Digestion occurs in the small intestine. Small intestine, its functions and sections

The functional units are the crypt and the villus. A villus is an outgrowth of the intestinal mucosa, a crypt is, on the contrary, a depression.

INTESTINAL JUICE is slightly alkaline (pH=7.5-8), consists of two parts: (a) the liquid part of the juice (water, salts, without enzymes) is secreted by crypt cells; (b) the dense part of the juice (“mucous lumps”) consists of epithelial cells that are continuously exfoliated from the top of the villi. (The entire mucous membrane of the small intestine is completely renewed in 3-5 days). The dense part contains more than 20 enzymes. Some enzymes are adsorbed on the surface of the glycocalyx (intestinal, pancreatic enzymes), the other part of the enzymes is part of the cell membrane of microvilli.. (A microvillus is an outgrowth of the cell membrane of enterocytes. Microvilli form a “brush border”, which significantly increases the area on which hydrolysis and suction). Enzymes are highly specialized, necessary for the final stages of hydrolysis.

Cavitary and parietal digestion occurs in the small intestine.

Cavity digestion– splitting of large polymer molecules into oligomers in the intestinal cavity under the action of intestinal juice enzymes.

Parietal digestion– cleavage of oligomers to monomers on the surface of microvilli under the action of enzymes fixed on this surface.

IMPORTANCE OF WALL DIGESTION: (1) high rate of hydrolysis,

(2) in a sterile environment, because microbes do not penetrate the “brush border” and cannot feed on hydrolysis products, which (3) are immediately absorbed, because the final stages of hydrolysis are associated with the transport of monomers across the cell membrane into the enterocyte.

REGULATION OF SECRETION IN THE SMALL INTESTINE. The main mechanism of regulation is local nervous due to the submucosal plexuses of the enteric nervous system. Reflex arcs close intramurally, in the intestinal wall. (The influences of the sympathetic and parasympathetic nerves are long-term, adaptive).

Humoral regulation: (a) paracrine (also local) and (b) endocrine (long-term, adaptive in nature).

STUDY OF INTESTINAL SECRETION in animal experiments is carried out using an intestinal fistula (Thiri-Vella fistula): both ends of an isolated intestinal loop are brought to the surface of the abdominal wall. The mesentery with the vessels and nerves passing through it is preserved. The release of intestinal juice from the fistula occurs only in response to irritation of the mucous membrane of an isolated loop of the small intestine (local nervous regulation mechanism).

MOTORITY OF THE SMALL INTESTINE

(1) Tone, slow tonic waves. Myogenic regulation (the ability of smooth muscles to automate, which increases in response to myocyte stretching).

(2) Stirring(non-propulsive) movements: (a) rhythmic segmentation (periodic contraction of small sections of circular muscles); (b) pendulum movements (periodic contraction and relaxation of longitudinal muscles).

(3) Promoting(peristaltic) movements. Peristalsis- These are complex coordinated contractions of the circular and longitudinal muscle layers with the participation of excitatory and inhibitory neurons of the enteric nervous system. As a result, chyme moves in a strictly defined direction - from the oral end of the gastrointestinal tract to the anal.

(In the large intestine, antiperistalsis normally exists, i.e. the movement of chyme in the opposite direction).

Parasympathetic nerves enhance intestinal motility, sympathetic nerves-slow down.

ABSORPTION IN THE SMALL INTESTINE

Villi is an organ of absorption. The villus is covered with a layer of enterocytes; blood and lymphatic capillaries and nerve fibers pass inside it. The villus works like a pump by contracting and relaxing smooth muscle elements.

Absorption is based on the mechanisms of active and passive transport of substances through the cell membrane of enterocytes.

Passive mechanisms: filtration, diffusion, osmosis.

Active mechanisms: primary active transport (mainly the potassium-sodium pump in the basal part of the membrane); secondary active transport (sodium-dependent transport in the apical part of the membrane) and endocytosis.

Glucose– secondary active sodium-dependent transport into the enterocyte and facilitated diffusion from the enterocyte into the intercellular fluid and further into the blood.

Amino acids– four transport systems for different groups of amino acids, working on the same principle. In addition, similar transport systems exist for tri- and dipeptides.

Monoglycerides and fatty acids– in the intestinal lumen they are included in micelles consisting of bile acids and phospholipids. In this complex they are delivered to the absorptive surface (microvilli of enterocytes). The products of fat breakdown, dissolving in the cell membrane, pass into the enterocyte, where neutral fats are synthesized from them. Then, in combination with proteins (chylomicrons), fats enter the lymphatic capillaries of the villi. Bile acids remain in the intestinal lumen, are recycled, and are absorbed into the blood in the distal ileum (ileum).

To study absorption in animal experiments, methods of applying a common lymphatic duct fistula and angiostomy are used.

