The structure of the large intestine is . The length of the colon is on average 1.5-2 m, its diameter in the initial section is about 7-14 cm, in the final section - about 4-6 cm.
The microflora of the large intestine promotes and facilitates the absorption of certain nutrients and the formation of vitamins.
This is due to the vital activity of the microflora of the large intestine - the microbes that live in the large intestine. These microbes make their living from food waste that enters the large intestine, and in doing so, benefit human body, producing some vitamins and amino acids for it.

represented by three main groups:
- the main or obligate (mandatory) microflora - it includes the microorganisms of the large intestine - bifidumbacteria, which make up about 95% of the normal microflora of the large intestine

They create a dense bacterial barrier, especially in the region of the caecum, preventing it from being populated by other pathological microorganisms, and protect the mucous membrane of the large intestine from inflammation.

Bifidumbacteria produce acetic and lactic acid, creating an acidic environment in the large intestine (this blocks the reproduction of pathological putrefactive and gas-forming microbes, prevents increased gas formation, and normalizes the contractile function of the intestine).

Bifidumbacteria are involved in the synthesis and absorption of vitamins C, B, B6, Bp, K, D, E, and promote the absorption of calcium, iron, vitamins, and water. They neutralize nitrates from food, inactivate the allergen - histamine;

The accompanying microflora or symbiotic - is represented mainly by lactic acid bacteria (lactobacilli) and E. coli. Their number is small - they make up about 5% of the normal microflora of the large intestine.

They contribute to the main microorganisms of the first group;
Conditionally pathogenic or facultative microflora - it includes rare microorganisms, such as staphylococci, proteus, Pseudomonas aeruginosa, enterobacteria, some types of fungi.

They make up no more than 0.01% - 0.001% of the total number of microbes. In a normal, healthy colon, the latter two groups coexist peacefully, without causing harm or showing aggressive qualities.

Dysbacteriosis of the large intestine

With a change in the qualitative and quantitative ratio of microorganisms of these three groups, dysbacteriosis develops in the intestine.
There are 4 stages of colon dysbacteriosis:
Stage 1: the number of bifidumbacteria and lactobacilli decreases.

Stage 2: the amount of accompanying microflora, mainly E. coli, increases significantly and its qualities change (along with a decrease in the content of bifidumbacteria and lactobacilli). Atypical or defective forms of Escherichia coli appear. In other cases, the amount of normal Escherichia coli decreases sharply along with the appearance of atypical and defective forms.

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1 Structure and function of the large intestine. Importance of intestinal microflora. Influence of nutritional factors on the large intestine

The structure and functions of the large intestine

The large intestine is the last section of the gastrointestinal tract and consists of six sections:

The caecum (cecum, cecum) with an appendix (vermiform appendix);

ascending colon;

Transverse colon;

descending colon;

Sigmoid colon;

Rectum.

The total length of the large intestine is 1-2 meters, the diameter in the region of the caecum is 7 cm and gradually decreases towards the ascending colon to 4 cm. Distinctive features large intestine compared to the small intestine are:

The presence of three special longitudinal muscle cords or ribbons that begin near the appendix and end at the beginning of the rectum; they are located at an equal distance from each other (in diameter);

The presence of characteristic swellings, which on the outside look like protrusions, and on the inside - bag-shaped depressions;

The presence of processes of the serous membrane 4-5 cm long, which contain adipose tissue.

The cells of the mucous membrane of the colon do not have villi, since the intensity of absorption processes in it is significantly reduced.

In the large intestine, water absorption ends and feces are formed. Mucus is secreted by the cells of the mucous membrane for their formation and movement through the sections of the large intestine.

In the lumen of the colon, a large number of microorganisms live, with which the human body normally establishes symbiosis. On the one hand, microbes absorb food residues and synthesize vitamins, a number of enzymes, amino acids and other compounds. At the same time, a change in the quantitative and especially quality composition microorganisms leads to significant violations of the functional activity of the organism as a whole. This can happen when the rules of nutrition are violated - the consumption of large quantities of refined foods with a low content of dietary fiber, excess food, etc.

