The small intestine is divided into three sections: duodenum (duodenum), jejunum (jejunum) And ileum (ileum).

Duodenum represents the initial section of the small intestine, has the shape of a horseshoe, length 25-27 cm.

Food coming from the stomach at 12 duodenum exposed to pancreatic juice, bile and intestinal juice, As a result, the final products of digestion are easily absorbed into the blood. Active action juices manifests itself in an alkaline environment. Pancreatic juice is produced by the pancreas, bile by the liver, intestinal juice by many small glands present in the mucous membrane of the intestinal wall.

Pancreas (pancreas) - a complex gland located behind the stomach, length 12-15 cm. It has intra- and exocrine functions.

Intrasecretory function- hormone production insulin and g lucagon directly into the blood, regulating carbohydrate metabolism.

Exocrine function - products pancreatic juice, entering through the excretory duct into the duodenum.

Pancreatic (pancreatic) juice- colorless clear liquid alkaline reaction (pH 7.8-8.4) due to the presence of sodium bicarbonate. About 1 liter is produced per day. under gastric juice. It contains enzymes that digest proteins, fats and carbohydrates into final products suitable for absorption and assimilation by the body's cells. Enzymes that digest proteins ( trypsin And chymotrypsin) act, unlike pepsin, in an alkaline environment and break down proteins into amino acids. The juice contains lipase, which carries out the main digestion of fats to glycerol and fatty acids; amylase, lactase And maltase, breaking down carbohydrates into monosaccharides; nucleases, cleaving nucleic acids.

Pancreatic juice begins to secrete 2-3 minutes after the start of a meal. Irritation of oral receptors by food reflexively excites the pancreas. Further separation of juice is ensured by irritation of the duodenal mucosa with food gruel, hydrochloric acid gastric juice and formed in the mucous membrane itself active hormones secretin And pancreozymin.

Stimulate digestive function of the pancreas food acids, cabbage, onion, diluted vegetable juices, fats, fatty acids, water, small doses of alcohol, etc.

Braking pancreatic secretion - alkaline mineral salts, whey, etc.

Liver (hepar) - a large glandular organ weighing about 1.5 kg, located in the right hypochondrium. The liver is involved in digestion, glycogen deposition, neutralization of toxic substances, synthesizes proteins fibrinogen and prothrombin, participates in blood clotting, metabolism of proteins, fats, carbohydrates, vitamins, minerals, hormones, etc., i.e. is a multifunctional element of homeostasis.

Liver cells continuously produce bile, which enters the duodenum through a system of ducts only during digestion. When digestion stops, bile is collected in the gallbladder, which holds 40-70 ml of bile. Here it is concentrated 7-8 times as a result of water absorption. 500–1200 ml of bile is produced per day.

Bile consists of 90% water and 10% organic and inorganic substances (bile pigments, bile acids, cholesterol, lecithin, fats, mucin, etc.). The color of liver bile is golden yellow, bladder bile is yellow-brown.

The importance of bile in digestion mainly related to bile acids and is as follows:

bile activates enzymes, especially lipase pancreatic and intestinal juices, which in the presence of bile acts 15-20 times faster;

emulsifies fats, i.e. under its influence, fat is crushed into small particles, which increases the area of ​​interaction with enzymes;

promotes the dissolution of fatty acids and their absorption;

neutralizes the acidic reaction of food gruel coming from the stomach;

provides suction fat-soluble vitamins, calcium, iron and magnesium;

enhances motor function intestines;

has bactericidal properties, inhibits putrefactive processes in the intestines.

Bile salts keep water-insoluble cholesterol in the bile in a dissolved state. With a lack of bile acids, cholesterol precipitates, which leads to the formation of stones in the bile ducts and the formation cholelithiasis. If the outflow of bile into the intestines is disrupted (stones, inflammation), part of the bile from the bile ducts enters the blood, which causes a yellow coloration of the skin, mucous membranes and whites of the eyes (jaundice).

The process of bile formation intensifies reflexively in the presence of food in the stomach and duodenum, as well as by certain substances (secretin, bile acids) acting on liver cells.

Brakes bile secretion cold, overheating of the body, hypoxia, fasting, hormones (glucagon, etc.).

Influence nutritional factors for bile secretion .

