Process of digestion of nutrients. Features of the physiology of digestion in the human stomach cavity

Digestion and absorption of food. Metabolism.

Digestion process

Food entering the human body cannot be assimilated and used for plastic purposes and the formation of vital energy, since its physical state and chemical composition are very complex. To transform food into a state easily digestible by the body, humans have special organs that carry out digestion.

Digestion is a set of processes that ensure physical change and chemical breakdown nutrients into simple compound water-soluble compounds that can be easily absorbed into the blood and participate in the vital functions of the human body.

Diagram of the digestive apparatus:

1 - oral cavity; 2 - salivary glands;

3 - pharynx; 4 - esophagus; 5 - stomach;

6 - duodenum; 7 - liver;

8 - gallbladder; 9 - bile duct;

10 - pancreas;

11 - small intestines; 12 - large intestines;

13 - rectum.

During the day, a person secretes about 7 liters of digestive juices, which include: water, which dilutes food gruel, mucus, which promotes better movement of food, salts and enzyme catalysts of biochemical processes that break down food substances into simple compounds. Depending on the effect on certain substances, enzymes are divided into proteases, breaking down proteins (proteins), amylase, breaking down carbohydrates, and lipases, breaking down fats (lipids). Each enzyme is active only in a certain environment (acidic, alkaline, or neutral). As a result of the breakdown of proteins, amino acids are obtained, from fats - glycerol and fatty acid, carbohydrates are mainly glucose. Water, mineral salts, and vitamins contained in food do not undergo changes during the digestion process.

Digestion in the oral cavity. The oral cavity is the anterior primary department digestive apparatus. With the help of teeth, tongue and cheek muscles, food undergoes initial mechanical processing, and with the help of saliva - chemical processing.

Saliva is a slightly alkaline digestive juice produced by three pairs of salivary glands (parotid, sublingual, submandibular) and entering the oral cavity through ducts. In addition, saliva is secreted salivary glands lips, cheeks and tongue. Saliva contains enzymes amylase or ptyalin, which breaks down starch into maltose, an enzyme maltase, which breaks down maltose into glucose, and an enzyme lysozyme, having an antimicrobial effect. Food remains in the oral cavity for a relatively short time (10-25 s). Digestion in the mouth consists mainly of the formation of a bolus of food prepared for swallowing. The bolus of food, with the help of coordinated movements of the tongue and cheeks, moves towards the pharynx, where the act of swallowing occurs. From the mouth, food enters the esophagus.

Esophagus- a muscular tube 25-30 cm long, along which, due to muscle contraction, food bolus moves to the stomach in 1-9 seconds, depending on the consistency of the food.

Digestion in the stomach. The stomach, the widest part of the digestive tract, is a hollow organ consisting of an inlet, a fundus, a body and an outlet. The inlet and outlet openings are closed with a muscle roller (pulp). The volume of an adult's stomach is about 2 liters, but can increase to 5 liters. The inner mucous membrane of the stomach is collected in

folds. In the thickness of the mucous membrane there are up to 25,000,000 glands that produce gastric juice and mucus. Gastric juice is a colorless acidic liquid containing 0.4-0.5% hydrochloric acid, which activates gastric juice enzymes and has a bactericidal effect on microbes that enter the stomach with food. The composition of gastric juice includes enzymes: pepsin, chymosin(rennet enzyme), lipase. The human body secretes 1.5-2.5 liters of gastric juice per day, depending on the amount and composition of food. Food in the stomach is digested from 3 to 10 hours, depending on the composition, volume, consistency and method of its processing. Fatty and dense foods stay in the stomach longer than liquid foods containing carbohydrates. After digestion in the stomach, food gruel enters the initial section of the small intestine in small portions - duodenum, where the food mass is actively exposed to the digestive juices of the pancreas, liver and the mucous membrane of the intestine itself.

The role of the pancreas in the digestive process. The pancreas is a digestive organ that consists of cells that form lobules that have excretory ducts that connect to form a common duct. Through this duct, the digestive juice of the pancreas enters the duodenum (up to 0.8 liters per day). Digestive juice of the pancreas is a colorless transparent liquid of an alkaline reaction. It contains enzymes: trypsin, chymotrypsin, lipase, amylase, maltase. In addition, the pancreas has special cells (islets of Langerhans) that produce hormone insulin, entering the blood. This hormone regulates carbohydrate metabolism, facilitating the absorption of sugar by the body. In the absence of insulin, diabetes mellitus occurs.

The role of the liver in the digestive process. The liver is a large gland weighing up to 1.5-2 kg, consisting of cells that produce bile up to 1 liter per day. Bile is a liquid from light yellow to dark green in color, slightly alkaline, activates the enzyme lipase of pancreatic and intestinal juice, emulsifies fats, promotes the absorption of fatty acids, enhances intestinal movement (peristalsis), suppresses putrefactive processes in the intestines. Bile from the hepatic ducts enters the gallbladder - a thin-walled pear-shaped sac with a volume of 60 ml. During the digestion process, bile flows from the gallbladder through the duct into the duodenum. In addition to the digestion process, the liver is involved in metabolism, hematopoiesis, retention and neutralization of toxic substances that enter the blood during the digestion process.

