The pancreas is considered one of the vital organs. It not only actively participates in the process of food digestion, but also has endocrine functions. Internal secretion is carried out thanks to special cells located in the tail of this anatomical formation. The site where pancreatic hormones are produced is called the islet of Langerhans. This anatomical education has a huge functional value. Thanks to him it is ensured carbohydrate metabolism.

What is the islet of Langerhans: purpose

Endocrine cells are located throughout the body. One of the places where they accumulate is the pancreas. The islets of Langerhans are localized in the caudal part of the organ. They are cellular clusters that produce biologically active substances- hormones. The importance of the islets of Langerhans is enormous. It consists in the production of a normal amount of hormones necessary for metabolic processes. The islets of Langerhans of the pancreas have the following functions:

1. Glycemic control.
2. Regulation of enzyme activity.
3. Participation in fat metabolism.

Due to the normal functioning of the islet apparatus, conditions such as diabetes and hypoglycemia do not develop. Cell damage occurs during acute and chronic inflammation- pancreatitis.

Histological structure of islets

The islet of Langerhans was discovered in the 19th century. It represents a concentration of endocrine elements. In children, these formations occupy about 6% of the total area of ​​the organ. By adulthood, the endocrine part decreases and amounts to only 2%. The parenchyma of the tail contains about a million islets of Langerhans. They have their own abundant blood supply and innervation. Each island consists of lobules, which are covered by connective tissue. In addition, it is also located outside endocrine formations. The cells inside the islets are arranged in a mosaic pattern. The activity of endocrine clusters is provided by the vagus and sympathetic nerves. Insular cells are located in the center of the lobule. They reduce blood glucose levels. In the peripheral part of the lobules there are alpha and delta cells. The first produce a counter-insular hormone - glucagon. The latter are necessary for the regulation of endocrine and exocrine activity.

What cells are there in the islets of Langerhans?

The islets of Langerhans produce several types of cells. All of them are involved in the release of biologically active substances - peptides and hormones. Most of the islets of Langerhans are represented by beta cells. They are located in the center of each lobule. These cells are very important because they produce insulin.

The second most important are the alpha cells of the pancreas. They occupy a quarter of the island's area. Alpha cells are required for the production of glucagon. This hormone is an insulin antagonist.

In the peripheral part of the islets of Langerhans, PP and delta cells are produced. The number of the former is about 1/20 of the part. The function of these formations is the production of pancreatic polypeptide. Delta cells are required to produce somatostatin. This substance is involved in the regulation of carbohydrate metabolism.

Islet cells are difficult to regenerate. Therefore, when these structures are damaged, it is often impossible to restore their function.

Hormonal activity of the islets of Langerhans

Despite the fact that the islet of Langerhans is small and occupies only a small part of the pancreas, the significance of this fragment is great. It produces the most important hormones involved in metabolic processes. The islets of Langerhans produce insulin, glucagon, somatostatin and pancreatic polypeptide.

The first 2 hormones are necessary for life. Insulin starts the process of breaking down glucose into smaller molecular compounds. As a result, blood sugar levels decrease. In addition, insulin is involved in fat metabolism. Due to the actions of this hormone in the liver and muscle tissue glycogen accumulates. Insulin has an anabolic effect on overall metabolism, that is, it speeds up all processes.

Glucagon has the opposite effect. This hormone is produced in smaller quantities compared to insulin. It is involved in gluconeogenesis. Sugar is necessary in the body as it is a source of energy.

Somatostatin regulates the production digestive enzymes and hormones. Under the influence of this substance, the production of glucagon and insulin is reduced. There are very few PP cells in the islets of Langerhans, but pancreatic polypeptide is essential for the body. It is involved in the regulation of the secretion of digestive glands (liver, stomach). With insufficient hormonal activity, severe diseases develop.

Damage to the endocrine pancreas

Islet cell dysfunction may occur due to various reasons. Often, the insufficiency of these structures relates to congenital anomalies (genetic pathologies). Acquired damage to the islets of Langerhans develops due to viral and bacterial infections, chronic alcohol intoxication, neurological diseases.

Insulin deficiency leads to type 1 diabetes. This disease occurs in childhood and at a young age. Increased blood glucose leads to damage to blood vessels and nerves. With a deficiency of other islet cells, a hypoglycemic state develops and increased production of digestive juices. Increased hormone production occurs when benign tumors tail of the pancreas.

Transplantation of islets of Langerhans

The treatment for diabetes mellitus is replacement therapy insulin. IN last years are being developed alternative ways. These include the introduction of an artificial pancreas and islet cell transplantation. In practice, it turned out that hormone-producing structures take root in the new organism. In this case, carbohydrate metabolism can be completely restored. Transplantation of islets of Langerhans has not yet been received wide application in practice.

The human body is a perfect creation. It has internal organs with unique sets of functions. One of these delicate, precise in functioning and most important organs for maintaining healthy longevity is the pancreas - a generator of hormones and pancreatic juice. It is important to have an understanding of the device in order to restore its functionality.

Structures of the pancreas (islets of Langerhans)

An organ with a distributed, diverse alveolar-tubular structure has glandular elements that perform unique intra- and extrinsic secretory functions. It is located behind the stomach in abdominal cavity, its weight is up to 80 g. Connective tissue divides the gland into lobes by partitions.

They house vessels circulatory system and outgoing channels. Inside the lobes there are sections of exocrine secretion (including up to 97% of the total number of cellular structures) and endocrine formations (islets of Langerhans). A significant exocrine part of the organ periodically duodenum pancreatic juice containing digestive enzymes is secreted.

Cell clusters (from 1 to 2 million) ranging in size from 0.1 to 0.3 mm are responsible for intrasecretory and exocrine functions. Each of them contains 20 - 40 pieces. Each cell produces hormones insulin, glucagon, etc. into the blood that control lipid and carbohydrate metabolism. This feature is provided by a branched system of capillaries and small vessels that penetrate their associations.

More often these are spherical islands, there are diffuse accumulations in the form of strands, all of them do not have excretory ducts. , secreted by the pancreas, control the digestion process and regulate the composition and level nutrients entering the blood. Thus, uniting within one organ, intrasecretory and exocrine cellular components work as a single whole. The isolated island clusters contain five types of endocrine cellular structures that ensure the production of unique hormones.

Alpha cells

Located within peripheral clusters. They make up about 1/4 of all organ cells and contain glucagon in their granules. Their function is to generate the hormone glucagon, which, unlike insulin formed by the gland, is used to trigger the conversion of glycogen-polymer sugar molecules into glucose on the internal receptors of cellular structures (200,000 receptor units per cellular structure) of the liver. The latter, being a carrier of energy, is released into the bloodstream. This function is implemented continuously to provide the body with energy.