Stimulate the production of bile - organic acids, extractive substances of meat and fish. Increases the excretion of bile into the duodenum vegetable oils, meat, milk, egg yolks, fiber, xylitol, sorbitol, warm foods, magnesium salts, some mineral water(Slavyanovskaya, Essentuki, Berezovskaya, etc.). Cold food causes spasm (narrowing) of the bile ducts.

Excessive consumption of animal fats, proteins, table salt, essential oils, and fast food and long-term dietary disturbances.

Skinny and ileum

The jejunum is about 2/5 the length and the ileum is about 3/5 the length of the small intestine. The following physiological functions are carried out in these sections: secretion of intestinal juice, mixing and movement of chyme, breakdown and active absorption of digestion products, water and salts.

Intestinal juice produced by many intestinal glands, embedded in the folds of the mucous membrane, only under the influence of mechanical and chemical stimuli at the location of the food mass. About 2.5 liters of intestinal juice are released per day. It is an opaque, colorless, opalescent alkaline liquid. Comprises liquid And dense parts. Dense part represents glandular cells of the intestinal mucosa that have accumulated enzymes and are rejected into its lumen. As they disintegrate, they release enzymes into the surrounding liquid. Intestinal juice contains 22 enzymes. The main ones are: enterokinase, pancreatic juice trypsinogen activator, peptidases, cleaving polypeptides, lipase and amylase(in a small concentration ), alkaline phosphatase and sucrase (alpha-glucosidase), an enzyme not found anywhere else.

Small bowel movement carried out due to the contraction of longitudinal and circular muscles. There are two types of movements: pendulum-like and peristaltic, which mix and move food towards the large intestine.

Pendulum-like movements provide mixing of food due to alternate contraction and relaxation of longitudinal and circular muscles in a short section of the intestine.

Peristaltic or vermiform movement provides a slow wave-like movement of chyme to the large intestine as a result of contraction of the circular muscles of one section of the intestine while simultaneously expanding the lower section.

IN small intestine the processing process ends nutrients, which began in the stomach and duodenum. Enzymes in the intestinal juice of the small intestine ensure the final breakdown of nutrients.

The digestion process in the small intestine is carried out in the form of cavity and parietal digestion.

Cavity digestion characterized by the fact that intestinal juice enzymes enter the food mass in a free form, break down food substances into simple ones and are transported through the intestinal epithelium into the blood.

Parietal (membrane) digestion discovered by academician A.M. Coal in the 60s of the twentieth century and is due to the structure of the mucous membrane of the small intestine, which forms many folds. In the folds there are protrusions of the mucous membrane called villi. The height of the villi is 0.5-1.5 mm; there are 18-40 villi per 1 mm2. In the center of each villi there is a lymphatic capillary, blood vessel and nerve endings. On top, the villus is covered with a layer of cylindrical epithelial cells, the outer side of which faces the intestinal lumen and has a border formed by filamentous outgrowths - microvilli. The outer side of this marginal epithelium is a semi-permeable biological membrane on which enzymes are adsorbed and the processes of digestion and absorption occur. The presence of microvilli increases the absorption area to 500-1000 m2.

The initial stages of digestion occur exclusively in the cavity of the small intestine. Small molecules formed as a result of cavity hydrolysis enter the villi membranes, where digestive enzymes act. Due to membrane hydrolysis, monomeric compounds are formed, which are absorbed into the blood and lymph. The products of fat processing enter the lymph, and amino acids and simple carbohydrates enter the blood.

Absorption is also facilitated by contraction of the villi. The walls of the villi contain smooth muscles, which, when contracting, squeeze the contents of the lymphatic capillary into a larger lymphatic vessel. The movements of the villi are caused by the breakdown products of nutrients - bile acids, glucose, peptones, and some amino acids.

The influence of dietary factors on the activity of the small intestine.

Motor and secretory function the small intestines are enhanced by coarse, dense foods rich in dietary fiber. Food acids, carbon dioxide, alkaline salts, lactose, vitamin B1 (thiamine), choline, spices, hydrolysis products of nutrients, especially fats (fatty acids), have a similar effect.

Colon. Processes occurring in the TC. Factors influencing the condition of the large intestine.