Digestion in small intestine. The length of the small intestine is 5-6 m. It completes the digestion process thanks to pancreatic juice, bile and intestinal juice secreted by the glands of the intestinal mucosa (up to 2 liters per day). Intestinal juice is a cloudy liquid of an alkaline reaction, which contains mucus and enzymes. In the small intestine, food gruel (chyme) is mixed and distributed in a thin layer along the wall, where the final digestion process occurs - suction products of the breakdown of nutrients, as well as vitamins, minerals, and water into the blood. Here aqueous solutions nutrients formed during digestion through the mucous membrane gastrointestinal tract penetrate into the blood and lymphatic vessels. Next, the blood flows through the portal vein to the liver, where, having been cleared of toxic digestive substances, it supplies all tissues and organs with nutrients.

The role of the large intestine in the digestive process. Undigested food remains enter the large intestine. A small number of glands of the large intestine secrete inactive digestive juice, which partially continues the digestion of nutrients. The large intestines contain large numbers of bacteria that cause fermentation carbohydrate residues, rotting protein residues and partial breakdown of fiber. In this case, a number of toxic substances harmful to the body are formed (indole, skatole, phenol, cresol), which are absorbed into the blood and then neutralized in the liver. The composition of bacteria in the large intestine depends on the composition of the incoming food. Thus, dairy-vegetable foods create favorable conditions for the development of lactic acid bacteria, and foods rich in protein promote the development of putrefactive microbes. In the large intestines, the bulk of water is absorbed into the blood, as a result of which the intestinal contents become denser and move towards the outlet. Removal of feces from the body is carried out through rectum and is called defecation.

Digestibility of food

Digested food, absorbed into the blood and used for plastic processes and energy restoration is called learned. From the amino acids of digested food, the body forms protein characteristic of humans, and from glycerol and fatty acids - fat characteristic of humans. Glucose is used to generate energy and is deposited in the liver in the form of a reserve substance - glycogen. All these processes occur with the participation minerals, vitamins and water. The digestibility of food is influenced by: chemical composition, its culinary processing, appearance, volume, diet, eating conditions, state of the digestive system, etc. The digestibility of food of animal origin is on average 90%, of plant origin - 65%, mixed - 85% . Culinary processing of food promotes digestion, and therefore its absorption. Mashed and boiled food is digested better than lumpy and raw food. Appearance, taste, smell of food enhance the secretion of digestive juices, promoting its digestibility. The diet and the correct distribution of the daily amount of food during the day, the conditions for eating food (the interior of the dining room, polite, friendly service, the cleanliness of the dishes, the neat appearance of the cooks), and a person’s mood also increase its digestibility.

General concept of metabolism

In the process of life, the human body spends energy on work internal organs, maintaining body temperature and performing labor processes. The release of energy occurs as a result of the oxidation of complex organic substances that make up human cells, tissues and organs to the formation of simpler compounds. The consumption of these nutrients by the body is called dissimilation. Simple substances formed during the oxidation process (water, carbon dioxide, ammonia, urea) are excreted from the body through urine, feces, exhaled air, and through the skin. The dissimilation process is directly dependent on energy consumption for physical work and heat transfer. The restoration and creation of complex organic substances of human cells, tissues, and organs occurs due to simple substances digested food. The process of storing these nutrients and energy in the body is called assimilation. The assimilation process depends on the composition of the food, which provides the body with all the nutrients. The processes of dissimilation and assimilation occur simultaneously, in close interaction and have common name- metabolic process. It consists of the metabolism of proteins, fats, carbohydrates, minerals, vitamins and water metabolism. Metabolism is directly dependent on energy consumption (for labor, heat exchange and the work of internal organs) and the composition of food. During the period of human growth and development, in pregnant and lactating women, the process of assimilation predominates, since at this time new cells appear, and therefore nutrients accumulate in the body. With increased physical activity, fasting, and serious illnesses, the process of dissimilation prevails, which leads to the consumption of nutrients and a person’s weight loss. In adulthood, a balance in metabolism is established; in old age, a decrease in the intensity of all processes is observed. Metabolism in the human body is regulated by the central nervous system directly and through hormones produced by the glands internal secretion. Yes, on protein metabolism affects the hormone thyroid gland(thyroxine), on carbohydrate - pancreatic hormone (insulin), for fat metabolism- hormones of the thyroid gland, pituitary gland, adrenal glands. To provide a person with food that corresponds to his energy expenditure and plastic processes, it is necessary to determine the daily energy expenditure. The unit of measurement for human energy is the kilocalorie. During the day, a person spends energy on the work of internal organs (heart, digestive system, lungs, liver, kidneys, etc.), heat exchange and performing socially useful activities (work, study, housework, walks, rest). The energy expended on the functioning of internal organs and heat exchange is called basal metabolism. At an air temperature of 20° C, complete rest, on an empty stomach, the main metabolism is 1 kcal per 1 hour per 1 kg of human body weight. Consequently, basal metabolism depends on body weight, as well as the sex and age of a person.

Table of basal metabolic rate of the adult population depending on body weight, age and gender

To determine a person’s daily energy expenditure, the physical activity coefficient (PFA) was introduced - this is the ratio of total energy expenditure for all types of human activity with the value of basal metabolism. The coefficient of physical activity is the main physiological criterion for assigning the population to a particular labor group depending on the intensity of work, i.e. from energy consumption.