DIGESTION IN THE LARGE INTESTINE

There are no villi, only crypts. Liquid intestinal juice contains practically no enzymes. The mucous membrane of the colon is renewed in 1-1.5 months.

Normal is important microflora large intestine: (1) fermentation of fiber (short-chain fatty acids are formed, which are necessary to nourish the epithelial cells of the colon itself); (2) rotting of proteins (in addition to toxic substances, biologically active amines are formed); (3) synthesis of B vitamins; (4) suppression of the growth of pathogenic microflora.

In the large intestine, water and electrolytes are absorbed, as a result of which a small amount of dense masses is formed from liquid chyme. 1-3 times a day, a powerful contraction of the colon moves the contents into the rectum and removes it out (defecation).

Test questions on the topic “Digestion”

What is digestion?

The importance of digestion for the body.

What chemical process underlies digestion?

Name the initial and final products of digestion.

Name 3 digestive functions of the gastrointestinal tract.

Name the non-digestive functions of the gastrointestinal tract.

What digestive processes occur in the oral cavity?

What nutrients are broken down in the mouth?

Name three pairs of major salivary glands.

Composition of saliva.

Functions of saliva.

Name the enzymes in saliva. What nutrients do they break down?

What determines the amount and composition of saliva?

What is the adaptive nature of salivation?

Why is the regulation of the salivary glands called complex-reflex?

Innervation of the salivary glands.

The influence of parasympathetic nerves on salivation (mediator?)

The influence of sympathetic nerves on salivation (mediator?)

Diagram of the reflex arc of the salivary reflex.

Methods for studying salivation in animals and humans.

Composition of gastric juice.

Characteristics of gastric juice enzymes.

The meaning of hydrochloric acid.

Features of secretion in the fundic and pyloric sections of the stomach.

Three phases of gastric secretion.

Name the secretory nerves of the stomach.

What is gastrin? How does it affect gastric secretion?

What is secretin? How does it affect gastric secretion?

What is cholecystokinin? How does it affect gastric secretion?

How does the transition of chyme from the stomach to the duodenum occur?

The secretion of which glands enters the duodenum?

Composition of pancreatic juice.

Why is pancreatic juice slightly alkaline?

Three phases of pancreatic secretion.

Name the secretory nerves of the pancreas.

How do secretin and cholecystokinin affect pancreatic secretion?

Composition of bile.

The meaning of bile.

How is gallbladder bile different from liver bile?

Where does bile formation occur? How is it regulated?

How does bile secretion occur? How is it regulated?

What is the bile acid cycle?

Intestinal juice. Its features.

What is parietal digestion?

The meaning of parietal digestion.

The main mechanism for regulating secretion in the small intestine.

Does intestinal juice leak from the Thiri-Vella fistula if food is in the oral cavity?

Does intestinal juice leak from the Thiri-Vella fistula if food is in the stomach?

Does intestinal juice leak from a Thiri-Vella fistula if the normal digestion process occurs in the main part of the small intestine?

What is the organ of absorption in the small intestine?

What mechanisms underlie absorption?

How does glucose absorption occur?

How are amino acids absorbed?

How are fat breakdown products absorbed?

What are the features of secretion in the large intestine?

What are the features of motility in the large intestine?

What are the features of absorption in the large intestine?

The importance of the microflora of the large intestine.

Food from the stomach enters the small intestine, or more specifically, the duodenum. The duodenum is the thickest section of the human small intestine, its length is about 30 cm. The small intestine also includes the jejunum (length about 2.5 m), ileum (length about 3 m).

The inner walls of the duodenum are essentially composed of many small villi. Under the mucus layer there are small glands whose enzyme helps break down proteins. carbohydrates. This is where fats and proteins are. Carbohydrates, under the influence of digestive juices and enzymes, are broken down so that the body can easily absorb them. First of all, the pancreatic duct and the bile duct open into the duodenum. So, the food here is affected by:

intestinal juice;
pancreatic juice;
bile.

Types of digestion in the small intestine

Contact digestion: with the help of enzymes (maltase, sucrase), digestion occurs into simple particles such as amino acids and monosaccharides. This splitting occurs directly in the small intestine itself. But at the same time, small particles of food remain, which were broken down by the action of intestinal juice and bile, but not enough for them to be absorbed by the body.

Such particles fall into the cavity between the villi, which cover the mucous membrane in this section with a dense layer. Parietal digestion takes place here. The concentration of enzymes here is much higher. And therefore, in this way, the process speeds up noticeably.

The initial purpose of the villi, by the way, was to increase the total area of the suction surface. The length of the duodenum is quite short. Before food reaches the large intestine, the body needs time to take all the nutrients from the processed food.

Small intestinal absorption

Thanks to the huge number of different villi, folds and sections, as well as the special structure of the lining epithelial cells, the intestines can absorb up to 3 liters of fluid consumed per hour (both consumed in pure form and with food).

