DIGESTIVE FUNCTIONS OF THE DIGESTIVE TRACT

The digestive tract (gastrointestinal tract) is a part of the digestive system that has a tubular structure and includes the esophagus, stomach, large and small intestines, in which mechanical and chemical processing of food and absorption of hydrolysis products occur.

Secretion of the digestive glands

Secretion is an intracellular process of formation of a specific product (secret) of a certain functional purpose from substances that have entered the cell and its release from the glandular cell. Secrets enter through the system of secretory passages and ducts into the cavity of the digestive tract.

The secretion of the digestive glands ensures the delivery of secrets to the cavity of the digestive tract, the ingredients of which hydrolyze nutrients (secretion of hydrolytic enzymes and their activators), optimize the conditions for this (according to pH and other parameters - the secretion of electrolytes) and the state of the hydrolysable substrate (emulsification of lipids with bile salts, denaturation of proteins with hydrochloric acid), perform a protective role (mucus, bactericidal substances, immunoglobulins). .

The secretion of the digestive glands is controlled by nervous, humoral and paracrine mechanisms. The effect of these influences - excitation, inhibition, modulation of glandulocyte secretion - depends on the type of efferent nerves and their mediators, hormones and other physiologically active substances, glandulocytes, membrane receptors on them, the mechanism of action of these substances on intracellular processes. The secretion of the glands is directly dependent on the level of their blood supply, which in turn is determined by the secretory activity of the glands, the formation of metabolites in them - vasodilators, the effect of secretion stimulants as vasodilators. The amount of secretion of the gland depends on the number of glandulocytes simultaneously secreting in it. Each gland consists of glandulocytes that produce different secretion components and has significant regulatory features. This provides a wide variation in the composition and properties of the secret secreted by the gland. It also changes as you move along the ductal system of the glands, where some components of the secret are absorbed, others are released into the duct by its glandulocytes. Changes in the quantity and quality of the secret are adapted to the type of food taken, the composition and properties of the contents of the digestive tract.

For the digestive glands, the main secretion-stimulating nerve fibers are the parasympathetic cholinergic axons of the postganglionic neurons. Parasympathetic denervation of glands causes hypersecretion of glands (especially salivary glands, to a lesser extent gastric glands) of varying duration (for several days and weeks) - paralytic secretion, which is based on several mechanisms (see section 9.6.3).

Sympathetic neurons inhibit stimulated secretion and exert trophic influences on the glands, enhancing the synthesis of secretion components. The effects depend on the type of membrane receptors - α- and β-adrenergic receptors through which they are realized.

Many gastrointestinal regulatory peptides act as stimulants, inhibitors, and modulators of glandular secretion.

Under natural conditions, the quantity, composition and dynamics of the secretion of the digestive glands are determined by the ratio of simultaneously and sequentially acting regulatory mechanisms.

Answer from Kristingo[guru]
The digestive glands include the liver, gallbladder, and pancreas.
The main task of the liver is to produce the vital substances that the body receives in food: carbohydrates, proteins and fats.
Proteins are important for growth, cell renewal, and the production of hormones and enzymes. In the liver, proteins are decomposed and converted into endogenous structures.
This process takes place in the liver cells. Carbohydrates are converted into energy, especially a lot of them in food rich in sugar. The liver converts sugar into glucose for immediate use and into glycogen for storage. Fats also provide energy and, like sugar, are converted by the liver into endogenous fat.
In addition to storing and producing chemicals, the liver is also responsible for breaking down toxins and waste products. This occurs within the liver cells by decomposition or neutralization. Decay products from the blood are excreted with the help of bile, which is produced by liver cells.
The produced bile enters the hepatic canal through numerous ducts. It is stored in the gallbladder and exits through the bile duct (at which point it replaces the hepatic duct) into the duodenum as needed.
The pancreas is actually a combination of two glandular systems: especially important hormones such as insulin and glucagon are secreted directly into the blood by the endocrine part of the pancreas. The exocrine pancreas secretes digestive enzymes into the duodenum through a duct system.

Answer from 2 answers[guru]

Hello! Here is a selection of topics with answers to your question: what is the role of the digestive glands?

Answer from Yatiana Kuzmina[guru]
Apparently, food to digest, judging by the name.