Physical activity coefficient KFA

A total of 5 labor groups have been defined for men and 4 for women. Each work group corresponds to a certain coefficient of physical activity. To calculate daily energy expenditure, it is necessary to multiply the basal metabolic rate (corresponding to a person’s age and body weight) by the physical activity coefficient (PFA) of a certain population group.

I group - workers predominantly of mental labor, very light physical activity, KFA-1,4: scientists, students of humanities, computer operators, controllers, teachers, dispatchers, control panel workers, medical workers, accounting workers, secretaries, etc. Daily energy consumption, depending on gender and age, is 1800-2450 kcal.

II group - workers engaged in light labor, light physical activity, KFA-1.6: transport drivers, conveyor workers, weighers, packers, garment workers, radio-electronic industry workers, agronomists, nurses, orderlies, communication workers, service workers, sellers of manufactured goods, etc. Daily energy consumption, depending on gender and age, is 2100-2800 kcal.

III group - workers of moderate labor, average physical activity, KFA-1.9: mechanics, adjusters, adjusters, machine operators, drillers, drivers of excavators, bulldozers, coal combines, buses, surgeons, textile workers, shoe makers, railway workers, food sellers, water workers, equipment operators, metallurgists, blast furnace workers, chemical plant workers, catering workers, etc. Daily energy consumption, depending on gender and age, is 2500-3300 kcal.

IV group - workers of heavy physical labor, high physical activity, KFA-2,2: construction workers, driller's assistants, tunnelers, cotton pickers, agricultural workers and machine operators, milkmaids, vegetable growers, woodworkers, metallurgists, foundry workers, etc. Daily energy consumption depending on gender and age is 2850-3850 kcal.

V group - workers of particularly heavy physical labor, very high physical activity, KFA-2,4: machine operators and agricultural workers during the sowing and harvesting periods, miners, fellers, concrete workers, masons, diggers, loaders of non-mechanized labor, reindeer herders, etc. Daily energy consumption depending on gender and age, it is 3750-4200 kcal.

When choosing food products in the supermarket and preparing food from them, we first of all think about the calorie content of the food, its chemical composition and expiration date, but we don’t ask ourselves: how long does it take for food to be digested? Meanwhile, the process of assimilation of different nutrients occurs in different ways. And our well-being and health depend on how food is digested. The digestion time of food for different foods is different, and therefore mixed food can create heaviness in the stomach, intensify the processes of fermentation and putrefaction, and clog the body with toxins. But first things first…

The food we eat, once ingested, is a source of nutrients needed for growth, energy, metabolic processes. The body is a real chemical laboratory where food must be broken down into chemical components and then used for its intended purpose. The digestion time of food in different departments varies significantly.

Food passes through the digestive system, undergoing a number of transformations, mechanical and enzymatic, in each section:

1. In the mouth, food is crushed and moistened with saliva. In saliva, the enzyme amylase begins the breakdown of carbohydrates.
2. Several enzymes are already “working” in the stomach, aimed at digesting proteins and fats and curdling dairy products. Hydrochloric acid helps break down, simultaneously destroying microbes and neutralizing some poisons. Absorption of nutrients does not occur in the stomach. The products are there for a maximum of 3-4 hours.
3. Enzymes continue to work in the duodenum, breaking down food into even smaller components, turning it into mush. This is where the absorption of substances into the intestines partially begins.
4. There is already an active process of absorption of the chemical components of food, which enter the blood, are cleansed in the liver and flow to their destination (cells). All these processes take 7-8 hours.
5. Remains of batteries are absorbed. Here, the remains of undigested food (slags) can remain for up to 20 hours.
6. Unnecessary products are eliminated from the body through the large intestine.

The gastrointestinal tract pushes food through digestive tract with the help of periodic contractions of smooth muscles, this process is called peristalsis. It is not difficult to calculate how much time the body spends on digesting food. The entire digestion process takes approximately 24 hours. From several kilograms of food eaten per day and 2-3 liters of liquid drunk, 200-300 g of undigested residues are removed.

Important! Even before eating, a conditioned reflex “wakes up”: saliva is released in response to the feeling of hunger, and gastric juice is released in response to tasty smells. Enzymes also begin to be released at a certain time if you eat food strictly according to the clock.

Digestion in the stomach

A person prone to overeating throws different foods into his body as if it were a furnace. But firewood burns for approximately the same time, and to digest different foods you need different period. Knowing how much a particular product is processed, you can intelligently approach the creation of a menu, selecting food that decomposes in approximately the same time.

Important! Proteins, fats and carbohydrates need different times to break down. Try not to eat too often, knowing that the previous portion is still in the stomach. If you add hard-to-digest foods to your diet, you are guaranteed. Also, stop eating at least 4 hours before bed.

Product groups by digestibility time

All products can be divided into four groups according to the duration of their processing by the stomach. How long does it take to digest what we eat?

Group 1. This includes mainly carbohydrates, processing time: 30-35 minutes. These are broths, light salads, natural juices, as well as fresh (raw) vegetables and fruits.

Group 3. These are products containing starch and complex carbohydrates, processing time: 2-3 hours. This includes nuts, legumes, cottage cheese, hard cheese, potatoes and cereals.