Under these conditions, the so-called putrefactive bacteria begin to predominate, releasing substances in the process of vital activity that have a negative effect on humans. This condition is defined as intestinal dysbiosis. We will talk about it in detail in the section on the colon.

Fecal (fecal) masses move through the intestines due to wave-like movements colon(peristalsis) and reach the rectum - the last section, which serves for their accumulation and excretion. In its lowest section there are two sphincters - internal and external, which close anus and open during bowel movements. The opening of these sphincters is normally regulated by the central nervous system. The urge to defecate in a person appears with mechanical irritation of the receptors of the anus.

Importance of intestinal microflora

The human gastrointestinal tract is inhabited by numerous microorganisms, the metabolism of which is closely integrated into the metabolism of the macroorganism. Microorganisms inhabit all departments gastrointestinal tract, however, in the most significant quantities and diversity are presented in the large intestine.

The most important and studied functions of the intestinal microflora are the provision of anti-infective protection, stimulation immune functions macroorganism, nutrition of the colon, absorption of minerals and water, synthesis of B and K vitamins, regulation of lipid and nitrogen metabolism, regulation of intestinal motility.

Anti-infective protection performed by intestinal microorganisms is largely associated with the antagonism of representatives of the normal microflora in relation to other microbes. The suppression of the activity of some bacteria by others is carried out in several ways. These include competition for substrates for growth, competition for fixation sites, induction of an immune response of a macroorganism, stimulation of peristalsis, creation of an unfavorable environment, modification/deconjugation of bile acids (as one of the ways to modify environmental conditions), and synthesis of antibiotic-like substances.

The metabolic effects of the normal intestinal microflora associated with the synthesis of short chain fatty acids (SCFA) have been well studied. The latter are formed as a result of anaerobic fermentation of di-, oligo- and polysaccharides available to bacteria. Locally, SCFA determine the decrease in pH and provide colonization resistance, and also take part in the regulation of intestinal motility. The formation of butyrate is extremely important for the epithelium of the colon, because. it is butyrate that colonocytes use to meet their energy needs. In addition, butyrate is a regulator of apoptosis, differentiation and proliferation processes, and therefore anticarcinogenic effects are associated with it. Finally, butyrate is directly involved in the absorption of water, sodium, chlorine, calcium and magnesium. Therefore, its formation is necessary to maintain the water and electrolyte balance in the body, as well as to provide the macroorganism with calcium and magnesium.

In addition, the decrease in pH associated with the formation of SCFAs leads to the fact that ammonia, which is formed in the colon in connection with the microbial metabolism of proteins and amino acids, passes into ammonium ions and in this form cannot freely diffuse through the intestinal wall into the blood, but excreted in the feces in the form of ammonium salts.

Another important function of the microflora is to convert bilirubin to urobilinogen, which is partly absorbed and excreted in the urine and partly excreted in the feces.

Finally, the participation of the colon microflora in lipid metabolism seems to be extremely important. Microbes metabolize cholesterol that enters the large intestine into coprostanol and then into coprostanone. Acetate and propionate formed as a result of fermentation, having been absorbed into the bloodstream and reaching the liver, can affect the synthesis of cholesterol. In particular, it has been shown that acetate stimulates its synthesis, while propionate inhibits it. The third way of influence of microflora on lipid metabolism in the macroorganism is associated with the ability of bacteria to metabolize bile acids, in particular, cholic acid. Conjugated cholic acid not absorbed in the distal ileum in the colon undergoes deconjugation by microbial choleglycine hydrolase and dehydroxylation with the participation of 7-alpha-dehydroxylase. This process is stimulated by an increase in the pH values ​​in the intestine. The resulting deoxycholic acid binds to dietary fiber and is excreted from the body. With an increase in pH, deoxycholic acid is ionized and well absorbed in the large intestine, and when it decreases, it is excreted. The absorption of deoxycholic acid provides not only replenishment of the pool of bile acids in the body, but is also an important factor stimulating the synthesis of cholesterol. An increase in pH values ​​in the colon, which may be due to various reasons, leads to an increase in the activity of enzymes leading to the synthesis of deoxycholic acid, to an increase in its solubility and absorption, and, as a result, an increase in the blood level of bile acids, cholesterol and triglycerides. One of the reasons for the increase in pH may be the lack of prebiotic components in the diet, which disrupt the growth of normal microflora, incl. bifido- and lactobacilli.