The large intestine is located between the small intestine and the anus. It begins with the cecum, which has a vermiform appendix, then continues into the colon (ascending, transverse, descending), then into the sigmoid colon and ends with the rectum. total length The large intestine is 1.5-2 m, width in the upper sections is 7 cm, in the lower sections about 4 cm. The small intestine is separated from the large intestine by a valve that allows food mass to pass only in the direction of the large intestine. Three longitudinal muscle bands run along the wall of the colon, tightening it and forming swellings (haustra).

The mucous membrane of the large intestine has semilunar folds and no villi. The mucous membrane contains intestinal glands that secrete intestinal juice. The juice is alkaline, contains a large amount of mucus, and there are practically no enzymes.

Food enters the large intestine almost completely digested, with the exception of fiber and very small amounts of proteins, fats and carbohydrates.

In the large intestine, water is predominantly absorbed (about 0.5 liters per day), the absorption of nutrients is insignificant.

Colon rich in microorganisms(more than 260 types of microbes). In 1 g of intestinal contents there are 10 9 -10 11 microbial cells. About 30% of the dry mass of feces is microbes; an adult excretes about 17 trillion microorganisms in excrement per day. Numerically, anaerobes (bifidobacteria, bacteroides, etc.) predominate - 96-99%, facultative anaerobic microorganisms make up 1-4% (including coliform bacteria).

Under the influence of intestinal microflora, fiber is broken down, which reaches the large intestine unchanged. As a result of fermentation, fiber is broken down into simple carbohydrates and is partially absorbed into the blood. A person digests on average 30-50% of the fiber contained in food.

Putrefactive bacteria present in the large intestine form toxic substances from protein breakdown products: indole, skatole, phenol etc., which enter the blood and are neutralized in the liver (detoxification). Therefore, excessive protein consumption, as well as irregular bowel movements, can cause self-poisoning of the body.

The microflora of the large intestine is capable of synthesizing a number vitamins(endogenous synthesis) groups B, K (phylloquinone), nicotinic, pantothenic and folic acids.

Relatively recently it has been proven that microflora supplies the body with additional energy(6-9%) due to the absorption of volatile fatty acids formed during the fermentation of fiber.

In addition, intestinal lactobacilli and bifidobacteria form bactericidal substances(acids, alcohols, lysozyme), as well as prevents carcinogenesis(antitumor effect).

The motor function of the large intestine is carried out thanks to the smooth muscles of the intestinal wall. The movements are slow, because the muscles are poorly developed. Are being carried out pendulum-shaped, peristaltic And antiperistaltic movements, as a result of which the food is mixed, compacted, and glued together by the mucus of the intestinal juice, resulting in the formation of feces that are evacuated through the rectum. Emptying the rectum (defecation) is a reflex act influenced by the cerebral cortex.

In general, the entire digestion process in humans lasts 24-48 hours. Moreover, half of this time occurs in the large intestine, where the digestion process ends.

With a normal mixed diet, approximately 10% of the food taken is not digested.

Factors affecting the condition of the large intestine .

The functions of the large intestine are directly dependent on the nature of a person’s work, age, composition of food consumed, etc. Thus, in people with mental work who lead a sedentary lifestyle and are subject to physical inactivity, intestinal motor function decreases. With increasing age, the activity of motor, secretory and other functions of the large intestine also decreases. Consequently, when organizing nutrition for these population groups, it is necessary to include “food irritants” that have laxative effect(wholemeal bread, bran, vegetables and fruits, except astringents, prunes, cold vegetable juices, mineral waters, compote, lactic acid drinks, vegetable oil, sorbitol, xylitol, etc.).

Weaken intestinal motility (have fixing action) hot dishes, flour products(pies, pancakes, fresh bread, pasta, soft-boiled eggs, cottage cheese, rice and semolina porridge, strong tea, cocoa, chocolate, blueberries, etc.).

Refined carbohydrates reduce the motor and excretory functions of the large intestine. Overloading the diet with meat products increases the processes of decay, and excess carbohydrates enhances fermentation.

Deficiency in dietary fiber and dysbiosis intestines are a risk factor for carcinogenesis.

Regulation of digestive processes

Regulation of digestion is ensured at the central and local levels.

