What cells of the pancreatic islet produce somatostatin. What are islets of langerhans

The islets of Langerhans located in the pancreas are a collection of endocrine cells responsible for the production of hormones. In the middle of the 19th century, the scientist Paul Langergansk 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 caudal pancreas. Their mass is 2% of total weight glands. Total islets in the parenchyma - approximately 1,000,000.

Interesting is the fact that in newborns, the mass of islets occupies 6% of the weight of the pancreas.

As the years go by specific gravity body structures with endocrine activity, the pancreas, decreases. By the age of 50, only 1-2% of the islets remain

What cells are clusters made of?

In their composition, 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 blood sugar levels. Alpha cells occupy 20% of the weight of the remaining cells;
• beta cells are responsible for the synthesis of amelin and insulin, they occupy 80% of the weight of the islet;
• the production of somatostatin, which can inhibit the secretion of other organs, is provided by delta cells. Their mass is from 3 to 10%;
• PP cells are required for the production of the pancreatic polypeptide. The hormone enhances the secretory function of the stomach and suppresses the secretion of the parenchyma;
• Ghrelin, which is responsible for the appearance of a person's feeling of hunger, is produced by epsilon cells.

How are islands arranged and what are they for?

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

Islets of Langerhans in the pancreas complex structure. In fact, each of them is an active, full-fledged functional education. The structure of the islet ensures the exchange between the 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 with each other, 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 surround connective tissue, blood capillaries pass inside the cells.

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

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

1. Insulin activates the function of beta cells and depresses alpha cells.
2. Alpha cells activate glucagon, and those act on delta cells.
3. The work of alpha and beta cells is inhibited by somatostatin.

Important! When immune mechanisms fail, immune bodies directed against beta cells are formed. Cells are destroyed and lead to a terrible disease called "diabetes mellitus".

What is a transplant and why is it needed

A worthy alternative to transplantation of the parenchyma of the gland is transplantation of the islet apparatus. In this case, the installation of an artificial organ is not required. Transplantation gives diabetics a chance to restore the structure of beta cells and is not required in full.

Based clinical research it has been shown that in patients with type 1 diabetes mellitus who received donor islet cells transplantation, the regulation of carbohydrate levels is completely restored. In order to prevent rejection of donor tissues, such patients underwent powerful immunosuppressive therapy.

There is another material for the restoration of 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 the susceptibility of the immune system, otherwise the newly transplanted cells will be rejected or destroyed after a while.

Today, regenerative therapy is rapidly developing, it offers new techniques in all areas. Xenotransplantation is also promising - transplantation of a human porcine pancreas.

Pig parenchyma extracts have been used to treat diabetes before the discovery of insulin. It turns out that the human and pig glands differ in only one amino acid.

Since it develops as a result of the defeat of the islets of Langerhans, their study has great prospects for effective treatment diseases.

In the 19th century, a young scientist from Germany discovered the heterogeneity of pancreatic tissue. Cells that differed from the main mass were located in small clusters, islets. Groups of cells were later named after the pathologist - islets of Langerhans (OL).

Their share in the total volume of tissues is no more than 1-2%, however, this small part of the gland performs its function, different from the digestive one.

Purpose of the Islets of Langerhans

The main part of the cells of the pancreas (PZh) produces enzymes that promote digestion. The function of island clusters is different - they synthesize hormones, so they are referred to as the endocrine system.

Thus, the pancreas is part of two main body systems - digestive and endocrine. Islets are microorganism that produce 5 types of hormones.

Most of the pancreatic groups are located in the tail of the pancreas, although chaotic, mosaic inclusions capture the entire exocrine tissue.

OL are responsible for the regulation of carbohydrate metabolism and support the work of other endocrine organs.

Histological structure

Each island is a self-functioning element. Together they make up a complex archipelago that is made up of individual cells and larger formations. Their sizes vary considerably, from one endocrine cell to a mature, large island (>100 µm).

In pancreatic groups, a hierarchy of cell arrangements is built, there are 5 types of them, all perform their role. Each islet is surrounded by connective tissue, has lobules where capillaries are located.

Groups of beta cells are located in the center, along the edges of the formations are alpha and delta cells. How larger size islet, the more peripheral cells it contains.

The islets do not have ducts, the hormones produced are excreted through the capillary system.

cell types

Different groups of cells produce their own type of hormone, regulating digestion, lipid and carbohydrate metabolism.

