Pituitary Gland – Development, Age Features, Anatomy, Hormones

The pituitary gland (hypophysis, s.glandula pituitaria) is located in the pituitary fossa of the Turkish saddle of the sphenoid bone and is separated from the skull cavity by the process of the hard shell of the brain, which forms the saddle diaphragm. Through a hole in this diaphragm, the pituitary gland is connected to the funnel of the hypothalamus of the diencephalon. The transverse dimension of the pituitary gland is 10-17 mm, anteroposterior – 5-15 mm, vertical – 5-10 mm. The mass of the pituitary gland in men is approximately 0.5 g, in women – 0.6 g. Outside, the pituitary gland is covered with a capsule.

In accordance with the development of the pituitary gland, from two different primordia in the organ, two lobes are distinguished – anterior and posterior. The adenohypophysis, or the anterior lobe (adenohypophysis, s.lobus anterior), is larger, accounting for 70-80% of the total mass of the pituitary gland. It is denser than the posterior lobe. In the anterior lobe, the distal part (pars distalis) is distinguished, which occupies the anterior part of the pituitary fossa, the intermediate part (pars intermedia), located on the border with the posterior lobe, and the tuberous part (pars tuberalis), which extends upward and connects to the funnel of the hypothalamus. Due to the abundance of blood vessels, the anterior lobe has a pale yellow color with a reddish tint.

The parenchyma of the anterior pituitary gland is represented by several types of glandular cells, between the cords of which there are sinusoidal blood capillaries. Half (50%) of the cells of the adenohypophysis are chromaphilic adenocytes, which have fine-grained granules in their cytoplasm that are well stained with chromium salts. These are acidophilic adenocytes (40% of all cells of the adenohypophysis) and basophilic adenocytes (10%). The basophilic adenocytes include gonadotropic, corticotropic and thyroid-stimulating endocrinocytes. Chromophobic adenocytes are small, they have a large nucleus and a small amount of cytoplasm. These cells are considered precursors of chromophilic adenocytes. The other 50% of the cells of the adenohypophysis are chromophobic adenocytes. corticotropic and thyroid-stimulating endocrinocytes. Chromophobic adenocytes are small, they have a large nucleus and a small amount of cytoplasm.

These cells are considered precursors of chromophilic adenocytes. The other 50% of the cells of the adenohypophysis are chromophobic adenocytes. corticotropic and thyroid-stimulating endocrinocytes. Chromophobic adenocytes are small, they have a large nucleus and a small amount of cytoplasm. These cells are considered precursors of chromophilic adenocytes. The other 50% of the cells of the adenohypophysis are chromophobic adenocytes.

 

The neurohypophysis, or posterior lobe (neurohypophysis, s.lobus posterior), consists of a nerve lobe (lobus nervosus), which is located in the posterior part of the pituitary fossa, and a funnel (infundibulum), located behind the tuberous part of the adenohypophysis. The posterior lobe of the pituitary gland is formed by neuroglial cells (pituicites), nerve fibers coming from the neurosecretory nuclei of the hypothalamus to the neurohypophysis, and neurosecretory bodies.

The pituitary gland, with the help of nerve fibers (pathways) and blood vessels, is functionally connected with the hypothalamus of the diencephalon, which regulates the activity of the pituitary gland. The pituitary gland and hypothalamus, together with their neuroendocrine, vascular and nerve connections, are usually considered as the hypothalamic-pituitary system.

The hormones of the anterior and posterior lobes of the pituitary gland affect many bodily functions, primarily through other endocrine glands. In the anterior lobe of the pituitary glandacidophilic adenocytes (alpha cells) produce somotropic hormone (growth hormone), which takes part in the regulation of the growth and development of a young organism. Corticotropic endocrinocytessecrete adrenocorticotropic hormone (ACTH), which stimulates the secretion of steroid hormones by the adrenal glandsThyrotropic endocrinocytessecrete thyrotropic hormone (TSH), which affects the development of the thyroid gland and activates the production of its hormones. Gonadotropic hormones: follicle-stimulating (FSH), luteinizing (LH) and prolactin – affect the body’s puberty, regulate and stimulate the development of follicles in the ovary, ovulation, breast growth and milk production in women, the process of spermatogenesis in men. These hormones are produced by thebasophilic adenocytes of the beta cellsHere lipotropic factors of the pituitary gland are secreted, which influence the mobilization and utilization of fats in the body. In the intermediate part of the anterior lobe, a melanocyte-stimulating hormone is formed, which controls the formation of pigments – melanins – in the body.

