The sequence of food passage through the digestive organs. Human digestive system

Eating is a process for which every person leaves all his affairs and worries several times a day, because nutrition supplies his body with energy, strength and all the substances necessary for normal life. It is also important that food provides it with material for plastic processes, so that body tissues can grow and repair, and destroyed cells are replaced with new ones. After the body has received everything it needs from food, it turns into waste, which is eliminated from the body naturally.

Well-coordinated work of such complex mechanism is possible thanks to the digestive system, which digests food (its physical and chemical processing), absorbs breakdown products (they are absorbed into the lymph and blood through the mucous membrane) and removes undigested residues.

Thus, the digestive system performs several important functions:

• Motor-mechanical (food is crushed, moved and excreted)
• Secretory (enzymes, digestive juices, saliva and bile are produced)
• Absorbent (proteins, fats, carbohydrates, vitamins, minerals and water are absorbed)
• Excretory (undigested food residues, excess of a number of ions, heavy metal salts are eliminated)

A little about the development of the digestive organs

Digestive system begins to be formed in the first stages of development of the human embryo. After 7-8 days of development of the fertilized egg, the primary gut is formed from the endoderm (inner germ layer). On the 12th day, it is divided into two parts: the yolk sac (extra-embryonic part) and the future digestive tract - the gastrointestinal tract (intra-embryonic part).

Initially, the primary gut is not connected to the oropharyngeal and cloacal membranes. The first melts after 3 weeks of intrauterine development, and the second - after 3 months. If for some reason the membrane melting process is disrupted, anomalies appear in development.

After 4 weeks of embryo development, sections of the digestive tract begin to form:

• Pharynx, esophagus, stomach, segment duodenum(the liver and pancreas begin to develop) - derivatives of the foregut
• Distal part, jejunum and ileum - derivatives of the midgut
• Sections of the large intestine - derivatives of the hindgut

The basis of the pancreas is made up of outgrowths of the foregut. Simultaneously with the glandular parenchyma, pancreatic islands are formed, consisting of epithelial strands. 8 weeks later, the hormone glucagon is detected in alpha cells by immunochemical means, and at week 12, the hormone insulin is detected in beta cells. Between the 18th and 20th weeks of gestation (pregnancy, the duration of which is determined by the number of complete weeks of gestation that have passed from the 1st day of the last menstruation to the moment of cutting the umbilical cord of the newborn), the activity of alpha and beta cells increases.

After the baby is born, the gastrointestinal tract continues to grow and develop. The formation of the gastrointestinal tract ends approximately at three years old.

Digestive organs and their functions

Along with studying the digestive organs and their functions, we will also analyze the path taken by food from the moment it enters the oral cavity.

Main function The transformation of food into substances necessary for the human body, as has already become clear, is carried out by the gastrointestinal tract. It’s called a tract for a reason, because... is a nature-designed path for food, and its length is about 8 meters! The gastrointestinal tract is filled with all sorts of “regulatory devices”, with the help of which food, making stops, gradually goes its way.

The beginning of the digestive tract is the oral cavity, in which solid food is moistened with saliva and ground by the teeth. Saliva is secreted into it by three pairs of large and many small glands. During the process of eating, the secretion of saliva increases many times. In general, the glands secrete approximately 1 liter of saliva in 24 hours.

Saliva is required to moisten food lumps so that they can move further more easily, and also supplies an important enzyme - amylase or ptyalin, with the help of which carbohydrates begin to break down already in the oral cavity. In addition, saliva removes from the cavity any substances that irritate the mucous membrane (they enter the cavity by accident and are not food).

Lumps of food, chewed by teeth and moistened with saliva, when a person makes swallowing movements, pass through the mouth into the pharynx, bypass it and then go into the esophagus.

The esophagus can be described as a narrow (about 2-2.5 cm in diameter and about 25 cm in length) vertical tube that connects the pharynx and stomach. Despite the fact that the esophagus is not actively involved in food processing, its structure is similar to that of the underlying sections of the digestive system - the stomach and intestines: each of these organs has walls consisting of three layers.

What are these layers?

• The inner layer is formed by the mucous membrane. It contains different glands that differ in their characteristics in all parts of the gastrointestinal tract. Digestive juices are secreted from the glands, thanks to which food products can be broken down. They also secrete mucus, which is necessary to protect the inner surface of the digestive canal from the effects of spicy, rough and other irritating foods.
• Middle layer lies under the mucous membrane. It is a muscular sheath composed of longitudinal and circular muscles. The contractions of these muscles allow the food lumps to be tightly grasped, and then, using wave-like movements (these movements are called peristalsis), to push them further. Note that the muscles of the digestive canal are muscles of the smooth muscle group, and their contraction occurs involuntarily, unlike the muscles of the limbs, torso and face. For this reason, a person cannot relax or contract them at will. You can intentionally contract only the rectum with striated, not smooth, muscles.
• The outer layer is called the serosa. It has a shiny and smooth surface, and is composed mainly of dense connective tissue. A wide connective tissue plate called the mesentery originates from the outer layer of the stomach and intestines along its entire length. With its help, the digestive organs are connected to the back wall abdominal cavity. The mesentery contains lymphatic and blood vessels - they supply lymph and blood to the digestive organs and nerves that are responsible for their movements and secretion.