Central level carried out by the central nervous system, where the subcortical nuclei of the hypothalamus are located food center. Its action is multifaceted, it regulates the motor, secretory, absorption, excretory and other functions of the gastrointestinal tract. The food center provides the appearance of complex subjective sensations - hunger, appetite, feeling of fullness, etc. The food center consists of hunger center and satiety center. These centers are closely connected with each other. Thus, with a decrease in nutrients in the blood and emptying of the stomach, the activity of the saturation center decreases and at the same time the hunger center is stimulated. This leads to the appearance of appetite and activation eating behavior. And vice versa - after eating, the satiety center begins to dominate.

Regulation of digestive processes local level carried out by the nervous system, and representing a complex of interconnected nerve plexuses located in the thickness of the walls of the digestive canal. They include sensory, motor and interneurons of the sympathetic and parasympathetic nervous system.

Besides, in gastrointestinal tract there are endocrine cells (diffuse endocrine system ), located in the epithelium of the mucous membrane and in the pancreas. They produce hormones and other biologically active substances that are formed during the mechanical and chemical effects of food on endocrine cells.

1 The importance of nutrients for the functions of the neurohumoral system

2 The importance of nutritional factors for the digestive system

3 The influence of nutrition on cardiovascular system

4 The influence of nutrition on respiratory system

5 The influence of nutrition on the activity of the excretory system (kidneys)

6 Effect of food on skin function

1. The composition of food affects functional state neurohumoral system, formation of mediators. It has been established that a lack of protein in the diet leads to a sharp inhibition of the development of the central nervous system, a deterioration in the formation conditioned reflexes, the ability to learn, remember, weaken inhibitory and excitatory processes in the cerebral cortex. With an excess of proteins, the excitability of the central nervous system increases.

Many amino acids serve as the starting material for the formation of a number of neurotransmitters and hormones.

· Carbohydrates are the main source of energy for brain function and must be constantly supplied in the blood in the form of glucose, since glycogen is in nerve cells very little. With a lack of glucose in the blood, inhibition of the cerebral cortex develops and then the subcortical centers are released from its control - emotional reactions intensify. This state occurs before a meal (on an “empty” stomach), which should be taken into account when serving visitors (resolving all issues after a meal).

Easily digestible carbohydrates tone the cerebral cortex, relieving fatigue. Therefore, although carbohydrates are not essential nutrients, their constant consumption is necessary (in normal doses).

In the tissues of the brain and spinal cord contains many different lipids and lipoids (phosphatides, sterols, etc.). A special role belongs to lecithin and cephalin, which are found in cell membranes nerve cells and membranes nerve fibers. To meet the need for these substances, their sources should be included in the diet: unrefined vegetable oils, butter, egg yolk and so on.

Vitamins are necessary for the synthesis of mediators. Thus, choline forms an ester (acetylcholine) with acetic acid, which is a mediator of the parasympathetic nervous system. Thiamine participates in its synthesis and inhibits the activity of the enzyme acetylcholinesterase, which breaks down this mediator. With a lack of thiamine, the conditioned reflex activity of the brain is disrupted, excitation processes are significantly weakened and inhibition increases, which leads to a decrease in human performance.

The mediator of the sympathetic nervous system, norepinephrine, is formed as a result of the oxidation of phenylalanine and subsequent decarboxylation of the resulting compound. This process requires pyridoxine (vitamin B 6). It is also involved in the formation of some other mediators (serotonin, gamma-aminobutyric acid). Riboflavin improves the activity of the visual analyzer, providing color vision.

The higher parts of the nervous system are especially sensitive to insufficient levels of vitamin PP in the diet. It leads to profound changes in the central nervous system due to neuronal damage.

Thus, a deficiency of any of the B vitamins causes disruption of the central nervous system.

Ascorbic acid (vitamin C) is involved in the formation of norepinephrine, and also protects adrenaline from oxidation and restores its reversibly oxidized derivatives.

The function of neurons depends on the adequacy of the body's supply of minerals. Thus, sodium, potassium, and calcium ions are involved in the transmission of information to the executive organs. These minerals, as well as magnesium and phosphorus, affect the activity of enzymes that catalyze the main metabolic processes in nerve cells and the formation of mediators.

The conditioned reflex activity of the brain is influenced by copper ions, the content of which in the brain cortex is much higher than in other organs and tissues. Copper also affects the processes of excitation and inhibition in the cerebral cortex. Manganese ions increase the excitability of the central nervous system.

· From the above it follows that for normal functioning The neuroendocrine system needs to provide the human body with all food ingredients.

