Endocrine glands or endocrine glands produce. Hierarchy (subordination) and interaction of endocrine glands. Secretory organs of the reproductive system

01.03.2022

Introduction.

Endocrine glands, or endocrine organs, are called glands that do not have excretory ducts. They produce special substances - hormones that enter directly into the blood. Hormones have an exciting or depressing effect on the activity of various organ systems. They affect the metabolism, the activity of the cardiovascular system, the reproductive system and other organ systems. Disturbances in the activity of the endocrine glands are accompanied by changes throughout the body. An increase in the activity of a particular gland, or, conversely, its decrease can cause serious consequences in the state of the human and animal body. The biological activity of hormones is very high: some of them have an effect when diluted 1:1000,000.

The endocrine glands include: the lower cerebral appendage (pituitary gland), the upper cerebral appendage (pineal gland), the thyroid gland, the parathyroid glands, the thymus gland, the insular part of the pancreas, the adrenal glands and the intrasecretory part of the gonads. Each gland is composed of glandular epithelial tissue rich in blood vessels. The gland is supplied with nerve fibers (from the autonomic nervous system). It is important that all endocrine glands are interconnected and represent a single system in which the leading role belongs to the pituitary gland, and it, in turn, is associated with the central nervous system. The pituitary gland produces special substances that stimulate the activity of other endocrine glands - it secretes the so-called troponostimulating hormones. Hormones enter the blood, and their influence is called humoral. The activity of the glands is regulated by the nervous system. Regulation is carried out both directly through the nerves suitable for the glands, and neuro-humorally (through the pituitary gland). The hormones themselves, in turn, affect the functions of various parts of the nervous system. To date, the chemical nature of many hormones has been established, which made it possible to obtain some hormones industrially.

The hormones of the endocrine glands enter directly into the blood and travel long distances with it. Hormones affect certain target organs.

The cells of the target organ perceive the hormone through special chemoreceptors, which can be located both on the cell surface and directly in the cytoplasm:

Receptors located on the surface are perceived: insulin, adrenaline, norepinephrine. The gland secretes a hormone into the blood, it approaches the cell, the receptor is excited, and a hormone receptor complex is formed. As a result, a signal arises that enters the cell, where intracellular enzymes (adeniate cyclase) are activated.

Receptors located in the cytoplasm perceive steroid hormones. The hormone easily penetrates into the cell, where it interacts with receptors; after the formation of the hormone-receptor complex, it (hormone) penetrates into the nucleus, where it acts on the genome. It affects DNA synthesis, which can alter protein synthesis.

Thyroid located on the neck in front of the larynx. It is supplied with a dense network of blood and lymph vessels, innervated by sympathetic and parasympathetic nerves; consists of three lobules: two lateral and one middle. Inside the gland there are small vesicles, or follicles, the walls of which are formed by glandular epithelium and filled with a special (colloidal) substance. This substance contains thyroid hormones - thyroxine, which contains iodine, and triiodothyronine, the action of which is several times stronger than thyroxine. Both hormones affect metabolism, growth and development of the body, excitability of the nervous system, heart activity, blood circulation, etc. The most important indicator of the activity of the thyroid gland is the level of basic metabolism. Increased or decreased basal metabolism is the most important indicator in the activity of the thyroid gland. With hyperfunction of the thyroid gland, metabolism increases, the excitability of the nervous system and fatigue increase. Hypothyroidism also leads to various changes throughout the body. With hypofunction, underdevelopment may appear, accompanied by a disproportionate body (short limbs). To prevent diseases of animals and humans associated with the thyroid gland, iodine is used (iodized salt, iodine-containing vitamin complexes.)

Parathyroid glands located on the posterior surface of the thyroid gland. The parathyroid hormone is called parathyroidin(parathyroid hormone). It affects the exchange of calcium and phosphorus. Removal or degeneration of the parathyroid gland leads to tetany, accompanied by muscle cramps, including respiratory ones. With the hypofunction of these glands, convulsions appear throughout the body, tooth decay and hair loss are observed. Glycogen disappears in the liver, the ability of the liver to retain ammonia decreases and less urea is formed in it, and the calcium content in the blood decreases. The introduction of calcium into the blood during convulsions stops the attack, after a while the calcium content decreases again and convulsions resume. The action of parathyroidin and vitamin D on calcium metabolism is similar.

Thymus located behind the chest. The substance of the gland consists of small lobules, in which the cortical and medulla layers are distinguished. There are a large number of lymphocytes in the cortical substance, there are fewer of them in the medulla, but Hassall's bodies are located there, which probably have secretory activity. The function of the thymus gland has not been studied enough, but there is a definite relationship between the age of the organism and its activity. Iron has the greatest effect on the body during puberty. There is an opinion that before puberty, the thymus gland functions intensively and suppresses the action of the gonads. With the onset of puberty, it gradually decreases and a significant part of it turns into fat. However, between the lobes of fat, there are areas of secreting tissue that play a certain role in the activity of the adult organism. Removal of the thymus gland causes a violation of mineral metabolism: the bones become soft and brittle, the healing of fractures is slow, muscle weakness and sluggishness appear.

Pancreas is a gland of external and internal secretion. In addition to pancreatic juice entering the duodenum, the gland produces the hormones insulin and glucagon, which enter the bloodstream. The glandular tissue that secretes hormones forms the islets of Langerhans, located in the thickness of the pancreas. With a violation of the activity of the insular part, diabetes develops. This is manifested by a decrease in the ability of body cells to oxidize sugar in large quantities. This disrupts the ability of the liver to form glycogen. The result is an increase in blood sugar. At the same time, the kidneys do not pass sugar and the excreted urine does not contain it. If the blood sugar level rises, sugar appears in the urine. The animal is constantly thirsty due to the significant release of water. Disorder of carbohydrate metabolism leads to a violation of the metabolism of proteins and fats. Violation of protein metabolism lies in the fact that almost 60% of the protein that enters the body is converted into carbohydrates, followed by the formation of a large amount of intermediate acidic products. Acidic breakdown products of proteins, together with ketone bodies, cause a change in the ABR of the blood to the acid side, i.e. acidosis. Insulin promotes the oxidation of carbohydrates in body tissues and the deposition of glycogen in the liver and muscles.