These are the main characteristics of the three layers of the walls of the digestive tract. Of course, each department has its differences, however general principle is the same for everyone, starting with the esophagus and ending with the rectum.

After passing through the esophagus, which takes about 6 seconds, the food enters the stomach.

The stomach is a so-called pouch, which has an elongated shape and an oblique location in the upper region of the abdominal cavity. The main part of the stomach is located to the left of the central section of the torso. It begins at the left dome of the diaphragm (the muscular septum that separates the abdominal and thoracic cavities). The entrance to the stomach is where it connects to the esophagus. Just like the exit (pylorus), it is distinguished by the circular obturator muscles - sphincter. Thanks to the contractions, the sphincter separates the gastric cavity from the duodenum, which is located behind it, as well as from the esophagus.

To put it figuratively, the stomach seems to “know” that food will soon enter it. And he begins to prepare for her new intake even before the moment when the food enters his mouth. Remember that moment when you see some tasty dish and your mouth begins to water. Along with these “drools” that occur in the mouth, digestive juice begins to be released in the stomach (this is exactly what happens before a person begins to eat directly). By the way, this juice was called by Academician I.P. Pavlov igniting or appetizing juice, and the scientist assigned it a large role in the process of subsequent digestion. Appetizing juice serves as a catalyst for more complex chemical processes that take a major part in the digestion of food entering the stomach.

Note that if the appearance of the food does not evoke appetizing juice, if the eater is absolutely indifferent to the food in front of him, this can create certain obstacles to successful digestion, which means that the food will enter the stomach, which is not sufficiently prepared for its digestion. This is why it is customary to attach such great importance to the beautiful table setting and appetizing appearance of the dishes. Know that in the central nervous system (CNS) of a person, conditioned reflex connections are formed between the smell and type of food and the work of the gastric glands. These connections help determine a person’s attitude towards food even at a distance, i.e. in some cases he experiences pleasure, and in others - no feelings or even disgust.

It would not be superfluous to note one more side of this conditioned reflex process: in the case when the ignition juice has already been caused for some reason, i.e. If you are already salivating, it is not recommended to delay eating. Otherwise, the connection between the activities of the gastrointestinal tract areas is disrupted, and the stomach begins to work “idle”. If such violations are frequent, the likelihood of certain ailments, such as stomach ulcers or catarrh, will increase.

When food enters the oral cavity, the intensity of secretion from the glands of the gastric mucosa increases; Innate reflexes in the work of the above-mentioned glands come into force. The reflex is transmitted along the sensitive endings of the taste nerves of the pharynx and tongue to the medulla oblongata, and then sent to the nerve plexuses embedded in the layers of the walls of the stomach. Interestingly, digestive juices are released only when only edible foods enter the oral cavity.

It turns out that by the time the crushed food moistened with saliva ends up in the stomach, it is already absolutely ready for work, representing like a machine for digesting food. Lumps of food, entering the stomach and automatically irritating its walls with the chemical elements present in them, contribute to an even more active secretion of digestive juices, affecting individual elements of food.

The digestive juice of the stomach contains hydrochloric acid and pepsin, a special enzyme. Together they break down proteins into albumoses and peptones. The juice also contains chymosin, a rennet enzyme that curdles dairy products, and lipase, an enzyme necessary for the initial breakdown of fats. Among other things, mucus is secreted from some glands, which protects the inner walls of the stomach from the overly irritating effects of food. Hydrochloric acid, which helps digest proteins, performs a similar protective function - it neutralizes toxic substances that enter the stomach along with food.

Almost no food breakdown products enter the blood vessels from the stomach. For the most part, alcohol and substances containing alcohol, for example, dissolved in alcohol, are absorbed in the stomach.

The “metamorphoses” of food in the stomach are so great that in cases where digestion is somehow disrupted, all parts of the gastrointestinal tract suffer. Based on this, you must always adhere to. This can be called the main condition for protecting the stomach from any kind of disorders.

Food stays in the stomach for approximately 4-5 hours, after which it is redirected to another part of the gastrointestinal tract - the duodenum. It passes into it in small parts and gradually.

As soon as a new portion of food has entered the intestine, the pyloric muscle contraction occurs, and the next portion will not leave the stomach until the hydrochloric acid, which ends up in the duodenum along with the already received lump of food, is neutralized by alkalis contained in the intestinal juices.

The duodenum was called the duodenum by ancient scientists, the reason for which was its length - about 26-30 cm, which can be compared with the width of 12 fingers located side by side. The shape of this intestine resembles a horseshoe, and the pancreas is located in its bend.

Digestive juice is secreted from the pancreas, flowing into the cavity of the duodenum through a separate channel. The bile produced by the liver also enters here. Together with the enzyme lipase (found in pancreatic juice), bile breaks down fats.

The pancreatic juice also contains the enzyme trypsin - it helps the body digest proteins, as well as the enzyme amylase - it promotes the breakdown of carbohydrates to the intermediate stage of disaccharides. As a result, the duodenum serves as a place where all the organic components of food (proteins, fats and carbohydrates) are actively affected by a variety of enzymes.