Beta cells

They are central clusters. Beta cells of the pancreas make up about 3/4 of all cellular structures of the organ and contain insulin. Their function is to generate the hormone insulin, which, unlike glucagon formed by the gland, is used to trigger the conversion of glucose into polymer glycogen molecules on the internal receptors of cellular structures (150,000 receptor units per one) of the liver. This substance, being stored energy, is removed from the bloodstream.

Thus, the amount of sugar in the blood is normalized by insulin. Insufficient insulin production leads to persistence higher level sugar and diabetes. Its hallmark is antibodies to pancreatic beta cells (type 1 diabetes), detected in blood tests. They reduce the production of insulin, disrupting its balance with glycogen in the blood. U healthy person these antibodies are absent in the blood.

Delta cells

They make up up to 1/10 of all cellular structures of the organ. The cells produce the hormone somatostatin, which suppresses the secretory activity of hormone generation. In particular, it reduces the secretion of glucagon and insulin, as well as the exocrine secretion of juices for digestion and the motility of the digestive system.

VIP cells

They have a reduced presence in the organ. A vasointestinal peptide is formed in the cells, which indirectly improves blood flow and organ secretion. It widens the lumens of blood vessels, lowers pressure in the arteries, and inhibits the formation of the gastric mucosa of hydrochloric acid, the gland activates the generation of antagonist hormones - insulin and glucagon.

The pancreas is a truly unique organ, on which the vital activity of the entire human body largely depends. And one of the main tasks of the pancreas is to regulate the amount of sugar in the blood by releasing the hormone insulin. It is realized thanks to the endocrine function, in particular the islets of Langerhans. What are these cells, what are their main features, and is it possible to transplant endocrine cells of the islets of Langerhans into patients with type 1 diabetes?

Islets of Langerhans: structure and role for the pancreas

Each of the pancreatic islets of the pancreas, designed to perform endocrine functions, consists of groups of cells that are surrounded by capillaries. Interestingly, their mass and size are so minimal that there are about 1.5 - 2 million of them directly in the gland. The pancreatic islets of Langerhans are distributed throughout the pancreas, but the largest number is still located in the tail.

Despite the fact that endocrine cells of the pancreas of this type perform one of the most important functions for the entire body, their total mass is no more than 1-2% of the total weight of the pancreas. What is important, the pancreatic islets of Langerhans are represented various types endocrine cells, which allows them to produce several hormones simultaneously, thereby controlling metabolism.

Their basis is cells called insulocytes. Thus, A-cells are responsible for the production of glucagon, constituting approximately a quarter of all endocrine cell aggregates present in this part of the organ. Most pancreatic cells are B-type, responsible for the production of insulin, which is why disruptions in their work will lead to diabetes.

Secretion is provided by endocrine cells of type D, as well as D1, the number of which is approximately equal to 10 percent of the total. And, of course, the role of PP cells of the pancreas is no less important, the number of which is small, but it is they who control the amount of pancreatic juice so that its excess or deficiency does not harm the functioning of the entire gastrointestinal tract.

Islets of Langerhans: endocrine function and antibodies to pancreatic cells

As is known, the main task of the pancreatic islets of Langerhans is to implement the endocrine function of the pancreas. First of all, this is the release of main hormones called insulin and glucagon, aimed at controlling blood sugar levels. So, insulin reduces its amount if the levels exceed the norm, and glucagon, on the contrary, increases it.

It is worth noting that if the endocrine cells of the pancreatic islets do not cope with their work in full, and accordingly, the hormones that the body needs are not released in the required quantities, then there is a high probability of diabetes mellitus. This disease occurs due to excess sugar in the body, and its treatment requires constant administration of insulin. Type 1 of this disease is especially dangerous, since in this case the endocrine cells of the pancreas are destroyed en masse, and accordingly, the patient’s condition does not worsen gradually, but rapidly, and requires urgent and constant treatment. There can be many reasons for this, for example, the body’s production of antibodies against the background of immune diseases.

What is important, there is a method for treating and restoring the endocrine functions of the pancreas through transplantation of cells from the islets of Langerhans. But in this case, it will be necessary to first test for antibodies to endocrine cells of the pancreas, since the transplantation technique will only be effective for a certain type of diabetes. But with cancer or other diseases of the pancreas, it does not give the desired result.

Transplantation of islet cells of Langerhans into patients with type 1 diabetes

Today, islets of Langerhans make it possible to treat type 1 diabetes thanks to their transplantation. This method was discovered not so long ago by Canadian specialists, and although it requires very significant financial costs, and the procedure itself is incredibly complex and risky, it is nevertheless quite real and provides a chance for a gradual restoration of the endocrine function of the pancreas, and, accordingly, possible relief for patients from a dangerous disease .

The essence of the transplant is that healthy endocrine cells obtained from a donor are introduced into the body of a person with type 1 diabetes using a catheter, as a result of which gradually, due to their influence, the amount of insulin that is necessary to maintain glucose in the blood begins to be produced. within normal limits. It is important to understand that islets of Langerhans for transplantation into diabetic patients are removed only from a corpse that fully meets all the required parameters, which reduces the risk of rejection, especially since the antibodies present in the body are aimed at destroying foreign bodies. What is important is that the transplantation of endocrine cells of pancreatic islets gives an effect quite quickly, and therefore after a couple of weeks the condition of a patient with type 1 diabetes rapidly begins to improve.

It is important to understand that transplantation of islets of Langerhans carries the risk that the antibodies in the body of a diabetic patient will lead to rejection of the pancreatic gland. That is why the most important role in the success of the procedure is played drug treatment, aimed at temporarily blocking the action of certain immune and antibody responses that can lead to tissue destruction. In this case, drugs for treating the patient are selected in such a way as to not completely, but only partially block certain immune reactions, in particular, those producing antibodies to the cells of the islets of Langerhans, which makes it possible to minimize the risk for the endocrine function of the pancreas.

In practice, the technique showed quite good results for patients, especially since there were no cases of death as a result of transplantation of pancreatic gland cells and their subsequent rejection under the influence of antibodies. Also, a certain number of sick patients no longer required insulin administration at all, while some still needed it, but most indicators related to the functioning of the endocrine function of the pancreas improved significantly, which allowed us to hope for a very favorable prognosis in the future.

However, it is worth noting that in in this case There are certain disadvantages that need to be taken into account. Thus, under the influence of antibodies to the islets of Langerhans, there is a high risk of all kinds of side effects in patients, namely disturbances in the production of pancreatic juice, diarrhea, dehydration, as well as more serious complications. In addition, even after the procedure, it is necessary throughout life to constantly take those medications that are necessary so that the body does not begin to reject the transplanted cells. And due to the fact that these medications are aimed at blocking immune reactions, in particular certain antibodies, then taking them increases the risk of all kinds of infections.