Group 4. This list includes foods that take longer to digest than others or are not digested at all. This includes coffee, canned food, stewed meat, mushrooms, bread and pasta.

Table of digestion times for individual foods in the stomach

The table shows that the body digests carbohydrates the fastest. Next in ascending order are proteins and fats.

Important! Water without impurities does not need to be digested. It passes almost immediately into the intestines, which takes 10-15 minutes. In addition, it is an important component of our body, because every cell in the body consists of 80% water.

In addition to the types of foods, other factors also play an important role in the speed of digestion.

What affects the duration of food digestion?

1. Temperature. Hot foods take longer to digest than cold ones. For example, okroshka requires less time to be digested by the stomach than borscht or oven-baked casserole.
2. Meal time. Food is most actively processed during the day, during lunch. Food taken at breakfast and dinner takes longer to reach the intestines.
3. Treatment. In welded and fried foods During the cooking process, enzymes characteristic of raw food are destroyed, and the stomach takes one and a half times longer to absorb them.
4. Combination. Their processing depends on how and with what a person mixes products. For example, an apple takes half an hour to digest, and hard cheese takes five hours.
5. And the body processes a soft-boiled egg faster than a hard-boiled one.

Important! There is no need to eat until the stomach is empty of the previous portion of food. Then the problem will solve itself excess weight and without heavy and strict diets it is easy to lose those hated kilograms.

Separate Power Basics

Often tasty and healthy food– mutually exclusive concepts. Even so-called haute cuisine often consists of products with at different times absorption by the body. Therefore, a restaurant menu suitable for special occasions, should not be made your daily food.

It is useful to eat foods with the same digestion time at one time. And only after complete absorption of the nutrients received by the body, begin to next appointment absorption of food. A diet that contains mixed foods with different digestion times leads to “cluttering” of the gastrointestinal tract, since some foods have already been digested, while others have not yet been digested.

With such inconsistent nutrition, the processes of fermentation and putrefaction begin, which are accompanied by bloating, belching and flatulence. Next, waste accumulates in the intestines. Over time, they will interfere with the absorption of food, as the intestinal walls become clogged. Digestive disorders are also possible.

Principles separate power supply are based on the following rules:

• a single serving should contain compatible products that are consumed at the same time;
• the interval between meals should be at least 2 hours (the only exception is fruit);
• Do not mix solid food with drinks;
• liquid foods should be consumed before meals, not after them;
• Chew food slowly and thoroughly, and do not swallow in chunks.
• You should definitely add dry herbs and a variety of spices to your food, as they promote the production of enzymes.

All this will help the functioning of the gastrointestinal tract, good health, lightness. This way you will avoid overeating and...

We often try to pamper ourselves by including foods that have little or no compatibility in our diet. But eating tasty food does not mean eating right. Here you need to think through the menu in order to combine business with pleasure. Unfortunately, we do not always have enough time, energy and desire for this. However, in order not to make your body sick, you should take the time to develop a balanced daily menu.

Anton palaznikov

Gastroenterologist, therapist

Work experience more than 7 years.

Professional skills: diagnosis and treatment of diseases of the gastrointestinal tract and biliary system.

(hereinafter referred to as “P.”) is a set of processes that ensure mechanical grinding and chemical (mainly enzymatic) breakdown of nutrients into components that lack species specificity and are suitable for absorption and participation in the body of animals and humans. Food entering the body is comprehensively processed under the influence of various digestive enzymes Digestive enzymes- are produced by the digestive organs and break down complex food substances into simpler compounds that are easily digestible by the body. Proteins are broken down by proteases (trypsin, pepsin, etc.), fats by lipases, carbohydrates by glycosidases (amylase)., synthesized by specialized cells, and the breakdown of complex nutrients (, and carbohydrates Carbohydrates- one of the main components of cells and tissues of living organisms. Provide all living cells with energy (glucose and its reserve forms - starch, glycogen), participate in defensive reactions body (immunity). From food products Vegetables, fruits, and flour products are the richest in carbohydrates.) into increasingly smaller fragments occurs with the addition of a water molecule to them. Proteins are ultimately broken down into amino acids Amino acids- a class of organic compounds that have the properties of both acids and bases. Participate in the metabolism of nitrogenous substances in the body (initial compounds in the biosynthesis of hormones, vitamins, mediators, pigments, purine bases, alkaloids, etc.). About 20 essential amino acids serve as monomeric units from which all proteins are built., fats - into glycerol and fatty acids, carbohydrates - into monosaccharides. These relatively simple substances are absorbed, and from them complex organic compounds are synthesized again in organs and tissues.

Types of digestion

Rice. 1. Localization of hydrolysis of nutrients during extracellular, distant digestion: 1 - extracellular fluid; 2 - intracellular fluid; 4 - core; 5 - cell membrane; 6 -

Undigested or incompletely digested food substrate enters the cell, where it undergoes further hydrolysis by enzymes. This evolutionarily more ancient type of P. is common in all unicellular organisms, in some lower multicellular organisms (for example, sponges), and in higher animals. In the latter case, we mean the phagocytic properties of white cells (see) and the reticuloendothelial system, as well as one of the varieties - the so-called pinocytosis, characteristic of cells of ectodermal and endodermal origin. Intracellular digestion can be realized not only in the cytoplasm, but also in special intracellular cavities - digestive vacuoles, which exist constantly or are formed during phagocytosis and pinocytosis. It is assumed that they may participate in intracellular digestion, the enzymes of which enter the digestive vacuoles.

