41% polysaccharides, which apparently prevent its digestion. After activation, trypsin activates chymotrypsinogen and other enzymes, and trypsin itself activates trypsinogen (autocatalytic chain reaction).
Trypsin and chymotrypsin break down whole proteins and oligopeptides into peptides of various sizes, but not to amino acids. Carboxypeptidase breaks down peptides into amino acids, thereby completing their digestion.
Activation of trypsin in the pancreas will lead to its self-digestion. Therefore, it is not surprising that the pancreas normally contains a trypsin inhibitor.
Enzyme activation pancreatic juice shown in Fig.41.

Fig.41. Activation of pancreatic enzymes

Fig.42. Secretion of bicarbonates.

Regulation of secretion of pancreatic juice.
The main stimulants of pancreatic secretion:
1) Acetylcholine (ACCh), is released from the endings of the vagus nerves, as well as other nerves of the enteric nervous system.
2) Gastrin, is released in large quantities during the gastric phase of gastric juice secretion.
3) Cholecystokinin (CCK), is secreted by the mucous membrane of the duodenum and the initial part of the jejunum when food enters them.
4) Secretin, secreted by the duodenal mucosa in response to the action of CCK, which is secreted by the duodenal mucosa when acidic chyme enters it.
ACH, gastrin and CCK stimulate acinar cells to a much greater extent than ductal cells. Consequently, they cause the secretion of a large amount of digestive enzymes in a small amount of liquid and mineral salts. Without fluid, most enzymes are temporarily stored in the acini and ducts until fluid secretion increases to flush them into the duodenum.
Secretin, on the contrary, stimulates mainly the secretion of sodium bicarbonate.
Pancreatic secretion proceeds in 3 phases, corresponding to the phases of secretion of gastric juice (cerebral, gastric and intestinal).

The composition of bile

Bile is the secret of hepatocytes. There are 2 processes: bile formation and bile secretion.
bile formation. Bile formation occurs partly by filtering bile components directly from the blood, and partly by their secretion by hepatocytes. Thus, bile acids are formed with the participation of the rough endoplasmic reticulum of liver cells, then enter the Golgi complex and then into bile ducts. Bile formation occurs constantly, bile is collected in gallbladder and concentrate there. In addition to bile acids, bile contains cholesterol, bilirubin, biliverdin, as well as mineral salts and proteins, which are dissolved in an alkaline electrolyte resembling pancreatic juice.
Regulation of bile formation (choleresis). The formation of bile is continuous and is regulated by the neurohumoral pathway. From 500 to 1200 ml of bile are secreted daily.
Nervous regulation: vagus stimulates, sympathetic nerves inhibit choleresis.
Humoral regulation: stimulate - bile acids, secretin, CCK, gastrin, enteroglucagon. Secretin can increase by 2 times (the secretion of water and bicarbonates increases, and the secretion of bile acids does not change). In addition, the very intake of food, especially fatty, stimulates secretion. Inhibits the secretion of somatostatin.
Functions of bile. Due to the presence of bile acids in bile, it is of great importance in the digestion of food and its absorption. Bile acids help to emulsify fat and make it available to the action of lipase, and also promote the absorption of fat digestion products and fat-soluble vitamins. Some blood products (bilirubin and excess cholesterol) are excreted in bile.
Bile acids (FA). Liver cells produce 0.5 g of bile acids daily. The precursor of bile acids is cholesterol, which comes either from food or is formed in the liver. Cholesterol is converted into cholic and chenodeoxycholic acids. These acids then bind mainly to glycine and, to a lesser extent, to taurine; as a result, glyco- and taurocholic acids are formed.
The function of bile acids. Detergent effect on fats. This reduces the surface tension of the particles, creating the possibility of their mixing in the intestine and disintegration into smaller particles. This is called fat emulsification. Bile acids promote the absorption of fatty acids, monoglycerides, lipids, cholesterol, etc. from the intestine. This is due to the formation of small complexes with these lipids, which are called micelles. Micelles are highly soluble. In this form, fatty acids are transported to the intestinal mucosa, where they are absorbed. If bile acids do not enter the intestines, then up to 40% of fat is excreted with feces, and a person develops a metabolic disorder.
Enterohepatic circulation of bile acids. Up to 94% of the bile acids secreted into the duodenum are reabsorbed in the small intestine (in the distal ileum) and enter the liver through the portal vein. In the liver, they are completely captured by hepatocytes and again secreted into bile.
The amount of bile secreted daily is largely dependent on the bile salts involved in the enterohepatic circulation (2.5 g).
If you do not allow bile to flow into the duodenum, i.e. bile acids cannot be absorbed in the intestines, then in the liver the production of bile acids increases 10 times.
secretion of cholesterol. Bile acids are formed by liver cells from cholesterol, and during the secretion of bile acids, about 1/10 of their part is cholesterol. This amounts to 1-2 g per day.
Cholesterol does not perform a specific function in bile.
Note that cholesterol is insoluble in water, but bile salts and lecithin in bile combine with cholesterol and form ultramicroscopic micelles that are soluble. Consequently, a violation in bile of the ratio of bile acids, cholesterol and phospholipids can lead to precipitation of cholesterol and the formation of gallstones.
Bile secretion (cholekinesis). Bile secretion is the process of periodic emptying of the gallbladder. This is possible when the sphincters of the bile ducts relax during contraction of the walls of the gallbladder.