Thus, the pancreatic islets perform an endocrine function important for the entire body, providing the production of hormones necessary for metabolism and control of blood glucose levels. That is why, in some cases, for patients with type 1 diabetes, transplantation of endocrine cell clusters may be relevant, which gradually normalizes the functioning of the body, and accordingly, the much-needed insulin is produced in the proper volume.

Internal secretion is carried out thanks to special cells located in the tail of this anatomical formation. The site where pancreatic hormones are produced is called the islet of Langerhans. This anatomical formation is of great functional importance. Thanks to it, carbohydrate metabolism is ensured.

What is the islet of Langerhans: purpose

Endocrine cells are located throughout the body. One of the places where they accumulate is the pancreas. The islets of Langerhans are localized in the caudal part of the organ. They are cellular clusters that produce biologically active substances - hormones. The importance of the islets of Langerhans is enormous. It consists in the production of a normal amount of hormones necessary for metabolic processes. The islets of Langerhans of the pancreas have the following functions:

1. Glycemic control.
2. Regulation of enzyme activity.
3. Participation in fat metabolism.

Due to the normal functioning of the islet apparatus, conditions such as diabetes and hypoglycemia do not develop. Cell damage occurs during acute and chronic inflammation - pancreatitis.

Histological structure of islets

The islet of Langerhans was discovered in the 19th century. It represents a concentration of endocrine elements. In children, these formations occupy about 6% of the total area of ​​the organ. By adulthood, the endocrine part decreases and amounts to only 2%. The parenchyma of the tail contains about a million islets of Langerhans. They have their own abundant blood supply and innervation. Each island consists of lobules, which are covered connective tissue. In addition, it is also located outside endocrine formations. The cells inside the islets are arranged in a mosaic pattern. The activity of endocrine clusters is provided by the vagus and sympathetic nerves. Insular cells are located in the center of the lobule. They reduce blood glucose levels. In the peripheral part of the lobules there are alpha and delta cells. The first produce a counter-insular hormone - glucagon. The latter are necessary for the regulation of endocrine and exocrine activity.

What cells are there in the islets of Langerhans?

The islets of Langerhans produce several types of cells. All of them are involved in the release of biologically active substances - peptides and hormones. Most of the islets of Langerhans are represented by beta cells. They are located in the center of each lobule. These cells are very important because they produce insulin.

The second most important are the alpha cells of the pancreas. They occupy a quarter of the island's area. Alpha cells are required for the production of glucagon. This hormone is an insulin antagonist.

In the peripheral part of the islets of Langerhans, PP and delta cells are produced. The number of the former is about 1/20 of the part. The function of these formations is the production of pancreatic polypeptide. Delta cells are required to produce somatostatin. This substance is involved in the regulation of carbohydrate metabolism.

Islet cells are difficult to regenerate. Therefore, when these structures are damaged, it is often impossible to restore their function.

Hormonal activity of the islets of Langerhans

Despite the fact that the islet of Langerhans is small and occupies only a small part of the pancreas, the significance of this fragment is great. It produces the most important hormones involved in metabolic processes. The islets of Langerhans produce insulin, glucagon, somatostatin and pancreatic polypeptide.

The first 2 hormones are necessary for life. Insulin starts the process of breaking down glucose into smaller molecular compounds. As a result, blood sugar levels decrease. In addition, insulin is involved in fat metabolism. Thanks to the actions of this hormone, glycogen accumulates in the liver and muscle tissue. Insulin has an anabolic effect on overall metabolism, that is, it speeds up all processes.

Glucagon has the opposite effect. This hormone is produced in smaller quantities compared to insulin. It is involved in gluconeogenesis. Sugar is necessary in the body as it is a source of energy.

Somatostatin regulates the production of digestive enzymes and hormones. Under the influence of this substance, the production of glucagon and insulin is reduced. There are very few PP cells in the islets of Langerhans, but pancreatic polypeptide is essential for the body. It is involved in the regulation of the secretion of digestive glands (liver, stomach). With insufficient hormonal activity, severe diseases develop.

Damage to the endocrine pancreas

Islet cell dysfunction can occur for a variety of reasons. Often, the deficiency of these structures is related to congenital anomalies (genetic pathologies). Acquired damage to the islets of Langerhans develops as a result of viral and bacterial infections, chronic alcohol intoxication, and neurological diseases.

Insulin deficiency leads to type 1 diabetes. This disease occurs in childhood and young adulthood. Increased blood glucose leads to damage to blood vessels and nerves. With a deficiency of other islet cells, a hypoglycemic state develops and increased production of digestive juices. Increased production of hormones occurs with benign tumors of the tail of the pancreas.

Transplantation of islets of Langerhans

The treatment for diabetes mellitus is insulin replacement therapy. In recent years, alternative methods have been developed. These include the introduction of an artificial pancreas and islet cell transplantation. In practice, it turned out that hormone-producing structures take root in the new organism. In this case, carbohydrate metabolism can be completely restored. Transplantation of the islets of Langerhans has not yet been widely used in practice.

Biology and medicine

Pancreatic islets (Langerhans)

The pancreas consists of exocrine and endocrine parts. The exocrine part is described in the section “Digestive Organs”. The endocrine part is formed by groups of pancreatic islets (islets of Langerhans), which are formed by cellular clusters rich in capillaries. Total The number of islets ranges from 1-2 million (1-2% of the mass of the entire gland), and the diameter of each is within microns. This is a complex intrasecretory apparatus consisting of oval clusters of endocrine cells different types: in alpha cells the hormone glucagon is formed - a regulator of carbohydrate metabolism and fat metabolism (it is also formed in gastrointestinal tract); in beta cells - insulin - regulator of carbohydrate metabolism, protein metabolism and fat metabolism; D cells (definitive cells) apparently synthesize three hormones - somatostatin, pancreagastrin and secretin. Islet cells contain many membrane-coated granules. Beta cells predominate (60-80%), alpha cells from 10 to 30%), D cells - about 10%).

Pancreatic islets, responsible for its endocrine function, are scattered throughout the pancreatic parenchyma. Each mature islet, in addition to alpha, beta and delta cells, contains PP cells (produce pancreatic polypeptide).

Cells of all types produce small amounts of other biologically active peptides.

Developing islets contain immature cells that secrete a number of additional peptide hormones, including gastrin, VIP, ACTH.

A tumor can arise from any type of cell.

Islet cell tumors typically secrete one or more hormones and present characteristic syndromes(Table 95.2).

What are the islets of Langerhans

The islets of Langerhans, located in the pancreas, are a cluster of endocrine cells responsible for the production of hormones. In the mid-19th century, the scientist Paul Langerhansk discovered entire groups of these cells, so the clusters were named after him.

During the day, the islets produce 2 mg of insulin.

Islet cells are concentrated mainly in the tail of the pancreas. Their mass makes up 2% of the total weight of the gland. The total number of islets in the parenchyma is approximately.