All substances that enter the blood this way are transported through the veins to the liver. This is, of course, important for the body, for the very reason that not only useful substances can be consumed with food, but also various toxins and poisons - this is connected, first of all, with the environment, as well as with a large intake of medications, poor-quality food and etc. In the liver, such blood is disinfected and purified. In 1 minute, the liver can process up to 1.5 liters of blood.

Finally, through the sphincter, the remains of unprocessed food from the ileum enter the large intestine, and there the final process of digestion occurs, namely the formation of feces.

It should also be noted that in the large intestine, digestion practically no longer occurs. Basically, only fiber is digested, and then also under the influence of enzymes obtained in the small intestine. The length of the large intestine is up to 2 meters. In the large intestine, in fact, mainly only the formation of feces and fermentation occurs. This is why it is so important to monitor the health and normal functioning of the small intestine, because if any problems arise with the duodenum, the processing of consumed food will not be completed properly and, accordingly, the body will not receive a whole range of nutrients.

Three points affecting the absorption of food

1. Intestinal juice

It is produced directly by the glands of the small intestine and is complemented by its action to the general process of digestion in this department.

The consistency of intestinal juice is a colorless, cloudy liquid mixed with mucus and epithelial cells. Has an alkaline reaction. The composition includes more than 20 important digestive enzymes (aminopeptidases, dipeptidases).

2. Pancreatic (pancreatic) juice

The pancreas is the second largest in the human body. The weight can reach 100g, and the length can be 22 cm. Essentially, the pancreas is divided into 2 separate glands:

exocrine (produces about 700 ml of pancreatic juice per day);
endocrine (synthesizes hormones).

Pancreatic juice is essentially a clear, colorless liquid with a pH of 7.8 - 8.4. The production of pancreatic juice begins 3 minutes after eating and lasts 6-14 hours. Most pancreatic juice is secreted when eating highly fatty foods.

The endocrine gland simultaneously synthesizes several hormones that have an important effect on processed food:

trypsin. Responsible for the breakdown of proteins into amino acids. Initially, trypsin is produced as inactive, but in combination with enterokinase it is activated;
lipase. Breaks down fats into fatty acids or glycerol. The effect of lipase is enhanced after interaction with bile;
maltase. It is responsible for the breakdown into monosaccharides.

Scientists have found that the activity of enzymes and their quantitative composition in the human body directly depends on the human diet. The more he consumes a particular food, the more enzymes are produced that are necessary specifically for its breakdown.

3. Bile

The largest gland in the body of any person is the liver. It is responsible for the synthesis of bile, which is subsequently accumulated by the gallbladder. The volume of the gallbladder is relatively small - about 40 ml. Bile in this part of the human body is contained in a very concentrated form. Its concentration is approximately 5 times higher than the initially produced liver bile. It’s just that mineral salts and water are absorbed into the body all the time, and only the concentrate remains, which has a thick greenish consistency with a large number of pigments. Bile begins to enter the human small intestine approximately 10 minutes after eating and is produced while the food is in the stomach.

Bile not only affects the breakdown of fats and the absorption of fatty acids, but also increases the secretion of pancreatic juice and improves peristalsis in each part of the intestine.

Up to 1 liter of bile is secreted into the intestines of a healthy person per day. It consists mainly of fats, cholesterol, mucus, soap and lecithin.

Possible diseases

As mentioned earlier, problems with the small intestine can lead to dire consequences - the body will not receive enough nutrients necessary for the normal functioning of the body. This is why it is so important to identify any problem at an early stage in order to begin treatment as quickly as possible. So, possible diseases of the small intestine:

Chronic inflammation. It may occur after a severe infection due to a decrease in the amount of enzymes produced. In this case, first of all, a strict diet is prescribed. Inflammation can also develop after surgery as a result of pathogenic bacteria or some kind of infection.
Allergy. It can manifest itself as a component of the body’s general allergic reaction to the action of an allergen or have a local location. Pain in this case is a reaction to an allergen. First of all, it is worth eliminating its effect on the body.
Celiac enteropathy is a serious disease accompanied by an emergency condition. The disease is the inability of the body to completely process and absorb proteins. As a result, severe intoxication of the body occurs with unprocessed food particles. The patient will have to follow a strict diet throughout his life, completely eliminating grains and other foods containing gluten from the diet.

Causes of diseases of the small intestine

Sometimes diseases of the small intestine can be associated with age-related changes, hereditary predisposition or congenital pathology. But there are a number of provoking factors that, if possible, should be excluded from life in order to prevent future health problems:

smoking, alcohol abuse;
unhealthy diet (too much food consumed, abuse of fatty, smoked, salty and spicy foods);
too many medications consumed;
stress, depression;
infectious diseases (advanced stages).