Answer from Olga Osipova[guru]
The secretion of the digestive glands ensures the delivery of secrets into the cavity of the digestive tract, the ingredients of which hydrolyze nutrients (secretion of hydrolytic enzymes and their activators), optimize the conditions for this (according to pH and other parameters - the secretion of electrolytes) and the state of the hydrolysable substrate (emulsification of lipids by bile salts, denaturation of proteins with hydrochloric acid), perform a protective role (mucus, bactericidal substances, immunoglobulins). .
The secretion of the digestive glands is controlled by nervous, humoral and paracrine mechanisms. The effect of these influences - excitation, inhibition, modulation of glandulocyte secretion - depends on the type of efferent nerves and their mediators, hormones and other physiologically active substances, glandulocytes, membrane receptors on them, the mechanism of action of these substances on intracellular processes. The secretion of the glands is directly dependent on the level of their blood supply, which in turn is determined by the secretory activity of the glands, the formation of metabolites in them - vasodilators, the effect of secretion stimulants as vasodilators. The amount of secretion of the gland depends on the number of glandulocytes simultaneously secreting in it. Each gland consists of glandulocytes that produce different secretion components and has significant regulatory features. This provides a wide variation in the composition and properties of the secret secreted by the gland. It also changes as you move along the ductal system of the glands, where some components of the secret are absorbed, others are released into the duct by its glandulocytes. Changes in the quantity and quality of the secret are adapted to the type of food taken, the composition and properties of the contents of the digestive tract.
For the digestive glands, the main secretion-stimulating nerve fibers are the parasympathetic cholinergic axons of the postganglionic neurons. Parasympathetic denervation of glands causes hypersecretion of glands (especially salivary glands, to a lesser extent gastric glands) of varying duration (for several days and weeks) - paralytic secretion, which is based on several mechanisms (see section 9.6.3).
Sympathetic neurons inhibit stimulated secretion and exert trophic influences on the glands, enhancing the synthesis of secretion components. The effects depend on the type of membrane receptors - α- and β-adrenergic receptors through which they are realized.

Digestive glands:

The digestive glands include the liver, gallbladder, and pancreas.

Liver. It is located in the right hypochondrium. Its weight is 1.5 kg. Has a soft texture. The color of the liver is red-brown. On the liver, the upper and lower surfaces, as well as the anterior and posterior edges, are distinguished. On the liver there are grooves that divide it into 4 lobes: right, left, square and caudal. The right furrow in its anterior section expands and forms a fossa in which the gallbladder.

The main task of the liver is to produce the vital substances that the body receives in food: carbohydrates, proteins and fats. Proteins are important for growth, cell renewal, and the production of hormones and enzymes. In the liver, proteins are decomposed and converted into endogenous structures. This process takes place in the liver cells. Carbohydrates are converted into energy, especially a lot of them in food rich in sugar. The liver converts sugar into glucose for immediate use and into glycogen for storage. Fats also provide energy and, like sugar, are converted by the liver into endogenous fat. In addition to storing and producing chemicals, the liver is also responsible for breaking down toxins and waste products. This occurs within the liver cells by decomposition or neutralization. Decay products from the blood are excreted with the help of bile, which is produced by liver cells.

Structural unit of the liver - a lobule or hepatic acinus - the formation of a prismatic shape, 1-2 mm in diameter. Each lobule of hepatic beams is located along the radius to the central vein. They consist of 2 rows of epithelial cells, and between them is a bile capillary. Hepatic beams are tubular glands from which the liver is built. The secret from the bile capillaries then enters the hepatic duct leaving the liver.

Gallbladder. Has a bottom, body and neck. The gallbladder, the excretory duct of the liver, forms the common bile duct, which flows into the duodenum. Length 8-12cm, width 3-5cm, capacity 40-60cm3. The wall of the mucous and muscular membranes, the lower surface is covered with a serous membrane, the peritoneum.

Pancreas. It secretes a secret into the duodenum. Weighs 70-80g. Has a soft texture. It has a head, body and tail. The length of the gland is 16-22 cm. The general direction is transverse. Somewhat flattened in the anteroposterior direction. It has an anterior, posterior, and inferior surface. It secretes up to 2 liters of digestive juice per day, containing amylase, lipase, trypsinogen. In the alveolar glandular part, the islets of Langerhans are located, which forms the hormone insulin, which regulates the process of absorption of carbohydrates by cells.

Glands of the stomach. 3 types: cardiac (mucus secretion, simple tubular), fundic (the form of branched tubes that open in the gastric pits, secrete pepsin) and pyloric (branched, produce pepsin and mucous secretion).

Secretion of the digestive glands. Secretion is an intracellular process of formation of a specific product (secret) of a certain functional purpose from substances that have entered the cell and its release from the glandular cell. Secrets enter through the system of secretory passages and ducts into the cavity of the digestive tract.