An interesting fact is that in newborns the mass of the islets occupies 6% of the weight of the pancreas.

Over the years specific gravity structures of the body that have endocrine activity, the pancreas, decreases. By the age of 50 years of human existence, only 1-2% of islands remain

What cells do the clusters consist of?

The islets of Langerhans have cells of different functionality and morphology.

The endocrine pancreas consists of:

• glucagon-producing alpha cells. The hormone is an insulin antagonist and increases sugar levels in the bloodstream. Alpha cells occupy 20% of the weight of the remaining cells;
• Beta cells are responsible for the synthesis of ameline and insulin; they occupy 80% of the islet’s weight;
• The production of somatostatin, which can inhibit the secretions of other organs, is provided by delta cells. Their mass ranges from 3 to 10%;
• PP cells are required for the production of pancreatic polypeptide. The hormone enhances secretory function stomach and suppression of parenchyma secretion;
• Ghrelin, which is responsible for the feeling of hunger in humans, is produced by epsilon cells.

How are islands arranged and what are they for?

The main function performed by the islets of Langerhans is to maintain the correct level of carbohydrates in the body and control other endocrine organs. The islets are innervated by sympathetic and vagus nerves and are abundantly supplied with blood.

The islets of Langerhans in the pancreas have a complex structure. In fact, each of them is an active, full-fledged functional formation. The structure of the islet ensures the exchange between biologically active substances of the parenchyma and other glands. This is necessary for the smooth secretion of insulin.

The cells of the islets are mixed among themselves, that is, they are arranged in the form of a mosaic. A mature islet in the pancreas has proper organization. The islet consists of lobules that are surrounded by connective tissue; blood capillaries pass inside the cells.

In the center of the lobules there are beta cells, while in the peripheral part there are alpha and delta cells. Therefore, the structure of the islets of Langerhans depends entirely on their size.

Why are antibodies formed against islets? What is their endocrine function? It turns out that when islet cells interact, a mechanism develops feedback, and then these cells influence other cells located nearby.

1. Insulin activates the function of beta cells and inhibits alpha cells.
2. Alpha cells are activated by glucagon, which acts on delta cells.
3. The work of alpha and beta cells is inhibited by somatostatin.

Important! On failure immune mechanisms immune bodies directed against beta cells are formed. Cells are destroyed and lead to terrible disease, called “diabetes mellitus”.

What is a transplant and why is it needed?

A worthy alternative to gland parenchyma transplantation is islet transplantation. In this case, installation artificial organ not required. The transplant gives diabetics a chance to restore their beta cell structure and does not require a full pancreas transplant.

Based clinical trials it has been proven that patients diabetes mellitus type 1, which were transplanted with donor islet cells, the regulation of carbohydrate levels is completely restored. To prevent rejection of donor tissue, such patients were given powerful immunosuppressive therapy.

There is another material for restoring islets - stem cells. Since the reserves of donor cells are not unlimited, this alternative is very relevant.

It is very important for the body to restore sensitivity immune systems s, otherwise the newly transplanted cells will be rejected or destroyed after some time.

Today, regeneration therapy is developing rapidly, offering new techniques in all areas. Xenotransplantation, the transplantation of a pig pancreas into a person, is also promising.

Porcine parenchyma extracts were used to treat diabetes mellitus even before the discovery of insulin. It turns out that human and pork glands differ in only one amino acid.

Since diabetes mellitus develops as a result of damage to the islets of Langerhans, their study has great prospects for effective treatment diseases.

Functions and pathology of the islets of Langerhans: failure of secreted hormones 🏥💉

Pancreatic tissue is represented by two types of cellular formations: the acinus, which produces enzymes and is involved in digestive function, and the islet of Langerhans, whose main function is to synthesize hormones.

There are few islets in the gland itself: they make up 1-2% of the total mass of the organ. The cells of the islets of Langerhans differ in structure and function. There are 5 types of them. They secrete active substances that regulate carbohydrate metabolism, digestion, and can participate in the response to stress reactions.

What are the islets of Langerhans?

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The islets of Langerhans (OL) are polyhormonal microorgans consisting of endocrine cells located throughout the entire length of the pancreatic parenchyma, which performs exocrine functions. Their bulk is localized in the tail part. The size of the islets of Langerhans is 0.1-0.2 mm, their total number in the human pancreas ranges from 200 thousand to 1.8 million.

The cells form separate groups, between which capillary vessels pass. They are delimited from the glandular epithelium of the acini by connective tissue and fibers running there. nerve cells. These elements nervous system and the islet cells form the neuroinsular complex.

The structural elements of the islets - hormones - perform intrasecretory functions: regulate carbohydrate, lipid metabolism, digestive processes, metabolism. The child's gland contains 6% of these hormonal formations of the total area of ​​the organ. In an adult, this part of the pancreas is significantly reduced and accounts for 2% of the surface of the gland.

History of discovery

Clusters of cells, different in appearance and morphological structure from the main tissue of the gland and located in small groups mainly in the tail of the pancreas, were first discovered in 1869 by the German pathologist Paul Langerhans (1849-1888).

In 1881, the outstanding Russian scientist, pathophysiologist K.P. Ulezko-Stroganova (1858-1943) carried out fundamental physiological and histological work on the study of the pancreas. The results were published in the journal “Doctor”, 1883, No. 21 - article “On the structure of the pancreas under conditions of its rest and activity.” In it, for the first time at that time, she expressed a hypothesis about the endocrine function of individual pancreatic formations.

Based on her work in 1889-1892. in Germany, O. Minkovsky and D. Mehring found that when the pancreas is removed, diabetes mellitus develops, which can be eliminated by transplanting part of a healthy pancreas under the skin of the operated animal.

Domestic scientist L.V. Sobolev (1876-1921) was one of the first, based on the conducted research work showed the importance of the islets discovered by Langerhans and named after him in the production of a substance related to the occurrence of diabetes mellitus.

Subsequently, thanks to a large number of studies conducted by physiologists in Russia and other countries, new scientific data on the endocrine function of the pancreas were discovered. In 1990, the first transplantation of islets of Langerhans into humans was performed.

Types of islet cells and their functions

OB cells differ in their morphological structure, functions, and localization. Inside the islands they have a mosaic arrangement. Each island has an orderly organization. In the center are cells that secrete insulin. At the edges there are peripheral cells, the number of which depends on the size of the OB. Unlike acini, the OB does not contain its own ducts - hormones enter directly into the blood through capillaries.

There are 5 main types of OB cells. Each of them synthesizes a certain type of hormone, regulating digestion, carbohydrate and protein metabolism:

Alpha cells

Alpha cells occupy a quarter of the islet area (25%) and are second in importance: they produce glucagon, an insulin antagonist. It controls the process of lipid breakdown, helps increase blood sugar levels, and is involved in reducing calcium and phosphorus levels in the blood.