The neurosecretory cells of the supraoptic and paraventricular nuclei in the hypothalamus produce vasopressin and oxytocin. These hormones are transported to the cells of the posterior pituitary gland by axons that make up the hypothalamic-pituitary tract. From the posterior lobe of the pituitary gland, these substances enter the blood. The hormone vasopressin has a vasoconstrictor and antidiuretic effect, for which it also received the name antidiuretic hormone (ADH). Oxytocin has a stimulating effect on the contractility of the musculature of the uterus, enhances milk secretion by the lactating mammary gland, inhibits the development and function of the corpus luteum, and affects the change in the tone of smooth (unmarked) muscles of the gastrointestinal tract.

Development of the pituitary gland

The anterior lobe of the pituitary gland develops from the epithelium of the dorsal wall of the mouth bay in the form of an annular outgrowth (Rathke’s pocket). This ectodermal protrusion grows towards the bottom of the future III ventricle. Towards him from the lower surface of the second cerebral bladder (the future bottom of the third ventricle), a process grows, from which the gray tubercle of the funnel and the posterior lobe of the pituitary gland develop.

Vessels and nerves of the pituitary gland

From the internal carotid arteries and vessels of the arterial circle of the cerebrum, the upper and lower pituitary arteries are directed to the pituitary gland. The superior pituitary arteries go to the gray nucleus and the funnel of the hypothalamus, anastomose here with each other and form capillaries penetrating into the brain tissue – the primary hemocapillary network. From the long and short loops of this network, portal veins are formed, which are directed to the anterior lobe of the pituitary gland. In the parenchyma of the anterior pituitary gland, these veins disintegrate into wide sinusoidal capillaries, forming a secondary hemocapillary network. The posterior lobe of the pituitary gland is supplied primarily by the inferior pituitary artery. There are long arterial anastomoses between the superior and inferior pituitary arteries. The outflow of venous blood from the secondary hemocapillary network is carried out through the vein system,

In the innervation of the pituitary gland, sympathetic fibers are involved, which penetrate the organ along with the arteries. Postganglionic sympathetic nerve fibers depart from the plexus of the internal carotid artery. In addition, in the posterior lobe of the pituitary gland, numerous endings of processes of neurosecretory cells are found that lie in the nuclei of the hypothalamus.

Age features of the pituitary gland

The average mass of the pituitary gland in newborns reaches 0.12 g. The mass of the organ doubles by 10 and triples by 15 years. By the age of 20, the mass of the pituitary gland reaches its maximum (530-560 mg) and in subsequent age periods hardly changes. After 60 years, there is a slight decrease in the mass of this endocrine gland.

 

Pituitary gland hormones

The unity of the nervous and hormonal regulation in the body is ensured by the close anatomical and functional connection between the pituitary gland and the hypothalamus. This complex determines the state and functioning of the entire endocrine system.

The main endocrine gland, which produces a number of peptide hormones that directly regulate the function of peripheral glands, is the pituitary gland. It is a reddish-gray bean-shaped formation, covered with a fibrous capsule weighing 0.5-0.6 g. It varies slightly depending on the sex and age of the person. It remains generally accepted to divide the pituitary gland into two lobes, different in development, structure and functions: the anterior distal – the adenohypophysis and the posterior – the neurohypophysis. The first is about 70% of the total mass of the gland and is conventionally divided into distal, funnel and intermediate parts, the second – into the posterior part, or lobe, and the pituitary pedicle. The gland is located in the pituitary fossa of the sella turcica of the sphenoid bone and is connected to the brain through the leg. The upper part of the anterior lobe is covered by the optic chiasm and optic tracts. The blood supply to the pituitary gland is very abundant and is carried out by the branches of the internal carotid artery (superior and inferior pituitary arteries), as well as by the branches of the arterial circle of the large brain. The upper pituitary arteries are involved in the blood supply to the adenohypophysis, and the lower ones – to the neurohypophysis, in contact with the neurosecretory endings of the axons of the large cell nuclei of the hypothalamus. The first enter the median elevation of the hypothalamus, where they disintegrate into the capillary network (primary capillary plexus). These capillaries (which are in contact with the axon terminals of small neurosecretory cells of the mediobasal hypothalamus) collect in the portal veins that descend along the pituitary pedicle into the parenchyma of the adenohypophysis, where they again divide into a network of sinusoidal capillaries (secondary capillary plexus). So blood