Composition and properties of intestinal juice

In the intestine, digestion proceeds under the influence of pancreatic juice, bile and intestinal juice proper. Intestinal juice is secreted by the Brunner and Lieberkühn glands. It is a turbid, rather viscous liquid. This juice has no independent value. It can be obtained with a Tiri-Vell fistula.

Cavitary and membrane hydrolysis of nutrients
in various parts of the small intestine

Digestion in the large intestine

The remains of the food taken, not digested in the small intestine (300-500 ml / day), enters through the ileocecal valve into the caecum. Chyme is concentrated in the large intestine by absorption of water. Absorption of electrolytes, water-soluble vitamins, fatty acids, and carbohydrates also continues here.
In the absence of mechanical irritation, that is, in the absence of chyme in the intestine, a very small amount of juice is released. When irritated, juice production increases by 8-10 times. The juice contains mucus and sloughed epithelial cells. In addition, the epithelial cells of the mucosa secrete bicarbonates and other inorganic compounds, creating a juice pH of about 8.0. The digestive function of the juice is insignificant. The main purpose of the juice is to protect the mucous membrane from mechanical, chemical damage and provide a slightly alkaline reaction.
Regulation of secretory processes in the large intestine. In the large intestine, secretion is determined by local reflexes caused by mechanical irritation.
The microflora of the large intestine. In the large intestine, nutrients are exposed to the action of microflora, since under its influence enterokinase, alkaline phosphatase, trypsin, and amylase enzymes are inactivated. Microorganisms take part in the decomposition of paired bile acids, a number of organic substances with the formation organic acids, and their ammonium salts, amines and other substances in the metabolism of proteins, phospholipids, bile and fatty acids, bilirubin and cholesterol.
Indigestible proteins in the large intestine under the influence of putrefactive bacteria undergo decay, resulting in the formation of toxic substances (volatile amines): indole, skatole, phenol, cresol, which are neutralized in the liver by combining with sulfuric and glucuronic acids.
Normal microflora suppresses pathogenic microorganisms and protects the body from their reproduction and introduction. Violation of it during diseases or prolonged administration of antibacterial drugs often leads to complications caused by the rapid reproduction of yeast, staphylococci, Proteus and other microorganisms in the intestine.
The intestinal microflora synthesizes vitamins of group B, K, etc.
It is possible that other substances important for the body are also synthesized in it. For example, in “microbial-free rats” grown under sterile conditions, the caecum of the intestine is extremely enlarged, the absorption of water and amino acids is sharply reduced, which can be the cause of death.
Many factors influence the intestinal microflora: the intake of microorganisms with food, the nature of the diet, the properties of digestive secrets (having more or less pronounced bactericidal properties), intestinal motility (which contributes to the removal of microorganisms from it), the presence of immunoglobulins in the intestinal mucosa. Normal microflora is controlled by antibodies, the production of which increases in response to an increase in one or another type of microorganism. In the regulation of their adhesion on the surface of the mucous membrane, the importance of leukocytes is great.
Formation of intestinal gases. There are 3 sources of gas in the gastrointestinal tract. Swallowed air, including air released from food and carbohydrate-rich foods entering the stomach. Most of these gases are expelled from the stomach by belching or pass along with chyme into the small intestine.
The formation of gas in the large intestine occurs as a result of the activity of bacteria that colonize distal ileum and colon. A small amount of gas enters the large intestine from the blood.
The composition of gases formed in the large intestine differs from the gases of the small intestine. A small amount of gas in the small intestine is mostly swallowed gas. A large amount of gas is produced in the large intestine, up to 7-10 liters per day.
Gas in the large intestine is formed from the breakdown of undigested food. The main component of this gas is CO 2 , CH 4 , H 2 and nitrogen. Since all these gases, except for nitrogen, are able to diffuse through the intestinal mucosa, the volume of gas can increase or decrease up to 600 ml / day.