The secretion of the digestive glands ensures the delivery of secrets to the cavity of the digestive tract, the ingredients of which hydrolyze nutrients, optimize the conditions for this and the state of the hydrolyzed substrate, perform a protective role (mucus, bactericidal substances, immunoglobulins). The secretion of the digestive glands is controlled by nervous, humoral and paracrine mechanisms. The effect of these influences - excitation, inhibition, modulation of glandulocyte secretion - depends on the type of efferent nerves and their mediators, hormones and other physiologically active substances, glandulocytes, membrane receptors on them, the mechanism of action of these substances on intracellular processes. The secretion of the glands is directly dependent on the level of their blood supply, which in turn is determined by the secretory activity of the glands, the formation of metabolites in them - vasodilators, the effect of secretion stimulants as vasodilators. The amount of secretion of the gland depends on the number of glandulocytes simultaneously secreting in it. Each gland consists of glandulocytes that produce different secretion components and has significant regulatory features. This provides a wide variation in the composition and properties of the secret secreted by the gland. It also changes as you move along the ductal system of the glands, where some components of the secret are absorbed, others are released into the duct by its glandulocytes. Changes in the quantity and quality of the secret are adapted to the type of food taken, the composition and properties of the contents of the digestive tract. For the digestive glands, the main secretion-stimulating nerve fibers are the parasympathetic cholinergic axons of the postganglionic neurons. Parasympathetic denervation of the glands causes hypersecretion of glands of varying duration - paralytic secretion, which is based on several mechanisms. Sympathetic neurons inhibit stimulated secretion and exert trophic influences on the glands, enhancing the synthesis of secretion components. The effects depend on the type of membrane receptors - α- and β-adrenergic receptors through which they are realized. Many gastrointestinal regulatory peptides act as stimulants, inhibitors, and modulators of glandular secretion.

Liver functions: 1. Protein metabolism. 2. Carbohydrate metabolism. 3. Lipid metabolism. 4. Exchange of vitamins. 5. Water and mineral metabolism. 6. Exchange of bile acids and bile formation. 7.Pigment exchange. 8. Hormone exchange. 9.Detoxifying function.

Table of contents of the topic "Functions of the Digestive System (GIT). Types of Digestion. Hormones of the Gastrointestinal Tract. Motor Function of the Gastrointestinal Tract.":
1. Physiology of digestion. Physiology of the digestive system. Functions of the digestive system (GIT).
2. The state of hunger and satiety. Hunger. Feeling full. Hyperphagia. Aphagia.

4. Types of digestion. Own type of digestion. autolytic type. intracellular digestion. extracellular digestion.
5. Hormones of the gastrointestinal tract. Place of formation of gastrointestinal hormones. Effects caused by hormones of the gastrointestinal tract.
6. Motor function of the gastrointestinal tract. Smooth muscles of the digestive tract. Gastrointestinal sphincters. Contractile activity of the intestine.
7. Coordination of contractile activity. Slow rhythmic vibrations. Longitudinal muscle layer. Effect of catecholamines on myocytes.

secretory function- the activity of the digestive glands that produce a secret (digestive juice), with the help of enzymes of which the physicochemical transformation of the food taken is carried out in the gastrointestinal tract.

Secretion- the process of formation of a secret of a certain functional purpose from substances that have come from the blood into the secretory cells (glandulocytes) and its release from the glandular cells into the ducts of the digestive glands.

Secretory cycle of the glandular cell consists of three successive and interrelated stages - the absorption of substances from the blood, the synthesis of them secretory product and secretion I. The cells of the digestive glands, according to the nature of the secretion produced, are divided into protein-, mucoid- and mineral-secreting.

digestive glands are richly vascularised. From the blood flowing through the vessels of the gland, secretory cells absorb water, inorganic and organic low molecular weight substances (amino acids, monosaccharides, fatty acids). This process is carried out due to the activity of ion channels, basement membranes of capillary endotheliocytes, membranes of the secretory cells themselves. From the absorbed substances on the ribosomes of the granular endoplasmic reticulum, primary secretory product, which undergoes further biochemical transformations in the Golgi apparatus and accumulates in the condensing vacuoles of glandulocytes. Vacuoles turn into zymogen (proenzyme) granules covered with a lipoprotein membrane, with the help of which the final secretory product is transported through the glandulocyte membrane into the gland ducts.

Zymogen granules are removed from the secretory cell by the mechanism of exocytosis: after the granule moves to the apical part of the glandulocyte, two membranes (granules and cells) merge, and through the holes formed, the contents of the granules enter the passages and ducts of the gland.