With tumors of the pancreas, a decrease in blood sugar is observed: in this case, convulsions appear, a decrease in body temperature.

The preparation of the pancreatic hormone was proposed by the Russian doctor L. Sobolev in 1901, and the Canadian researchers Banting and Best in 1922 discovered the hormone insulin. Currently, insulin is produced industrially - by extraction from the pancreas of cattle.

In addition to insulin, other hormones are produced in the pancreas: glucagon is an insulin antagonist, causing the breakdown of glycogen in tissues, padutin lowers blood pressure and causes the expansion of small vessels in the organs, lipocaine regulates fat metabolism in the liver.

adrenal glands are located in the lumbar region and are adjacent to the upper parts of the kidneys. In each adrenal gland, two layers are distinguished: the outer one - the cortex and the inner one - the medulla, each of which is an independent secreting organ. These layers differ from each other in microscopic structure and secrete various hormones, the most important for the body being the cortical substance.

The adrenal cortex is rich in cholesterol and ascorbic acid. In the cortex, several hormones are produced under the general name corcosteroids. Currently, more than 25 active substances of the adrenal cortex have been isolated. They are divided into two groups: glucocorticoids, i.e. corticosteroids, affecting mainly carbohydrate metabolism, and mineralocorticoids - corticosteroids that affect mineral metabolism. The first ones are cortisone, hydrocortisone, caticosterone etc. - they contribute to the deposition of glycogen in the muscles and liver and maintain a sufficient concentration of glucose in the blood. With hypofunction of the adrenal cortex, the content of sugar in the blood and glycogen in the muscles and liver decreases. There is a decrease in appetite, a drop in blood pressure, a decrease in blood sugar, sometimes death can occur. The introduction of the hormone of the adrenal cortex reduces fatigue. Cortical hormones weaken the action of a number of poisons - diphtheria poison, nicotine and strychnine. A tumor of the adrenal cortex causes increased production of hormones, leading to various changes in the body (beard in women). Glucocorticoids affect not only carbohydrate, but also protein metabolism, contributing to the breakdown of proteins and delaying their synthesis in the body.

The mineralocorticoid contains the hormone oldosterone and an intermediate product during its formation - deoxycorticosterone. They affect the water-salt metabolism. With hypofunction, sodium, chlorine, water are excreted from the body with urine and potassium is retained. In addition, the adrenal cortex secretes active substances (androgens) that are similar in their action to sex hormones. Currently, corticosteroids are used to treat various diseases. The pituitary-adrenal cortex system, according to Selye's theory, plays an important role in organizing the protection of the body when exposed to particularly harmful stimuli (infections, burns, injuries). When stimulated, the pituitary gland intensively secretes adrenocorticotropic hormone, which through the blood affects the adrenal cortex - a large number of hormones are released from them that contribute to the adaptation of the body. This also increases the secretion of the hormone by the adrenal medulla. Such a joint reaction of the pituitary and adrenal glands, aimed at strengthening the body's resistance to harmful influences, is called the stress reaction. Changes in the body in response to harmful effects are also due to the influence of the nervous system.

Adrenal medulla hormone Adrenalin isolated at the beginning of the 20th century. Known for its chemical nature, it is manufactured industrially. The effect of adrenaline is similar to that of the sympathetic nerve. Like the sympathetic system, adrenaline causes an increase and increase in cardiac activity, contraction of the walls of blood vessels (with the exception of the vessels of the heart and brain), inhibition of intestinal motility, contraction of the muscles of the uterus and the muscle that dilates the pupil, relaxation of the muscles of the bronchial wall, etc. But the muscles of the urinary and gall bladders with the introduction of adrenaline relax. With the introduction of adrenaline, due to increased heart contractions and narrowing of blood vessels, blood pressure rises, and the performance of skeletal muscles increases. During a period of fear or anger, the secretion of adrenaline increases. Of particular importance is the effect of adrenaline on carbohydrate metabolism. Its action is opposite to the action of insulin, which contributes to the preservation of a relatively constant content of glucose in the blood. The adrenal medulla is innervated by the sympathetic division of the nervous system. Increased secretion of adrenaline is accompanied by excitation of the sympathetic system.

In addition to adrenaline, another substance is formed in the adrenal medulla - norepinephrine its action is close to that of adrenaline. Norepinephrine, as established, when the sympathetic system is excited, is released by the endings of nerve fibers and participates as a mediator in the transmission of nerve excitation from nerve endings to organ tissue.

Hypothalamus forms and releases biologically active substances.

Liberins - stimulate the release and formation of pituitary hormones (7 BAS)

Statins - inhibit the formation and release of pituitary hormones (samostatin, melanostatin, prolactostatin).

Special cells of the hypothalamus produce the hormones Oxytocin and Vysopressin, which flow down the axons to the posterior pituitary gland.

Pituitary located in the cranial cavity and consists of three lobes: anterior, intermediate, posterior. Part of its secret enters the blood, and part enters the cerebrospinal fluid. The boundaries between the lobes are distinguishable only under a microscope. The anterior lobe produces several hormones: a growth hormone, affecting metabolism; thyrotropic hormone affecting the thyroid gland; adrenocorticotropic hormone, stimulating the function of the adrenal cortex; gonadotropin, affecting the sex glands. In the hypothalamus, special substances are secreted that regulate the release of hormones by the pituitary gland - this is how the neuro-humoral regulation of the activity of the pituitary gland and other endocrine glands is carried out.

With an excess of growth hormones, underdevelopment of the genital organs, muscle weakness can be observed. Reduced excretion leads to dwarfism. If hormones are not secreted at all, then a change occurs in other endocrine glands.

The posterior pituitary secretes hormones oxytocin, vasopressin and antidiuretic hormone. Oxytocin affects uterine contractions. Vasopressin causes vasoconstriction. Reduced function of the pituitary gland or its posterior lobe leads to a violation of water metabolism: there is profuse urination (polyuria) or diabetes insipidus. With hypofunction of the posterior pituitary gland, metabolism is disturbed, leading to obesity. Sexual activity is also disturbed.