Another important metabolic function of the intestinal microflora is the synthesis of vitamins. In particular, B vitamins and vitamin K are synthesized. The latter is necessary in the body for the so-called. calcium-binding proteins that ensure the functioning of the blood coagulation system, neuromuscular transmission, bone structure, etc. Vitamin K is a complex of chemical compounds, among which are vitamin K1 - phylloquinone - of plant origin, as well as vitamin K2 - a group of compounds called menaquinones - synthesized microflora in the small intestine. The synthesis of menaquinones is stimulated with a lack of phyloquinone in the diet and may increase with excessive growth of the small intestine microflora, for example, while taking drugs that reduce gastric secretion. Conversely, the use of antibiotics, leading to the suppression of the small intestine microflora, can lead to the development of antibiotic-induced hemorrhagic diathesis (hypoprothrombinemia).

The fulfillment of the listed and many other metabolic functions is possible only if the normal microflora is fully provided with the nutrients necessary for its growth and development. The most important energy sources for it are carbohydrates: di-, oligo- and polysaccharides that do not break down in the lumen small intestine which are called prebiotics. The microflora receives nitrogenous components for its growth to a large extent during the breakdown of mucin, a component of mucus in the large intestine. The resulting ammonia must be eliminated under conditions reduced values pH, which is provided by short-chain fatty acids formed as a result of the metabolism of prebiotics. The detoxifying effect of non-digestible disaccharides (lactulose) is well known and has long been used in clinical practice. For normal life, colon bacteria also need vitamins, some of which they synthesize themselves. At the same time, part of the synthesized vitamins is absorbed and used by the macroorganism, but the situation is different with some of them. For example, a number of bacteria living in the colon, in particular, representatives of Enterobacteriacea, Pseudomonas, Klebsiella, can synthesize vitamin B12, but this vitamin cannot be absorbed in the colon and is inaccessible to the macroorganism.

In this regard, the nature of the child's nutrition to a large extent determines the degree of integration of microflora into his own metabolism. This is especially pronounced in children of the first year of life who are on a natural or artificial feeding. The intake of prebiotics (lactose and oligosaccharides) with human milk contributes to the successful development of the normal intestinal microflora of a newborn child with a predominance of bifido- and lactoflora, while with artificial feeding with mixtures based on cow's milk without prebiotics, streptococci, bacteroids, representatives of Enterobacteriacea are predominant. Accordingly, the spectrum of bacterial metabolites in the intestine and the nature of metabolic processes also change. So, the predominant SCFAs with natural feeding are acetate and lactate, and with artificial feeding - acetate and propionate. In the intestines of children who are bottle-fed in large quantities protein metabolites (phenols, cresol, ammonia) are formed, and their detoxification, on the contrary, is reduced. Also, the activity of beta-glucuronidase and beta-glucosidase is higher (typical for Bacteroides and Closridium). The result of this is not only a decrease in metabolic functions, but also a direct damaging effect on the intestines.

In addition, there is a certain sequence of formation of metabolic functions, which should be taken into account when determining the diet of a child in the first year of life. So normally, the breakdown of mucin is determined after 3 months. life and is formed by the end of the first year, deconjugation of bile acids - from the 1st month. life, the synthesis of coprostanol - in the 2nd half of the year, the synthesis of urobilinogen - in 11-21 months. The activity of beta-glucuronidase and beta-glucosidase in the normal development of intestinal microbiocenosis in the first year remains low.

Thus, the intestinal microflora performs numerous functions that are vital for the macroorganism. The formation of a normal microbiocenosis is inextricably linked with rational nutrition intestinal bacteria. An important component nutrition are prebiotics, which are part of human milk or as part of mixtures for artificial feeding.

Influence of nutritional factors on the large intestine

The most important irritants of the colon are dietary fiber, B vitamins, especially thiamine. A laxative effect when taken in sufficient doses is provided by sources of high concentrations of sugar, honey, beetroot puree, carrots, dried fruits (especially plums), xylitol, sorbitol, mineral water rich in magnesium salts, sulfates (such as Batalineka). Disturbances in the motor and excretory functions of the large intestine develop with the predominant consumption of refined and other products devoid of ballast substances (white bread, pasta, rice, semolina, eggs, etc.), as well as with a lack of vitamins, especially group B.

