thymus- the central organ of lymphoid hematopoiesis and immune protection organism. In the thymus, antigen-independent differentiation of bone marrow precursors of T-lymphocytes into immunocompetent cells - T-lymphocytes occurs. The latter carry out reactions of cellular immunity and participate in the regulation of humoral immunity, which occurs, however, not in the thymus, but in the peripheral organs of hematopoiesis and immune defense. In addition, more than 20 biologically active substances, including distant ones, were found in thymus extracts, which makes it possible to classify thymus as a gland of the endocrine system.

thymus development. The thymus is formed on the 2nd month of embryogenesis in the form of small protrusions of the walls of the 3rd and 4th pairs of gill pockets. On the 6th week, the rudiment of the gland has a distinct epithelial character. On the 7th week, he loses contact with the wall of the head intestine. The epithelium of the anlage of the gland, forming outgrowths into the mesenchyme, acquires a network structure. Initially, the dense epithelial anlage of the gland is loosened due to its colonization with lymphocytes. Their number is growing rapidly, and the gland acquires the structure of a lymphoepithelial organ.

Ingrowing mesenchyme with blood vessels subdivides thymus on slices. In each lobule, a cortex and a medulla are distinguished. In the histogenesis of the thymus in the medulla of the lobules, layered epithelial formations are formed - epithelial pearls, or Hassal's bodies. In their composition, dense epithelial cells are determined, concentrically layering each other.

The structure of the thymus. Outside, the thymus gland is covered with a connective tissue capsule. Partitions extending from it - septa - subdivide the thymus into lobules. The basis of the lobule is made up of process epithelial cells - epithelioreticulocytes, in the reticular skeleton of which are thymic lymphocytes (thymocytes). The source of development of T-lymphocytes are bone marrow stem hematopoietic cells. Further, the precursors of T-lymphocytes (prethymocytes) enter the thymus with blood and turn into lymphoblasts here.

In the thymus cortex some of them, under the action of peptide hormones secreted by epithelial cells - thymosin, thymopoietin, etc., as well as macrophages, are converted into antigen-reactive T-lymphocytes - they acquire receptors for strictly defined antigens. They leave the thymus without entering the medulla and populate thymus-dependent zones lymph nodes and spleen. Here, in the peripheral organs of immunogenesis, they further mature into T-killers (cytotoxic), T-helpers, after which they are capable of recycling, cloning (proliferation), and the formation of memory cells.

Other T lymphoblasts turn into autoimmune cells that are reactive to autoantigens. They undergo destruction by apoptosis (approximately 95% of cells) and are phagocytosed by macrophages.

The process of specialization of T-lymphocytes in the cortical substance of the thymus lobules occurs under conditions that protect against excessive action of antigens on them. This is achieved through the formation of a hematothymic histion (barrier), consisting of the endothelium of hemocapillaries with a distinct continuous basement membrane, the pericapillary space with intercellular substance and macrophages, as well as epithelioreticulocytes with their basement membrane. The thymus cortex has an independent microvasculature. In contrast, in the thymus medulla capillary network does not perform a barrier role, and through the endothelium of these capillaries, mature lymphocytes can leave and return to the thymus, i.e., recirculate.

in the thymus these lymphocytes are found in the medulla. Mature lymphocytes leave the thymus through the wall of the postcapillary venule.

The medulla of the thymus has a lighter color, since there are fewer lymphocytes here than in the cortical substance. The epithelial backbone is more distinct, and the epithelioreticulocytes here are larger and more numerous. In the middle part of the medulla there are stratified epithelial bodies of Hassall. With age, their number and size increase. In the thymus stroma, in addition to epithelioreticulocytes, there are macrophages, dendritic cells of bone marrow origin, neuroendocrine cells - derivatives of the neural crest, and myoid cells.

Age-related changes and reactivity of the thymus.