Turning into food gruel in the duodenum (called chyme), food continues on its way and enters the small intestine. The presented segment of the gastrointestinal tract is the longest - approximately 6 meters in length and 2-3 cm in diameter. Enzymes finally break down complex substances into simpler organic elements along this path. And already these elements become the beginning of a new process - they are absorbed into the blood and lymphatic vessels of the mesentery.

In the small intestine, the food taken by a person is finally transformed into substances that are absorbed into the lymph and blood, and then used by the cells of the body for their own purposes. The small intestine has loops that are in constant motion. This peristalsis ensures complete mixing and movement of food masses to the large intestine. This process is quite long: for example, ordinary mixed food included in the human diet passes through the small intestine in 6-7 hours.

Even if you look closely at the mucous membrane of the small intestine without a microscope, you can see small hairs - villi, approximately 1 mm high - all over its surface. One square millimeter of mucous membrane contains 20-40 villi.

When food passes through the small intestines, the villi constantly (and each of the villi has its own rhythm) contract by about ½ of its size, and then stretch upward again. Thanks to the combination of these movements, a suction action appears - it is this that allows broken down food products to pass from the intestines into the blood.

A large number of villi help to increase the absorption surface of the small intestine. Its area is 4-4.5 square meters. m (which is almost 2.5 times more outer surface bodies!).

But not all substances are absorbed in the small intestine. The remains are sent to the large intestine, about 1 m long and about 5-6 cm in diameter. The large intestine is separated from the small intestine by a valve - the bauhinium valve, which from time to time allows parts of the chyme to pass through to the initial segment of the large intestine. The large intestine is called the cecum. On its lower surface there is a process resembling a worm - this is the well-known appendix.

The large intestine is distinguished by its U-shape and raised upper corners. It consists of several segments, including the cecum, ascending, transverse colon, descending and sigmoid colon (the latter is curved like the Greek letter sigma).

The large intestine is home to many bacteria that produce fermentation processes. These processes help break down fiber, which is abundantly found in foods of plant origin. And along with its absorption, water is also absorbed, which enters the large intestine with chyme. This is where feces begin to form.

The large intestines are not as active as the small intestines. For this reason, chyme stays in them much longer - up to 12 hours. During this time, food goes through the final stages of digestion and dehydration.

The entire volume of food entering the body (as well as water) undergoes a lot of various changes. As a result, it is significantly reduced in the large intestine, and from several kilograms of food only 150 to 350 grams remain. These remains are subject to defecation, which occurs due to contraction of the striated muscles of the rectum, abdominal muscles and perineum. The process of defecation completes the path of food passing through the gastrointestinal tract.

A healthy body spends from 21 to 23 hours to completely digest food. If any deviations are noticed, they should under no circumstances be ignored, because they indicate that there are problems in some parts of the digestive canal or even in individual organs. In case of any violation, it is necessary to contact a specialist - this will not allow the disease to become chronic and lead to complications.

Speaking about the digestive organs, we should say not only about the main, but also about the auxiliary organs. We have already talked about one of them (the pancreas), so it remains to mention the liver and gallbladder.

The liver is one of the vital unpaired organs. It is located in the abdominal cavity under the right dome of the diaphragm and performs a huge number of different physiological functions.

Liver cells form hepatic beams that receive blood from the arterial and portal veins. From the beams, the blood flows to the inferior vena cava, where the paths through which bile is drained into the gallbladder and duodenum begin. And bile, as we already know, takes an active part in digestion, as do pancreatic enzymes.

The gallbladder is a sac-like reservoir located on the lower surface of the liver where bile produced by the body is collected. The reservoir has an elongated shape with two ends - wide and narrow. The length of the bubble reaches 8-14 cm, and the width - 3-5 cm. Its volume is approximately 40-70 cubic meters. cm.

The bubble has bile duct, connecting to the hepatic duct at the porta hepatis. The fusion of the two ducts forms the common bile duct, which unites with the pancreatic duct and opens into the duodenum through the sphincter of Oddi.

The importance of the gallbladder and the function of bile cannot be underestimated, because they perform a number of important operations. They are involved in the digestion of fats, create an alkaline environment, activate digestive enzymes, stimulate intestinal motility and remove toxins from the body.

In general, the gastrointestinal tract is a real conveyor belt for the continuous movement of food. His work is subject to strict consistency. Each stage affects food in a specific way, so that it supplies the body with the energy it needs to function properly. And another important characteristic of the gastrointestinal tract is that it adapts quite easily to different types food.

However, the gastrointestinal tract is “needed” not only for processing food and removing unusable residues. In fact, its functions are much wider, because... As a result of metabolism (metabolism), unnecessary products appear in all cells of the body, which must be removed, otherwise their poisons can poison a person.

A large proportion of toxic metabolic products enters the intestines through blood vessels. There these substances break down and are excreted along with feces during bowel movements. It follows that the gastrointestinal tract helps the body get rid of many toxic substances that appear in it during life.