The outflow of blood saturated with adeno-hypophyseal hormones from the numerous capillaries of the secondary plexus is carried out through the vein system, which in turn flows into the venous sinuses of the dura mater and further into the general bloodstream. Thus, the portal system of the pituitary gland with a descending direction of blood flow from the hypothalamus is a morphofunctional component of the complex mechanism of neurohumoral control of the tropic functions of the adenohypophysis.

The innervation of the pituitary gland is carried out by sympathetic fibers that follow the pituitary arteries. They are started by postganglionic fibers passing through the internal carotid plexus connected with the upper cervical nodes. There is no direct innervation of the adenohypophysis from the hypothalamus. Nerve fibers of the hypothalamic neurosecretory nuclei enter the posterior lobe.

According to histological architectonics, the adenohypophysis is a very complex formation. It distinguishes between two types of glandular cellschromophobic and chromophobic and homophilic. The latter, in turn, are divided into acidophilic and basophilic (a detailed histological description of the pituitary gland is given in the corresponding section of the manual). However, it should be noted that the hormones produced by the glandular cells that are part of the parenchyma of the adenohypophysis, due to the diversity of the latter, are somewhat different in their chemical nature, and the fine structure of the secreting cells must correspond to the biosynthesis characteristics of each of them. But sometimes in the adenohypophysis, transitional forms of glandular cells can also be observed, which are capable of producing several hormones. There is information about

Under the diaphragm of the sella turcica is the funnel portion of the anterior lobe. It covers the pituitary gland in contact with the gray tubercle. This part of the adenohypophysis is characterized by the presence of epithelial cells in it and an abundant blood supply. It is also hormonally active.

The intermediate (middle) part of the pituitary gland consists of several layers of large secretory-active basophilic cells.

The pituitary gland performs various functions through its hormones. In its anterior lobe, adrenocorticotropic (ACTH), thyroid-stimulating (TSH), follicle-stimulating (FSH), luteinizing (LH), lipotropic hormones, as well as growth hormonesomatotropic (STO and prolactin) are produced. In the intermediate lobe, melanocyte-stimulating hormone in the back vasopressin and oxytocin accumulate.

 

ACTH – Adrenocorticotrophic hormone (Pituitary Gland Hormone)

Pituitary hormones are a group of protein and peptide hormones and glycoproteins. Of the hormones of the anterior pituitary gland, ACTH is the most studied. It is produced by basophilic cells. Its main physiological function is the stimulation of biosynthesis and the secretion of steroid hormones by the adrenal cortexACTH also exhibits melanocyte-stimulating and lipotropic activity. In 1953 it was isolated in its purest form. Later, its chemical structure was established, consisting of 39 amino acid residues in humans and a number of mammals. ACTH is not species specific. At present, chemical synthesis of both the hormone itself and various, more active than natural hormones, fragments of its molecule has been carried out. In the structure of the hormone there are two sections of the peptide chain, one of which ensures the detection and binding of ACTH to the receptor, and the other has a biological effect. It appears to bind to the ACTH receptor through the interaction of electrical charges between the hormone and the receptor. The role of the biological effector of ACTH is performed by the 4-10 molecule fragment (Met-Glu-Gis-Phen-Arg-Tri-Tri).