Under the influence of antidiuretic hormone in the renal tubules, the absorption of water into the blood increases, which leads to a decrease in diuresis. Vasopressin, causing a narrowing of the blood vessels of the Malpighian glomerulus, helps to reduce urine filtration. Thus, the posterior pituitary gland reduces urine production in two ways - by increasing the reverse absorption of water in the convoluted tubules and by weakening the filtration of primary urine. Recently, there is an opinion that the hormones secreted by the posterior pituitary gland are produced not in the pituitary gland, but in the nerve nuclei of the hypothalamus, and already from it they are deposited (enter) into the posterior pituitary gland.

Function epiphysis, located behind the visual tubercles above the quadrigemina, has not been sufficiently studied. The pineal gland reaches its greatest development in childhood, and in an adult organism it consists of almost one connective tissue. There is evidence that the pineal gland inhibits the premature development of the gonads.

The most studied hormone serotonin, which is a CNS mediator. It also provides regulation of blood pressure, body temperature and respiration, namely, it activates intestinal motility, bronchial tone.

Melatonin provides regulation and development of the reproductive system. Adrenoglomerotropin is a stimulator of aldosterone in the glomerular zone of the adrenal cortex. In general, these hormones provide control of circadian rhythms in the body (control of the body clock).

gonads belong to the glands of mixed secretion. External secretion consists in the formation and release of germ cells, or germ cells - sperm and eggs. Internal secretion consists in the formation of sex hormones entering the blood. The onset of puberty depends on the degree of development of the sex glands and the entry of sex hormones into the body. Puberty is characterized by the appearance of sexual characteristics. Sex hormones also affect metabolism, and all changes are under the control of the nervous system.

male sex hormones testosterone and androsterone- are formed in the testicles. They affect sexual development, enhance the activity of the genital organs and the feeling of sexual desire, participate in the regulation of metabolism and other body functions.

female sex hormones estradiol (folliculin) and progestin (lutein)- are produced in the ovaries, with the first being formed in the follicles, and the second in the corpus luteum. Estradiol affects puberty, the development of the mammary glands, regulates sexual cycles. Progestin affects the normal course of pregnancy. Female hormones are also involved in the regulation of metabolism.

Removal of the gonads leads to a change in the skeleton, disproportionate development of the limbs

Conclusion

The endocrine glands, together with the nervous system, ensure the harmonious unity of the humoral and nervous regulation of all processes occurring in the body. In this role, the endocrine glands and the nervous system not only complement, but also reinforce each other, but they themselves are under mutual influence. Each violation in these relationships leads to profound morphological and functional changes, accompanied by severe disorders of the vital activity of the whole organism.

Introduction

Thyroid

Parathyroid glands

Thymus

Pancreas

adrenal glands

Hypothalamus

gonads
Conclusion
Bibliography

Literature:

Endocrinology. Favorable Ya. V., Shlyakhto E. V., Babenko A. Yu.

Endocrinology of small domestic animals. E. Torrance, K. Mooney. Aquarium print 2006

Large workshop on human and animal physiology. Nozdrachev A. . Academy 2007

Anatomy of domestic animals. A. F. Klimov, A. I. Akayevsky. Lan 2003

lecture material.

Complex interactions develop between the endocrine glands, which are realized in the following main ways:

1. The activity of each organ, each function is simultaneously influenced by several hormones secreted by different endocrine glands;

2. Hormones produced by some glands can affect the function of other endocrine glands (both directly and indirectly through the nervous system).

These interactions can be implemented according to the principle of positive direct and negative feedback. Let us dwell on specific examples of such interactions. So, in the anterior lobe of the pituitary gland, the hormone thyrotropin is produced, which stimulates the formation of thyroid hormones. If the anterior lobe of the pituitary gland is removed from an animal, then the activity of the thyroid gland stops and its atrophy occurs (direct positive relationship).

An increase in the level of thyroid hormones above normal inhibits the formation of thyrotropin in the anterior pituitary gland, thereby reducing the production of thyroid hormones (negative feedback).

In some cases, two or more hormones produced by different glands have a unidirectional (synergistic) effect on the function of an organ. So, adrenaline, produced by the adrenal medulla, and glucagon, synthesized by the ß-cells of the pancreatic islet apparatus, activate the breakdown of glycogen in the liver and cause an increase in blood glucose.

Insulin and epinephrine have seemingly opposite (antagonistic) effects on blood glucose levels. Insulin lowers and adrenaline raises blood glucose levels. However, it is the joint action of these two hormones that leads to an improvement in the supply of tissues with carbohydrates. Adrenaline promotes the conversion of a reserve carbohydrate - liver glycogen into glucose and its release into the blood, and insulin ensures the penetration of the latter into cells and its further intracellular metabolism.

A similar synergism is found in the action of the hormones glucagon and insulin. Glucagon stimulates the breakdown of glycogen in the liver and the release of glucose into the blood, as well as the breakdown of fat in adipose tissue to form free fatty acids. Insulin also increases the permeability of cell membranes of a number of tissues for these substrates. That is, insulin and glucagon jointly control the supply of tissues with nutrients and energy sources. Their joint action determines the pathways for the transformation of amino acids, fats and carbohydrates in the body, adapting their metabolism to specific conditions of life.

Some hormones have a so-called permissive (allowing, allowing) effect, which consists in the fact that the hormone itself does not have any effect, but creates favorable conditions for the action of another hormone. Thus, glucocorticoids do not affect either vascular tone or the breakdown of glycogen in the liver. However, they create conditions in which subthreshold (very low) concentrations of adrenaline increase blood pressure and stimulate the breakdown of glycogen in the liver.

Endocrine glands, or endocrine glands (ZHVS) are called glandular organs, the secret of which enters directly into the blood. Unlike the glands of external secretion, the products of which enter the cavities of the body that communicate with the external environment, the GI do not have excretory ducts. Their secrets are called hormones. Released into the blood, they are carried throughout the body and have effects on various organ systems.

What are the endocrine glands

The organs related to the endocrine glands and the hormones they produce are presented in the table:

* The pancreas has both external and internal secretions.