Beta cells

Beta cells make up the inner (central) layer of the lobule and are the main ones (60%). They are responsible for the production of insulin and amylin, a companion of insulin in the regulation of blood glucose. Insulin performs several functions in the body, the main one being normalization of sugar levels. If its synthesis is disrupted, diabetes mellitus develops.

Delta cells

Delta cells (10%) form the outer layer in the islet. They produce somatostatin, a hormone, a significant part of which is synthesized in the hypothalamus (the structure of the brain), and is also found in the stomach and intestines.

Functionally, it is also closely related to the pituitary gland, regulates the work of certain hormones that are produced by this department, and also suppresses the formation and release of hormonally active peptides and serotonin in the stomach, intestines, liver and pancreas itself.

PP cells

PP cells (5%) are located on the periphery, their number is approximately 1/20 of the islet. They can secrete vasoactive intestinal polypeptide (VIP), pancreatic polypeptide (PP). The maximum amount of VIP (vasointense peptide) is found in digestive organs And genitourinary system(V urethra). It affects the condition of the digestive tract, performs many functions, including having antispasmodic properties against the smooth muscles of the gallbladder and sphincters of the digestive organs.

Epsilon cells

The rarest of those included in the OB are epsilon cells. Microscopic analysis of a preparation from a lobule of the pancreas can determine that their number in the total composition is less than 1%. Cells synthesize ghrelin. Among its many functions, the most studied is its ability to influence appetite.

What pathologies occur in the islet apparatus?

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Damage to OB cells leads to severe consequences. With the development of the autoimmune process and the production of antibodies (AB) to OB cells, the number of all of the listed structural elements decreases sharply. Damage to 90% of cells is accompanied by a sharp decrease in insulin synthesis, which leads to diabetes mellitus. The production of antibodies to pancreatic islet cells occurs mainly in young people.

Pancreatitis leads to serious consequences due to damage to the islets - inflammatory process in the tissues of the pancreas. It often occurs in a severe form in the form of pancreatic necrosis, in which total death of organ cells occurs.

Determination of antibodies to the islets of Langerhans

If for some reason a malfunction occurs in the body, and the active production of antibodies against its own tissues begins, this leads to tragic consequences. When beta cells are exposed to antibodies, type 1 diabetes mellitus develops due to insufficient insulin production. Each type of antibody produced acts against a specific type of protein. In the case of the islets of Langerhans, these are beta cell structures responsible for the synthesis of insulin. The process proceeds progressively, the cells die completely, carbohydrate metabolism is disrupted, and with normal nutrition the patient may die of starvation due to irreversible changes in the organs.

Diagnostic methods have been developed to determine the presence of antibodies to insulin in the human body. Indications for such a study are:

• obesity based on family history;
• any pathology of the pancreas, including previous injuries;
• severe infections: mainly viral, which can trigger the development of an autoimmune process;
• severe stress, mental stress.

There are 3 types of antibodies through which type 1 diabetes is diagnosed:

• to glutamic acid decarboxylase (one of the essential amino acids in the body);
• to the produced insulin;
• to OB cells.

These are unique specific markers that must be included in the examination plan for patients with existing risk factors. Of the listed volume of research, the detection of antibodies to the glutamic amino acid component is early diagnostic sign SD. They appear when Clinical signs There are no diseases yet. They are detected mainly at a young age and can be used to identify people with a predisposition to developing the disease.

Islet cell transplantation

Transplantation of OB cells is an alternative to transplantation of the pancreas or part thereof, as well as the installation of an artificial organ. This is due to high sensitivity and the tenderness of the pancreas tissue to any influence: it is easily injured and has difficulty restoring its functions.

Islet transplantation today makes it possible to treat type I diabetes mellitus in cases where insulin replacement therapy has reached its limits and becomes ineffective. The method was first used by Canadian specialists and consists of introducing healthy endocrine donor cells into the patient using a catheter. portal vein liver. It is aimed at making the remaining own beta cells work.

Due to the functioning of the transplanted cells, the necessary for maintaining normal level blood glucose amount of insulin. The effect comes quickly: with a successful operation, after two weeks the patient’s condition begins to improve, replacement therapy wears off, and the pancreas begins to independently synthesize insulin.

The danger of the operation lies in the rejection of the transplanted cells. We use cadaveric materials that are carefully selected according to all parameters of tissue compatibility. Since there are about 20 such criteria, antibodies present in the body can lead to the destruction of pancreatic tissue. That's why important role proper drug treatment aimed at reducing immune reactions plays a role. The drugs are selected in such a way as to selectively block some of them that affect the production of antibodies to the cells of the transplanted islets of Langerhans. This allows you to minimize the risk to the pancreas.

In practice, pancreatic cell transplantation for type I diabetes mellitus shows good results: there have been no recorded deaths after such an operation. A certain number of patients significantly reduced their insulin dose, and some of the operated patients no longer needed it. Other impaired functions of the organ were also restored, and health improved. A significant part has returned to a normal lifestyle, which allows us to hope for a further favorable prognosis.

As with other organ transplants, pancreatic surgery, in addition to rejection, is dangerous in other ways side effects due to violation varying degrees secretory activity pancreas. In severe cases this leads to:

• to pancreatic diarrhea;
• to nausea and vomiting;
• to severe dehydration;
• to other dyspeptic phenomena;
• to general exhaustion.

After the procedure, the patient must continuously receive immunosuppressive drugs throughout his life to prevent rejection of foreign cells. The action of these drugs is aimed at reducing immune reactions - the production of antibodies. In turn, the lack of immunity increases the risk of developing any infection, even a simple one, which can become complicated and cause serious consequences.

Research continues on pancreatic transplantation from pigs - xenotransplantation. It is known that the anatomy of the gland and pork insulin are most similar to human insulin and differ from it in one amino acid. Before the discovery of insulin, an extract from the pig pancreas was used in the treatment of severe diabetes mellitus.

Why is a transplant performed?

Damaged pancreatic tissue is not restored. In cases of complicated diabetes mellitus, when the patient is on high doses of insulin, this surgery saves the patient, gives a chance to restore the structure of beta cells. In a number of clinical studies, these cells were transplanted from donors into patients. As a result, the regulation of carbohydrate metabolism was restored. But at the same time, patients have to undergo powerful immunosuppressive therapy to prevent rejection of donor tissue.

Not all patients with type 1 diabetes are candidates for cell transplantation. There are strict indications:

• lack of results from the applied conservative treatment;
• insulin resistance;
• expressed metabolic disorders in organism;
• severe complications of the disease.

Where is the operation performed and how much does it cost?