1. Alpha cells. This group of OLs is located along the edge of the islets, their volume is 15-20% of overall size. They synthesize glucagon, a hormone that regulates the amount of glucose in the blood.
2. beta cells. They are grouped in the center of the islets and make up the bulk of their volume, 60-80%. They synthesize insulin, about 2 mg per day.
3. delta cells. Responsible for the production of somatostatin, they are from 3 to 10%.
4. Epsilon cells. The amount of the total mass is not more than 1%. Their product is ghrelin.
5. PP cells. The hormone pancreatic polypeptide is produced by this part of the OB. They make up to 5% of the islets.

Over the course of life, the proportion of the endocrine component of the pancreas decreases - from 6% in the first months of life to 1-2% by the age of 50.

Hormonal activity

The hormonal role of the pancreas is great.

The active substances synthesized in small islets are delivered by the bloodstream to the organs and regulate the metabolism of carbohydrates:

1. The main task of insulin is to minimize blood sugar levels. It increases glucose absorption cell walls, accelerates its oxidation and helps to store it as glycogen. Violation of the synthesis of the hormone leads to the development of type 1 diabetes. In this case, blood tests show the presence of antibodies to beta cells. Type 2 diabetes develops when tissues become less sensitive to insulin.
2. Glucagon performs the opposite function - it increases sugar levels, regulates the production of glucose in the liver, and accelerates the breakdown of lipids. Two hormones, complementing the action of each other, harmonize the content of glucose - a substance that ensures the vital activity of the body at the cellular level.
3. Somatostatin slows down the action of many hormones. In this case, there is a decrease in the rate of absorption of sugar from food, a decrease in the synthesis digestive enzymes a decrease in the amount of glucagon.
4. Pancreatic polypeptide reduces the amount of enzymes, slows down the release of bile and bilirubin. It is believed that it stops the consumption of digestive enzymes, keeping them until the next meal.
5. Ghrelin is considered the hunger or satiety hormone. Its production gives a signal to the body about the feeling of hunger.

The amount of hormones produced depends on the glucose received from food and the rate of its oxidation. With an increase in its amount, insulin production increases. Synthesis is triggered at a concentration of 5.5 mmol/l in plasma.

Provoke the production of insulin can not only eating. At healthy person the maximum concentration is observed during the period of strong physical stress, stress.

The endocrine part of the pancreas produces hormones that have a decisive effect on the entire body. Pathological changes in the OB can disrupt the functioning of all organs.

Video about the tasks of insulin in the human body:

The defeat of the endocrine part of the pancreas and its treatment

The cause of the defeat of OL can be a genetic predisposition, infections and poisonings, inflammatory diseases, immune problems.

As a result, there is a cessation or a significant decrease in the production of hormones by different cells of the islets.

As a result, it may develop:

1. SD type 1. It is characterized by the absence or deficiency of insulin.
2. SD type 2. It is determined by the inability of the body to use the hormone produced.
3. Gestational diabetes develops during pregnancy.
4. Other types of diabetes mellitus (MODY).
5. neuroendocrine tumors.

The main principles of the treatment of type 1 diabetes mellitus are the introduction of insulin into the body, the production of which is impaired or reduced. There are two types of insulin - fast-acting and long-acting. The latter type mimics the production of pancreatic hormone.

Type 2 diabetes requires a strict diet, moderate exercise and taking drugs that help burn sugar.

Diabetes is on the rise worldwide and is already being called the plague of the 21st century. Therefore, medical research centers are looking for ways to combat diseases of the islets of Langerhans.

Processes in the pancreas develop rapidly and lead to the death of the islets, which should synthesize hormones.

AT last years became known:

• stem cells transplanted to the pancreas tissue take root well and are able to produce the hormone in the future, as they begin to work as beta cells;
• OL produce more hormones if part of the glandular tissue of the pancreas is removed.

This allows patients to refuse continuous use medicines, strict diet and return to a normal lifestyle. The problem remains the immune system, which can reject transplanted cells.

Another possible way treatment considers transplantation from a donor part of the islet tissue. This method replaces the installation of an artificial pancreas or its complete transplantation from a donor. At the same time, it is possible to stop the progression of the disease and normalize blood glucose.

Successful operations have been performed, after which patients with type 1 diabetes no longer need to administer insulin. The body restored the population of beta cells, the synthesis of its own insulin resumed. Postoperatively, immunosuppressive therapy was administered to prevent rejection.

Video material about the functions of glucose and diabetes:

Medical institutes are working to study the possibility of transplanting a pancreas from a pig. The first drugs for the treatment of diabetes just used parts of the pancreas of pigs.