After 20 years, age involution occurs thymus. This is accompanied by a decrease in the number of lymphocytes and the development of adipose tissue. In cases where the thymus gland does not undergo reverse development, there is a reduced resistance of the body to infections and intoxications.

fabrics thymus are highly reactive structures. Under the action of damaging factors (intoxication, trauma, etc.), the release of T-lymphocytes into the blood and their mass death, mainly in the cortical substance, are observed. The involution of the thymus that occurs under such stressful influences is called temporary, rapidly passing, or accidental. The observed phenomena of lymphocytolysis and phagocytosis by macrophages of dying lymphocytes are considered as possible ways release of growth factors and DNA necessary for tissue repair processes. With the death of lymphocytes under these conditions, the selection of T-lymphoblasts is also associated.

jet changes thymus are in close correlation with functional changes in the adrenal cortex and the level of glucocorticoids in the blood. The thymus revealed adrenergic and cholinergic nerve fibers that enter the organ along with the vessels.

The thymus gland is a paired lobular organ located in upper section anterior mediastinum. It consists of two lobes of unequal size, interconnected by a layer of connective

fabrics. The thymus is innervated by parasympathetic (vagus) and sympathetic nerves originating from the lower cervical and upper thoracic sympathetic ganglia. The thymus produces several hormones: thymosin, homostatic thymic hormone, thymopoietinI, thymopoietinII and thymic humoral factor. All of them are polypeptides. Thymus hormones play an important role in the development of the body's immunological defense reactions, stimulating the formation of antibodies that provide the body's response to a foreign protein.

The thymus controls the development and distribution of lymphocytes involved in immunological reactions. This function is carried out either by saturating the lymphoid tissue with lymphocytes, or by producing hormones that stimulate the development of these blood cells, which are necessary to provide protective immunological reactions. Undifferentiated stem cells that form in the bone marrow enter the bloodstream and enter the thymus gland. In the thymus, they multiply and differentiate into thymic-derived lymphocytes (T-lymphocytes). These lymphocytes are believed to be responsible for the development of cellular immunity. T-lymphocytes make up the majority of lymphocytes circulating in the blood (60-80%).

The secretion of the thymus hormone is regulated by the hypothalamus - the anterior pituitary gland. Somatotropin(growth hormone) promotes the entry of thymus hormones into the blood.

The thymus reaches its maximum development in childhood. After the onset of puberty, it stops in development and begins to atrophy. In this regard, it is believed that iron stimulates the growth of the body and inhibits the development of the reproductive system.

The physiological significance of the thymus gland is due to the fact that it contains a large amount of vitamin C in its cellular structures, yielding in this respect only to the adrenal glands.

With an increase in the thymus gland in children, there is thymic-lymphatic status. It is believed that this condition is an innate constitutional feature of the organism. With this status, in addition to an increase in the thymus, there is an overgrowth of lymphatic tissue. characteristic appearance patient: pasty, puffy face, friability of subcutaneous tissue,

obesity, thin skin, soft hair. There is an opinion that an increase in the thymus gland in children is a manifestation of adrenal insufficiency.

Clinically, thymic-lymphatic status can manifest itself in repeated causeless vomiting, changes in breathing, and even cardiovascular collapse (acute heart failure). In severe cases, death may occur.

10.9. Pancreas

10.9.1. STRUCTURAL AND FUNCTIONAL CHARACTERISTICS

The pancreas is a mixed function gland. The acinar tissue of this gland produces digestive pancreatic juice, which is secreted through the excretory duct into the duodenal cavity. The intrasecretory activity of the pancreas is v its ability to form hormones that come from the gland directly into the blood.

For the first time, German scientists J. Mehring and O. Minkowski (1889) paid attention to the endocrine role of the pancreas. They found that after removal of the pancreas in dogs, symptoms develop that are noted in humans with diabetes mellitus: blood sugar levels rise sharply, it is excreted in significant quantities in the urine; there is an increased appetite, thirst, there is an increased separation of urine. If such animals are transplanted under the skin of the pancreas, then all the marked changes disappear. In 1901, the Russian doctor L.V. Sobolev confirmed the data that the pancreas performs an endocrine function. According to L.V. Sobolev, the pancreas secretes hormones that are involved in the regulation of carbohydrate metabolism. However, these hormones could not be isolated from pancreatic tissue for a long time. This is due to the fact that pancreatic hormones are polypeptides that are destroyed under the influence of proteolytic enzymes of pancreatic juice. L.V. Sobolev was the first to propose two methods for obtaining the hormone of the pancreas - insulin. In the first method, the animal's excretory duct is tied up a few days before the removal of the pancreas. In this case, there is no release of pancreatic juice into the cavity of the duodenum, acinar tissue atrophies. As a result, the possibility of the influence of pancreatic juice enzymes on insulin is excluded and it can be isolated from the gland tissue. Moreover,

L.V. Sobolev proposed to extract insulin from the pancreas of embryos and newborn calves. During this period, the pancreas does not yet form digestive juice, but the synthesis of insulin is already taking place. 20 years after the publication of these works, Canadian scientists F. Banting and S. Best received active insulin preparations.