Nausea, vomiting, diarrhea, weakness, abdominal pain are the most pronounced symptoms of pathologies, after detection of which you should immediately consult a doctor.

The sooner the disease is diagnosed and then treatment is started, the higher the likelihood of soon forgetting about the problem without any consequences for the body.

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Processes occur in the human small intestine

Human small intestine: anatomy, functions and process of food digestion

The anatomy of the digestive system includes the oral cavity, esophagus, gastrointestinal tract and accessory organs. All parts of the digestive system are functionally interconnected - food processing begins in the oral cavity, and final processing of food is ensured in the stomach and intestines.

The human small intestine is part of the digestive tract. This department is responsible for the final processing of substrates and absorption (absorption).

What is the small intestine?

Vitamin B12 is absorbed in the small intestine.

The human small intestine is a narrow tube about six meters long.

This section of the digestive tract got its name due to its proportional features - the diameter and width of the small intestine are much smaller than those of the large intestine.

The small intestine is divided into the duodenum, jejunum and ileum. The duodenum is the first segment of the small intestine, located between the stomach and jejunum.

The most active digestive processes take place here; it is here that pancreatic and gallbladder enzymes are secreted. The jejunum follows the duodenum, its length on average is one and a half meters. Anatomically, the jejunum and ileum are not separated.

The mucous membrane of the jejunum on the inner surface is covered with microvilli that absorb nutrients, carbohydrates, amino acids, sugar, fatty acids, electrolytes and water. The surface of the jejunum increases due to special fields and folds.

Vitamin B12 and other water-soluble vitamins are absorbed in the ileum. In addition, this part of the small intestine is also involved in the absorption of nutrients. The functions of the small intestine are somewhat different from the stomach. In the stomach, food is crushed, ground and initially decomposed.

In the small intestine, substrates are broken down into their constituent parts and absorbed for transport to all parts of the body.

Anatomy of the small intestine

The small intestine is in contact with the pancreas.

As we noted above, in the digestive tract the small intestine follows immediately after the stomach. The duodenum is the initial section of the small intestine, following the pyloric section of the stomach.

The duodenum begins with the bulb, bypasses the head of the pancreas and ends in the abdominal cavity with the ligament of Treitz.

The peritoneal cavity is a thin connective tissue surface covering some of the abdominal organs.

The rest of the small intestine is literally suspended in the abdominal cavity by the mesentery, which is attached to the posterior abdominal wall. This structure allows parts of the small intestine to be freely moved during surgery.

The jejunum occupies the left side of the abdominal cavity, while the ileum is located on the upper right side of the abdominal cavity. The inner surface of the small intestine contains mucous folds called circular rings. Such anatomical structures are more numerous in the initial part of the small intestine and contract closer to the distal ileum.

The assimilation of food substrates is carried out with the help of primary cells of the epithelial layer. Cubic cells located throughout the entire area of the mucous membrane secrete mucus, which protects the intestinal walls from an aggressive environment.

Enteric endocrine cells secrete hormones into the blood vessels. These hormones are essential for digestion. Flat cells of the epithelial layer secrete lysozyme, an enzyme that destroys bacteria. The walls of the small intestine are tightly connected to the capillary networks of the circulatory and lymphatic systems.

The walls of the small intestine consist of four layers: mucosa, submucosa, muscularis and adventitia.

Functional significance

The small intestine consists of several sections.

The human small intestine is functionally connected to all organs of the gastrointestinal tract; the digestion of 90% of food substrates ends here, the remaining 10% is absorbed in the large intestine.

The main function of the small intestine is to absorb nutrients and minerals from food. The digestion process consists of two main parts.

The first part involves the mechanical processing of food by chewing, grinding, beating and mixing - all this occurs in the mouth and stomach. The second part of food digestion involves the chemical processing of substrates, which uses enzymes, bile acids and other substances.

Read: Small intestine: length and role in the digestive process

All this is necessary in order to decompose whole products into individual components and absorb them. Chemical digestion occurs in the small intestine - this is where the most active enzymes and excipients are found.

Ensuring digestion

In the small intestine, proteins are broken down and fats are digested.

After rough processing of products in the stomach, it is necessary to decompose the substrates into separate components accessible for absorption.

Protein decomposition. Proteins, peptides and amino acids are affected by special enzymes, including trypsin, chymotrypsin and intestinal wall enzymes. These substances break down proteins into small peptides. The process of protein digestion begins in the stomach and ends in the small intestine.
Digestion of fats. Special enzymes (lipases) secreted by the pancreas serve this purpose. Enzymes break down triglycerides into free fatty acids and monoglycerides. An auxiliary function is provided by bile juices secreted by the liver and gall bladder. Bile juices emulsify fats - they separate them into small drops accessible to the action of enzymes.
Digestion of carbohydrates. Carbohydrates are divided into simple sugars, disaccharides and polysaccharides. The body needs the main monosaccharide – glucose. Pancreatic enzymes act on polysaccharides and disaccharides, promoting the decomposition of substances into monosaccharides. Some carbohydrates are not fully absorbed in the small intestine and end up in the large intestine, where they become food for intestinal bacteria.