Rice. 2. Localization of hydrolysis of nutrients during intracellular digestion: 1 - extracellular fluid; 2 - intracellular fluid; 3 - intracellular vacuole; 4 - core; 5 - cell membrane; 6 - enzymes

Enzymes synthesized in cells are transferred to the extracellular environment of the body and carry out their action at a distance from the secreting cells. Extracellular P. predominates in annelids, crustaceans, insects, cephalopods, tunicates, and chordates, except for the lancelet. In most highly organized animals, secretory cells are located quite far from the cavities where the action of digestive enzymes is realized (and in mammals). If distant digestion occurs in special cavities, it is customary to speak of cavity digestion. Distant P. can occur outside the body that produces the enzymes. Thus, during distant extracavity P., insects introduce digestive enzymes into immobilized prey, and bacteria Bacteria- a group of microscopic, predominantly unicellular organisms. Globular (cocci), rod-shaped (bacillus, clostridia, pseudomonads), convoluted (vibrones, spirilla, spirochetes). Capable of growing both in the presence of atmospheric oxygen (aerobes) and in its absence (anaerobes). Many bacteria are causative agents of diseases in animals and humans. There are bacteria necessary for normal process vital activity ( coli is involved in the processing of nutrients in the intestines, but when it is detected, for example, in urine, the same bacterium is considered as the causative agent of kidney and urinary tract infections). secrete a variety of enzymes into the culture medium.

Rice. 3. Localization of hydrolysis of nutrients during membrane digestion: 1 - extracellular fluid; 2 - intracellular fluid; 4 - core; 5 - cell membrane; 6 - enzymes

Carried out by enzymes localized on structures cell membrane, and occupies an intermediate position between extracellular and intracellular. In the majority of highly organized animals, such transformation occurs on the surface of the membranes of the microvilli of intestinal cells and is the main mechanism of the intermediate and final stages of hydrolysis. Membrane digestion ensures the perfect coupling of digestive and transport processes and their maximum convergence in space and time. This is achieved as a result special organization digestive and transport functions of the cell membrane in the form of a kind of digestive and transport “conveyor” that facilitates the transfer of the final products of hydrolysis from the enzyme to the carrier or entrance to transport system(Fig. 4). Membrane P. has been found in humans, mammals, birds, amphibians, fish, cyclostomes, and many representatives of invertebrate animals (insects, crustaceans, mollusks, worms).

Rice. 4. Digestive transport conveyor (hypothetical model): 1 - enzyme; 2 - carrier; 3 - intestinal cell membrane; 4 - dimer; 5 - monomers formed during the final stages of hydrolysis

Each of three types digestion has both certain advantages and limitations. In the process of evolution Evolution(in biology) - irreversible historical development wildlife. Determined by variability, heredity and natural selection organisms. It is accompanied by their adaptation to the conditions of existence, the formation and extinction of species, the transformation of biogeocenoses and the biosphere as a whole. most organisms began to combine these processes; more often they are combined in the same organism, which contributes to optimal efficiency and economy of the digestive system.

In humans, higher and many lower animals, the digestive apparatus is divided into a number of sections that perform specific functions:

1) perceiver;

2) conductive, which in some animal species is expanded to form a special one;

3) digestive sections- a) grinding and initial stages P. (in some cases it ends in this section), b) subsequent P. and absorption;

4) water absorption; this section is of particular importance for terrestrial animals; it absorbs most of water entering (English scientist J. Jennings, 1972). In each of the departments, the food mass, depending on its properties and the specialization of the departments, is retained for a certain time or transferred to the next department.

Digestion in the mouth

In mammals, most other vertebrates and many invertebrate animals, food is subjected in the oral cavity (in humans it is here for an average of 10 - 15 seconds) to both mechanical grinding by chewing and initial chemical processing under the influence of , which, by wetting the food mass, ensures the formation food bolus. Chemical processing of food in the mouth consists mainly of the digestion (in humans and omnivores) of carbohydrates by salivary amylase. Here (mainly on the tongue) are the taste organs that taste food. With the help of movements of the tongue and cheeks, the food bolus is fed to the root of the tongue and, as a result of swallowing, enters into, and then into.

Digestion in the stomach

Rice. 5. Actually intestinal enzymes and enzymes adsorbed from the cavity of the small intestine during membrane digestion (schematic representation of a fragment outer surface microvilli): A - distribution of enzymes; B - relationship between enzymes, carriers and substrates; I - cavity of the small intestine; II - glycocalyx; III - membrane surface; IV - three-layer membrane of the intestinal cell; 1 - intestinal enzymes themselves; 2 - adsorbed enzymes; 3 - carriers; 4 - substrates.

The intermediate and final stages of digestion are carried out by enzymes localized on the surface of the membranes of intestinal cells, where absorption begins. Membranous digestion involves: 1) pancreatic juice enzymes (β-amylase, lipase, trypsin, chymotrypsin, elastase, etc.), adsorbed in various layers of the so-called glycocalyx, which covers the microvilli and is a three-dimensional mucopolysaccharide network; 2) intestinal enzymes themselves (β-amylase, oligosaccharidases and disaccharidases, various tetrapeptidases, tripeptidases and dipeptidases, aminopeptidase, alkaline and its isoenzymes, monoglyceride lipase and others), synthesized by intestinal cells and transferred to the surface of their membranes, where they carry out digestive functions.