The delay in the release of decay products (constipation) causes an increase in the flow of toxic substances into the liver, which aggravates its function, leads to the development of atherosclerosis and other diseases, and to early aging. Overloading the diet with meat products increases the processes of decay. So, indole is formed from tryptophan, it contributes to the manifestation of the action of some chemical carcinogens. To suppress the activity of putrefactive microflora in the large intestine, II Mechnikov considered it expedient to consume lactic acid products.

An excess of carbohydrates in the diet causes the development of fermentation processes.

Thus, the final section of the digestive tract is involved in the excretion of toxins from the body, and also performs a number of other functions. With the help of nutrition, it is possible to influence the activity of the large intestine and the microflora inhabiting it.

The concept of the coefficient of assimilation. Comparing the composition of food and excrement excreted through the large intestine, it is possible to determine the degree of absorption of nutrients by the body. So, to determine the digestibility of this type of protein, the amount of nitrogen in food and feces is compared. As you know, proteins are the main source of nitrogen in the body. On average, despite the diversity of these substances in nature, they contain about 16% nitrogen (hence, 1 g of nitrogen corresponds to 6.25 g of protein). The absorption coefficient is equal to the difference between the amounts of nitrogen in consumed products and feces, expressed as a percentage; it corresponds to the proportion of protein retained in the body. Example: the diet contained 90 g of protein, which corresponds to 14.4 g of nitrogen; 2 g of nitrogen was excreted with excrement. Consequently, 12.4 g of nitrogen was retained in the body, which corresponds to 77.5 g of protein, i.e. 86% of the administered with food.

The digestibility of nutrients is influenced by many factors: food composition, including the amount of ballast compounds, technological processing of products, their combination, functional state digestive apparatus etc. Digestibility deteriorates with age. This must be taken into account when selecting products and methods of their technological processing for the diets of the elderly. The degree of digestibility is affected by the volume of food, so it is necessary to distribute the mass of food into several meals during the day, taking into account living conditions and health status.

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Normal intestinal microflora is the balance of various microbes of the lower divisions digestive system, that is, their quantitative and qualitative ratio, necessary to maintain the biochemical, metabolic, immunological balance of the body and maintain human health.

• protective function. Normal microflora has a pronounced resistance against pathogenic and opportunistic microorganisms. Beneficial bacteria prevent the colonization of the intestines by other infectious pathogens that are not characteristic of it. In the event of a decrease in the amount of normal microflora, potentially dangerous microorganisms begin to multiply. Purulent-inflammatory processes develop, bacterial infection of the blood (septicemia) occurs. Therefore, it is important not to allow a decrease in the amount of normal microflora.
• digestive function. The intestinal microflora is involved in the fermentation of proteins, fats, high molecular weight carbohydrates. Beneficial bacteria destroy the main mass of fiber and chyme residues under the action of water, maintain the necessary level of acidity (pH) in the intestines. The microflora inactivates ( alkaline phosphatase, enterokinase), participates in the formation of protein breakdown products (phenol, indole, skatole) and stimulates peristalsis. Also, the microorganisms of the digestive tract regulate the metabolism and bile acids. Contribute to the transformation of bilirubin (bile pigment) into stercobilin and urobilin. Beneficial bacteria play an important role in the final stages of cholesterol conversion. It produces coprosterol, which is not absorbed in the large intestine and is excreted in the feces. Normoflora is able to reduce the production of bile acids by the liver and control the normal level of cholesterol in the body.
• Synthetic (metabolic) function. Beneficial bacteria of the digestive tract produce vitamins (C, K, H, PP, E, group B) and essential amino acids. Intestinal microflora promotes better absorption of iron and calcium, and therefore prevents the development of diseases such as anemia and rickets. Due to the action of beneficial bacteria, there is an active absorption of vitamins (D 3, B 12 and folic acid) that regulate the hematopoietic system. metabolic function intestinal microflora is also manifested in their ability to synthesize antibiotic-like substances (acidophilus, lactocidin, colicin and others) and biologically active compounds(histamine, dimethylamine, tyramine, etc.), which prevent the growth and reproduction of pathogenic microorganisms.
• detoxification function. This function is associated with the ability of the intestinal microflora to reduce the amount and remove dangerous toxic products with feces: salts heavy metals, nitrites, mutagens, xenobiotics and others. Harmful compounds do not linger in body tissues. Beneficial bacteria prevent their toxic effects.
• immune function. The normal flora of the intestine stimulates the synthesis of immunoglobulins - special proteins that increase the body's defenses against dangerous infections. Also, beneficial bacteria contribute to the maturation of a system of phagocytic cells (nonspecific immunity), capable of absorbing and destroying pathogenic microbes (see).