Absorption of food in the small intestine

Decomposed into small components, nutrients are absorbed by the mucous membrane of the small intestine and move into the blood and lymph of the body.

Absorption is ensured by special transport systems of digestive cells - each type of substrate is provided with a separate method of absorption.

The small intestine has a significant internal surface area, which is essential for absorption. The circular circles of the intestine contain a large number of villi that actively absorb food substrates. Types of transport in the small intestine:

Fats undergo passive or simple diffusion.
Fatty acids are absorbed by diffusion.
Amino acids enter the intestinal wall using active transport.
Glucose enters through secondary active transport.
Fructose is absorbed by facilitated diffusion.

Read: Small intestine: length and role in the digestive process

To better understand the processes, it is necessary to clarify the terminology. Diffusion is the process of absorption along a concentration gradient of substances; it does not require energy. All other types of transport require cellular energy. We have found that the human small intestine is the main section of food digestion in the digestive tract.

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How does digestion occur in the small intestine, what enzymes are involved in this, and the mechanism of their action?

Digestion in the small intestine

intestinal juice;
pancreatic juice;
bile.

Types of digestion in the small intestine

Small intestinal absorption

Finally, through the sphincter, the remains of unprocessed food from the ileum enter the large intestine, and there the final process of digestion occurs, namely the formation of feces.

Three points affecting the absorption of food

1. Intestinal juice

It is produced directly by the glands of the small intestine and is complemented by its action to the general process of digestion in this department.

2. Pancreatic (pancreatic) juice

The pancreas is the second largest in the human body. The weight can reach 100g, and the length can be 22 cm. Essentially, the pancreas is divided into 2 separate glands:

exocrine (produces about 700 ml of pancreatic juice per day);
endocrine (synthesizes hormones).

The endocrine gland simultaneously synthesizes several hormones that have an important effect on processed food:

trypsin. Responsible for the breakdown of proteins into amino acids. Initially, trypsin is produced as inactive, but in combination with enterokinase it is activated;
lipase. Breaks down fats into fatty acids or glycerol. The effect of lipase is enhanced after interaction with bile;
maltase. It is responsible for the breakdown into monosaccharides.

3. Bile

Bile not only affects the breakdown of fats and the absorption of fatty acids, but also increases the secretion of pancreatic juice and improves peristalsis in each part of the intestine.

Up to 1 liter of bile is secreted into the intestines of a healthy person per day. It consists mainly of fats, cholesterol, mucus, soap and lecithin.

Possible diseases

Chronic inflammation. It may occur after a severe infection due to a decrease in the amount of enzymes produced. In this case, first of all, a strict diet is prescribed. Inflammation can also develop after surgery as a result of pathogenic bacteria or some kind of infection.
Allergy. It can manifest itself as a component of the body’s general allergic reaction to the action of an allergen or have a local location. Pain in this case is a reaction to an allergen. First of all, it is worth eliminating its effect on the body.
Celiac enteropathy is a serious disease accompanied by an emergency condition. The disease is the inability of the body to completely process and absorb proteins. As a result, severe intoxication of the body occurs with unprocessed food particles. The patient will have to follow a strict diet throughout his life, completely eliminating grains and other foods containing gluten from the diet.

Causes of diseases of the small intestine

smoking, alcohol abuse;
unhealthy diet (too much food consumed, abuse of fatty, smoked, salty and spicy foods);
too many medications consumed;
stress, depression;
infectious diseases (advanced stages).

Nausea, vomiting, diarrhea, weakness, abdominal pain are the most pronounced symptoms of pathologies, after detection of which you should immediately consult a doctor.

The sooner the disease is diagnosed and then treatment is started, the higher the likelihood of soon forgetting about the problem without any consequences for the body.

ozdravin.ru

The process of digestion in the human body: by time

Nutrition is a complex process, as a result of which substances necessary for the body are supplied, digested and absorbed. Over the past ten years, a special science dedicated to nutrition - nutritionology - has been actively developing. In this article we will look at the process of digestion in the human body, how long it lasts and how to manage without a gallbladder.

The structure of the digestive system

The digestive system is represented by a set of organs that ensure the absorption of nutrients by the body, which are a source of energy for it, necessary for cell renewal and growth.

The digestive system consists of: the oral cavity, pharynx, esophagus, stomach, small intestine, colon and rectum.