In some sources, the thymus (thymus gland) is also referred to the endocrine glands, in which the substances necessary to regulate the immune system are formed. Like all VVS, it does not really have ducts and secretes its products directly into the bloodstream. However, the thymus actively functions until adolescence, then it involution occurs (replacement of the parenchyma with adipose tissue).

Anatomy and functions of the endocrine apparatus

All endocrine glands have different anatomy and a set of synthesized hormones, therefore, the functions of each of them are radically different.

These include the hypothalamus, pituitary, epiphysis, thyroid, parathyroid, pancreas and gonads, adrenal glands.

Hypothalamus

The hypothalamus is an important anatomical formation of the central nervous system, which has a powerful blood supply and is well innervated. In addition to regulating all autonomic functions of the body, it secretes hormones that stimulate or inhibit the work of the pituitary gland (releasing hormones).

Activating agents:

thyroliberin;
corticoliberin;
gonadoliberin;
somatoliberin.

Hypothalamic hormones that inhibit the activity of the pituitary gland include:

somatostatin;
melanostatin.

Most releasing factors of the hypothalamus are not selective. Each acts immediately on several tropic hormones of the pituitary gland. For example, thyroliberin activates the synthesis of thyrotropin and prolactin, and somatostatin inhibits the formation of most peptide hormones, but mainly growth hormone and corticotropin.

In the anterior-lateral region of the hypothalamus, there are clusters of special cells (nuclei) in which vasopressin (antidiuretic hormone) and oxytocin are formed.

Vasopressin, acting on the receptors of the distal renal tubules, stimulates the reverse reabsorption of water from the primary urine, thereby retaining fluid in the body and reducing diuresis. Another effect of the substance is an increase in total peripheral vascular resistance (vasospasm) and an increase in blood pressure.

Oxytocin has to a small extent the same properties as vasopressin, but its main function is to stimulate labor (uterine contractions), as well as increase the secretion of milk from the mammary glands. The task of this hormone in the male body has not yet been established.

Pituitary

The pituitary gland is the central gland in the human body that regulates the work of all pituitary-dependent glands (except for the pancreas, pineal gland and parathyroid glands). It is located in the Turkish saddle of the sphenoid bone, has very small dimensions (weight about 0.5 g; diameter - 1 cm). It is divided into 2 lobes: anterior (adenohypophysis) and posterior (neurohypophysis). The pituitary stalk, which is connected with the hypothalamus, delivers releasing hormones to the adenohypophysis, and oxytocin and vasopressin to the neurohypophysis (where they accumulate).

The pituitary gland in the Turkish saddle of the sphenoid bone. The adenohypophysis is colored bright pink, the neurohypophysis is painted pale pink.

The hormones by which the pituitary gland controls the peripheral glands are called tropic. The regulation of the formation of these substances occurs not only due to the releasing factors of the hypothalamus, but also the products of the activity of the peripheral glands themselves. In physiology, this mechanism is called negative feedback. For example, with excessively high production of thyroid hormones, thyrotropin synthesis is inhibited, and with a decrease in the level of thyroid hormones, its concentration increases.

Prolactin is the only non-tropic hormone of the pituitary gland (that is, it does not realize its effect at the expense of other glands). Its main task is to stimulate lactation in lactating women.

Somatotropic hormone (somatotropin, growth hormone, growth hormone) also conditionally refers to tropic. The main role of this peptide in the body is to stimulate development. However, this effect is not realized by STG itself. It activates the formation of so-called insulin-like growth factors (somatomedins) in the liver, which have a stimulating effect on the development and division of cells. STH causes a number of other effects, for example, it is involved in carbohydrate metabolism by activating gluconeogenesis.

Adrenocorticotropic hormone (corticotropin) is a substance that regulates the functioning of the adrenal cortex. However, ACTH has almost no effect on the formation of aldosterone. Its synthesis is regulated by the renin-angiotensin-aldosterone system. Under the action of ACTH, the production of cortisol and sex steroids in the adrenal glands is activated.

Thyroid-stimulating hormone (thyrotropin) has a stimulating effect on the function of the thyroid gland, increasing the formation of thyroxine and triiodothyronine.

Gonadotropic hormones - follicle-stimulating (FSH) and luteinizing (LH) activate the activity of the gonads. In men, they are necessary for the regulation of testosterone synthesis and the formation of spermatozoa in the testicles, in women - for the implementation of ovulation and the formation of estrogens and progestogens in the ovaries.

epiphysis

The pineal gland is a small gland weighing only 250 mg. This endocrine organ is located in the region of the midbrain.

The function of the pineal gland has not yet been fully understood. The only known compound is melatonin. This substance is the "internal clock". By changing its concentration, the human body recognizes the time of day. It is with the function of the epiphysis that adaptation to other time zones is associated.

Thyroid

The thyroid gland (TG) is located on the front surface of the neck under the thyroid cartilage of the larynx. It consists of 2 lobes (right and left) and the isthmus. In some cases, an additional pyramidal lobe departs from the isthmus.

The size of the thyroid gland is very variable, therefore, when determining compliance with the norm, they talk about the volume of the thyroid gland. In women, it should not exceed 18 ml, in men - 25 ml.

In the thyroid gland, thyroxine (T4) and triiodothyronine (T3) are formed, which play an important role in human life, affecting the metabolic processes of all tissues and organs. They increase the oxygen consumption of cells, thereby stimulating the production of energy. With their deficiency, the body suffers from energy hunger, and with an excess, dystrophic processes develop in tissues and organs.

These hormones are especially important during the period of intrauterine growth, since their deficiency disrupts the formation of the fetal brain, which is accompanied by mental retardation and impaired physical development.

Calcitonin is produced in C-cells of the thyroid gland, the main function of which is to reduce the level of calcium in the blood.

parathyroid glands

The parathyroid glands are located on the posterior surface of the thyroid gland (in some cases they are included in the thyroid gland or are located in atypical places - the thymus, the paratracheal groove, etc.). The diameter of these rounded formations does not exceed 5 mm, and the number can vary from 2 to 12 pairs.