The melanocyte-stimulating activity of ACTH is due to the presence in the molecule of the N-terminal region, consisting of 13 amino acid residues and repeating the structure of the alpha-melanocyte-stimulating hormone. The same site contains a heptapeptide that is present in other pituitary hormones and has some adrenocorticotropic, melanocyte-stimulating and lipotropic activities.

The key moment in the action of ACTH should be considered the activation of the enzyme protein kinase in the cytoplasm with the participation of cAMP. Phosphorylated protein kinase activates the enzyme esterase, which converts cholesterol esters into free substance in fat droplets. The protein synthesized in the cytoplasm as a result of ribosome phosphorylation stimulates the binding of free cholesterol to cytochrome P-450 and its transfer from lipid droplets to mitochondria, where all the enzymes that convert cholesterol into corticosteroids are present.

 

Thyroid-stimulating hormone (Pituitary Gland Hormone)

TSH thyrotropin – the main regulator of the development and functioning of the thyroid gland, the processes of synthesis and secretion of thyroid hormones. This complex protein, a glycoprotein, is composed of alpha and beta subunits. The structure of the first subunit coincides with the alpha subunit of luteinizing hormone. Moreover, it is largely the same in different animal species. The sequence of amino acid residues in the beta subunit of human TSH has been deciphered and consists of 119 amino acid residues. It can be noted that the TSH beta subunits of humans and cattle are in many ways similar. The biological properties and nature of the biological activity of glycoprotein hormones are determined by the beta subunit. It also allows the hormone to interact with receptors in various target organs. However, the beta subunit in most animals exhibits specific activity only after combining it with the alpha subunit, which acts as a kind of hormone activator. In this case, the latter with the same probability induces luteinizing, follicle-stimulating and thyroid-stimulating activities, determined by the properties of the beta subunit. The found similarity allows us to make a conclusion about the emergence of these hormones in the process of evolution from one common precursor, the beta subunit also determines the immunological properties of hormones. There is an assumption that the alpha subunit protects the beta subunit from the action of proteolytic enzymes, and also facilitates its transport from the pituitary gland to the peripheral target organs. acting as a kind of hormone activator. In this case, the latter with the same probability induces luteinizing, follicle-stimulating and thyroid-stimulating activities, determined by the properties of the beta subunit. The found similarity allows us to make a conclusion about the emergence of these hormones in the process of evolution from one common precursor, the beta subunit also determines the immunological properties of hormones. There is an assumption that the alpha subunit protects the beta subunit from the action of proteolytic enzymes, and also facilitates its transport from the pituitary gland to the peripheral target organs. acting as a kind of hormone activator. In this case, the latter with the same probability induces luteinizing, follicle-stimulating and thyroid-stimulating activities, determined by the properties of the beta subunit. The found similarity allows us to make a conclusion about the emergence of these hormones in the process of evolution from one common precursor, the beta subunit also determines the immunological properties of hormones. There is an assumption that the alpha subunit protects the beta subunit from the action of proteolytic enzymes, and also facilitates its transport from the pituitary gland to the peripheral target organs. The found similarity allows us to make a conclusion about the emergence of these hormones in the process of evolution from one common precursor, the beta subunit also determines the immunological properties of hormones. There is an assumption that the alpha subunit protects the beta subunit from the action of proteolytic enzymes, and also facilitates its transport from the pituitary gland to the peripheral target organs. The found similarity allows us to make a conclusion about the emergence of these hormones in the process of evolution from one common precursor, the beta subunit also determines the immunological properties of hormones. There is an assumption that the alpha subunit protects the beta subunit from the action of proteolytic enzymes, and also facilitates its transport from the pituitary gland to the peripheral target organs.

Gonadotropic hormones

Gonadotropins are present in the body as LH and FSH. The functional purpose of these hormones is generally reduced to ensuring reproductive processes in individuals of both sexes. They, like TSH, are complex proteins – glycoproteins. FSH induces maturation of follicles in the ovaries in females and stimulates spermatogenesis in males. LH causes rupture of the follicle in females with the formation of a corpus luteum and stimulates the secretion of estrogen and progesterone. In males, the same hormone accelerates the development of interstitial tissue and the secretion of androgens. The effects of gonadotropins are dependent on each other and occur synchronously.