Digestion in the human oral cavity

The process of digestion in the mouth involves grinding food. In this process, vigorous processing of food with saliva occurs, interaction between microorganisms and enzymes. After treatment with saliva, some of the substances dissolve and their taste appears. The physiological process of digestion in the oral cavity involves the breakdown of starch into sugars by the amylase enzyme contained in saliva.

Let's follow the action of amylase using an example: while chewing bread for a minute, you can feel a sweet taste. The breakdown of proteins and fats does not occur in the mouth. On average, the digestion process in the human body takes approximately 15-20 seconds.

Digestive department - stomach

The stomach is the widest part of the digestive tract, has the ability to expand in size, and can accommodate huge amounts of food. As a result of the rhythmic contraction of the muscles of its walls, the process of digestion in the human body begins with thorough mixing of food with gastric juice, which has an acidic environment.

Once a lump of food enters the stomach, it remains there for 3-5 hours, during which time it is subjected to mechanical and chemical treatment. Digestion in the stomach begins with exposure of food to gastric juice and the hydrochloric acid that is present in it, as well as pepsin.

As a result of digestion in the human stomach, proteins are digested with the help of enzymes into low molecular weight peptides and amino acids. The digestion of carbohydrates, which begins in the mouth, stops in the stomach, which is explained by the loss of amylases’ activity in an acidic environment.

Digestion in the stomach cavity

The process of digestion in the human body occurs under the influence of gastric juice containing lipase, which is capable of breaking down fats. In this case, great importance is given to the hydrochloric acid of gastric juice. Under the influence of hydrochloric acid, the activity of enzymes increases, denaturation and swelling of proteins is caused, and a bactericidal effect is exerted.

The physiology of digestion in the stomach is that food enriched with carbohydrates, which remains in the stomach for about two hours, undergoes an evacuation process faster than food containing proteins or fats, which lingers in the stomach for 8-10 hours.

Food that is mixed with gastric juice and partially digested, being in a liquid or semi-liquid consistency, passes into the small intestine in small portions at simultaneous intervals. In which department does the digestion process still take place in the human body?

Digestive department - small intestine

Digestion in the small intestine, into which the bolus of food enters from the stomach, has the most important place, from the point of view of the biochemistry of the absorption of substances.

In this section, the intestinal juice consists of an alkaline environment due to the arrival of bile, pancreatic juice and secretions of the intestinal walls into the small intestine. The digestive process in the small intestine does not go quickly for everyone. This is facilitated by the presence of an insufficient amount of the lactase enzyme, which hydrolyzes milk sugar, which is associated with the indigestibility of whole milk. During the digestion process, more than 20 enzymes are consumed in this part of the human body, for example, peptidases, nucleases, amylase, lactase, sucrose, etc.

The activity of this process in the small intestine depends on the three intersecting sections of which it consists - the duodenum, jejunum and ileum. Bile formed in the liver enters the duodenum. Here food is digested thanks to the pancreatic juice and bile that act on it. Pancreatic juice, which is a colorless liquid, contains enzymes that promote the breakdown of proteins and polypeptides: trypsin, chymotrypsin, elastase, carboxypeptidase and aminopeptidase.

Role of the liver

An important role in the process of digestion in the human body (we will briefly mention this) is played by the liver, in which bile is formed. The peculiarity of the digestive process in the small intestine is due to the assistance of bile in emulsifying fats, absorbing triglycerides, activating lipase, also helps stimulate peristalsis, inactivate pepsin in the duodenum, has a bactericidal and bacteriostatic effect, increases hydrolysis and absorption of proteins and carbohydrates.

Bile does not contain digestive enzymes, but is important in the dissolution and absorption of fats and fat-soluble vitamins. If bile is not produced enough or is secreted into the intestines, then the processes of digestion and absorption of fats are disrupted, as well as an increase in their excretion in their original form with feces.

What happens in the absence of a gallbladder?

The person is left without the so-called small sac, in which bile was previously deposited “in reserve.”

Bile is needed in the duodenum only if there is food in it. And this is not a constant process, only during the period after eating. After some time, the duodenum is emptied. Accordingly, the need for bile disappears.

However, the work of the liver does not stop there; it continues to produce bile. It is for this purpose that nature created the gallbladder, so that the bile secreted in the intervals between meals does not deteriorate and is stored until the need for it arises.

And here the question arises about the absence of this “bile storage”. As it turns out, a person can do without a gallbladder. If the operation is performed on time and other diseases associated with the digestive organs are not provoked, then the absence of a gallbladder in the body is easily tolerated. The timing of the digestion process in the human body is of interest to many.

After surgery, bile can only be stored in the bile ducts. After bile is produced by liver cells, it is released into the ducts, from where it is easily and continuously sent to the duodenum. Moreover, this does not depend on whether the food is taken or not. It follows that after the gallbladder has been removed, food must be taken frequently and in small portions for the first time. This is explained by the fact that there is not enough bile to process large portions of bile. After all, there is no longer a place for its accumulation, but it enters the intestine continuously, albeit in small quantities.