The clear and harmonious operation of all systems of the digestive canal is the result of regulation, for which the nervous system is largely responsible. Some processes, for example, the act of swallowing food, the act of chewing it, or the act of defecation, are controlled by the human consciousness. But others, such as the release of enzymes, the breakdown and absorption of substances, contractions of the intestines and stomach, etc., occur on their own, without conscious effort. The autonomic nervous system is responsible for this. In addition, these processes are associated with the central nervous system, and in particular with the cerebral cortex. So any person (joy, fear, stress, excitement, etc.) immediately affects the activity of the digestive system. But this is a conversation on a slightly different topic. We are summing up the first lesson.

In the second lesson, we will talk in detail about what food consists of, tell you why the human body requires certain substances, and also provide a table of the content of useful elements in foods.

Test your knowledge

If you want to test your knowledge on the topic of this lesson, you can take a short test consisting of several questions. For each question, only 1 option can be correct. After you select one of the options, the system automatically moves on to the next question. The points you receive are affected by the correctness of your answers and the time spent on completion. Please note that the questions are different each time and the options are mixed.

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, allowing them 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 the metabolism of the 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 oblongata, which are 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. Then the food enters the oral cavity, where it is mechanically crushed by chewing with the 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. Hydrochloric acid is of great importance; under its influence, enzymes are activated, denaturation and swelling of proteins occurs, and the bactericidal property of stomach juice is activated.

Please note: Carbohydrate foods remain in this organ for 2 hours during digestion, then they move 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 organ contains intestinal juice, which has an alkaline environment and consists of bile that enters 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 lactase enzyme, which processes milk sugar, so milk is poorly digestible. 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 jejunum and ileum under the action 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 the large area of ​​the 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. Ballast is of great importance in the processing of food in the large intestine. 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

The cycle of food processing and absorption of necessary elements in a 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.

VISUAL PHYS0L0GY | S. Silbernagl, A. Despopoulos | Translation from English by A. S. Belyakova, A. A. Sinyushin | Moscow | BINOMIAL. Knowledge Laboratory

Quite often you hear the question about how long it will take for food to be absorbed after it is swallowed. There are a great many answers to this question on the Internet, and not all of them are correct or justified. But in fact, the question itself is not as simple as it might initially seem. And the point here is not so much the lack of qualifications of certain authors, but rather the rather meager amount of information in available scientific sources on this topic.

And yes, let me clarify, we are not talking about suction and effective use of one or another nutrient before it reaches adipocytes, muscles, muscle cell and not about the biochemistry of nutrient absorption and so on, but specifically about the transportation of food from the moment it is chewed to the moment it enters the large intestine. I will still not describe the fact of defecation (although it is discussed in sufficient detail in textbooks on human physiology).

The main difficulty in correctly determining the time a particular dish is in gastrointestinal tract, lies in a fairly wide range of interrelated factors: type of nutrient, their combination, quantity of incoming food, individual characteristics of the human enzymatic system, type of diet, health status, stress factors, reproductive status, age, gender, food temperature, difficulty of correct assessment the process itself and many others. Those. Yes, there are quite a lot of influencing factors. In addition, food entering the body does not move evenly through the digestive system, in some places faster and in others slower under the influence of certain factors.

As an example, you can look at the following graph, where scientists in 1989 studied the passage of mixed food through the volunteer’s gastrointestinal tract.
Camilleri M, Colemont LJ, Phillips SF, Brown ML, Thomforde GM, Chapman N, Zinsmeister AR. Human gastric emptying and colonic filling of solids characterized by a new method. Am J Physiol. 1989 Aug;257(2 Pt 1):G284-90.

But again, this is an individual case, which would be incorrect to extrapolate to everyone.

Or on the diagram you can see the time of gastric emptying of liquid and liquid food.

Rate of gastric emptying. Martin Culen, Anna Rezacova, Josef Jampilek and Jiri Dohnal. .

SO WHAT DO EXISTING OFFICIAL SOURCES SAY?

For the most part, the materials that I could find say something like the following (we are talking about SOLID FOOD; liquid food, and especially one less enriched with fats and other dense food particles, leaves the stomach and is generally absorbed quite quickly):
1. For chewing food(machining; in this case oral cavity The main processes of food processing are grinding, wetting with saliva and swelling; as a result of these processes, a food bolus is formed from food) takes about 5-30 seconds.
2. Transport to the stomach through the esophagus takes about 10 seconds.

3. Time spent by food in the stomach(solid food components do not pass through the pylorus until they are crushed to particles no larger than 2-3 mm in size, 90% of particles leaving the stomach have a diameter of no more than 0.25 mm.) from 2 hours to 10 hours (at Some sources have information about 24 hours, for example some types of dried meat or even raw meat). Moreover, about 50% of the contents of the stomach leaves it after 3-4 hours (on average).
4. Residence time in the small intestine about 3-4 more hours. More precisely, at least about 50% of the food mass leaves the small intestine during this time.

5. Residence time in the large intestine from 18 to 72 hours (for rural residents of Africa, who consume a lot of fibrous substances, the average evacuation time from the large intestine is 36 hours, and the weight of feces is 480 g, while for residents of European cities the corresponding values ​​are 72 hours and 110 g). But food particles located in the center of the chyme can pass through the large intestine in a shorter time.