Methods for studying absorption in humans.

1. According to the rate of occurrence of the pharmacological effect (nicotinic acid - reddening of the skin of the face). 2. Radioisotope method(labeled substances pass from the intestines into the blood).

Study of the excretory function of the digestive tract.

Excretory function is studied by the amount of a substance in the contents of various sections of the gastrointestinal tract at certain time intervals after the introduction of this substance into the blood.

Secretion is the process of synthesis by secretory cells of specific

substances, mainly enzymes, which, together with water and salts, are released into the lumen of the gastrointestinal tract and form digestive juices.

The production of secrets is carried out by secretory cells that combine in the gland.

The digestive tract contains the following types of glands :

1. Unicellular (goblet cells of the intestine). 2. Multicellular glands . They are subdivided on the:

a) simple - one duct (glands of the stomach, intestines); b) complex glands - several ducts, formed by a large number of heterogeneous cells (large salivary, pancreas, liver).

By the nature of functioning There are two types of glands:

1. Glands with continuous secretion . These include glands that produce mucus; liver. 2. Glands with intermittent secretion . These include some salivary, gastric, intestinal glands, and the pancreas.

In the study of the mechanisms of formation of secrets,

three mechanisms of secretion : 1. Holocrine - secretion is accompanied by cell destruction. 2. Apocrine - the secret accumulates in the apex, the cell loses the apex, which then collapses in the cavity of the organ. 3. Merocrine - the secret is released without morphological changes in the cell.

Types of digestion(from hydrolysis origin) :

1. Autolytic- due to enzymes found in foods of plant and animal origin. 2. Symbiotic - enzymes are produced by bacteria and protozoa of this macroorganism;

3. Own- due to enzymes synthesized by the digestive tract: a ) Intracellular - the most ancient type (not cells secrete enzymes, but the substance enters the cell and is broken down by enzymes there). b) Extracellular (distant, cavitary ) - enzymes are secreted into the lumen of the gastrointestinal tract, acting at a distance; in) Membrane (wall, contact) - in the mucous layer and the zone of the brush border of enterocytes adsorbed on enzymes (significantly higher hydrolysis rate).

All secrets are

1. water 2. dry residue.

In the dry matter contains two groups of substances:

1. Substances that perform a specific function in this department digestive tract. 2. Enzymes . They are divided into: proteases, carbohydrases, lipases and nucleases.

Factors affecting enzyme activity:

1. Temperature, 2. pH of the medium, 3. The presence of activators for some of them (produced in an inactive form so that autolysis of the gland does not occur), 4. The presence of enzyme inhibitors

The activity of the glands and the composition of the juices depend on diet and dietary patterns. The total amount of digestive juices per day is 6-8 liters.

Secretion in the mouth

In the oral cavity, saliva is produced by 3 pairs of large and many small salivary glands. The sublingual and small glands secrete a secret constantly. Parotid and submandibular - during stimulation.

1) The time spent by food in the oral cavity is on average 16-18 seconds. 2) The volume of daily secretion is 0.5-2 liters. Abdominal digestion 3) Secretion rate - from 0.25 ml / min. up to 200 ml / min. 4) pH - 5.25-8.0. The optimal environment for the action of enzymes is slightly alkaline. 5) The composition of saliva: BUT). Water - 99.5%. B). ions K, Na, Ca, Mg, Fe, Cl, F, PO 4 , SO 4 , CO 3 .B) . Squirrels (albumins, globulins, free amino acids), nitrogen-containing compounds of non-protein nature (ammonia, urea, creatinine). Their content increases with renal failure. G). Specific Substances : -mucin (mucopolysaccharide), gives saliva viscosity, forms a food bolus. - lysozyme (muromidase) substance that provides bactericidal action (dogs lick the wound), - saliva nuclease - antiviral action, - immunoglobulin A - binds exotoxins. D) active white blood cells - phagocytosis (in cm 3 of saliva - 4000 pieces). E) normal microflora oral cavity, which depresses the pathological. AND). saliva enzymes . Refer to carbohydrase :1. Alpha amylase - breaks down starch into disaccharides.2. Alpha glucosidase - into sucrose and maltose - split to monosaccharides (active in a slightly alkaline environment).