2 . Information on the importance of nutritional factors for the function of various parts of the digestive system is summarized in Table 1.

3. To form red blood cells, the diet must include sources of well-absorbed iron, vitamins B12, folic and ascorbic acids. Participates in the protective function of leukocytes ascorbic acid. The diet should contain sufficient sources of calcium and vitamin K, which are involved in the blood clotting process. Excessive use foods rich in cholesterol or table salt, poor in lipotropic substances, can contribute to the development of vascular sclerosis and reduce life expectancy.

Excess linoleic acid in the diet contributes to the formation of intravascular blood clots due to the formation of arachidonic acid, which is a source of thromboxanes. These substances cause platelet aggregation. Seafood containing fatty acid, counteract increased blood clotting.

4. Ciliated epithelium respiratory tract– villi – very sensitive to a lack of vitamin A in food, which prevents the keratinization of the epithelium. The need for this vitamin increases among people in contact with dust (flour and cement industries, road workers, miners, etc.). Important has the correct ratio of sources of acidic and alkaline radicals in the diet. With an excess of the former (meat, fish, eggs), the release of CO 2 by the lungs increases and their hyperventilation occurs. When prevailing alkaline groups (plant food) hypoventilation develops. Thus, the nature of nutrition is important for the functioning of the respiratory system.

5. The richer the diet in proteins, the higher the content of nitrogenous substances in the urine; with increasing consumption of sources of acid radicals (meat, fish), the content of salts of the corresponding acids in the urine increases. Daily diuresis is significantly influenced by the content of table salt in the diet; it promotes fluid retention in the body, while potassium salts stimulate its excretion. A significant part of the transformation products is removed through the kidneys foreign substances, including medications.

6. Normal function skin is closely related to the presence of B vitamins in the diet, especially B1, B2, PP, B6, and its overall balance; The content of potassium and sodium ions in food and drinking regimen are also important.

Table 1 - The importance of nutritional factors for the digestive system

Continuation of the table. 1

Continuation of the table. 1

Lecture 4 Energy costs and energy value of food

The importance of nutritional factors for the digestive system

Information on the importance of nutritional factors for the function of various parts of the digestive system is summarized in the table.

The effect of nutrition on the cardiovascular system

For the formation of red blood cells, it is necessary to include in the diet sources of well-absorbed iron, vitamins B12, folic and ascorbic acids. Ascorbic acid is involved in the protective function of leukocytes. The diet should contain sufficient sources of calcium and vitamin K, which are involved in the blood clotting process. Excessive consumption of foods rich in cholesterol or table salt, poor in lipotropic substances, can contribute to the development of vascular sclerosis and a reduction in life expectancy.

Excess linoleic acid in the diet contributes to the formation of intravascular blood clots due to its conversion to arachidonic acid, which is a source of thromboxanes. These substances cause platelet aggregation. Seafood containing fatty acids counteracts increased blood clotting.

The effect of nutrition on the respiratory system

The ciliated epithelium of the respiratory tract (villi) is very sensitive to a lack of vitamin A in food, which prevents the keratinization of the epithelium. The need for this vitamin increases among people in contact with dust (flour and cement industries, road workers, miners, etc.). The correct ratio of sources of acidic and alkaline radicals in the diet is important. With an excess of the former (meat, fish, eggs), the release of CO 2 by the lungs increases and their hyperventilation occurs. When alkaline groups (plant foods) predominate, hypoventilation develops. Thus, the nature of nutrition is important for the functioning of the respiratory system.

The influence of nutrition on the activity of the excretory system (kidneys)

The richer the diet in proteins, the higher the content of nitrogenous substances in the urine; with increasing consumption of sources of acid radicals (meat, fish), the content of salts of the corresponding acids in the urine increases. Daily diuresis is significantly influenced by the content of table salt in the diet; it promotes fluid retention in the body, while potassium salts stimulate its excretion. Through the kidneys, a significant part of the transformation products of foreign substances, including medications, is removed.

Effect of food on skin function

The skin functions normally if there are B vitamins in the diet, especially B1, B2, PP, B6, and its overall balance; The content of potassium and sodium ions in food and drinking regimen are also important.

This is where most of the digestion and absorption processes take place. Digestive enzymes that break down fats, proteins and carbohydrates are secreted by the pancreas and contribute to the further processing of food gruel (chyme) partially digested in the stomach, preparing it for absorption in three parts of the small intestine: the duodenum, jejunum and ileum. The total length of these three sections is about 7 meters, but all these intestines are compactly packed in the abdominal cavity.