It often takes time for the body to learn to function without a gallbladder and to find the necessary place to store bile. This is how the digestion process works in the human body without a gallbladder.

Digestive department - large intestine

The remains of undigested food move into the large intestine and remain there for approximately 10 to 15 hours. Here the following digestive processes occur in the intestines: water absorption and microbial metabolization of nutrients.

In the digestion that occurs in the large intestine, food ballast substances, which include indigestible biochemical components: fiber, hemicellulose, lignin, gums, resins, waxes, play a huge role.

The structure of food affects the speed of absorption in the small intestine and the time of movement through the gastrointestinal tract.

Some of the dietary fiber that is not broken down by enzymes belonging to the gastrointestinal tract is destroyed by microflora.

The large intestine is the place of formation of feces, which includes: undigested food debris, mucus, dead cells of the mucous membrane and microbes that continuously multiply in the intestines and which cause the processes of fermentation and gas formation. How long does the digestion process in the human body last? This is a common question.

Breakdown and absorption of substances

The process of absorption of nutrients occurs throughout the entire digestive tract, which is covered with hairs. On 1 square millimeter of mucous membrane there are about 30-40 villi.

In order for the process of absorption of substances that dissolve in fats, or rather fat-soluble vitamins, to occur, fats and bile must be present in the intestines.

Absorption of water-soluble products such as amino acids, monosaccharides, mineral ions occurs with the participation of blood capillaries.

In a healthy person, the entire digestion process takes from 24 to 36 hours.

This is how long the digestion process in the human body lasts.

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Digestion in the human small intestine

The role of the small intestine in digestion is very important and, one might say, is the final stage in the hydrolysis of food to the final substances that our body needs.

General information about the human small intestine

The main stages of digestion are contained in the small intestine, which is the longest organ, with an absorption surface area of almost 200 square meters. It is in this part of the gastrointestinal tract that most beneficial substances are absorbed, as well as poisons, toxins, drugs, and xenobiotics that enter the body orally. In addition to digestion, absorption and transportation of all these substances, the small intestine performs the functions of hormone secretion, as well as immune defense.

The small intestine includes 3 sections:

duodenum;
jejunum;
ileum.

However, there is no clearly defined boundary between the last two sections.

All sections of the small intestine are layered and have 4 membranes:

mucous;
submucosa;
muscular;
serous.

How does digestion occur in the small intestine?

Food from the stomach enters the duodenum, where it is exposed to bile, as well as pancreatic enzymes and intestinal juices. Digestion in the human small intestine works to a greater extent on the absorption of useful substances, and therefore it is here that the final breakdown of eaten food occurs with the help of intestinal juice, which contains three groups of enzymes. At the same time, there are two types of digestion in the small intestine: cavity and parietal. Unlike strip digestion, parietal digestion in the small intestine carries about 80% of the final stages of hydrolysis and, at the same time, absorption of substances consumed in food.

Enzymes produced by the glands of the small intestine can only break down short chains of peptides and sugars that get there as a result of preliminary “work” with food from other organs. After the complete breakdown of food into glucose, vitamins, amino acids, fatty acids, minerals and others, the important process of their absorption into the blood occurs. In this way, the cells of the entire human body are saturated.

The epithelial cells of the small intestine also form a so-called mesh, through which only completely broken down substances will be passed, and unchanged molecules of starch or protein, for example, will not be able to penetrate and are transported for further “processing”.

The digestive system of the human body serves to provide important functions. It is designed to nourish our body with useful substances and remove toxins. It consists of the digestive organs - the pharynx and mouth, the stomach and esophagus, as well as the intestines, consisting of the small and large intestines. The digestive system also includes auxiliary organs (liver and gallbladder, salivary glands and others).

The small intestine is located in the body immediately after the stomach and ends with the large intestine. It is divided into several parts, representing the following types of intestines:

duodenum;
skinny;
ileum.

Processes occurring in the small intestine

The small intestine is involved in processes such as the digestion of food with its subsequent absorption, as well as the movement of remaining food to the following sections. The food entering the small intestine is a porridge that has been pre-treated with saliva and gastric juice.

Under the action of enzymes and bile, as well as intestinal juice, digested products are broken down and absorbed through the smallest villi into the circulatory system. The action of enzymes in the small intestine helps convert proteins and fats, as well as carbohydrates, into simpler substances. In addition to the absorption of nutrients, the small intestine absorbs drugs, poisons and toxins.