Schematic arrangement of the parathyroid glands.

The parathyroid glands produce parathyroid hormone, which affects the phosphorus-calcium metabolism:

increases bone resorption, releasing calcium and phosphorus from bones;
increases the excretion of phosphorus in the urine;
stimulates the formation of calcitriol in the kidneys (the active form of vitamin D), which leads to increased absorption of calcium in the intestine.

Under the action of parathyroid hormone, there is an increase in the level of calcium and a decrease in the concentration of phosphorus in the blood.

adrenal glands

The right and left adrenal glands are located above the upper poles of the respective kidneys. The right one resembles a triangle in outline, and the left one resembles a half moon. These glands weigh about 20 g.

Sectional view of the adrenal glands (diagram). The cortical substance is highlighted in light, the medulla is highlighted in dark.

On a cut in the adrenal gland, cortical and medulla substances are isolated. The first contains 3 microscopic functional layers:

glomerular (synthesis of aldosterone);
beam (production of cortisol);
reticular (synthesis of sex steroids).

Aldosterone is responsible for the regulation of electrolyte balance. Under its action, the reverse reabsorption of sodium (and water) and the excretion of potassium increase in the kidneys.

Cortisol has various effects on the body. It is a hormone that adapts a person to stress. Main functions:

increase in blood glucose levels due to the activation of gluconeogenesis;
increased protein breakdown;
specific effect on fat metabolism (increased lipid synthesis in the subcutaneous fat of the upper body and increased decay in the tissue of the extremities);
decreased reactivity of the immune system;
inhibition of collagen synthesis.

Sex steroids (androstenedione and dihydroepiandrosterone) cause effects similar to testosterone, but are inferior to it in their androgenic activity.

In the adrenal medulla, adrenaline and norepinephrine are synthesized, which are hormones of the sympathetic-adrenal system. Their main effects:

increased heart rate, increased cardiac output and blood pressure;
spasm of all sphincters (urinary retention and defecation);
slowing down the secretion of exocrine glands;
an increase in the lumen of the bronchi;
pupil dilation;
increased blood glucose levels (activation of gluconeogenesis and glycogenolysis);
acceleration of metabolism in muscle tissue (aerobic and anaerobic glycolysis).

The action of these hormones is aimed at the rapid activation of the body in emergency conditions (the need for flight, protection, etc.).

Endocrine apparatus of the pancreas

According to its significance, the pancreas is an organ of mixed secretion. It has a ductal system, through which digestive enzymes enter the intestines, but it also contains an endocrine system - the islets of Langerhans, most of which are located in the tail. They produce the following hormones:

insulin (islet beta cells);
glucagon (alpha cells);
somatostatin (D-cells).

Insulin regulates various types of metabolism:

reduces blood glucose levels by stimulating the entry of glucose into insulin-dependent tissues (adipose tissue, liver and muscles), inhibits the processes of gluconeogenesis (glucose synthesis) and glycogenolysis (glycogen breakdown);
activates the production of protein and fats.

Glucagon is a contrainsular hormone. Its main function is the activation of glycogenolysis.

Somatostatin inhibits the production of insulin and glucagon.

gonads

The gonads produce sex steroids.

In men, testosterone is the main sex hormone. It is produced in the testicles (Leydig cells), which are normally located in the scrotum and have an average size of 35-55 and 20-30 mm.

The main functions of testosterone:

stimulation of skeletal growth and distribution of muscle tissue according to the male type;
the development of the genitals, vocal cords, the appearance of male-type body hair;
formation of a male stereotype of sexual behavior;
participation in spermatogenesis.

For women, the main sex steroids are estradiol and progesterone. These hormones are produced in the ovarian follicles. In the maturing follicle, the main substance is estradiol. After the rupture of the follicle at the time of ovulation, a corpus luteum forms in its place, which secretes mainly progesterone.

The ovaries in women are located in the small pelvis on the sides of the uterus and measure 25-55 and 15-30 mm.

The main functions of estradiol:

the formation of physique, the distribution of subcutaneous fat according to the female type;
stimulation of proliferation of the ductal epithelium of the mammary glands;
activation of the formation of the functional layer of the endometrium;
stimulation of the ovulatory peak of gonadotropic hormones;
formation of female type of sexual behavior;
stimulation of positive bone metabolism.

The main effects of progesterone:

stimulation of the secretory activity of the endometrium and its preparation for embryo implantation;
suppression of the contractile activity of the uterus (preservation of pregnancy);
stimulation of differentiation of the ductal epithelium of the mammary glands, preparing them for lactation.

ENDOCRINE GLANDS(syn.: endocrine glands, endocrine glands) - organs specialized in the process of evolution, producing and releasing physiologically active substances (hormones) directly into the internal environment of the body. The concept of internal secretion (see) and of the endocrine glands was introduced by K. Bernard (1855).

Internal secretion is characteristic of all cells of a multicellular organism, since each of them releases metabolic products into the tissue fluid, lymph or blood. Some of them have an exciting or depressing effect on the body's functions, that is, they have fiziol, activity. If the formation of physiologically active substances is the main or one of the main functions of cells, then organs consisting of such cells are called endocrine.

In vertebrates (and humans) to Zh. N of page, producing exclusively hormones (see), pituitary gland (see), thyroid gland (see), parathyroid glands (see) and adrenal glands (see). Confirmation of endocrine value of a pineal body is received (see). Another group consists of organs that combine the production of hormones with other functions - the pancreas (see) the testicle (see), the ovaries (see) and the placenta (see). Endocrine activity is also characteristic of certain organs, usually not related to the endocrine system - the salivary glands, the organs went. - kish. a path, kidneys, perhaps a spleen, and also a thymus gland, edges, being the central body of an immunogenesis, develops also some active agents influencing development of lymphoid cells (see. Thymus gland).

Features of a structure and regulation of function Zh. with. depend on their development and specialization in the process of phylogenesis. Some endocrine glands - the adenohypophysis (anterior and middle lobes of the pituitary gland), the thyroid gland, parathyroid (parathyroid) glands - are laid in embryogenesis as external secretion glands, but with further development, secretion of secreted substances into the blood or lymph through the basal ends of adenocytes (glandular cells) becomes the dominant process, in connection with which the excretory ducts are reduced (see Glands). Other glands are laid at once and are formed as Zh. with.