Members of the intestinal microflora

The entire intestinal microflora is divided into:

1. normal (basic);
2. conditionally pathogenic;
3. pathogenic.

Among all representatives there are anaerobes and aerobes. Their difference from each other lies in the features of existence and life activity. Aerobes are microorganisms that can live and reproduce only under conditions permanent access oxygen. Representatives of the other group are divided into 2 types: obligate (strict) and facultative (conditional) anaerobes. Both those and others receive energy for their existence in the absence of oxygen. For obligate anaerobes, it is destructive, but not for facultative ones, that is, microorganisms can exist in its presence.

Normal microorganisms

These include gram-positive (bifidobacteria, lactobacilli, eubacteria, peptostreptococci) and gram-negative (bacteroids, fusobacteria, veillonella) anaerobes. This name is associated with the name of the Danish bacteriologist - Gram. He developed a special method for staining smears using aniline dye, iodine and alcohol. Under microscopy, some of the bacteria have a blue-violet color and are Gram-positive. Other microorganisms are discolored. For better visualization of these bacteria, a contrast dye (magenta) is used, which stains them in pink color. These are Gram-negative organisms.

All representatives of this group are strict anaerobes. They form the basis of the entire intestinal microflora (92-95%). Beneficial bacteria produce antibiotic-like substances that help to expel pathogens of dangerous infections from the habitat. Also, normal microorganisms create a zone of "acidification" (pH=4.0-5.0) inside the intestine and form a protective film on the surface of its mucous membrane. Thus, a barrier is formed that prevents the colonization of foreign bacteria that have entered from the outside. Beneficial microorganisms regulate the balance of opportunistic flora, preventing its excessive growth. Participate in the synthesis of vitamins.

These include gram-positive (clostridia, staphylococci, streptococci, bacilli) and gram-negative (escherichia - Escherichia coli and other members of the enterobacteria family: Proteus, Klebsiella, Enterobacter, Citrobacter, etc.) facultative anaerobes.

These microorganisms are opportunistic pathogens. That is, with well-being in the body, their influence is only positive, as in normal microflora. The impact of adverse factors leads to their excessive reproduction and transformation into pathogens. It develops with diarrhea, a change in the nature of the stool (liquid mixed with mucus, blood or pus) and a deterioration in general well-being. The quantitative growth of opportunistic microflora may be associated with weakened immunity, inflammatory diseases digestive system, malnutrition and use medicines(antibiotics, hormones, cytostatics, analgesics and other drugs).

The main representative of enterobacteria is with typical biological properties. It is able to activate the synthesis of immunoglobulins. specific proteins interact with pathogenic microorganisms from the Enterobacteriaceae family and prevent their penetration into the mucous membrane. In addition, E. coli produces substances - colicins with antibacterial activity. That is, normal Escherichia are able to inhibit the growth and reproduction of putrefactive and pathogenic microorganisms from the Enterobacteriaceae family - Escherichia coli with altered biological properties (hemolyzing strains), Klebsiella, Proteus and others. Escherichia are involved in the synthesis of vitamin K.