The useful area of ​​the small intestine is significantly increased by numerous tiny finger-like projections on inner surface, which are called villi. They secrete enzymes, absorb essential nutrients, and prevent food particles and potentially dangerous substances from entering the bloodstream. These sensitive processes can be disrupted by antibiotics and other medicines, alcohol and/or excessive sugar consumption. When exposed to these substances, the tiny spaces between the villi become inflamed and expand, allowing unwanted particles to enter the bloodstream. This is called leaky gut or "leaky gut" and can lead to food intolerance, headaches, fatigue, skin diseases and arthritic pain in the bones and muscles of the whole body.

Bile enters the duodenum, which is produced in the liver, and then concentrates and accumulates in the gallbladder. Bile is necessary for grinding particles of partially digested fats, as a result of which they acquire the ability to be absorbed. The pancreas produces bicarbonates, which neutralize or reduce the acidity of gastric juice, and also secretes three digestive enzyme- protease, lipase and amylase, necessary for the digestion of proteins, fats and carbohydrates, respectively.

To heal stomach ulcers, drink potato broth (boil potato skins and strain the liquid) daily or potato juice(squeeze the juice from raw potatoes, and add carrot or celery juice for taste). Never use green-skinned potatoes.

The jejunum and ileum serve as the main site for the absorption of remaining nutrients, including proteins, amino acids, water-soluble vitamins, cholesterol and bile salts.

Ileocecal valve

Large intestine, or colon, consists of three consecutive sections (ascending, transverse and descending colon), and ends with the rectum and anus. The large intestine, through active movements, helps to mix the contents (water, bacteria, insoluble fiber and waste products formed after the digestion of nutrients) and move it towards the rectum and anus. The contents of the large intestine are expelled through the anus in the form of feces.

Immediately after swallowing, the entire further process of digestion depends on the contraction of the muscles of the pharynx, and then the esophagus, through which food bolus moves forward thanks to muscle contractions, like a crawling snake.

When you feel the urge to relieve yourself, it is advisable to go to the toilet and empty your bowels, since when feces are retained even for a couple of hours, further absorption of water occurs, and as a result, the feces become drier, which contributes to constipation. This is also one of the causes of hemorrhoids.

It is considered “normal” to have a bowel movement at least once a day. People with active digestion may experience bowel movements after every meal. On the other hand, stool retention can occur for several days - and then toxic substances again enter the blood through the intestinal wall. That is why sometimes we are visited by a feeling of incomprehensible fatigue, headache, nausea and general malaise. This explains the questions about the nature of our stool that the doctor asks us at the appointment for almost any reason.

Other stool-related problems are discussed further.

Healthy Colon

To keep your colon in perfect condition, you need to eat vegetables, fruits and insoluble fiber every day, which is found in grains and legumes. These products also contain magnesium, which is necessary for the normal functioning of the intestinal muscles. If you can get magnesium from vegetable or fruit juices, then in order to stock up on fiber, which helps remove toxins from the intestines and improves intestinal motility, you need to eat whole vegetables and fruits at least a little.

People who have had any abdominal operations, in the postoperative period it is necessary to especially carefully monitor your diet, since the administration of natural needs may be complicated for several days. In the first days, it is advisable to eat simple foods that do not burden the intestines and reduce the likelihood of constipation. Vegetable soups, salads, steamed vegetables and rice are all ideal for postoperative period. These foods are nutritionally rich, easy to digest and contain enough fiber to quickly restore rectal function.

Digestive immune system

The digestive tract contains 60-70% of the body’s entire immune system, and this is not at all surprising when you consider the colossal number of pathogens and potentially hazardous substances enter our body through the mouth - the gateway of the digestive system. In the most oral cavity, the esophagus and small intestine are home to billions of beneficial bacteria, while there are trillions of them in the large intestine. But in the stomach, where an acidic environment reigns, there are not too many of them, since there are few pathogenic microbes able to survive in such harsh conditions.