According to the nature of the selection secret this cell type is merocrine.

For holocrine cells(cells of the superficial epithelium of the stomach) is characterized by the transformation of the entire mass of the cell into a secret as a result of its enzymatic destruction. Apocrine cells secrete a secret with the apical (apical) part of their cytoplasm (cells of the ducts of the human salivary glands during embryogenesis).

Secrets of the digestive glands consist of water, inorganic and organic substances. Of greatest importance for the chemical transformation of food substances are enzymes (substances of a protein nature), which are catalysts for biochemical reactions. They belong to the group of hydrolases capable of attaching H + and OH to the digested substrate, turning high-molecular substances into low-molecular ones. Depending on the ability to break down certain substances enzymes are divided into 3 groups: glucolytic (hydrolyzing carbohydrates to di- and monosaccharides), proteolytic (hydrolyzing proteins to peptides, peptones and amino acids) and lipolytic (hydrolyzing fats to glycerol and fatty acids). The hydrolytic activity of enzymes increases within certain limits with an increase in the temperature of the digested substrate and the presence of activators in it, their activity decreases under the influence of inhibitors.

Maximum hydrolytic activity of enzymes saliva, gastric and intestinal juices are found at different pH optimums.

The gastric cavity is one of the important organs. This is where the digestion of food begins. When food enters the mouth, gastric juice begins to be actively produced. When it enters the stomach, it lends itself to the action of hydrochloric acid and enzymes. This phenomenon occurs as a result of the activity of the digestive glands of the stomach.

The stomach is part of the digestive system. In appearance, it resembles an oblong cavity ball. When the next portion of food arrives, gastric juice begins to actively stand out in it. It consists of different substances, have an unusual consistency or volume.

First, food enters the mouth, where it is mechanically processed. It then enters the stomach through the esophagus. In this organ, food is prepared for further assimilation by the body under the action of acids and enzymes. The food lump takes on a liquefied or mushy state. It gradually passes into the small intestine, and then into the large intestine.

Appearance of the stomach

Each organism is individual. This also applies to the state of internal organs. Their sizes may vary, but there is a certain norm.

1. The length of the stomach is in the range of 16-18 centimeters.
2. Width can vary from 12 to 15 centimeters.
3. The thickness of the walls is 2-3 centimeters.
4. Capacity reaches 3 liters in an adult with a full stomach. On an empty stomach, its volume does not exceed 1 liter. In childhood, the organ is much smaller.

The gastric cavity is divided into several sections:

• cardiac region. Located at the top closer to the esophagus;
• body of the stomach. It is the main part of the body. In size and volume, it is the largest;
• bottom. This is the lower part of the organ;
• pyloric section. It is located at the outlet and connects to the small intestine.

The epithelium of the stomach is covered with glands. The main function is considered to be the synthesis of important components that help in the digestion and absorption of food.

This list includes:

• hydrochloric acid;
• pepsin;
• slime;
• gastrin and other types of enzymes.

Most of it is excreted through the ducts and enters the lumen of the organ. If they are combined together, then the digestive juice is obtained, which helps in metabolic processes.

Classification of the gastric glands

The glands of the stomach differ in location, the nature of the secreted contents and the method of excretion. In medicine, there is a certain classification of glands:

• own or fundic glands of the stomach. They are located at the bottom and in the body of the stomach;
• pyloric or secretory glands. They are located in the pyloric region of the stomach. Responsible for the formation of the food bolus;
• cardiac glands. Located in the cardial part of the organ.

Each of them performs its functions.

Glands of their own type

These are the most common glands. There are about 35 million pieces in the stomach. Each of the glands covers an area of ​​100 millimeters. If you calculate the total area, then it reaches a huge size and reaches the mark of 4 square meters.

Own glands are usually divided into 5 types.

1. Major exocrinocytes. They are located at the bottom and in the body of the stomach. Cellular structures are rounded. It has a pronounced synthetic apparatus and basophilia. The apical region is covered with microvilli. The diameter of one granule is 1 micromillimeter. This type of cell structure is responsible for the production of pepsinogen. When mixed with hydrochloric acid, pepsin is formed.
2. Overlaying cell structures. Settled outside. They come into contact with the basal parts of the mucous or main exocrinocytes. They are large and irregular. This type of cellular structures are placed singly. They can be found in the area of ​​the body and neck of the stomach.
3. Mucous or cervical mucocytes. Such cells are divided into two types. One of them is located in the body of the gland and has dense nuclei in the basal area. The apical part is covered with a large number of oval and rounded granules. These cells also contain mitochondria and the Golgi apparatus. If we talk about other cellular structures, then they are located in the neck of their own glands. Their nuclei are flattened. In rare cases, they take an irregular shape and are located at the base of the endocrinocytes.
4. Argyrophilic cells. They are part of the glandular composition and belong to the APUD system.
5. undifferentiated epithelial cells.