The conditionally pathogenic microflora also includes yeast-like fungi of the genus Candida. They are rarely found in healthy children and adults. Their detection in the feces, even in small quantities, should be accompanied by clinical examination the patient in order to exclude (excessive growth and reproduction of yeast-like fungi). This is especially true in young children and patients with reduced immunity.

pathogenic microorganisms

These are bacteria that enter digestive tract from the outside and causing acute intestinal infections. Infection with pathogenic microorganisms can occur when eating contaminated food (vegetables, fruits, etc.) and water, in violation of the rules of personal hygiene and contact with the patient. Normally, they are not found in the intestine. These include pathogenic pathogens of dangerous infections - pseudotuberculosis and other diseases. The most common representatives of this group are shigella, salmonella, yersinia, etc. Some pathogens ( Staphylococcus aureus, Pseudomonas aeruginosa, atypical E. coli) may occur among medical personnel(carriers of the pathogenic strain) and in hospitals. They cause serious nosocomial infections.

All pathogenic bacteria provoke the development of intestinal inflammation by type or with a disorder of the stool (diarrhea, mucus in the feces, blood, pus) and the development of intoxication of the body. Beneficial microflora is suppressed.

Bacteria content in the intestines

Beneficial bacteria

CFU/g is the number of colony forming units of microbes in 1 gram of feces.

Opportunistic bacteria

Beneficial gut bacteria

Gram-positive strict anaerobes:

Gram-negative strict anaerobes:

• Bacteroids- polymorphic (having a different size and shape) sticks. Together with bifidobacteria, they colonize the intestines of newborns by the 6-7th day of life. When breastfeeding, bacteroids are detected in 50% of children. With artificial nutrition, they are sown in most cases. Bacteroides are involved in digestion and the breakdown of bile acids.
• Fusobacteria- polymorphic rod-shaped microorganisms. Characteristic of the intestinal microflora of adults. Often they are sown from pathological material with purulent complications of various localization. Able to secrete leukotoxin (a biological substance with a toxic effect on leukocytes) and platelet aggregation factor, which is responsible for thromboembolism in severe septicemia.
• Waylonelles- coccal microorganisms. In children who are breastfed, they are detected in less than 50% of cases. In babies on artificial nutrition, mixtures are sown in high concentrations. Waylonellas are capable of large gas production. With their excessive reproduction, this distinctive feature can lead to dyspeptic disorders (flatulence, belching and diarrhea).

How to check the normal microflora?

A bacteriological examination of feces should be carried out by inoculation on special nutrient media. The material is taken with a sterile spatula from the last portion of the feces. The required amount of feces is 20 grams. The material for research is placed in a sterile dish without preservatives. It is necessary to take into account the fact that microorganisms - anaerobes must be reliably protected from the action of oxygen from the moment of fecal sampling to its sowing. It is recommended to use test tubes filled with a special gas mixture (carbon dioxide (5%) + hydrogen (10%) + nitrogen (85%)) with a tightly ground lid. From the moment of material sampling to the beginning of bacteriological examination, no more than 2 hours should pass.

This analysis of feces allows you to detect a wide range of microorganisms, calculate their ratio and diagnose visible disorders - dysbacteriosis. Violations in the composition of the intestinal microflora are characterized by a decrease in the proportion of beneficial bacteria, an increase in the number of opportunistic flora with a change in its normal biological properties, as well as the appearance of pathogens.

Low content of normal microflora - what to do?

The imbalance of microorganisms is corrected with the help of special preparations:

1. contribute to the colonization of the intestine by the main microflora due to the selective stimulation of the growth and metabolic activity of one or more groups of bacteria. These drugs are not medicines. These include undigested food ingredients that are a substrate for beneficial bacteria and are not affected by digestive enzymes. Preparations: “Hilak forte”, “Duphalak” (“Normaze”), “Calcium Pantothenate”, “Lysozyme” and others.
2. – These are living microorganisms that normalize the balance of intestinal bacteria and compete with conditionally pathogenic flora. Beneficial effect on human health. They contain useful bifidobacteria, lactobacilli, lactic streptococcus, etc. Preparations: “Acilact”, “Linex”, “Bactisubtil”, “Enterol”, “Colibacterin”, “Lactobacterin”, “Bifidumbacterin”, “Bifikol”, “Primadophilus " and others.
3. Immunostimulating agents. They are used to maintain normal intestinal microbiocenosis and increase the body's defenses. Preparations: “KIP”, “Immunal”, “Echinacea”, etc.
4. Drugs that regulate the transit of intestinal contents. Used to improve digestion and evacuation of food. Preparations:, vitamins, etc.