The dynamics of the secretion of gonadotropins in women changes during the menstrual cycle and has been studied in sufficient detail. In the preovulatory (follicular) phase of the cycle, the LH content is at a rather low level, and FSH is increased. As the follicle matures, the secretion of estradiol increases, which contributes to an increase in the production of gonadotropins by the pituitary gland and the occurrence of both LH and FSH cycles, i.e., sex steroids stimulate the secretion of gonadotropins.

Currently, the structure of the LH has been determined. Like TSH, it consists of 2 subunits: alpha and beta. The structure of the LH alpha subunit in different animal species is largely the same, it corresponds to the structure of the TSH alpha subunit.

The structure of the beta subunit of LH differs markedly from the structure of the beta subunit of TSH, although it has four identical regions of the peptide chain, consisting of 4-5 amino acid residues. In TSH, they are localized in positions 27-31, 51-54, 65-68 and 78-83. Since the beta subunit of LH and TSH determines the specific biological activity of hormones, it can be assumed that the homologous regions in the structure of LH and TSH should ensure the connection of the beta subunits with the alpha subunit, and regions that are different in structure should be responsible for the specificity of the biological activity of hormones.

Native LH is very stable to the action of proteolytic enzymes, however, the beta subunit is rapidly cleaved by chymotrypsin, and the a-subunit is difficult to hydrolyze by the enzyme, i.e., it plays a protective role, preventing chymotrypsin from accessing peptide bonds.

As for the chemical structure of FSH, at present, researchers have not received definitive results. Like LH, FSH is composed of two subunits, but the beta subunit of FSH is different from the beta subunit of LH.

 

Prolactin

Another hormone, prolactin (lactogenic hormone), is actively involved in the reproduction process. The main physiological properties of prolactin in mammals are manifested in the form of stimulation of the development of mammary glands and lactation, the growth of the sebaceous glands and internal organs. It promotes the manifestation of the effect of steroids on secondary sexual characteristics in males, stimulates the secretory activity of the corpus luteum in mice and rats, and is involved in the regulation of fat metabolism. Much attention has been paid to prolactin in recent years as a regulator of maternal behavior; this multifunctionality is explained by its evolutionary development. It is one of the oldest pituitary hormones and is found even in amphibians. At present, the structure of prolactin in some mammalian species has been completely deciphered. However, until recently, scientists have expressed doubts about the existence of such a hormone in humans. Many believed that growth hormone fulfills its function. Now convincing evidence of the presence of prolactin in humans has been obtained and its structure has been partially deciphered. Prolactin receptors actively bind growth hormone and placental lactogen, which indicates a single mechanism of action of the three hormones.

 

Somatotropin

Growth hormone, somatotropin, has an even wider spectrum of action than prolactin. Like prolactin, it is produced by acidophilic cells of the adenohypophysis. STH stimulates the growth of the skeleton, activates protein biosynthesis, gives a fat-mobilizing effect, and helps to increase body size. In addition, he coordinates metabolic processes.

The participation of the hormone in the latter is confirmed by the fact of a sharp increase in its secretion by the pituitary gland, for example, with a decrease in blood sugar.

The chemical structure of this human hormone is now fully established – 191 amino acid residues. Its primary structure is similar to the structure of chorionic somatomammotropin or placental lactogen. These data indicate a significant evolutionary affinity for the two hormones, although they exhibit differences in biological activity.

It is necessary to emphasize the great species specificity of the hormone in question – for example, STH of animal origin is inactive in humans. This is due to both the reaction between human and animal STH receptors and the structure of the hormone itself. Currently, research is underway to identify active centers in the complex structure of STH that exhibit biological activity. Separate fragments of the molecule that exhibit different properties are being studied. For example, after hydrolysis of human STH with pepsin, a peptide consisting of 14 amino acid residues and corresponding to the region of the molecule 31-44 was isolated. It did not have the effect of growth, but in lipotropic activity it significantly exceeded the native hormone. Human growth hormone, in contrast to the analogous hormone of animals, has significant lactogenic activity.