The morphological substrate of the endocrine function of the pancreas is the islet apparatus of the pancreas (Islets of Langerhans), scattered among the acinar tissue of the gland. Islets are distributed unevenly throughout the gland. They are predominantly located in its caudal part, and only a small number of them are present in the head section of the gland.

In humans, there are 3-25 thousand islets of Langerhans per 1 g of the gland. The islets of Langerhans consist of alpha (A), beta (B), delta, PP and G cells. The bulk of the islets of Langerhans are beta cells. About 1/5 of the total number of cells is accounted for by alpha cells. The latter are larger in size than beta cells and are located mainly along the periphery of the islet.

Produced in beta cells insulin from its predecessor, proinsulin. Synthesis of the latter is carried out in the endoplasmic reticulum of islet cells. Then it is transferred to the Golgi cell apparatus, where the initial stages of the conversion of proinsulin to insulin take place. Alpha cells synthesize glucagon, delta cells - somatostatin. PP cells form in small numbers pancreatic polypeptide- antagonist of cholecystokinin. G cells produce gastrin. In the epithelium of the small excretory ducts, a lipocaic substance is formed, which some researchers attribute to pancreatic hormones, while others consider it as a substance of an enzymatic nature.

The pancreas is innervated by sympathetic and parasympathetic nerves. Sympathetic nerves are represented by fibers coming from the solar plexus, parasympathetic - by the vagus nerve. Their role is to regulate both the formation and secretion of hormones and the blood supply to the pancreas.

Histochemically it was found that the insular tissue of the gland contains a large number of zinc. Zinc is also a component of insulin. The pancreas has an abundant blood supply.

10.9.2. PANCREATIC HORMONES

Insulin takes part in the regulation of carbohydrate metabolism. Under the action of this hormone, there is a decrease in the concentration of glucose in the blood (normal blood glucose is 4.45-4.65 mmol / l, or 80-120 mg%) - hypoglycemia occurs. The decrease in blood glucose levels under the influence of insulin is due to the fact that the hormone promotes the conversion of glucose into glycogen in the liver and muscles. In addition, insulin increases the permeability of cell membranes to glucose. In this regard, there is an increased penetration of glucose into the cells, where its increased absorption is carried out. Insulin stimulates protein synthesis from amino acids and their active transport into cells, delays the breakdown of proteins and their conversion into glucose. Insulin also regulates fat metabolism - promotes the formation of higher fatty acids from carbohydrate metabolism products, and also inhibits the mobilization of fat from adipose tissue.

Insulin receptors are located on the membrane of the target cell (Fig. 10.5), therefore, the hormone primarily exerts its effect without penetrating into the cell. The binding of insulin to a specific cell receptor leads to processes that increase the rate of formation and accumulation of glycogen, protein and lipids. Insulin activity is expressed in laboratory and clinical units. A laboratory, or rabbit, unit is the amount of hormone that, in a healthy rabbit weighing 2 kg, reduces blood glucose to 2.22 mmol / l (40 mg%). For one unit of action (ED) or international unit (IU), the activity of 0.04082 mg of crystalline insulin is taken. The clinical unit is!/$ laboratory.

The basis of the regulation of the formation and secretion of insulin is the content of glucose in the blood. Hyperglycemia leads to increased production and release of insulin into the blood. Hypoglycemia reduces the formation and entry of the hormone into the vascular bed. This is done, firstly, with the help of paraventricular nuclei of the hypothalamic region. With an increase in the concentration of glucose in the blood, an increase in the activity of nerve cells of the paraventricular nucleus occurs. The impulses that have arisen in the neurons are transmitted to the dorsal nuclei of the vagus nerve, and along its fibers to the beta cells of the islets of Langerhans, and the formation and secretion of insufficiency are enhanced in them.

line (diagram 10.3). The action of the latter reduces the level of glucose in the blood. With a decrease in the amount of glucose in the blood below normal, opposite reactions occur. Excitation of the sympathetic nervous systems It inhibits the secretion of insulin.