"...In the oral cavity, the main processes of food processing are grinding, wetting with saliva and swelling. As a result of these processes, a food bolus is formed from food. In addition to the indicated physical and physicochemical processes, in the oral cavity, under the influence of saliva, chemical processes associated with depolymerization.

Due to the too short stay of food in the mouth, complete breakdown of starch into glucose does not occur here; a mixture is formed consisting mainly of oligosaccharides.

The bolus of food from the root of the tongue through the pharynx and esophagus enters the stomach, which is a hollow organ with a normal volume of about 2 liters. with a folded inner surface that produces mucus and pancreatic juice. In the stomach, digestion continues for 3.5-10.0 hours. Further wetting and swelling of the food bolus, penetration of gastric juice into it, coagulation of proteins, and curdling of milk occur here. Along with physicochemical processes, chemical processes begin in which enzymes of gastric juice participate..."

"... Solid food components do not pass through the pylorus of the stomach until they are crushed to particles no larger than 2-3 mm in size, 90% of particles leaving the stomach have a diameter of no more than 0.25 mm. When peristaltic waves reach the distal area of ​​the antrum, the pylorus contracts.

The pylorus, which forms the narrowest part of the stomach...at its junction with the duodenum, closes even before the antrum is completely sealed off from the body of the stomach. Food is forced back into the stomach under pressure, causing solid particles to rub against each other and break down further.
Gastric emptying is regulated by autonomic nervous system, intramural nerve plexuses and hormones. In the absence of impulses from the vagus nerve (for example, when it is cut), gastric peristalsis is significantly weakened and gastric emptying slows down. Gastric peristalsis is enhanced by hormones such as cholecystokinin and, especially, gastrin, and is suppressed by secretin, glucagon, VIP and somatostatin.

Due to the free passage of fluid through the pylorus, the rate of its evacuation depends mainly on the pressure difference in the stomach and duodenum, with the main regulator being the pressure in the proximal stomach. Evacuation of solid food particles from the stomach depends mainly on the resistance of the pylorus, and therefore on the size of the particles. In addition to its filling, particle size and viscosity of the contents, small intestinal receptors play a role in regulating gastric emptying.

Acidic contents are evacuated from the stomach more slowly than neutral ones, hyperosmolar contents are evacuated more slowly than hypoosmolar ones, and lipids (especially those containing fatty acids with chains of more than 14 carbon atoms) are slower than the breakdown products of proteins (except tryptophan). Both nervous and hormonal mechanisms are involved in the regulation of evacuation, and secretin plays a particularly important role in its inhibition.
Large solid particles cannot be eliminated from the stomach during the digestive emptying phase. Such indigestible particles with a diameter of more than 3 mm can pass through the pylorus only in the fasting phase with the participation of a special mechanism of the myoelectric complex.
Basal acid secretion in the stomach occurs at a rate of 2-3 mmol H+ (hydrogen ions) per hour (..., and in the presence of a tumor secreting gastrin, it increases 10-20 times). The maximum secretion rate per 1 kg of weight is 10-35 mmol H + per hour. For women this value is slightly less than for men. In patients with duodenal ulcer, the average value is higher than in healthy people, however, there are large individual differences..."

"...Protein denaturation processes subsequently facilitate the action of proteases.

Three groups of enzymes work in the stomach: a) salivary enzymes - amylases, which act for the first 30-40 seconds - until an acidic environment appears; b) enzymes of gastric juice - proteases (pepsin, gastrixin, gelatinase), which break down proteins into polypeptides and gelatin; c) lipases that break down fats.

Approximately 10% of the peptide bonds in proteins are broken down in the stomach, resulting in the formation of water-soluble products. The duration and activity of lipases are short, since they usually act only on emulsified fats in a slightly alkaline environment. The products of depolymerization are partial glycerides.

From the stomach, the food mass, which has a liquid or semi-liquid consistency, enters the small intestine (total length 5-6 m), the upper part of which is called the duodenum (in it the processes of enzymatic hydrolysis are most intense).

In the duodenum, food is exposed to three types of digestive juices, which are the juice of the pancreas (pancreatic or pancreatic juice), the juice produced by liver cells (bile) and the juice produced by the mucous membrane of the intestine itself (intestinal juice).
The secretion of pancreatic juice begins 2-3 minutes after eating and lasts 6-14 hours, i.e. during the entire period of food remaining in the duodenum.

In addition to pancreatic juice, bile, which is produced by liver cells, enters the duodenum from the gallbladder. It has a slightly alkaline pH value and enters the duodenum 5-10 minutes after eating. The daily secretion of bile in an adult is 500-700 ml.

In the cavity of the duodenum, under the action of enzymes secreted by the pancreas, hydrolytic breakdown of most large molecules occurs - proteins (and the products of their incomplete hydrolysis), carbohydrates and fats. [Znatоk Ne: By the way, ] From the duodenum, food passes to the end of the small intestine.