Adsorbed enzymes carry out mainly intermediate, and intestinal enzymes themselves - the final stages of hydrolysis of nutrients. Oligopeptides entering the brush border area are broken down into amino acids capable of absorption, with the exception of glycylglycine and some dipeptides containing proline and hydroxyproline, which are absorbed as such. Disaccharides, which are formed as a result of the digestion of starch and glycogen, are hydrolyzed by intestinal glycosidases themselves to monosaccharides, which are transported across the intestinal barrier into internal environment body. Triglycerides are broken down not only by the action of pancreatic juice lipase, but also by the influence of the intestinal enzyme itself - monoglyceride lipase. Absorption occurs in the form of fatty acids and β-monoglycerides. Long-chain fatty acids in the mucous membrane of the small intestine are again esterified and enter in the form of chylomicrons (particles with a diameter of about 0.5 microns). Short-chain fatty acids are not resynthesized and enter the blood to a greater extent than the lymph.

In general, membrane digestion breaks down the majority of all glycosidic and peptide bonds and triglycerides. Membrane P., unlike cavity P., occurs in a sterile zone, because The microvilli of the brush border are a kind of bacterial filter that separates the final stages of hydrolysis of nutrients from the intestinal cavity populated by bacteria.

Normal in digestive processes important have microorganisms Microorganisms(microbes) - the smallest, mainly single-celled organisms, visible only through a microscope: bacteria, microscopic fungi, protozoa, sometimes these include viruses. Characterized by a huge diversity of species that can exist in different conditions(cold, heat, water, drought). Microorganisms are used in the production of antibiotics, vitamins, amino acids, protein, etc. Pathogens cause human diseases., and in some animals - the protozoa that inhabit various departments gastrointestinal tract. Digestive processes V small intestine distributed unequally both in the direction from its beginning to the end, and in the direction from the crypts to the tips of the villi, which is expressed in the corresponding topography of each of the digestive enzymes that carry out both cavity and membrane digestion.

Processes predominate in the large intestines reverse suction(reabsorption) of water, mineral and organic components of food gruel - chyme. Up to 95% of water is absorbed in the large intestines, as well as electrolytes, glucose, and some vitamins Vitamins - organic matter, formed in the body with the help of intestinal microflora or supplied with food, usually plant-based. Required for normal exchange substances and life activities. Long-term consumption of food devoid of vitamins causes diseases (vitaminosis, hypovitaminosis). Essential vitamins: A (retinol), D (calciferols), E (tocopherols), K (phylloquinone); N (biotin), PP ( a nicotinic acid), WITH ( ascorbic acid), B1 (thiamine), B2 (riboflavin), B3 (pantothenic acid), B6 ​​(pyridoxine), B12 (cyanocobalamin), Sun ( folic acid). AD, E and K are fat-soluble, the rest are water-soluble. and amino acids produced by microbes Microbes(from micro... and Greek bios - life) - the same as microorganisms. Microorganisms are tiny, mostly single-celled organisms visible only through a microscope: bacteria, microscopic fungi and algae, protozoa. Sometimes viruses are classified as microorganisms. intestinal flora. As the intestinal contents move and compact, feces is formed, the accumulation of which causes the act.

Digestive regulation

You can read more about digestion in the literature: Boris Petrovich Babkin, External secretion digestive glandsGlands- organs that produce and secrete specific substances (hormones, mucus, saliva, etc.) that are involved in various physiological functions and biochemical processes of the body. The endocrine glands (endocrine) secrete the products of their vital activity - hormones directly into the blood or lymph (pituitary gland, adrenal glands, etc.). Exocrine glands (exocrine) - on the surface of the body, mucous membranes or in the external environment (sweat, salivary, mammary glands). The activity of the glands is regulated by the nervous system, as well as hormonal factors., M. - L., 1927; Ivan Petrovich Pavlov, Lectures on the work of the main digestive glands, Complete. collection op., 2nd ed., vol. 2, book. 2, M. - L., 1951; Babkin B.P., Secretory mechanism of the digestive glands, L., 1960; Prosser L., Brown F., Comparative Physiology Physiology- the science of the life activity of the whole organism and its individual parts - cells, organs, functional systems. Physiology seeks to reveal the mechanism of the functions of a living organism (growth, reproduction, respiration, etc.), their connection with each other, regulation and adaptation to external environment, origin and formation in the process of evolution and individual development of an individual. animals, trans. from English, M., 1967; Alexander Mikhailovich Ugolev, Digestion and its adaptive evolution, M., 1961; his, Membrane digestion. Polysubstrate processes, organization and regulation, L., 1972; Bockus N. L., Gastroenterology, v. 1 - 3, Phil.-L., 1963-65; Davenport N. W., Physiology of the digestive tract, 2 ed., Chi., 1966; Handbook of physiology, sec. 6: Alimentary channel, v. 1 - 5, Wash., 1967 - 68; Jennings J. B., Feeding, digestion and assimilation in animals, 2 ed., L., 1972. (A. M. Ugolev, N. M. Timofeeva, N. N. Iezuitova)

Find something else interesting:

Majority useful substances To maintain vital functions, the human body receives it through the gastrointestinal tract.