Most Zh. c, consists of several tissue components arising from different embryonic rudiments and entering into a single functional and structural complex; for example, part of the pituitary gland flutters from the epithelium of the oral cavity, and the other - as an outgrowth of the distal end of the funnel of the third ventricle of the brain, and the formed pituitary gland, thus, consists of an epithelial adenohypophysis and a glial posterior lobe. The thyroid and parathyroid glands originate from different embryonic rudiments, function and are regulated completely separately, but are topographically united and receive a common blood supply and innervation. In the adrenal glands, two independent glands are combined - the cortical, originating from the whole-dermal epithelium, and the brain (medullary), which is a modified sympathetic ganglion. In the pancreas, the endocrine pancreatic islets are located between the exocrine acini. The testicles and ovaries combine generative (gametogenic) and follicular epithelium, as well as interstitial cells of mesenchymal origin. In the development and functioning of the placenta, the interaction of the membranes of the embryo and the endometrium of the mother is manifested.

Microscopically, a single principle of the structure of life is found. with.

Hormone-producing cells are in close contact with blood capillaries that have a special structure (fenestrated capillaries); plentiful blood supply is characteristic. with.

Most Zh. with. produces several hormones with different chemistries. composition and fiziol, effect. Thus, the anterior lobe of the pituitary gland secretes at least six different hormones, the middle lobe of the pituitary gland secretes two hormones, the thyroid gland of mammals produces three hormones, and so on. N of page, their fiziol, action and the diseases connected with dysfunction, - see the table.

On features of regulation of function Zh. with. can be divided into four groups. The first group includes the adenohypophysis, thyroid gland, testicles and ovaries (gonads), as well as the fascicular and reticular zones of the adrenal cortex. In this group, the anterior lobe of the pituitary gland occupies a central position, since it produces triple (crinotropic) hormones that regulate the activity of the other glands in this group.

To the second group Zh. with. (not directly dependent on the pituitary gland) belong to the parathyroid glands, pancreatic islets and the glomerular zone of the adrenal cortex, as well as the thymus gland. The regulation of the function of these glands is determined by the direct influence on them of the effects that arise in the body as a result of the action of their own hormones. So, parathyroid hormone increases the level of calcium in the blood, but excess calcium, in turn, inhibits the secretory activity of the parathyroid glands. The functional activity of the pancreatic islets correlates with the level of glycemia: hyperglycemia stimulates the secretion of insulin, and insulin lowers blood sugar. The functional activity of this group of glands allows us to conditionally characterize them as self-regulating Zh. with. Turning off the glands of this group leads to death, while the removal of pituitary-dependent glands and even the pituitary gland is compatible with the preservation of life, although it is accompanied by severe disorders of many body functions.

The third group of endocrine formations are hormone-producing glands or single cells of nervous origin; their activity does not depend on the anterior lobe of the pituitary gland. The emergence of Zh. with. from the nervous tissue is due to the fact that the nerve cells themselves are able to produce and secrete physiologically active substances - mediators that implement the transmission of impulses in synapses from a neuron to an effector or from one neuron to another. The regulating influence of nervous impulses is carried out humorally, as well as influence of hormones that testifies to unity of nervous and hormonal systems of an organism for fiziol, value of these systems consists in regulation of separate functions of an organism and their coordination. In some nerve cells, along with mediators, secretory substances are produced that appear in the cytoplasm of the perikaryon in the form of granules; such cells are called neurosecretory (Fig.), and the substances they produce are called neurosecrets (see Neurosecretion). Sharrer (E. Scharrer, 1952) found that neurosecretory cells, combining nervous and endocrine functions, perceive impulses coming to them from other parts of the nervous system and transmit them further in the form of neurosecrets carried with the blood stream. If neurons are characterized by the presence of processes that provide directional transmission of a nerve impulse, then neurosecretory cells may not have processes; for example, chromaffin cells of the adrenal medulla and paraganglia and parafollicular, or K-cells, of the thyroid gland.

Rice. 11. Scheme of hypothalamic-pituitary regulation of some peripheral endocrine organs. Hypothalamic adenohypophysiotropic hormones (releasing factors) are indicated by dashed lines; hormones of the anterior pituitary - dots, hormones of peripheral glands - solid lines: 1 - adenohypophysotropic zone of the mediobasal hypothalamus; 2 - medial eminence; 3 - pituitary leg; 4 - anterior pituitary gland (PDG); 5 - funnel; 6 - intermediate part of the pituitary gland; 7 - posterior lobe of the pituitary gland; 8 - cartilaginous epiphyseal plate of bone growth; 9-thyroid gland; 10- adrenal gland; 11 - testicle; 12-growing ovarian follicles; 13 - corpus luteum; 14 - mammary gland; 15 - neurosecretory cell producing somatotropic releasing factor (SRF); 16 - selection of SRF from PDH; 17 - neurosecretory cell producing thyrotropic releasing factor (TRF); 18 - release of thyroid-stimulating hormone from PDH; 19 - release of thyroid hormones; 20 - neurosecretory cell producing adrenocorticotropic (ACTH) releasing factor; 21 - isolation of ACTH from PDH; 22 - release of glucocorticoids and androgens from the adrenal cortex; 23 - neurosecretory cell producing releasing factors of follicle-stimulating (FSH-RF) and luteinizing hormones (LRF); 24 - allocation of FSH - RF from PDH; 25 - release of sex hormones from follicles (estrogen, progesterone); 26 - isolation of LRF from PDH; 27 - release of progesterone from the corpus luteum; 28 - transmission of FSH - RF and LRF to hormone-producing cells of the gonads; 29 - release of sex hormones from the testicle (estrogen, testosterone); 30 - neurosecretory cell producing prolactin releasing factor (PRF); 31 - selection of PRF from PDH.