In the adenohypophysis, many peptide and protein substances are synthesized that have a fat-mobilizing effect, and the tropic hormones of the pituitary glandACTH, STH, TSH and others – have a lipotropic effect. In recent years, beta and y-lipotropic hormones (LPH) have been highlighted. The biological properties of beta-LPG have been studied in most detail, which, in addition to lipotropic activity, also has a melanocyte-stimulating, corticotropin-stimulating and hypocalcemic effect, as well as an insulin-like effect.

Currently, the primary structure of sheep LPG (90 amino acid residues), pig and cattle lipotropic hormones has been deciphered. This hormone has species specificity, although the structure of the central region of beta-LPH is the same in different species. It determines the biological properties of the hormone. One of the fragments of this region is found in the structure of alpha-MSH, beta-MSH, ACTH and beta-LPG. It is suggested that these hormones evolved from the same precursor. y-LPG has a weaker lipotropic activity than beta-LPG.

 

Melanocyte-stimulating hormone

This hormone, synthesized in the intermediate lobe of the pituitary gland, by its biological function stimulates the biosynthesis of the skin pigment melanin, promotes an increase in the size and number of pigment cells of melanocytes in the skin of amphibians. These qualities of MSH are used in biological hormone testing. There are two types of hormone: alpha and beta MSH. It was shown that alpha-MSH has no species specificity and has the same chemical structure in all mammals. Its molecule is a peptide chain consisting of 13 amino acid residues. Beta-MSH, on the other hand, is species specific, and its structure differs in different animals. In most mammals, the beta-MSH molecule consists of 18 amino acid residues, and only in humans it is extended from the amino end by four amino acid residues. It should be noted.

 

Oxytocin and vasopressin

In the posterior lobe of the pituitary gland, vasopressin and oxytocin accumulate, which are synthesized in the hypothalamus: vasopressin – in the neurons of the supraoptic nucleus, and oxytocin – in the paraventricular nucleus. Then they are transferred to the pituitary gland. It should be emphasized that the precursor of the hormone vasopressin is first synthesized in the hypothalamus. At the same time, the protein neurophysin of the 1st and 2nd types is produced there. The former binds oxytocin, and the latter, vasopressin. These complexes migrate in the form of neurosecretory granules in the cytoplasm along the axon and reach the posterior lobe of the pituitary gland, where nerve fibers end in the vascular wall and the contents of the granules enter the blood. Vasopressin and oxytocin are the first pituitary hormones with a fully established amino acid sequence. By their chemical structure, they are nonapeptides with one disulfide bridge.

The hormones under consideration give various biological effects: they stimulate the transport of water and salts through membranes, have a vasopressor effect, increase the contractions of the smooth muscles of the uterus during childbirth, and increase the secretion of the mammary glands. It should be noted that vasopressin has a higher antidiuretic activity than oxytocin, while the latter has a stronger effect on the uterus and mammary gland. The main regulator of vasopressin secretion is water consumption; in the renal tubules, it binds to receptors in the cytoplasmic membranes with subsequent activation of the enzyme adenylate cyclase in them. Different parts of the molecule are responsible for the binding of the hormone to the receptor and for the biological effect.

The pituitary gland, connected through the hypothalamus with the entire nervous system, unites the endocrine system into a functional whole, which is involved in ensuring the constancy of the internal environment of the body (homeostasis). Within the endocrine system, homeostatic regulation is based on the principle of feedback between the anterior lobe of the pituitary gland and the target glands (thyroid gland, adrenal cortex, gonads). An excess of the hormone produced by the “target” gland inhibits, and its deficiency stimulates the secretion and release of the corresponding tropic hormone. The hypothalamus is included in the feedback system. It is in it that receptor zones sensitive to hormones of the target glands are located. By specifically binding to hormones circulating in the blood and changing the response depending on the concentration of hormones, hypothalamic receptors transmit their effect to the corresponding hypothalamic centers, which coordinate the work of the adenohypophysis, releasing hypothalamic adenohypophysotropic hormones. Thus, the hypothalamus should be considered as the neuro-endocrine brain.