However regular products that a person eats: bread, meat, vegetables - the body cannot use directly for its needs. To do this, food and drinks must be divided into smaller components - individual molecules.

These molecules are carried by the blood into the body's cells to build new cells and produce energy.

How is food digested?

The process of digestion involves mixing food with gastric juice and its movement through the gastrointestinal tract. During this movement, it is disassembled into components that are used for the needs of the body.

Digestion begins in the mouth - by chewing and swallowing food. And it ends in the small intestine.

How does food move through the gastrointestinal tract?

The large, hollow organs of the gastrointestinal tract—the stomach and intestines—have a layer of muscle that moves their walls. This movement allows food and liquid to move through digestive system and mix.

Contraction of the organs of the gastrointestinal tract is called peristalsis. It looks like a wave that moves along the entire digestive tract with the help of muscles.

The intestinal muscles create a constricted area that slowly moves forward, pushing food and liquid in front of it.

How does digestion happen?

Digestion begins in the oral cavity, when chewed food is abundantly moistened with saliva. Saliva contains enzymes that begin the breakdown of starch.

Swallowed food enters esophagus, which connects throat and stomach. At the junction of the esophagus and stomach there are circular muscles. This is the lower esophageal sphincter, which opens under the pressure of swallowed food and allows it to pass into the stomach.

The stomach has three main tasks:

1. Storage. To take in large amounts of food or liquid, the muscles in the upper part of the stomach relax. This allows the walls of the organ to stretch.

2. Mixing. The lower part of the stomach contracts to allow food and liquid to mix with gastric juices. This juice consists of hydrochloric acid and digestive enzymes that help in the breakdown of proteins. The walls of the stomach secrete a large number of mucus, which protects them from the effects of hydrochloric acid.

3. Transportation. Mixed food passes from the stomach to the small intestine.

From the stomach, food enters upper section small intestine - duodenum. Here the food is exposed to juice pancreas and enzymes small intestine, which promotes the digestion of fats, proteins and carbohydrates.

Here food is processed by bile, which is produced by the liver. Between meals, bile is stored in gallbladder . During eating, it is pushed into the duodenum, where it mixes with food.

Bile acids dissolve fat in the intestinal contents in much the same way as detergents– fat from the frying pan: they break it into tiny droplets. Once the fat is crushed, it is easily broken down by enzymes into its components.

Substances that are obtained from food digested by enzymes are absorbed through the walls of the small intestine.

The mucous membrane of the small intestine is covered with tiny villi, which create a huge surface area that allows the absorption of large amounts of nutrients.

Through special cells, these substances from the intestines enter the blood and are carried throughout the body - for storage or use.

Undigested parts of food go to colon, in which water and some vitamins are absorbed. After digestion waste is formed in feces and are deleted via rectum.

What disrupts the gastrointestinal tract?

The most important

The gastrointestinal tract allows the body to break down food into its simplest compounds, from which new tissue can be built and energy can be obtained.

Digestion occurs in all parts of the gastrointestinal tract - from the mouth to the rectum.

If we briefly characterize the process of digestion, it will be the movement of eaten food through the digestive organs, during which food is broken down into simpler elements. Small substances are able to be absorbed and assimilated by the body, and then pass into the blood and nourish all organs and tissues, giving them the opportunity to function normally.

Digestion is a process of mechanical crushing and chemical, mainly enzymatic, breakdown of food into substances that lack species specificity and are suitable for absorption and participation in metabolism human body. Food entering the body is processed by enzymes produced by special cells. Complex food structures, such as proteins, fats and carbohydrates, are broken down with the addition of a water molecule. Proteins break down during digestion into amino acids, fats into glycerol and fatty acids, and carbohydrates into simple sugars. These substances are well absorbed, and then again synthesized into complex compounds in tissues and organs.

The length of the human digestive tract is 9 meters. The process of complete processing of food lasts from 24 to 72 hours and varies from person to person. The digestive system includes the following organs: oral cavity, pharynx, esophagus, stomach, small intestine, large intestine and rectum.

The process of digestion itself is divided into stages of digestion in humans, and they consist of the head, gastric and intestinal phases.

Head phase of digestion

This is the stage where the recycling process begins. A person sees food and smells it, his cerebral cortex is activated, signals of taste and smell begin to enter the hypothalamus and medulla involved in the digestion process.

A lot of juice is released in the stomach, ready to accept food, enzymes are produced and saliva is actively secreted. The food then goes to oral cavity, where it is mechanically crushed by chewing with teeth. At the same time, food is mixed with saliva, and interaction with enzymes and microorganisms begins.

During the digestion process, a certain amount of food is broken down by saliva, which gives the taste of the food. Digestion in the oral cavity breaks down starch into simple sugars by the amylase enzyme found in saliva. Proteins and fats do not break down in the mouth. The whole process in the mouth lasts no more than 15-20 seconds.

The phase of processing food in the stomach of the body

The next phase of the digestion process continues in the stomach. This is the widest part of the digestive organs, capable of stretching and holding quite a lot of food. The stomach tends to contract rhythmically, and the incoming food is mixed with gastric juice. It contains hydrochloric acid, so it has an acidic environment necessary for breaking down food.