In vertebrates, neurosecretory cells are concentrated in the hypothalamus (see); they secrete a group of hormones (releasing hormones, or releasing factors) that activate or inhibit the secretion of adenohypophyseal hormones (see Hypothalamic neurohormones), as well as vasopressin (see) and oxytocin (see). In went.-kish. In the tract, neuroblasts that migrated during embryogenesis are included in the mucous membrane and are converted into argyrophilic cells, presumably producing gastrin, a specific hormone of the stomach. In the mucous membrane of the stomach and intestines, neuroblasts give rise to enterochromaffin cells (see Argentaffin cells), although the functional significance of these cells is not fully established, their endocrine activity is obvious. It is possible that enterochromaffin cells of the stomach produce secretin along with gastrin, and enterochromaffin cells of the intestine (Kulchitsky cells) produce secretin. There is a point of view that alpha and beta cells of pancreatic islets belong to the group of neuroendocrine cells.

The fourth group can include organs of the endocrine system of neuroglial origin, including the pineal gland (see). The pineal gland clearly inhibits the secretion of gonadotropic hormones of the anterior pituitary gland and, consequently, reduces the hormonal and reproductive functions of the gonads.

The ependyma of the floor of the third ventricle of the brain and its funnel gives rise to the posterior lobe of the pituitary gland (neurohypophysis) and the intermediate part (medial emission). The parenchyma of the posterior pituitary gland is neuroglia. The posterior lobe does not produce hormones, but is an auxiliary neurohemal organ of the hypothalamic-neurohypophyseal system, which ensures the accumulation and release into the blood of vasopressin and oxytocin produced by the neurosecretory cells of the anterior hypothalamus; the median eminence plays the same role in the hypothalamic-adenohypophyseal system. On the capillaries located in the median eminence, the axons of small neurosecretory cells of the mediobasal hypothalamus end; here Hypothalamic neurohormones are secreted into the blood, carrying them to the parenchyma of the anterior pituitary gland. The median eminence of the hypothalamus and the posterior lobe of the pituitary gland belong to the ependymal circumventricular organs, to which (in animals) also belong the subcommissural organ, the subfornikal organ, the vascular organs of the terminal plate and the areae postremae.

Funkts, the interdependence of individual organs and formations that produce hormones and regulate the homeostasis of the body, determines the association of Zh. with. into a single endocrine system (tsvetn. fig. 11); By dividing the components of this system into four groups, a classification of the endocrine organs can be outlined.

I. Group of adenohypophysis and peripheral endocrine glands dependent on it: adenohypophysis, thyroid gland, testis, ovary, adrenal cortex (fascicular and reticular zones).

II. A group of peripheral endocrine glands that are independent of the anterior pituitary gland: parathyroid glands, thymus gland, adrenal cortex (glomerular zone), pancreatic islets.

III. A group of endocrine organs of nervous origin (neuroendocrine). 1. Neuroendocrine cells with processes: a) large neurosecretory cells (so-called homoripositive) of the supervisory and paraventricular nuclei of the anterior hypothalamus and b) small neurosecretory cells of the adenohypophysotropic zone of the mediobasal hypothalamus. 2. Neuroendocrine cells lacking processes: chromaffin cells of the adrenal medulla and paraganglia; parafollicular, or K-cells, of the thyroid gland; argyrophilic cells of the stomach and intestines; enterochromaffin cells of the stomach and intestines.

IV. A group of endocrine organs of neuroglial origin: a) the pineal body; b) circumventricular organs (subcommissural, subfornical, vascular organ of the terminal plate, vascular organ areae postremae); c) neurohemal organs (posterior pituitary gland, median eminence).

In the neuroendocrine system, the hypothalamus is the regulatory center. The regulatory impulses sent by it reach the peripheral effectors either through the pituitary gland (humoral pathway), or, bypassing the pituitary gland, along the descending nerve pathways. Fundamentally the same dual mechanisms provide feedback, i.e., the influence of peripheral Zh. with. on the hypothalamus (see Neurohumoral regulation).

Preservation of hormonal balance in the body means that the degree of secretory activity of the endocrine gland is inversely proportional to the concentration of its hormone in the blood. Preservation of hormonal balance can occur at different levels of regulation. The initial and at the same time the most general form of regulation should be recognized as the direct action of hormones (or those changes in the body that they cause) on the gland that produces them. This form of interaction can also manifest itself in pituitary-dependent glands. The balance between the concentration of hormones in the blood and the degree of functional activity of dependent glands, closing at the level of the anterior pituitary gland and hypothalamus, is determined by the relationship between these dependent glands and the anterior pituitary gland. If a tropic hormone activates a peripheral endocrine gland (an effector gland, or a target gland), then the hormone (hormones) of the latter inhibits the production and secretion of the corresponding triple pituitary hormone, i.e., the relationship between the peripheral gland. with. and the anterior pituitary gland have the character of negative feedback. For example, a decrease in the level of thyroid hormones (caused by thyroidectomy or the administration of thyreostatic substances) leads to a significant increase in the production and secretion of thyrotropin by the anterior pituitary gland. Similarly, castration causes a distinct increase in the follicle-stimulating function of the pituitary gland, and insufficiency of hormones of the adrenal cortex - activation of its adrenocorticotropic function.

Summarizing these relationships, M. M. Zavadovsky (1933) formulated the principle of plus-minus interaction, considering it to be a universal mechanism that determines the maintenance of hormonal balance. In fact, this principle reflects only one of the particular forms of balance between the endocrine gland and the effect caused by its hormone. The reverse (afferent) influences emanating from the peripheral effector gland may not act directly on the anterior pituitary gland, but through the hypothalamus, inhibiting the formation of hypothalamic neurohormones that activate the corresponding functions of the anterior pituitary gland. At the same time, the hormones of the peripheral glands can also have an effect on the higher parts of the brain, from where information is transmitted through the hypothalamus and adenohypophysis to the endocrine gland that produces these hormones.

The relationship between the hypothalamus and the adenohypophysis also, apparently, has the character of negative feedbacks (the so-called small feedbacks).

In the general system of regulatory interactions Zh. with. two circles are outlined - a small one, which provides a functional balance between the hypothalamus and an adenohypophysis, and a large circle - the relationship between the hypothalamic-pituitary system (see) and peripheral Zh. with.