Thus, the normal microflora with its specific functions - protective, metabolic and immunostimulating - determines the microbial ecology of the digestive tract and is involved in maintaining the constancy of the internal environment of the body (homeostasis).

The small intestine almost completely digests and absorbs food. Digestion in the large intestine begins after the arrival of fragments that the small intestine has not digested. The work of the large intestine is that here the remnants of chyme (a lump of partially digested food and gastric juice) acquire a more solid state by releasing water. Here there is a breakdown of molecules, for example, fiber (its small intestine is not able to break down), with the help of digestive juice and bacterial flora. The main function of the colon is to convert food fragments into a semi-solid state for further excretion from the body.

Important processes of digestion occur in the large intestine, and their failure is fraught with a significant complication of human health.

The role of microflora

In this part of the gastrointestinal tract, there is a considerable proportion of microbes that form a "microbial community". Flora is divided into 3 classes:

• the first group (main) - bacteroids and bifidobacteria (approximately 90%);
• the second group (accompanying) - enterococci, lactobacilli and escherichia (approximately 10%);
• the third group (residual) - yeast, staphylococci, clostridia and others (about 1%).

The standard human flora performs a number of functions:

• colonization resistance - activation of the immune system, intermicrobial confrontation;
• detoxification - splitting the results of the process of metabolism of proteins, fats, carbohydrates;
• synthetic function - obtaining vitamins, hormones and other elements;
• digestive function - increased activity of the gastrointestinal tract.

The functions of natural stabilizers of the intestinal flora are performed by antimicrobial elements produced by the mucosa (lysozyme, lactoferrin). Normal contraction, pushing the chyme, has an effect on the degree of filling with microorganisms of a particular section of the gastrointestinal tract, keeping their distribution in the proximal direction. Disturbances in the work of the motor activity of the intestine contribute to the appearance of dysbacteriosis (a change in the composition of microorganisms, when pathogenic bacteria increase due to the disappearance of beneficial ones).

The imbalance of microflora can be associated with the following factors:

• frequent SARS, allergies;
• taking hormonal drugs, anti-inflammatory drugs (Paracetamol, Ibuprofen, Aspirin) or narcotic drugs;
• oncological diseases, HIV, AIDS;
• age-related physiological changes;
• infectious diseases of the intestine;
• work in heavy industry.

Involvement of plant fiber

The way the colon works depends on the substances that enter the body. Among the substances that ensure the process of multiplication of the microflora of the large intestine, it is worth highlighting vegetable fiber. The body is not able to digest it, but it is broken down by enzymes into acetic acid and glucose, which then pass into the blood. Excitation of motor activity is due to the release of methane, carbon dioxide and hydrogen. Fatty acids (acetic, butyric, propionic acids) give the body up to 10% of the total energy, and the final stage products that feed the walls of the mucous membrane are produced by the flora.

The microflora of the colon is involved in the formation of a number of useful substances necessary for the human body.

Microorganisms, absorbing waste, produce vitamins of several groups, biotin, amino acids, acids (folic, pantothenic), and other enzymes. With a positive flora, many useful biologically active elements are broken down and synthesized here, and the processes responsible for generating energy and warming the body are activated. Through beneficial flora, pathogens are suppressed, and positive activity of the immune system and body systems is ensured. Deactivation of enzymes from the small intestine occurs due to microorganisms.

Foods high in carbohydrates promote fermentation of proteins with putrefaction, which leads to the formation of toxic substances and gases. The components during the decomposition of the protein are absorbed into the blood and reach the liver, where they are destroyed with the participation of sulfuric and glucuronic acids. A diet that harmoniously contains carbohydrates and proteins balances fermentation and putrefaction. If there are discrepancies in these processes, digestive disorders and malfunctions in other body systems occur. Digestion in the large intestine comes to the final stage by absorption, the contents accumulate here and fecal masses are formed. Varieties of contraction of the large intestine and its regulation occur in much the same way that the small intestine works.