Secondly, an increased level of glucose in the blood directly excites the receptor apparatus of the pancreatic tissue, which also causes an increase in the formation and secretion of insulin and a decrease in glucose levels. When the amount of glucose in the blood falls, opposite reactions occur. Glucose stimulates the formation and secretion of insulin also due to a direct effect on the beta cells of the islets of Langerhans. It is believed that glucose interacts with a special receptor on the membrane of beta cells (glucose receptor), as a result of which they increase the synthesis and release of insulin into the bloodstream.

Insulin secretion also occurs reflexively when the receptors of a number of reflexogenic zones are stimulated. So, with an increase in the level of glucose in the blood, the chemoreceptors of the carotid sinus are excited, as a result of which a reflex release of insulin into the bloodstream occurs and the level of glucose in the blood is restored. Stimulates the production and secretion of insulin soma-totropin adenohypophysis through soma-tomedinov, gastrointestinal hormones secretin and cholecystokinin-pancreosymin, as well as prostaglandin E by increasing the adenylate cyclase activity of pancreatic beta cell membranes.

Somatostatin in contrast to somatotropin, it inhibits the formation and secretion of insulin by beta cells of the islets of Langerhans. It is produced in the nuclei of the hypothalamus and in the delta cells of the insular pancreas.

The amount of insulin in the blood is also determined by the activity of the enzyme insulinase, which destroys the hormone. The largest amount of the enzyme is found in the liver and skeletal muscles.

Glucagon also takes part in the regulation of carbohydrate metabolism. By the nature of its action on carbohydrate metabolism, it is an insulin antagonist. Under the influence of glucagon, glycogen is broken down in the liver to glucose. As a result, the concentration of glucose in the blood rises. In addition, glucagon stimulates the breakdown of fat in adipose tissue.

The mechanism of action of glucagon on carbohydrate metabolism is due to its interaction with specific specific receptors localized on the cell membrane. When glucagon binds to these cell receptors, the activity of the enzyme adenylate cyclase and the concentration of intracellular cyclic adenosine monophosphate (cAMP) increase. The latter promotes the process of glycogenolysis, i.e. conversion of glycogen to glucose (Scheme 10.4).

With an increase in the content of glucose in the blood, the formation and secretion of glucagon is inhibited, with a decrease - an increase. A growth hormone - growth hormone through somatomedina increases the activity of alpha cells, and they produce more hormone. Somatostatin inhibits the formation and secretion of glucagon. It is believed that this is due to the fact that somatostatin blocks the entry into the alpha cells of the pancreas of calcium ions, which are necessary for the formation and secretion of glucagon.

Insufficiency of the intrasecretory function of the pancreas, accompanied by a decrease in insulin secretion, leads to a disease called diabetes mellitus, or diabetes mellitus.

The thymus gland is the most mysterious in human body. Her middle name is thymus. Its existence has been known since ancient times, the ancient Greeks believed that it was there that the human soul was located and translated its name as “life force”.

The thymus gland is located in the sternum, reaches the root of the tongue. If you want to know where your thymus gland is located, put two fingers under the clavicular fossa - this is its approximate location.

Since antiquity, they knew that a person has a thymus gland, but they did not fully understand what it was. Doctors of past centuries called it goiter - because it is located next to the thyroid, they considered it a rudiment. And only in the middle of the last century did they understand its true purpose - this is one of the main organs immune system. Moreover, it is part of both the endocrine and the human immune system. She begins to work from the prenatal period, from about 6-8 weeks of pregnancy, her location is where the embryo had gill slits.

It works most actively only in the first few years of life, its peak is at the age of five. That is why it is sometimes called the "iron of childhood." By the end puberty her activity drops sharply, and by the age of 30 only half of what was in childhood is noted. By the age of 40, only 5% of people can find this gland, which practically does not work anymore. It is with the extinction of the work of the thymus gland that the decrease in immunity in the elderly is associated. The process of extinction of the work of the gland is called involution. The duration of its work is genetically determined, and the longer it functions, the better for a person, because it, in fact, slows down aging.