Own glands are responsible for the synthesis of hydrochloric acid. They also produce an important component in the form of a glycoprotein. It promotes the absorption of vitamin B12 in the ileal region of the intestine.

Pyloric type glands

This type of gland is located in the area where the stomach meets the small intestine. There are about 3.5 million of them. Pyloric glands have several distinguishing features in the form of:

• rare location on the surface;
• the presence of more branching;
• expanded lumen;
• lack of parental cellular structures.

Pyloric glands are divided into two main types.

1. Endogenous. Cells are not involved in the process of producing digestive juice. But they are able to produce substances that are instantly absorbed into the blood and are responsible for the reactions of the organ itself.
2. Mucocytes. They are responsible for the production of mucus. This process helps to protect the shell from the adverse effects of gastric juice, hydrochloric acid and pepsin. These components soften the food mass and facilitate its sliding through the intestinal canal.

The terminal section has a cellular composition that, in appearance, resembles its own glands. The nucleus has a flattened shape and is located closer to the base. Includes a large number of dipeptidases. The secret produced by the gland is distinguished by an alkaline environment.

The mucous membrane is dotted with deep pits. At the exit, it has a pronounced fold in the form of a ring. Such a pyloric sphincter is formed as a result of a strong circular layer in the muscle membrane. It helps to dose food and send it to the intestinal canal.

Glands of the cardiac type

They are located at the beginning of the organ. Close to the junction with the esophagus. The total number is 1.5 million. In appearance and secretion they are similar to pyloric. They are divided into 2 main types:

• endogenous cells;
• mucous cells. They are responsible for softening the food bolus and the preparatory process before digestion.

Such glands do not take part in the digestive process.

All three types of glands belong to the exocrine group. They are responsible for secretion production and its entry into the gastric cavity.

glands of the endocrine type

There is another category of glands, which are called endocrine. They do not take part in the digestion of food. But they have the ability to produce substances that enter directly into the blood and lymph. They are needed to stimulate or inhibit the functionality of organs and systems.

Endocrine glands can secrete:

• gastrin. Needed to stimulate the activity of the stomach;
• somatostatin. Responsible for the inhibition of the body;
• melatonin. They are responsible for the daily cycle of the digestive organs;
• histamine. Thanks to them, the process of accumulation of hydrochloric acid is launched. They also regulate the functionality of the vascular system in the digestive tract;
• enkephalin. Show an analgesic effect;
• vasointerstitial peptides. They show a double effect in the form of vasodilation and activation of the pancreas;
• bombesin. The processes of producing hydrochloric acid are launched, the functionality of the gallbladder is controlled.

Endocrine glands influence the development of the stomach, and also play an important role in the functioning of the stomach.

Scheme of the work of the glands of the stomach

Scientists have done a lot of research on the functionality of the stomach. And to determine his condition, they began to perform histology. This procedure involves taking material and examining it under a microscope.

Thanks to histological data, it was possible to imagine how the glands in the organ work.

1. Smell, sight, and taste trigger food receptors in your mouth. They are responsible for signaling that it is time to form gastric juice and prepare the organs for the digestion of products.
2. Mucus production begins in the cardiac region. It protects the epithelium from self-digestion, and also softens the food bolus.
3. Own or fundal cellular structures are engaged in the production of digestive enzymes and hydrochloric acid. Acid allows you to transfer products to a liquefied state, and also disinfects them. After that, enzymes are taken for the chemical breakdown of proteins, fats and carbohydrates to a molecular state.
4. Active production of all substances occurs at the initial stage of eating. The maximum is reached only by the second hour of the digestive process. Then all this is preserved until the food bolus passes into the intestinal canal. After emptying the stomach, the production of components stops.

If the stomach is affected, histology will indicate problems. The most common factors include the use of junk food and chewing gum, overeating, stressful situations, depression. All this can lead to the development of serious problems in the digestive tract.

To distinguish between the functionality of the glands, it is worth knowing the structure of the stomach. When problems arise, the doctor prescribes additional drugs that reduce excessive secretion, and also create a protective film that covers the walls and mucous membrane of the organ.