Scientists agree that it is necessary to study the features of the structure and work of the islets of Langerhans due to a large number important functions that the hormones synthesized in them perform.

The constant intake of artificial hormones does not help to defeat the disease and worsens the patient's quality of life. The defeat of this small part of the pancreas causes profound disruption of the entire body, so research continues.

Table of contents for "Hormone" parathyroid glands. Pineal hormones. Hormones of the pancreas. Sex hormones. thymus hormones.
1. Parathyroid glands. Parathyrin. Parathormone. Calcitriol. Regulatory functions of the parathyroid hormone.
2. Epiphysis. Melatonin. Pineal hormones. Regulatory functions of pineal hormones.
3. Pancreatic hormones. Islets of Langerhans. Somatostatin. Amylin. Regulatory functions of pancreatic hormones.
4. Insulin. Physiological effects of insulin. Scheme of glucose transport across cell membranes. Main effects of insulin.
5. Glucagon. Physiological effects of glucagon. Main effects of glucagon.
6. Sex glands. Sex hormones. Regulatory functions of gonadal hormones.
7. Androgens. Inhibin. Estrogens. Testosterone. Lutropin. Follitropin. Testicular hormones and their effects in the body.
8. Female sex hormones. Ovarian hormones and their effects in the body. Estrogens. Estradiol. Estrone. Estriol. Progesterone.
9. Hormones of the placenta. Estriol. Progesterone. Chorionic gonadotropin.
10. Thymus hormones. Thymosin. Thymopoietin. Timulin. Regulatory functions of thymus hormones.

Hormones of the pancreas. Islets of Langerhans. Somatostatin. Amylin. Regulatory functions of pancreatic hormones.

endocrine function in pancreas do not perform accumulations of cells of epithelial origin, called islets of Langerhans and making up only 1-2% of the mass of the pancreas - an exocrine organ that forms pancreatic digestive juice. The number of islets in the gland of an adult is very large and ranges from 200 thousand to one and a half million.

In the islets, several types of hormone-producing cells are distinguished: alpha cells form glucagon, beta cells - insulin, delta cells - somatostatin, ji-cells - gastrin and PP or F cells - pancreatic polypeptide. In addition to insulin, hormones are synthesized in beta cells. amylin, which has the opposite effect of insulin. The blood supply to the islets is more intense than the main parenchyma of the gland. Innervation is carried out by postganlion sympathetic and parasympathetic nerves, and among the cells of the islands there are nerve cells that form neuroinsular complexes.

Rice. 6.21. Functional organization of the islets of Langerhans as a "mini-organ". Solid arrows - stimulation, dotted arrows - suppression of hormonal secretions. The leading regulator - glucose - with the participation of calcium stimulates the secretion of insulin by β-cells and, on the contrary, inhibits the secretion of glucagon by alpha-cells. Amino acids absorbed in the stomach and intestines are stimulators of the function of all cellular elements of the "mini-organ". The leading "intraorganic" inhibitor of insulin and glucagon secretion is somatostatin, the activation of its secretion occurs under the influence of amino acids absorbed in the intestine and gastrointestinal hormones with the participation of Ca2+ ions. Glucagon is a stimulant of both somatostatin and insulin secretion.

Insulin is synthesized in the endoplasmic reticulum beta cells first in the form of pre-proinsulin, then the 23-amino acid chain is cleaved from it and the remaining molecule is called proinsulin. In the Golgi complex proinsulin It is packaged in granules, in which proinsulin is cleaved into insulin and a connecting peptide (C-peptide). In granules insulin deposited in the form of a polymer and partially in a complex with zinc. The amount of insulin deposited in granules is almost 10 times higher than daily requirement in hormone. Insulin secretion occurs by exocytosis of the granules, while an equimolar amount of insulin and C-peptide enters the blood. Determining the content of the latter in the blood is an important diagnostic test for assessing the secretory ability (3-cells.

secretion of insulin is a calcium dependent process. Under the influence of a stimulus - an increased level of glucose in the blood - the membrane of beta cells depolarizes, calcium ions enter the cells, which starts the process of contraction of the intracellular microtubular system and the movement of granules to plasma membrane followed by their exocytosis.

secretory function of various islet cells is interconnected, depends on the effects of the hormones they form, in connection with which the islets are considered as a kind of "mini-organ" (Fig. 6.21). Allocate two types of insulin secretion: basal and stimulated. Basal insulin secretion carried out constantly, even during fasting and blood glucose levels below 4 mmol / l.