Pathology of the thymus

In violation of immunogenesis, changes in the gland are observed, which are represented by such diseases as dysplasia, aplasia, accidental involution, atrophy, hyperplasia with lymphoid follicles, thymomegaly. Often, thymus pathology is associated either with endocrine disorder or with an autoimmune or oncological disease. most common cause the fall of cellular immunity is an age-related involution, in which there is a deficiency of melatonin in the pineal gland.

How to treat the thymus

As a rule, thymus pathologies are observed up to 6 years. Then they disappear or pass into more serious illness. If the child has an enlarged goiter gland, then a phthisiatrician, immunologist, pediatrician, endocrinologist and otolaryngologist should be observed. Parents should take precautions respiratory diseases. If symptoms such as bradycardia, weakness and/or apathy are present, urgent health care. Treatment of the thymus gland in children and adults is carried out by medical or surgical methods.

Medical treatment

When the immune system is weakened, to maintain the body, it requires the introduction of biologically active substances. These are the so-called immunomodulators that thymus therapy offers. Treatment of the goiter gland in most cases is carried out on an outpatient basis and consists of 15-20 injections that are injected into the gluteal muscle. The treatment regimen for thymus pathologies may vary, depending on clinical picture. In the presence of chronic diseases therapy can be carried out for 2-3 months, 2 injections per week.

Intramuscularly or subcutaneously, 5 ml of thymus extract isolated from the peptides of the goiter gland of animals is injected. It is a natural biological raw material without preservatives and additives. Noticeable improvement in 2 weeks general condition patient, because during the treatment, protective blood cells are activated. Thymus therapy has a long-term effect on the body after the therapy. A second course can be carried out after 4-6 months.

Surgery to remove the thymus

Thymectomy or removal of the thymus is indicated if the gland has a tumor (thymoma). The operation is carried out under general anesthesia which keeps the patient in a state of sleep during the entire surgical intervention. There are three types of thymectomy:

1. Transsternal. An incision is made in the skin, after which the sternum is separated. The thymus is separated from the tissues and removed. The incision is closed with staples or sutures.
2. Transcervical. An incision is made along the lower part of the neck, after which the gland is removed.
3. Video assisted surgery. Several small incisions are made in the upper mediastinum. A camera is inserted through one of them, displaying the image on the monitor in the operating room. During the operation, robotic arms are used, which are inserted into the incisions.

diet therapy

In the treatment of thymus pathologies important role plays diet therapy. Include foods rich in vitamin D in your diet: egg yolk, brewer's yeast, dairy products, fish fat. Recommended use walnut, beef, liver. When developing a diet, doctors advise including in the diet:

• parsley;
• broccoli, cauliflower;
• oranges, lemons;
• sea ​​buckthorn;
• syrup or decoction of wild rose.

Alternative treatment of the thymus gland

Children's doctor Komarovsky advises to warm up the thymus with a special massage to increase immunity. If an adult has an unreduced gland, then he should maintain immunity for prevention by taking herbal preparations with wild rose, black currant, raspberry, lingonberry. Thymus treatment folk remedies it is not recommended to carry out, since the pathology requires strict medical supervision.

Video: What is the thymus in the human body

The information presented in the article is for informational purposes only. The materials of the article do not call for self-treatment. Only a qualified doctor can make a diagnosis and make recommendations for treatment based on individual features specific patient.

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Anatomy and structure of the thymus gland

The thymus gland is undoubtedly one of the most important human organs. This anatomical structure was named that way for the reason that outwardly it is very similar to latin letter V, and also due to the fact that this organ extends to the neck in the form of a two-pronged fork. However, it also has other names. In particular, doctors often call it "thymus". Interestingly, in translation from Greek the word means "life force".

Another name for this organ is the thymus gland - this is how it was called in the past, apparently because of its proximity to the thyroid gland.

Below we will consider the structure and functions of this organ, and also try to understand where the thymus gland is located in humans.

The anatomy of the thymus has age features. It grows until the period of puberty and its weight from 12 at birth increases by this moment to 35-40 g. At about 15 years, the processes of reverse development of the organ begin. By the age of 25, its weight is 25 g, and by the age of 60 it is about less than 15 g. At 70, the mass of the goiter is only about 6 g.