The destruction of the main components of food is completed in the small intestine. In addition to cavity digestion, membrane digestion occurs in the small intestine, in which the same groups of enzymes located on the inner surface of the small intestine participate. The final stage of digestion occurs in the small intestine - the absorption of nutrients (products of the breakdown of macronutrients, micronutrients and water). It is estimated that up to 2-3 liters of liquid containing dissolved nutrients can be absorbed in the small intestine in an hour.

Like digestive processes, transport processes in the small intestine are unevenly distributed. Absorption of minerals, monosaccharides and partially fat-soluble vitamins occurs in the upper part of the small intestine. In the middle section, water- and fat-soluble vitamins, protein and fat monomers are absorbed, in the lower section, vitamin B12 and bile salts are absorbed.

In the large intestine, which is 1.5-4.0 m long, digestion is practically absent. Here water (up to 95%), salts, glucose, some vitamins and amino acids produced by intestinal microflora are absorbed (absorption is only 0.4-0.5 liters per day). The large intestine is the habitat and intensive reproduction of various microorganisms that consume indigestible food residues, resulting in the formation of organic acids (lactic, propionic, butyric, etc.), gases (carbon dioxide, methane, hydrogen sulfide), as well as some toxic substances (phenol , indole, etc.), neutralized in the liver..."

Food chemistry: Textbook for university students studying in the following areas: 552400 “Food Technology” / A.P. Nechaev, Svetlana Evgenievna Traubenberg, A.A. Kochetkova; Nechaev, Alexey Petrovich. - 2nd edition, revised and corrected. - SPb.: GIORD, 2003.- 640 p. : ill.5-901065-38-0, 3000 copies.

"...With a typical diet for residents of developed countries with a low content of coarse fiber substances in food, the time for the passage of chyme from the ileocecal valve to the rectum is 2-3 days. Food particles located in the center of the chyme can pass through the large intestine in a shorter time The transit time of 2-3 days was established experimentally. The subject was given small particles of a control substance (marker) along with food and the time required for 80% of the marker to be excreted in the feces was recorded. With an increase in the content of coarse fiber components in the food the evacuation time may be reduced while stool weight increases.In African rural residents, who consume a lot of fibrous substances, the average evacuation time from the large intestine is 36 hours, and the stool weight is 480 g, while for residents of European cities the corresponding values ​​are 72 hours and 110 g The long duration of evacuation from the large intestine indicates that its motility is mainly non-propulsive. Contractions of the circular muscles do not have an orderly, progressive nature; they can be observed in several places at the same time and serve rather to mix the intestinal contents than to promote it. With sequential contraction of the circular muscles of two adjacent haustra, the intestinal contents move approximately 10 cm, but the movement can occur in both proximal and distal directions. This reduction may sometimes involve more than two segments. Simple haustral contractions account for more than 90% of all colon motility..."
Textbook “HUMAN PHYSIOLOGY”, edited by R. Schmidt and G. Tevs, in 3 volumes, 3rd edition, volume 3. Translation from English by Ph.D. honey. Sciences N. N. Alipova, dr med. Sciences V.L. Bykova, Ph.D. biol. Sciences M. S. Morozova, Ph.D. biol. Sciences Zh.P. Shuranova, edited by academician. P. G. Kospok. page 780

A significant factor complicating the correct determination of the time of digestion of food and its presence in the gastrointestinal tract, as described at the very beginning of the note, is the very nature of the nutrient (I’m talking about proteins, fats and carbohydrates, of course) and their combinations. Establishing any unambiguous time values ​​in humans is actually quite difficult. Accordingly, among other methods of determining the time of assimilation of certain products, they are used as experiments in vivo(i.e. in natural conditions), and in vitro(i.e. in an artificially created environment close to natural conditions, these can be experiments “in vitro”, in specialized devices simulating the work of a particular environment/organ).

There is a fairly extensive study (on the number of tested nutrients and their combinations) in which the approximate time of absorption of certain nutrients and their combinations was studied “in vitro”. It is, of course, approximate, and these data cannot be used as the only correct ones, but the information itself is quite interesting. It's true she's on English language, and to be honest, I was too lazy to translate this entire array, but oh well, many words should be clear anyway, and if something is not clear, then any online translator will help you.

And yes, if you have (or already have) relevant sources of information (I mean scientific literature with an exact indication of the source) about the rate of absorption of certain products/nutrients/combinations thereof, then I will get this data and add it to the article .

Sun Jin Hura, Beong Ou Limb, Eric A. Deckerc, D. Julian McClementsc. In vitro human digestion models for food applications. Food Chemistry. Volume 125, Issue 1, 1 March 2011, Pages 1-12