Symptoms of hypothalamus damage

The hypothalamus is the fundus of the brain ventricle and consists of an accumulation of highly differentiated nuclei (32 pairs). There are three groups of hypothalamic nuclei – anterior, middle and posterior.

The anterior part of the hypothalamus includes the paraventricular supraoptic nuclei; to the middle section – the posterior parts of the supraoptic nuclei, the nuclei of the central gray matter of the ventricle, mastoid-funnel (anterior part), pallido-infundibular, interfornal nuclei; to the posterior section – the mastoid body, the mastoid-funnel nuclei (posterior part), the subthalamic nucleus. The anterior parts of the hypothalamus are related to the integration of the predominantly parasympathetic autonomic nervous system, the posterior ones are sympathetic, the middle ones provide the regulation of the activity of the endocrine glands and metabolism.

In the hypothalamic region, a subthalamic region is also distinguished, including a subthalamic nucleus, an undefined zone, Trout fields (H 1 and H 2 ) and some other formations. Functionally, the subthalamic region is part of the extrapyramidal system. In the lower part of the hypothalamus there are a gray tubercle and a funnel, which ends in the lower appendage of the brain – the pituitary gland. In the pituitary gland, the anterior zone (adenohypophysis), the posterior lobe (neurohypophysis) and the intermediate part located in the form of a border in the posterior part of the anterior lobe are distinguished.

The hypothalamus is an important vegetative center and has rich connections with the autonomic nuclei of the medulla oblongata, the reticular formation of the brainstem, with the pituitary gland, the pineal gland, the gray matter in the circumference of the ventricle and the aqueduct of the brain, with the thalamus, the striopallidal system, the olfactory brain, the cortex of the limbic region of the brain and other cortex.

Being an important part of the limbic-reticular complex, the hypothalamus affects all autonomic-visceral functions of the body. It participates in the regulation of sleep and wakefulness, body temperature, trophism of tissues, the respiratory, cardiovascular system, hematopoiesis and blood coagulation system, the acid-base state of the gastrointestinal tract, all types of metabolism, the function of striated muscles, the function of the endocrine glands, the sexual spheres. The hypothalamus is intimately connected with the pituitary gland, secretes, releases biologically active substances into the blood.

The hypothalamus plays an important role in the vegetative support of various forms of human somatic and mental activity. Therefore, the defeat entails not only vegetative-visceral, but also vegetative-somatic and vegetative-mental disorders.

When the hypothalamus is damaged, symptoms of prolapse appear in the regulation of various autonomic functions. More often, symptoms of irritation are observed, which manifest themselves in the form of paroxysmal conditions (crises, seizures). The nature of these paroxysmal disorders is predominantly vegetative-visceral.

The symptoms of hypothalamic lesions are extremely diverse. Sleep and wakefulness disorders are manifested in the form of paroxysmal or permanent hypersomnia, perversion of the sleep formula, and dyssomnia.

Vegetative-vascular syndrome (dystonia) is characterized by paroxysmal arising sympathetic-adrenal, vagoinsular and mixed sympatovagal crises with asthenic syndrome.

The neuroendocrine syndrome with pluriglandular dysfunction is characterized by various endocrine disorders, which are combined with neuro-trophic disorders (thinning and dry skin, ulcers of the gastrointestinal tract), changes in bones (osteoporosis, sclerosis) and neuromuscular disorders in the form of periodic weak paroxysmal muscles, their hypotension.

Among the neuroendocrine disorders are characteristic Itsenko-Cushing’s syndrome, adiposogenital dystrophy, dysfunction of the gonads, diabetes insipidus, cachexia.

With Itsenko-Cushing’s syndrome, fat is deposited in the face (“moon face”), neck, shoulder girdle (“bovine” type of obesity), chest, and abdomen. The limbs look thin against the background of obesity. Trophic disorders are observed in the form of striae on the skin of the inner surface of the axillary regions, the lateral surface of the chest and abdomen, in the region of the mammary glands, buttocks, and also in the form of dry skin. A persistent or transient increase in blood pressure, changes in the sugar curve (flattened, two-humped curve), and a decrease in the content of 17-corticosteroids in the urine are revealed.