The procedure for replacing the islets of Langerhans is widely carried out in the USA - this way they treat diabetes of any type on early stages. One of the diabetes research institutes in Miami is doing this. It is not possible to completely cure diabetes in this way, but good results are achieved. therapeutic effect, moreover, the risks severe complications are kept to a minimum.

The cost of such an intervention is about $100 thousand. Postoperative rehabilitation and carrying out immunosuppressive therapy ranges from $5 to $20 thousand. The cost of this treatment after surgery depends on the body's response to the transplanted cells.

Almost immediately after the manipulation, the pancreas begins to function normally on its own, and gradually its performance improves. The recovery process takes approximately 2 months.

Prevention: how to preserve the islet apparatus?

Since the function of the islets of Langerhans of the pancreas is to produce substances important for humans, lifestyle modification is necessary to maintain the health of this part of the pancreas. Key points:

HOW TO FORGET ABOUT PANCREATITIS FOREVER?

For the prevention and treatment of pancreatic diseases, our readers recommend Monastic tea. Unique composition, which includes 9 medicinal plants, useful for the pancreas, each of which not only complements, but also enhances the actions of each other. By using it, you will not only eliminate all the symptoms of inflammation of the gland, but also get rid of the cause of its occurrence forever.

• giving up alcohol and smoking;
• eliminating junk food;
• physical activity;
• minimizing acute stress and neuropsychic overload.

Alcohol causes the greatest harm to the pancreas: it destroys pancreatic tissue and leads to pancreatic necrosis - the total death of all types of organ cells that cannot be restored.

Excessive consumption of fatty and fried foods leads to similar consequences, especially if this happens on an empty stomach and regularly. The load on the pancreas increases significantly, the number of enzymes that are necessary to digest large amounts of fat increases and depletes the organ. This leads to fibrosis and changes in the remaining cells of the gland.

Therefore, at the slightest sign of digestive dysfunction, it is recommended to contact a gastroenterologist or therapist in order to timely correct changes and early prevention complications.

Ignoring or incorrect treatment Pancreatitis can lead to dire consequences:

• diabetes;
• liver and kidney failure;
• oncology that threatens partial or complete removal pancreas.

Not to mention strict diets, constant use of enzymes and periods of exacerbation, when there is no longer any strength to live. “But it is possible to forget about pancreatitis forever,” says the chief gastroenterologist of the Russian Federation.

Islets of Langerhans

The islets of Langerhans are clusters of hormone-producing (endocrine) cells, mainly in the tail of the pancreas. Discovered in 1869 by the German pathologist Paul Langerhans (1849-1888). The islets make up approximately 1...2% of the mass of the pancreas. The pancreas of an adult healthy person has about 1 million islets (with a total mass of one to one and a half grams), which are united by the concept endocrine system organ.

Islets of Langerhans, hematoxylin-eosin staining.

Pancreas of a dog. 250x.

Historical reference

Paul Langerhans, as a medical student working with Rudolf Virchow, in 1869 described clusters of cells in the pancreas that were different from the surrounding tissue, which were later named after him. In 1881, K.P. Ulezko-Stroganova first pointed out the endocrine role of these cells. The increatory function of the pancreas was proven in Strasbourg (Germany) in the clinic of the largest diabetologist Naunin Mering and Minkowski in 1889 - pancreatic diabetes was discovered and the role of the pancreas in its pathogenesis was proven for the first time. Russian scientist L.V. Sobolev (1876-1919) in his dissertation “On the morphology of the pancreas when ligating its duct in diabetes and some other conditions” showed that ligation of the excretory duct of the pancreas leads the acinar (exocrine) section to complete atrophy, while the pancreatic islets remain intact. Based on experiments, L.V. Sobolev came to the conclusion: “the function of the pancreatic islets is the regulation of carbohydrate metabolism in the body. The death of pancreatic islets and loss of this function causes a painful condition - diabetes mellitus."

Subsequently, thanks to a series of studies conducted by physiologists and pathophysiologists in various countries (pancreatectomy, selective necrosis of pancreatic beta cells chemical compound alloxan), new information was obtained about the increatory function of the pancreas.

In 1907, Lane & Bersley (University of Chicago) showed the difference between two types of islet cells, which they called type A (alpha cells) and type B (beta cells).

In 1909, the Belgian researcher Jan de Meyer proposed calling the secretion product of beta cells of the islets of Langerhans insulin (from the Latin. insula- island). However, direct evidence of the production of a hormone that affects carbohydrate metabolism could not be found.

In 1921, in the laboratory of physiology of Professor J. Macleod at the University of Toronto, the young Canadian surgeon Frederick Banting and his assistant medical student Charles Best managed to isolate insulin.

In 1962, Marlin et al discovered that aqueous extracts of the pancreas were capable of increasing glycemia. The substance causing hyperglycemia was called “hyperglycemic-glycogenolytic factor.” It was glucagon, one of the main physiological antagonists of insulin.

In 1967, Donathan Steiner and co-authors (University of Chicago) managed to discover the insulin precursor protein - proinsulin. They showed that the synthesis of insulin by beta cells begins with the formation of a proinsulin molecule, from which C-peptide and an insulin molecule are subsequently split off as needed.

In 1973, John Ensik (University of Washington), as well as a number of American and European scientists, carried out work on the purification and synthesis of glucagon and somatostatin.

In 1976, Gudworth & Bottaggo discovered a genetic defect in the insulin molecule, revealing two types of the hormone: normal and abnormal. the latter is an antagonist to normal insulin.

In 1979, thanks to the research of Lacy & Kemp and co-authors, it became possible to transplant individual islets and beta cells, it was possible to separate the islets from the exocrine part of the pancreas and carry out transplantation in an experiment. In 1979-1980 When transplanting beta cells, a species-specific barrier is overcome (cells from healthy laboratory animals are implanted into sick animals of a different species).

In 1990, pancreatic islet cells were transplanted for the first time into a patient with diabetes mellitus.

In the endocrine part of the pancreatic parenchyma there are isletsLangerhans. Their main structural units are secretory (α, β, Δ, F and others) cells.

A cells (α cells) islets are produced glucagon. It increases glycogenolysis in the liver, reduces glucose utilization in it, and also increases gluconeogenesis and the formation of ketone bodies. The result of these effects is an increase in blood glucose concentration. Outside the liver, glucagon increases lipolysis and decreases protein synthesis.

There are receptors on α-cells that, when the level of glucose in the extracellular environment decreases, increases the secretion of glucagon. Secretin inhibits glucagon production, while other gastrointestinal hormones stimulate it.

B cells ( -cells) synthesize and store insulin. This hormone increases the permeability of cell membranes to glucose and amino acids, and also promotes the conversion of glucose into glycogen, amino acids into proteins, and fatty acids into triglycerides.