LINKS:
1. VISUAL PHYS0L0GY | S. Silbernagl, A. Despopoulos | Translation from English by A. S. Belyakova, A. A. Sinyushin | Moscow | BINOMIAL. Knowledge Laboratory.
2. Camilleri M, Colemont LJ, Phillips SF, Brown ML, Thomforde GM, Chapman N, Zinsmeister AR. Human gastric emptying and colonic filling of solids characterized by a new method. Am J Physiol. 1989 Aug;257(2 Pt 1):G284-90.
3. "Gastrointestinal Transit: How Long Does It Take?" by R. Bowen.
4. Martin Culen, Anna Rezacova, Josef Jampilek and Jiri Dohnal. Designing a dynamic dissolution method: A review of instrumental options and corresponding physiology of stomach and small intestine.
5. Textbook “HUMAN PHYSIOLOGY”, edited by R. Schmidt and G. Tevs, in 3 volumes, 3rd edition, volume 3. Translation from English Ph.D. honey. Sciences N. N. Alipova, Dr. med. Sciences V.L. Bykova, Ph.D. biol. Sciences M. S. Morozova, Ph.D. biol. Sciences Zh.P. Shuranova, edited by academician. P. G. Kospok.
6. Food chemistry: Textbook for university students studying in the following areas: 552400 “Food Technology” / A.P. Nechaev, Svetlana Evgenievna Traubenberg, A.A. Kochetkova; Nechaev, Alexey Petrovich. - 2nd edition, revised and corrected. - SPb.: GIORD, 2003.- 640 p. : ill.5-901065-38-0, 3000 copies.
7. "Food Structures, Digestion and Health" Edited by Mike Boland, Matt Golding and Harjinder Singh.

The digestive system includes organs that perform mechanical and chemical processing of food, absorption of nutrients and water into the blood or lymph, formation and removal of undigested food debris. The digestive system consists of the alimentary canal and digestive glands, information about which is given in the figure.

Let us consider schematically the passage of food through the digestive tract.

Food first enters oral cavity which is limited by the jaws: upper (fixed) and lower (movable). The jaws contain teeth - organs used for biting and grinding (chewing) food. An adult has 28-32 teeth. An adult tooth consists of a soft part - pulp, penetrated blood vessels and nerve endings. The pulp is surrounded by dentin, a bone-like substance. Dentin makes up the basis of the tooth - it consists of most of the crown (the part of the tooth protruding above the gum), the neck (the part of the tooth located at the border of the gum) and the root (the part of the tooth located deep in the jaw). The crown of the tooth is covered with tooth enamel, the hardest substance human body, serving to protect the tooth from external influences (increased wear, pathogenic microbes, excessively cold or hot food, etc. factors).

Teeth According to their purpose, they are divided into: incisors, canines and molars. The first two types of teeth are used for biting food and have a sharp surface, and the last one is for chewing it and for this purpose it has a wide chewing surface. An adult has 4 canines and an incisor, and the remaining teeth are molars.

In the oral cavity, during the process of chewing food, it is not only crushed, but also mixed with saliva, turns into a food bolus. This mixing in the oral cavity is carried out using the tongue and cheek muscles.

The oral mucosa contains sensitive nerve endings– receptors with the help of which it perceives taste, temperature, consistency and other qualities of food. Excitation from the receptors is transmitted to the centers of the medulla oblongata. As a result, according to the laws of the reflex, the salivary, gastric and pancreatic glands begin to work sequentially, then the above-described act of chewing and swallowing occurs. Swallowing is an act characterized by pushing food into the pharynx using the tongue and then, as a result of contraction of the muscles of the larynx, into the esophagus.

Pharynx- funnel-shaped canal lined with mucous membrane. The upper wall of the pharynx is fused with the base of the skull; at the border between the VI and VII cervical vertebrae of the pharynx, narrowing, it passes into the esophagus. Food enters the esophagus from the mouth through the pharynx; in addition, air passes through it, coming from the nasal cavity and from the mouth to the larynx. (The crossover of the digestive and respiratory tracts occurs in the pharynx.)

Esophagus- a cylindrical muscular tube located between the pharynx and stomach, 22-30 cm long. The esophagus is lined with a mucous membrane; in its submucosa there are numerous own glands, the secretion of which moistens food as it passes through the esophagus into the stomach. The movement of the food bolus through the esophagus occurs due to wave-like contractions of its wall - contraction of individual sections alternates with their relaxation.

From the esophagus, food enters the stomach. Stomach- reminiscent of appearance retort, a distensible organ that is part of the digestive tract and is located between the esophagus and the duodenum. It connects to the esophagus through the cardiac opening, and to the duodenum through the pyloric opening. The inside of the stomach is covered with a mucous membrane, which contains glands that produce mucus, enzymes and hydrochloric acid.

The stomach is a reservoir for absorbed food, which is mixed in it and partially digested under the influence of gastric juice. Produced by the gastric glands located in the gastric mucosa, gastric juice contains hydrochloric acid and the enzyme pepsin; These substances take part in the chemical processing of food entering the stomach during the process of digestion. Here, under the influence of gastric juice, proteins are broken down.

This - along with the mixing effect exerted on the food muscle layers stomach - turns it into a partially digested semi-liquid mass (chyme), which then enters the duodenum. The mixing of chyme with gastric juice and its subsequent expulsion into the small intestine is carried out by contracting the muscles of the stomach walls.

Small intestine occupies most of the abdominal cavity and is located there in the form of loops. Its length reaches 4.5 m. The small intestine, in turn, is divided into the duodenum, jejunum and ileum. It is here that most of the processes of digestion of food and absorption of its contents take place. The inner surface area of ​​the small intestine is increased by the presence of a large number of finger-like projections called villi.