Within the oral cavity, saliva enzymes have practically no effect (due to the short time the food bolus is in the oral cavity). The main effect is in the esophagus and stomach (until the acidic contents soak the food bolus).

Secretion in the stomach

The residence time of food in the stomach is 3-10 hours. On an empty stomach in the stomach is about 50 ml of contents (saliva, gastric secretion and contents of the duodenum 12) neutral pH (6.0). The volume of daily secretion is 1.5 - 2.0 l / day, pH - 0.8- 1.5.

The glands of the stomach are made up of three types of cells.: chief cells - produce enzymes Parietal (cover)- HCl; Additional - slime.

The cellular composition of the glands changes in various parts of the stomach (in the antral - there are no main cells, in the pyloric - there are no parietal).

Digestion in the stomach is predominantly abdominal.

Composition of gastric juice

1. Water - 99 - 99,5%. 2. Specific Substances : Main inorganic component - HCl(m.b. in a free state and associated with proteins). The role of HCl in digestion : 1. Stimulates the secretion of the glands of the stomach.2. Activates the conversion of pepsinogen to pepsin.3. Creates optimal pH for enzymes. 4. Causes denaturation and swelling of proteins (easier to be broken down by enzymes). 5. Provides antibacterial action of gastric juice, and consequently, the preservative effect of food (there are no processes of decay and fermentation). 6. Stimulates gastric motility.7. Participates in the curdling of milk.8. Stimulates the production of gastrin and secretin ( intestinal hormones ). 9. Stimulates the secretion of enterokinase by the duodenal wall.

3. Organic specific substances: 1. Mucin - Protects the stomach from self-digestion. Mucin forms ( comes in 2 forms ):

a ) tightly bound with a cell, protects the mucosa from self-digestion;

b) loosely bound , covers the food bolus.2. Gastromucoprotein (Castle intrinsic factor) - necessary for the absorption of vitamin B12.

3. Urea, uric acid, lactic acid .4.Antienzymes.

Enzymes of gastric juice:

1) Basically - proteases , provide the initial hydrolysis of proteins (to peptides and a small amount of amino acids). Common name - pepsins.

Are produced in inactive form(as pepsinogens). Activation occurs in the lumen of the stomach with the help of HCl, which cleaves off the inhibitory protein complex. Subsequent activation in progress autocatalytically (pepsin ). Therefore, patients with anacid gastritis are forced to take an HCl solution before meals to start digestion. Pepsins split bonds formed by phenylalanine, tyrosine, tryptophan and a number of other amino acids.

Pepsins:

1. Pepsin A - (optimum pH - 1.5-2.0) splits large proteins into peptides. It is not produced in the antrum of the stomach. 2. Pepsin B (gelatinase)- breaks down protein connective tissue- gelatin (active at pH less than 5.0). 3. Pepsin C (gastrixin) - an enzyme that breaks down animal fats, especially hemoglobin (optimum pH - 3.0-3.5). four. Pepsin D (re nn in ) - Curdles milk casein. Basically - in cattle, especially in calves - it is used in the manufacture of cheese (therefore cheese is 99% absorbed by the body) In humans - chymosin (together with hydrochloric acid (curdles milk)). In children - fetal pepsin (optimum pH -3.5), curdles casein 1.5 times more actively than in adults. Curdled milk proteins are more easily digested.

2)Lipase. The gastric juice contains lipase, the activity of which is low, it acts only for emulsified fats(e.g. milk, fish oil). Break down fats into glycerol and fatty acids at pH 6-8(in a neutral environment). In children, gastric lipase breaks down up to 60% of milk fats.

3)Carbohydrates break down in the stomach by salivary enzymes(before their inactivation in acidic environment). Gastric juice does not contain its own carbohydrases.