Stimulated secretion of insulin is the answer beta cells islets on elevated level D-glucose in the blood flowing to beta cells. Under the influence of glucose, the energy receptor of beta cells is activated, which increases the transport of calcium ions into the cell, activates adenylate cyclase and the pool (fund) of cAMP. Through these mediators, glucose stimulates the release of insulin into the blood from specific secretory granules. Enhances the response of beta cells to the action of glucose hormone duodenum- gastric inhibitory peptide (GIP). In the regulation of insulin secretion, the vegetative nervous system. Nervus vagus and acetylcholine stimulate insulin secretion, while sympathetic nerves and norepinephrine inhibit insulin secretion through alpha-adrenergic receptors and stimulate the release of glucagon.

A specific inhibitor of insulin production is the hormone of the delta cells of the islets - somatostatin. This hormone is also formed in the intestine, where it inhibits glucose absorption and thereby reduces the response of beta cells to a glucose stimulus. The formation in the pancreas and intestines of peptides similar to mosgos, such as somatostatin, confirms the existence of a unified APUD system in the body. Glucagon secretion is stimulated by a decrease in blood glucose levels, hormones gastrointestinal tract(GIP gastrin, secretin, cholecystokinin-pancreozymin) and with a decrease in Ca2 + ions in the blood. Insulin, somatostatin, blood glucose and Ca2+ suppress the secretion of glucagon. In the endocrine cells of the intestine, glucagon-like peptide-1 is formed, which stimulates the absorption of glucose and the secretion of insulin after a meal. Cells of the gastrointestinal tract that produce hormones are a kind of "early warning devices" of the cells of the pancreatic islets about the intake of nutrients into the body, requiring the participation of pancreatic hormones for utilization and distribution. This functional relationship is reflected in the term " gastro-entero-pancreatic system».

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

What is the islet of Langerhans: purpose

Endocrine cells are located throughout the body. One of the places of their accumulation is the pancreas. The islets of Langerhans are located in the caudal part of the organ. They are cell clusters that produce biologically active substances - hormones. The importance of the islets of Langerhans is enormous. It lies in the product normal amount hormones needed 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.

Thanks to normal operation the insular apparatus does not develop conditions such as diabetes mellitus and hypoglycemia. Cell damage occurs during acute and chronic inflammation- pancreatitis.

Histological structure of the islets

The islet of Langerhans was discovered in the 19th century. It is a concentration of endocrine elements. In children, these formations occupy about 6% of the total area of ​​the body. By adult age, the endocrine part decreases and amounts to only 2%. There are about a million islets of Langerhans in the tail parenchyma. They have their own abundant blood supply and innervation. Each islet consists of lobules that are covered by connective tissue. In addition, it is located outside the endocrine formations. The cells within 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 lower blood glucose levels. In the peripheral part of the lobules are alpha and delta cells. The former produce the contra-insular hormone - glucagon. The latter are necessary for the regulation of endocrine and exocrine activity.

What are the cells of the islets of Langerhans?

Several types of cells are produced in the islets of Langerhans. All of them are involved in biological excretion active substances- peptides and hormones. Most of the islets of Langerhans are represented by beta cells. They are located in the center of each slice. These cells are very important as they produce insulin.

The second most important are the alpha cells of the pancreas. They occupy a quarter of the area of ​​the island. Alpha cells are essential 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 first is about 1/20 of the part. The function of these formations is the production of a pancreatic polypeptide. Delta cells are required to produce somatostatin. This substance is involved in the regulation of carbohydrate metabolism.

Islet cells are difficult to regenerative processes. Therefore, if 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 importance of this fragment is great. In it, the formation of the most important hormones involved in metabolic processes takes place. The islets of Langerhans produce insulin, glucagon, somatostatin, and pancreatic polypeptide.

The first 2 hormones are essential for life. Insulin starts the process of breakdown of glucose into smaller molecular compounds. As a result, blood sugar levels decrease. In addition, insulin is involved in the metabolism of fats. Due to the actions of this hormone in the liver and muscle tissue glycogen accumulates. Insulin has an anabolic effect on the 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 essential 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 decreases. There are very few PP cells in the islets of Langerhans, but the pancreatic polypeptide is necessary for the body. It is involved in the regulation of the secretion of the digestive glands (liver, stomach). With a lack of hormonal activity, serious diseases develop.

Damage to the endocrine pancreas

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

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

Transplantation of the islets of Langerhans

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