In this case, predominantly the lateral and partly lower parts of the gland atrophy, being replaced by adipose tissue. Because of this, the body becomes more elongated.

It is enough to look at the photo of the thymus gland above to understand that such a name was given to it for a reason.

Where is the thymus located in adults and children

Speaking about where the thymus gland is located, you need to remember the structure chest, which includes the ribs and sternum. In relation to them, this organ is projected 1-1.5 cm above the handle of the sternum, and the lower end reaches the 3rd, 4th, and sometimes 5th rib. But this is for children.

In an adult person, cervical region thymus is not developed, therefore the upper edge of the gland is located behind the handle of the sternum at various levels downward from the jugular notch. In this case, the lower edge reaches the 2nd intercostal space or 3rd rib.

The structure and role of the thymus gland

The structure of the thymus gland is lobulated. From the capsule, with which the thymus is covered on the outside, partitions extend into the organ, dividing it into lobules, each of which has a cortical substance formed by epithelial cells and lymphocytes, and a medulla consisting of the so-called thymus bodies (flattened and keratinized epithelial cells).

Both lobes of the organ are connected to one another with the help of a loose connective tissue. With their narrow upper ends, the lobes, as a rule, protrude beyond the boundaries of the chest, leaving it in the area top edge handles of the sternum. Sometimes they can even reach the thyroid gland.

Having an expansion in its lower part, the thymus lies in front of the heart and large vessels.

The importance of the thymus gland is difficult to exaggerate. She has importance for the immune system. It can even be said that the thymus is its central organ, due to the fact that the lymphocytes contained in it contribute to protection against cells that, due to certain injuries, are alien to the body.

The role of the thymus lies in the fact that it “trains” immune cells, forms them, and promotes their movement. V infancy it is the thymus that is burdened with all the protective functions. And only then, with the growth and development of other organs, security tasks are partially transferred to them.

The leading positions of the thymus in the processes of creating the body's defense in the form of the immune system were opened thanks to the experiments of the Australian scientist D. Miller in 1961. He removed the thymus gland in newborn mice, which ultimately led to a decrease in antibody production, plus, there was an increase in the viability of the transplanted tissue.

This proved the participation of the thymus in humoral-type immune reactions, consisting in the formation of antibodies, and also confirmed its participation in cell-type reactions due to which the alien transplanted (transplanted) tissue is rejected. Different classes of lymphocytes take part in these reactions. Stimulate the production of antibodies B-lymphocytes, contribute to the death of foreign material - T-lymphocytes.

However, in adulthood it also happens that, due to the pathology of this and other lymphoid organs develops quite dangerous violation immune processes, which in particular can lead to sudden death when anesthesia is given during surgery.

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Thymus: what is it and why does a person need it?

Controls skin regeneration and cell repair process

If the thymus gland has a "secret of beauty", then why is no one considering the option of thymus transplantation as one of the ways to rejuvenate? The whole problem is that Thymus transplant operations are very complex and quite traumatic.

Surgical intervention of this kind requires implantation of the gland along with the sternum and bone marrow.

Doctors have found a less dangerous way to rejuvenate - enough inject embryonic stem cells into the thymus. This procedure restores the thymus gland, which subsequently entails the rejuvenation of the patient.

Diseases

Thymus disease is rare. Possible hyperplasia, hypoplasia and aplasia of the thymus:

The degeneration of the thymus can stop by replenishing zinc. To restore and maintain the thymus, there are methods external influence: rubbing essential ointments, warm compresses, physiotherapy. But it is not recommended to get involved in such methods - no more than 10 days.

There is another fairly simple method - make light taps with your fingers on the place where the thymus is located. About 20 taps several times a day are enough, and soon you can feel a noticeable surge of vigor and strength.

The thymus, despite its early involution and atrophy, is an amazing organ. In the first couple of years after birth, a person acquires a set of cell receptors that are able to resist foreign antigens throughout life .

To maintain the longevity of the thymus eat more animal proteins, B vitamins. products containing a large amount of zinc and try to avoid stress. A good lymphatic drainage massage will also help keep the whole body in good shape.

Symptoms of thymus diseases in adults Features and course of lymphatic-hypoplastic diathesis Symptoms, treatment and prognosis of lymphosarcoma in adults and children Where is located Bone marrow a person and why is he needed?

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