Next to the stomach is the duodenum, which is isolated in the small intestine, because the cystic duct of the gallbladder and the pancreatic duct flow into it.

The duodenum is the first of three sections of the small intestine. Starts from gatekeeper stomach and reaches the jejunum. The duodenum receives bile from the gallbladder (via the common bile duct) and pancreatic juice from the pancreas.

In the walls of the duodenum there are a large number of glands that secrete an alkaline secretion rich in mucus, which protects the duodenum from the effects of acidic chyme entering it from the stomach.

Skinny intestine- part of the small intestine. The jejunum makes up approximately two-fifths of the entire small intestine. It connects the duodenum and ileum.

Small intestine contains many glands that secrete intestinal juice. This is where the main digestion of food and absorption of nutrients into the lymph and blood occurs. The movement of chyme in the small intestine occurs due to longitudinal and transverse contractions of the muscles of its wall.

From the small intestine, food enters colon 1.5 m long, which begins with a sac-like protrusion - cecum, from which a 15 cm appendix extends. It is believed to have some protective functions. Colon- the main part of the large intestine, which includes four sections: the ascending, transverse, descending and sigmoid colon.

The large intestine primarily absorbs water, electrolytes and fiber and ends in the rectum, which collects undigested food. Rectum- the terminal part of the large intestine (approximately 12 cm long), which starts from the sigmoid colon and ends at the anus.

During the act of defecation, feces pass through the rectum. Further, this undigested food through anus(anus) is excreted from the body.

So, nutrition should be rational. But what does this mean practically? What physiological and biochemical processes occur in the body when food enters it? What disorders and diseases does poor nutrition lead to?

First of all, let us recall, perhaps, forgotten school knowledge about the digestive system and its structure.

The digestive system begins with the oral cavity, which passes into the pharynx, and then into the esophagus. Next is the stomach, located slightly to the left of the lower row of ribs. Under the stomach is the pancreas, and on the right under the ribs is the liver, in the lower part of which the gallbladder and bile duct are located.

The stomach passes into the duodenum - the bile duct and pancreatic duct flow into it. Next is the jejunum. The small intestine ends with the ileum. It consists of the duodenum, jejunum and ileum. The latter passes into the large intestine, and directly at this “knee” is the cecum with the appendix. Following the cecum are the ascending and descending parts of the large intestine, the sigmoid colon and then the rectum. At the back, in the lumbar part, are the kidneys.

Each organ, each part of this complex life support factory plays its role and takes on certain functions.

Food undergoes physical and chemical changes when digested. The first ones boil down to the fact that it is crushed, mixed, and partially dissolved. The second are processes of extraordinary complexity that have a certain sequence. Thanks to the action of enzymes, proteins, fats and carbohydrates are broken down. The enzymes themselves are formed in special secretory cells of the digestive glands and enter the digestive system along with saliva, gastric, pancreatic and intestinal juices.

Let's briefly follow the passage of food through the digestive tract

In the oral cavity, it is chewed, moistened with saliva and enters the pharynx, esophagus, and then the stomach. Here it is digested under the influence of gastric juice for 6-8 hours. In this case, hydrochloric acid contained in gastric juice plays a major role in the ongoing reactions. It also contains proteases - they break down proteins and lipases that affect fats.

It is interesting that the secretion of gastric juice depends on nutrition - with prolonged use of carbohydrate foods, it decreases and increases with the systematic consumption of foods containing protein.

In the intestines, under the influence of pancreatic - otherwise pancreatic - juice, further processing occurs. It is extremely rich in digestive enzymes that break down proteins and polypeptides, as well as fats and carbohydrates.

The secretion of gastric juice begins almost immediately after eating and lasts 6-14 hours, and it is longest when we eat fatty foods.

In the duodenum, bile, produced by the liver, takes part in the digestion process. Its role is great, and disturbances in its formation entail changes in the process of digestion and absorption of fats.

Digestion continues in the small intestine under the influence of intestinal juice, which takes on an extremely important function - the activation of inactive enzymes of pancreatic juice. In the small intestine, the penultimate stage of protein hydrolysis is completed, that is, the ion exchange reaction between proteins and water.

Digested as a result of all these complex biochemical processes, food substances in the form of low-molecular compounds are absorbed into the lymph and blood.

The products of digestion of nutrients absorbed in the intestine enter the blood of the portal vein, which enters the liver. Here, glucose is formed from fructose and galactose and enters the general bloodstream. Its excess is converted into glycogen - the main storage carbohydrate - a polysaccharide formed in the liver and muscles. The exchange of amino acids occurs in the liver.

Feces accumulate in the large intestines and are eliminated from the body through the rectum.

It is easy to imagine what cataclysms can occur in this entire astronomically complex system, verified by nature and perfected, if failures begin in any areas of it. And they are caused by various reasons, and in many respects by unreasonable nutrition.

Of the most common inflammatory processes we could call gastritis (inflammation of the stomach), duodenitis (duodenum), enterocolitis (small and large intestine), proctitis (rectum), etc.

Obesity occupies a special place among the violations of rational nutrition. This is what we will talk about.