The processes of processing nutrients in the digestive system can also be divided according to the place of their passage, with cavity digestion and parietal digestion being distinguished. The first type of digestion occurs in the mouth, after which it continues in other parts of the digestive tract and at the same time has different severity of the process. Parietal digestion takes place in three stages: it begins in the mucous layer, then continues in the glycocalyx and in the superficial membrane of the enterocyte, where with the help of enzymes the final breakdown of complex nutrients into simple ones is carried out.

In addition to the fact that the small intestine takes part in the processes of absorption, digestion and transportation of food, it is also involved in the production of hormones and protects the immune system against foreign proteins.

Semi-liquid food gruel from the stomach passes in separate portions into the next section of the digestive canal - the intestines. It has three departments: duodenum, small intestine And colon.

25–30 cm long (about 12 fingers) is the initial section of the small intestine. It goes around the pancreas, the ducts of which, together with the bile duct of the liver, open in its descending part.

The main function of the small intestine is the final breakdown of nutrients and their absorption into the blood. In the duodenum and small intestine, proteins are broken down into amino acids, fats into glycerol and fatty acids, and carbohydrates into glucose.

The largest gland, the liver, plays a special role in digestion. Its weight is 1.5–2 kg, which is 1/40 of the total body weight.

The liver is located on the right side of the abdominal cavity. The liver is a vital organ of the human body, the diverse functions of which make it possible to call it the “main chemical laboratory” of the body. The liver neutralizes low-molecular toxic substances that enter the blood; bile is continuously produced, which accumulates in the gallbladder and enters the duodenum when the digestion process takes place in it.

In the liver, nutrients are deposited, some blood cells are destroyed, and blood is retained. 1.5 liters of blood flows through the liver within one minute, and up to 2000 liters per day. Blood in the liver flows very slowly through the capillaries. In addition to the hepatic veins and arteries, the liver enters the liver through special hepatic gates from below. portal vein. It is formed from many hundreds of veins carrying blood from all digestive organs. Not a single drop of blood from the digestive organs reaches the heart without passing through the liver.

The liver produces about 1 liter of bile per day. It activates enzymes of pancreatic and intestinal juices, crushes fats into tiny drops, increasing the surface of their interaction with enzymes. Bile increases the solubility of fatty acids, which facilitates their absorption, stimulates intestinal motility and delays putrefactive processes in the intestines.

The pancreas secretes digestive juice into the duodenum, which contains enzymes that break down all the nutrients in food. Under the influence of some enzymes, the breakdown of proteins into amino acids, which began in the stomach, is completed; under the influence of others, the breakdown of nucleic acids, carbohydrates and fats occurs.

I. P. Pavlov in his studies proved that pancreatic juice is secreted under the influence of hydrochloric acid entering the duodenum from the stomach. English scientists have found that the walls of the small intestine, under the influence of hydrochloric acid, secrete a special substance - secretin. Absorbed into the blood, it is brought to the pancreas and activates its activity. This influence was called humoral.

Small intestine 5–6 m long, forms many loops in the abdominal cavity. The mucous membrane of the small intestine contains many glands that secrete intestinal juice.

Intestinal mucosa, intestinal villi

The inner surface of the small intestine appears velvety due to the villi, through which the products of the breakdown of proteins, fats, and carbohydrates are absorbed. A huge number of villi (from 2000 to 3000 per 1 cm2) significantly increase the surface of the mucous membrane of the small intestine.

The walls of the villi consist of single-layer epithelium, and inside there are blood vessels and capillaries, a lymphatic vessel, nerves and smooth muscle cells that provide their motor activity.

Amino acids, glucose, vitamins, and mineral salts in the form of aqueous solutions are absorbed into the blood by the capillaries of the villi. Fatty acids and glycerol pass into the epithelial cells of the villi, where they form fat molecules characteristic of the human body, which enter the lymph and, after passing the barrier of the lymph nodes, enter the blood. The considerable length, folding of the small intestine and the presence of villi increase the absorption surface area of this section of the digestive system. Lymph nodes are part of the body's overall immune system. The appendix, the appendix, is especially rich in them, inflammation of which causes appendicitis.

Colon about 1.5–2 m long, it begins with the cecum, which has a vermiform appendix - the appendix, continues with the colon and ends with the rectum.

Undigested food remains pass through the large intestine within 12 hours. During this time, most of the water is absorbed into the blood. The mucous membrane of the large intestine does not have villi. Its glands produce juice containing few enzymes, but a lot of mucus, which facilitates the movement and elimination of undigested food residues. There are many bacteria in the large intestine. They are necessary for normal digestion; with their participation, some vitamins are formed. Feces formed in the colon enter the rectum and are expelled from there.

All blood from the digestive canal collects in the portal vein and passes through the liver. The liver neutralizes about 95% of toxic substances formed during the incomplete breakdown of proteins and as a result of the activity of microbes. This liver function was studied in detail by I.P. Pavlov, calling it a barrier function.