Adiposogenital dystrophy (Babinsky-Frohlich disease): pronounced fat deposition in the abdomen, chest, thighs, often clinodactyly, changes in the bone skeleton, underdevelopment of the genital organs and secondary sexual characteristics; trophic changes in the skin in the form of thinning, vulgaris, marbling, depigmentation, increased fragility of capillaries.

Lawrence-Moon-Biedl syndrome is a congenital developmental anomaly with dysfunction of the hypothalamic region, characterized by obesity, underdevelopment of the genitals, dementia, growth retardation, pigmentary retinopathy, polydactyly (syndactyly), progressive decrease in vision.

Premature puberty (pubertas praecox) can be caused by a tumor of the mastoid bodies of the posterior hypothalamus or pineal gland. More common in girls with accelerated body growth. Along with premature puberty, bulimia, polydipsia, polyuria, obesity, sleep and thermoregulation disorders, mental disorders (disorder of the emotional-volitional sphere with moral and ethical deviations, hypersexuality) are observed; such patients become rude, vicious, cruel, with a tendency to vagrancy, theft.

Delayed puberty during adolescence is more common in boys. Characterized by high growth, disproportionate physique, female obesity, hypoplasia of the genital organs, cryptorchidism, monorchism, hypospadias, gynecomastia. In girls – a delay in the onset of menarche, underdevelopment of the genitals, the absence of secondary hair growth. Puberty in adolescents is delayed until the age of 17-18.

Diabetes insipidus develops as a result of a decreased production of antidiuretic hormone by neurosecretory cells of the supraoptic and paraventricular nuclei: polydipsia, polyuria (with a relatively low relative density of urine).

Cerebral nanism is characterized by a slowdown in physical development: dwarf growth, short and thin bones, small head size and reduced size of the Turkish saddle; the external genitals are hypoplastic.

With foci in one half of the hypothalamus, vegetative asymmetry is found: skin temperature, sweating, piloerection, blood pressure, pigmentation of the skin and hair, hemiatrophy of the skin and muscles.

With the defeat of a foreign land (metathalamus), hearing and vision (homonymous hemnanopsia) are impaired due to dysfunction of the external and internal geniculate bodies.

With eosinophilic adenoma of the pituitary gland with excessive release of growth hormone or with increased stimulation of the adenohypophysis with the somatotropin-releasing hormone of the hypothalamus, acromegaly develops: the hands, feet, facial skeleton, internal organs increase, metabolism is disturbed.

 

Endocrine pancreas

The pancreas is composed of exocrine and endocrine parts. The endocrine part of the pancreas (pars endocrina pancreatis) is represented by groups of epithelial cells that form a peculiar form of pancreatic islets (islets of Langerhans; insulae pancreaticae), separated from the exocrine part of the gland by thin connective tissue layers. Pancreatic islets are found in all parts of the pancreas, but most of them in the tail region. The size of the islets ranges from 0.1 to 0.3 mm, and the total mass does not exceed 1/10 of the mass of the pancreas. The total number of islets is from 1 to 2 million. The islets are composed of endocrine cells. There are five main types of these cells. The bulk (60-80%) of cells are beta cells,located mainly in the inner parts of the islets and secreting insulin; alpha cells – 10-30%. They make glucagon. About 10% are D cells that release somatostatin. A few PP cells occupying the periphery of the islets synthesize the pancreatic polypeptide.

Insulin promotes the conversion of glucose into glycogen, enhances the metabolism of carbohydrates in the muscles. Glucagon enhances the formation of triglycerides from fatty acids, stimulates their oxidation in hepatocytes. As the concentration of glucose in the blood flowing through the pancreas increases, insulin secretion increases and blood glucose levels decrease. Somatostatin inhibits the production of somatotropic hormone by the pituitary gland, as well as the release of insulin and glucagon by A and B cells. Pancreatic polypeptides stimulate the secretion of gastric and pancreatic juice by exocrinocytes of the pancreas.

Pancreatic islets develop from the same epithelial primordium of the primary intestine as the exocrine part of the pancreas. They are abundantly supplied with blood from the wide blood capillaries that surround the islets and penetrate between cells.

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