Food in the stomach is processed during the digestion process for 3-5 hours, undergoing digestion in every possible way, mechanically and chemically. In addition to hydrochloric acid, the effect is also produced by pepsin. Therefore, the breakdown of proteins into smaller fragments begins: low molecular weight peptides and amino acids. But the breakdown of carbohydrates in the stomach during the digestion process stops, because amylase stops its action under pressure acidic environment. How does digestion occur in the stomach? Gastric juice contains lipase, which breaks down fats. Of great importance hydrochloric acid, under its influence enzymes are activated, denaturation and swelling of proteins occurs, it is triggered bactericidal property stomach juice.

Please note: Carbohydrate foods are retained in the digestive process. this body 2 hours, then it moves to the small intestine. But protein and fatty foods are processed in it for 8-10 hours.

Then the food, partially processed by the digestive process and having a liquid or semi-liquid structure, mixed with gastric juice, falls in portions into the small intestine. The stomach contracts at regular intervals during digestion and food is squeezed into the intestines.

Digestive phase in the small intestine of the human body

The logical pattern of food processing in the small intestine is considered the most important in the entire process, because this is where nutrients are most absorbed. This body operates intestinal juice having alkaline environment, and consists of bile entering the department, pancreatic juice and fluid from the intestinal walls. Digestion at this stage does not last for everyone a short time. This occurs due to a lack of the enzyme lactase, which processes milk sugar, so milk is poorly digested. Especially in people over 40 years of age. More than 20 different enzymes are involved in the intestinal tract to process food.

The small intestine consists of three parts that pass into each other and depend on the work of the neighbor:

• duodenum;
• skinny;
• ileum.

It is into the duodenum that bile flows from the liver and pancreatic juice during digestion, and it is their effect that leads to the digestion of food. Pancreatic juice contains enzymes that dissolve fats. Here carbohydrates are broken down into simple sugars and proteins. In this organ, the greatest absorption of food occurs; vitamins and nutrients are absorbed by the intestinal walls.

All carbohydrates, fats and parts of proteins are completely digested in the lean and ileum intestines under the influence of enzymes produced locally. The intestinal mucosa is strewn with villi - enterocytes. They absorb the products of protein and carbohydrate processing, which enter the blood, and fatty elements into the lymph. Due to large area intestinal walls and numerous villi, the absorption surface is approximately 500 square meters.

Next, the food enters the large intestine, where feces are formed, and the mucous membrane of the organ absorbs water and other useful microelements. The large intestine ends in a straight section connected to the anus.

The role of the liver in processing food in the body

The liver produces bile during digestion from 500 to 1500 ml per day. Bile is released into the small intestine and performs great job: helps emulsify fats, absorb triglycerides, stimulates lipase activity, improves peristalsis, inactivates pepsin in the duodenum, disinfects, improves hydrolysis and absorption of proteins and carbohydrates.

This is interesting: Bile does not contain enzymes, but is required for the breakdown of fats and fat-soluble vitamins. If it is produced in a small volume, then the processing and absorption of fats is disrupted, and they leave the body naturally.

How does digestion work without the gallbladder and bile?

Lately they are often produced surgical removals gallbladder - an organ in the form of a sac for storing and storing bile. The liver produces bile continuously, and it is required only at the time of food processing. When food is processed, the duodenum becomes empty and the need for bile disappears.

What happens when bile is absent and what is digestion without one of the main organs? If it is removed before changes begin in organs that are interdependent with it, its absence is tolerated normally. Bile, continuously produced by the liver, accumulates in its ducts during the digestion process, and then goes directly to the duodenum.

Important! Bile is released there, regardless of the presence of food in it, therefore, immediately after the operation you need to eat often, but little by little. This is required so that there will not be enough bile to process a large volume of food. Sometimes the body needs time to learn to live without the gallbladder and the bile it produces so that it finds a place to accumulate this fluid.

Digestion of food in the body's large intestine

The remains of unprocessed food then go to the large intestine, where they are digested for at least 10-15 hours. The large intestine measures 1.5 meters and contains three sections: cecum, transverse colon and rectum. The following processes occur in this organ: absorption of water and microbial metabolization of nutrients. Great importance in the processing of food in the large intestine there is ballast. It includes non-recyclable biochemical substances: fiber, resins, wax, hemicellulose, lignin, gums. That part of dietary fiber that is not broken down in the stomach and small intestine is processed in the colon by microorganisms. The structural and chemical composition of food affects the duration of absorption of substances in the small intestine and its movement through the gastrointestinal tract.

In the colon, during the digestion process, feces are formed, which include unprocessed food debris, mucus, dead cells of the intestinal mucosa, and microbes that constantly multiply in the intestine and cause fermentation and bloating.

Breakdown and absorption of nutrients in the body

Food processing and absorption cycle necessary elements at healthy person lasts from 24 to 36 hours. Throughout its entire length, mechanical and chemical effects occur on food in order to break it down into simple substances that can be absorbed into the blood. It occurs throughout the gastrointestinal tract during the digestion process, the mucous membrane of which is strewn with small villi.

This is interesting: Normal absorption of fat-soluble foods requires bile and fats in the intestines. Blood capillaries are used to absorb water-soluble substances such as amino acids and monosaccharides.

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