Digestive system

In total, from 400 to 500 species of different bacteria were found in the intestines, some of which have antitumor properties, while others, on the contrary, have carcinogenic properties; there are bacteria that synthesize vitamins B, A and K; others produce substances that fight certain infections; There are also bacteria that digest lactose ( milk sugar) and regulate muscle contraction and relaxation. Intestinal bacteria secrete natural antibiotics and fungicides - substances that suppress the proliferation of pathogenic bacteria and fungi, respectively. By releasing acid, they also destroy toxic products harmful bacteria, which often pose a much more serious threat than the pathogenic microbes themselves.

Besides, intestinal microflora protects us from metal poisoning - for example, mercury (from amalgam fillings or from contaminated fish), radionuclides (from antitumor therapy or from contaminated products), as well as pesticides and herbicides. There are also bacteria that produce hydrogen peroxide, in the presence of which they die cancer cells. However, as you will see below, there are many factors that disrupt the normal balance of intestinal microflora.

Beneficial bacteria should predominate in the intestines in the absence of harmful factors listed in the table (see below). If you eat poorly and monotonously, regularly drink alcohol, are exposed to stress, and often use antacids, painkillers and antibiotics, then the delicate balance will inevitably be disrupted. And then pathogenic bacteria will have the opportunity to multiply uncontrollably and displace beneficial microflora.

Unfortunately, this lifestyle is typical for quite a lot of people. Such people suffer from indigestion, bloating, flatulence, and cannot understand the causes of their troubles. The answer is simple: their intestines have become a battleground for beneficial and pathogenic bacteria.

Over the next six pages, we'll take a closer look at the most common digestive system diseases.

Typical Lifestyle Factors That Negatively Affect Digestive Efficiency

• Antibiotics
• Diet rich in fat
• Sugar
• Refined products
• Anti-inflammatory drugs
• fried food
• Alcohol
• Canned drinks (carbonated)
• Stress
• Bereavement
• Smoking
• Stimulant drugs

Digestion is a complex physiological and biochemical process. Food in the digestive tract undergoes physical and chemical changes. As a result, food components retain their plastic and energy value; acquire properties due to which they can be assimilated by the body and included in its normal exchange substances; lose species specificity.

Physiological changes food consists of its crushing, swelling, dissolution; chemical - in the sequential degradation of nutrients as a result of the action on them of components of digestive juices secreted into the cavity digestive tract his glands. Critical Role in this belongs to the hydrolytic enzymes of the secretions of the digestive glands and the striated rim of the small intestine.

The named processes take place in a certain sequence, “layering” along the sections of the digestive tract. The movement of the food bolus is ensured by the motor apparatus of the digestive tract, which distributes digestion in time and space and affects its intensity. As a result of the depolymerization of nutrients, products are formed, mainly monomers, which are absorbed from the intestines into the blood and lymph, transported to the tissues of the body and included in its metabolism. Water, mineral salts, and some organic food components (including vitamins) are absorbed into the blood unchanged.

Digestive system carries out First stage metabolism between external and internal environments body.

Control questions

1. Blood system.

2. Cardiovascular system.

3. Lymphatic system.

4. Respiratory system.

5. Excretory system.

7. Musculoskeletal system.

8. Immune system.

9. Physiology of analyzers.

10. The role of the digestive system for the life of the body.

11. The structure of the digestive system.

12. Physical and chemical changes in food proteins in each section of the digestive tract.

13. Features of the structure and functions of the stomach.

Purpose of laboratory work:become familiar with the functioning of the digestive system based on the degree of digestion egg white with normal and low acidity of gastric juice in the model system.

The operating principle is based on the detection of partially degraded protein in gastric juice through the color biuret reaction at the peptide bond of the protein.

Equipment, glassware and reagents: thermostat; rack with test tubes; pipettes 5 ml (2 pcs) and 2 ml (1 pc), dropper (1 pc); sodium hydroxide 10% solution; copper sulfate, 0.1% solution.

Technique for performing the work. Place in two test tubes a small piece coagulated egg white. 5 ml of gastric juice with normal acidity is poured into one test tube, and the same amount of juice with normal acidity into the other. low acidity. Both tubes are incubated in a thermostat at 37°C for 45 minutes. At the end of incubation, the samples are removed and the liquid from each is carefully poured into other test tubes so that no pieces of protein get into them. Then add 2 ml of sodium hydroxide (NaOH) and 1-2 drops of copper sulfate (biuret reaction). Note in which test tube the pink-violet color appeared and what its intensity is.