Insulin-synthesizing cells are able to respond to changes in the content of calorigenic molecules (glucose, amino acids and fatty acids). Of the amino acids, the stimulation of insulin secretion is most pronounced by arginine and lysine.

Damage to the islets of Langerhans leads to the death of the animal due to a lack of insulin in the body. Only this hormone reduces blood glucose levels.

D cells (Δ cells) islets are synthesized pancreatic somatostatin. In the pancreas, it has an inhibitory paracrine effect on the secretion of hormones by the islets of Langerhans (the predominant effect on β-cells), and by the exocrine apparatus - bicarbonates and enzymes.

The endocrine effect of pancreatic somatostatin is manifested by inhibition of secretory activity in the gastrointestinal tract, adenohypophysis, parathyroid gland and kidneys.

Along with secretion, pancreatic somatostatin reduces the contractile activity of the gallbladder and bile ducts, and throughout the gastrointestinal tract - reduces blood circulation, motility and absorption.

D cell activity increases with high content of amino acids (especially leucine and arginine) and glucose in the lumen of the digestive tract, as well as an increase in the concentration of CCP, gastrin, gastric inhibitory polypeptide (GIP) and secretin in the blood. At the same time, norepinephrine inhibits the release of somatostatin.

Pancreatic polypeptide synthesized by F cells (or PP cells) of the islets. It reduces the volume of pancreatic secretion and the concentration of trypsinogen in it, and also inhibits the excretion of bile, but stimulates the basal secretion of gastric juice.

The production of pancreatic polypeptide is stimulated by the parasympathetic nervous system, gastrin, secretin and CCP, as well as by fasting, protein-rich food, hypoglycemia and exercise.

The intensity of pancreatic hormone production is controlled by the autonomic nervous system (parasympathetic nerves cause hypoglycemia, and sympathetic nerves cause hyperglycemia). However, the main factors regulating the secretory activity of cells in the islets of Langerhans are the concentrations of nutrients in the blood and the lumen of the gastrointestinal tract. Thanks to this, timely reactions of the cells of the islet apparatus ensure the maintenance of a constant level of nutrients in the blood between meals.

ENDOCRINE FUNCTION OF THE GENITAL GLANDS

After the onset of puberty, the main sources of sex hormones in the body of animals become the permanent gonads (for males, the testes, and for females, the ovaries). In females, temporary endocrine glands may periodically appear (for example, the placenta during pregnancy).

Sex hormones are divided into male (androgens) and female (estrogens).

Androgens(testosterone, androstenedione, androsterone, etc.) specifically stimulate the growth, development and functioning of the male reproductive organs, and with the onset of puberty, the formation and maturation of male germ cells.

Even before birth, secondary sexual characteristics are formed in the fetus. This is largely regulated by androgens produced in the testes (secreted by Leydig cells) and factor secreted by Sertoli cells (located in the wall of the seminiferous tubule). Testosterone ensures the differentiation of the external genitalia according to the male type, and the secretion of Sertoli cells prevents the formation of the uterus and fallopian tubes.

During puberty, androgens accelerate the involution of the thymus, and in other tissues they stimulate the accumulation of nutrients, protein synthesis, the development of muscle and bone tissue, and increase physical performance and the body's resistance to adverse effects.

Androgens affect the central nervous system (for example, they cause manifestations of the sexual instinct). Therefore, removal of the gonads (castration) in males makes them calm and can lead to changes necessary for economic activity. For example, castrated animals fatten up faster, their meat is tastier and more tender.

Before birth, the secretion of androgens is ensured by the combined effect of female LH and human chorionic gonadotropin (HCG) on the fetus. After birth, the development of seminiferous tubules, sperm and the accompanying production of biologically active substances by Sertoli cells stimulates the male's own gonadotropin - FSH, and LH causes the secretion of testosterone by Leydig cells. Aging is accompanied by a decline in the activity of the gonads, but the production of sex hormones by the adrenal gland continues.

The specific features of Sertoli cells in the testes of stallions, bulls and boars include their ability, in addition to testosterone, to produce estrogens, which regulate metabolism in germ cells.

The ovaries in the body of a sexually mature female produce estrogens and gestagens. The main source of estrogens (estrone, estradiol and estriol) are follicles, and gestagens are the corpus luteum.

In an immature female, adrenal estrogens stimulate the development of the reproductive system (oviducts, uterus and vagina) and secondary sexual characteristics (certain physique, mammary glands, etc.). After the onset of puberty, the concentration of female sex hormones in the blood increases significantly due to their intensive production by the ovaries. The resulting levels of estrogen stimulate the maturation of germ cells, protein synthesis and the formation of muscle tissue in most of the female’s internal organs, and also increase her body’s resistance to harmful effects and cause changes in the organs of the animal associated with sexual cycles.

High concentrations of estrogen cause growth, expansion of the lumen and increased contractile activity of the oviducts. In the uterus, they increase blood supply, stimulate the proliferation of endometrial cells and the development of the uterine glands, and also change the sensitivity of the myometrium to oxytocin.

In females of many animal species, estrogens cause keratinization of vaginal epithelial cells before estrus. Therefore, the quality of the female’s hormonal preparation for mating and ovulation is determined by cytological analyzes of a vaginal smear.

Estrogens also contribute to the formation of the state of “hunting” and the corresponding sexual reflexes at the stage of the sexual cycle that is most favorable for fertilization.

After ovulation, a yellow body. The hormones it produces (gestagens) affect the uterus, mammary glands and central nervous system. Together with estrogens, they regulate the processes of conception, implantation of a fertilized egg, pregnancy, childbirth and lactation. The main representative of gestagens is progesterone. It stimulates the secretory activity of the uterine glands and makes the endometrium capable of responding to mechanical and chemical influences with growths that are necessary for the implantation of a fertilized egg and the formation of the placenta. Progesterone also reduces the sensitivity of the uterus to oxytocin and relaxes it. Therefore, a premature decrease in the concentration of gestagens in the blood of pregnant females causes childbirth before the fetus has fully matured.

If pregnancy does not occur, the corpus luteum undergoes involution (the production of gestagens stops) and a new ovarian cycle begins. Moderate amounts of progesterone in synergy with gonadotropins stimulate ovulation, and large amounts inhibit the secretion of gonadotropins and ovulation does not occur. Small amounts of progesterone are also needed to ensure estrus and readiness to mate. In addition, progesterone is involved in the formation dominants of pregnancy(gestational dominant), aimed at ensuring the development of future offspring.

After exposure to estrogen, progesterone promotes the development of glandular tissue in the mammary gland, which leads to the formation of secretory lobules and alveoli in it.

Along with steroid hormones, the corpus luteum, endometrium and placenta, mainly before childbirth, produce the hormone relaxin. Its production is stimulated by high concentrations of LH and causes an increase in the elasticity of the symphysis pubis, relaxation of the ligament of the pelvic bones, and immediately before childbirth it increases the sensitivity of the myometrium to oxytocin and causes expansion of the uterine pharynx.

Placenta occurs in several stages. First, during the fragmentation of a fertilized egg, a trophoblast. After the attachment of extraembryonic blood vessels to it, the trophoblast turns into chorion, which, after a tight connection with the uterus, becomes fully formed placenta.

In mammals, the placenta provides attachment, immunological protection and nutrition to the fetus, excretion of metabolic products, as well as the production of hormones (endocrine function) necessary for the normal course of pregnancy.

Already on early stages During pregnancy, chorionic villi are produced in the places where chorionic villi attach to the uterus. human chorionic gonadotropin. Its appearance accelerates the development of the embryo and prevents the involution of the corpus luteum. Thanks to this, the corpus luteum maintains a high level of progesterone in the blood until the placenta itself begins to synthesize it in the required quantity.

Non-pituitary gonadotropins produced in the body of pregnant females have specific characteristics, but can affect reproductive functions in other animal species. For example, introduction gonadotropin serum of pregnant mares(GSFA) causes the release of progesterone in many mammals. This is accompanied by a lengthening of the sexual cycle and delays the onset of heat. In cows and sheep, HSFA also causes the simultaneous release of several mature eggs, which is used in embryo transfer.

Placental estrogens produced by the placenta of most mammals (in primates - estrone, estradiol And estriol, and the horse - equilin And equilenin) mainly in the second half of pregnancy from dehydroepiandrosterone formed in the adrenal glands of the fetus.

Placental progesterone in a number of mammals (primates, carnivores, rodents) are secreted in quantities sufficient for normal gestation even after removal yellow bodies.

Placental lactotropin(placental lactogenic hormone, placental prolactin, chorionic somatomammotropin) supports fetal growth, and in the female it increases protein synthesis in cells and the concentration of FFA in the blood, stimulates the growth of the secretory sections of the mammary glands and their preparation for lactation, and also retains calcium ions in the body, reduces urinary excretion of phosphorus and potassium.

As pregnancy progresses, the level in the blood of females increases. placental corticoliberin, which increases the sensitivity of the myometrium to oxytocin. This liberin has virtually no effect on ACTH secretion. This is due to the fact that during pregnancy the protein content in the blood increases, which quickly neutralizes corticoliberin and it does not have time to act on the adenohypophysis.

THYMUS

Thymus (goitrous or thymus) is present in all vertebrates. In most mammals, it consists of two interconnected lobes located in the upper part of the chest just behind the sternum. However, in marsupials these thymic lobes usually remain separate organs. In reptiles and birds, the gland usually takes the form of chains located on both sides of the neck.

The thymus of most mammals reaches its largest size in relation to body weight at the time of birth. Then it grows slowly and reaches its maximum weight during puberty. In guinea pigs (and some other species of animals), a large thymus remains throughout life, but in most highly developed animals, after puberty, the gland gradually decreases (physiological involution), but complete atrophy does not occur.

In the thymus, epithelial cells produce thymic hormones that influence hematopoiesis, as well as the differentiation and activity of T cells through endocrine and paracrine pathways.

In the thymus, T-lymphocyte precursors act sequentially thymopoietin And thymosins. They make cells differentiating in the thymus sensitive to activated calcium thymulin(or thymic serum factor - TSF).

Note: An age-related decrease in the content of calcium ions in the body is the cause of a decrease in thymulin activity in old animals.

The secretory activity of the thymus is closely related to the activity of the hypothalamus and other endocrine glands (pituitary gland, pineal gland, adrenal glands, thyroid gland and gonads). Hypothalamic somatostatin, removal of the adrenal glands and thyroid gland reduce the production of thymic hormones, and the pineal gland and castration increase hormonopoiesis in the thymus. Corticosteroids regulate the distribution of thymic hormones between the thymus, spleen and lymph nodes, and thymectomy leads to hypertrophy of the adrenal cortex.

The listed examples indicate that the thymus gland ensures the integration of the neuro-endocrine and immune systems in the entire macroorganism.

EPIPHYSUS

Pineal gland(pineal gland) is located in vertebrates under the scalp or deep in the brain. The main cells of the pineal gland in mammals are pinealocytes, and more primitive animals also have photoreceptors. Therefore, along with the endocrine function, the pineal gland can provide a sense of the degree of illumination of objects. This allows deep-sea fish to carry out vertical migration depending on the change of day and night, and lampreys and reptiles to protect themselves from danger from above. In some migratory birds, the pineal gland probably functions as a navigation device during flight.

The pineal gland of amphibians is already capable of producing the hormone melatonin, which decrease in the amount of pigment in skin cells.

Pinealocytes continuously synthesize the hormone serotonin, which in the dark and with low activity of the sympathetic nervous system (in birds and mammals) is converted into melatonin. Therefore, the duration of day and night affects the content of these hormones in the pineal gland. The resulting rhythmic changes in their concentration in the pineal gland determine the daily (circadian) biological rhythm in animals (for example, the frequency of sleep and fluctuations in body temperature), and also affects the formation of such seasonal reactions as hibernation, migration, molting and reproduction.

An increase in melatonin content in the pineal gland has hypnotic, analgesic and sedative effects, and also inhibits puberty in young animals. Therefore, after removal of the pineal gland, chickens experience puberty faster, in male mammals the testes hypertrophy and sperm maturation increases, and in females, the life span of the corpus luteum lengthens and the uterus enlarges.

Melatonin reduces the secretion of LH, FSH, prolactin and oxytocin. Therefore, low levels of melatonin during daylight hours contribute to increased milk production and high sexual activity in animals at those times of the year when the nights are shortest (spring and summer). Melatonin also neutralizes the damaging effects of stressors and is a natural antioxidant.

In mammals, serotonin and melatonin perform their functions mainly in the pineal gland, and the distant hormones of the gland are probably polypeptides. A significant part of them, along with blood, is secreted in cerebrospinal fluid and through it enters various parts of the central nervous system. This has a predominantly inhibitory effect on the animal’s behavior and other brain functions.

About 40 biologically active peptides secreted into the blood and cerebrospinal fluid have already been discovered in the pineal gland. Of these, the most studied are antihypothalamic factors and adrenoglomerulotropin.

Antihypothalamic factors provide communication between the pineal gland and the hypothalamic-pituitary system. These include, for example, arginine-vasotocin(regulates the secretion of prolactin) and antigonadotropin(weakens LH secretion).

Adrenoglomerulotropin by stimulating the production of aldosterone by the adrenal gland, it affects water-salt metabolism.

Thus, the main function of the pineal gland is the regulation and coordination of biorhythms. By controlling the activity of the animal’s nervous and endocrine systems, the pineal gland ensures that its systems respond proactively to changes in time of day and season.