Table. CLINICAL AND PHYSIOLOGICAL CHARACTERISTICS OF THE INTERNAL SECRETION GLANDS

Endocrine glands	Hormone, its synonyms and chemical nature	Target organ (system). The biological action of the hormone	Diseases associated with dysfunction of the endocrine gland
Hypothalamus	ACTH - releasing factor (CRF), or corticoliberin Thyrotropin - releasing factor (TRF), or thyroliberin; omnopeptide	Anterior pituitary gland. Activates adrenocorticotropic function Anterior pituitary gland. Activates thyroid function	Diseases of the pituitary and endocrine glands regulated by ACTH TSH-regulated pituitary and thyroid disorders
	Somatotropin - releasing factor (SRF), or somatoliberin	Anterior pituitary gland. Activates somatotropic function
	Follicle-stimulating hormone releasing factor (FSH RF), or folliberin	Anterior pituitary gland. Activates the follicle-stimulating function
	Luteinizing hormone releasing factor (LRF), or luliberin; decapeptide	Anterior pituitary gland. Activates the luteinizing function	Diseases of the pituitary and gonads regulated by FSH
	Prolactin - releasing factor (PRF), or prolactoliberin Releasing factor of melanocyte-stimulating hormone (MPF), or melanoliberin; tripeptide	Anterior pituitary gland. Activates lactotropic function Intermediate part of the pituitary gland. Activates melanocyte-stimulating function	Diseases of the pituitary and gonads, regulated by prolactin; dysfunction of the mammary gland
	Somatotropin - inhibitory factor (SIF), or somatostatin; oligopeptide	Anterior pituitary gland. Inhibits somatotropic function	Diseases of the pituitary gland, dysplasia of the body
	Prolactin inhibitory factor (PRF), or prolactostatin	Anterior pituitary gland. Inhibits lactotropic function	Diseases of the pituitary gland, gonads, dysfunction of the mammary gland
	Melanocyte-stimulating hormone inhibitory factor (MIF), or melanostatin; tripeptide	Intermediate part of the pituitary gland. Inhibits melanocyte-stimulating function	Violation of pigmentation of the skin and mucous membranes
	Vasopressin (antidiuretic hormone); nonapeptide with a disulfide bond	Kidney (nephron). Stimulates water reabsorption and inhibits the reabsorption of potassium, sodium and chloride ions from primary urine (regulation of water-salt metabolism); causes contraction of the smooth muscles of blood vessels, in large doses increases blood pressure	Hyperproduction of vasopressin leads to the development of hydropectic syndrome (see); hyperproduction is associated with hypertension in Itsenko-Cushing's disease, some forms of pituitary obesity, eclampsia. Hypoproduction causes diabetes insipidus (see Diabetes insipidus); often accompanies acromegaly, pituitary cachexia, infantilism
	Oxytocin; nonapeptide with a disulfide bond (differs from vasopressin in amino acid residues)	Smooth muscles. Stimulates uterine contraction (estrogens increase, progesterone lowers the sensitivity of the uterus to oxytocin); influences a tone of smooth muscles went. - kish. tract, gallbladder and bladder; activates lactation, causing contraction of myoepithelial cells of the mammary glands	Wedge, displays of the isolated disturbance of secretion of oxytocin are studied insufficiently. With adiposogenital dystrophy and other diseases of hypothalamic origin, prolapse of the stomach, atony of the intestines and uterus (during childbirth), dyskinesia of the gallbladder are often noted, which is associated with hypoproduction of oxytocin
Pineal body	Melatonin; polypeptide	Intermedian antagonist. It is supposed to have an inhibitory effect on the gonadotropic function of the pituitary gland and sex glands, participation in the work of the “biol, clock” mechanism	Diseases associated with an isolated violation of individual functions of the gland are not well understood. The development of the syndrome of premature macrogenitosomia (Pellizzi's syndrome) is associated with hypofunction; with hyperfunction - isolated cases of hypogenitalism

anterior lobe	Adrenocorticotropic hormone (ACTH, dirk tropin); polypeptide	The bundle and reticular zones of the adrenal cortex. Activates glucocorticoid and androgenic functions; plays a leading role in the development of the adaptation syndrome (see). It has a lipolytic effect, promotes the deposition of glycogen in the muscles. Unsharp melanocyte-stimulating activity	Hyperproduction of ACTH (in violation of the hypothalamic regulation of the adrenocorticotropic function of the pituitary gland and basophilic pituitary adenoma, less often with ACTH-like activity of cancer of the lungs and bronchi, thymus and thyroid glands and other organs) leads to the development of Itsenko-Cushing's disease (see Itsenko-Cushing's disease). Hypoproduction of ACTH is a pathogenetic link of hypopituitarism syndromes (see Hypopituitarism), causes the development of secondary hypocorticism (see Addison's disease)
	luteinizing hormone (LH, a hormone that stimulates the interstitial cells of the gonads); glycoprotein	Ovary. Stimulates the secretion of estrogens, the growth of follicles, is necessary for the maturation of the corpus luteum. Testicle. Stimulates the development of glandulocytes (testicular glandulocytes - Leydig cells) and the secretion of testosterone. The action of LH is manifested only in synergy with FSH	Increased secretion of the hormone leads to the development of hypergonadism (see). Decrease - to the development of hypogonadism (see)
	Prolactin (lactotropic hormone, lactotropin); polypeptide	Breast. Stimulates the formation of milk, lactation. Supports functional activity (progesterone secretion) of the corpus luteum. In mammals it stimulates the maternal instinct, in birds it stimulates the nesting instinct.	Hyperproduction of prolactin leads to hypergalactia, the development of persistent lactation syndrome, obesity; hypoproduction - to hypogalactia (see Lactation)
	Somatotropic hormone (GH, somatotropin, growth hormone); polypeptide	Metabolism in the body, bone and cartilage tissue. Stimulates anabolic processes, activates proliferative processes (chondrogenesis, osteogenesis, hematopoiesis), has lipolytic and hyperglycemic (increased gluconeogenesis in the liver) action. Stimulates secretion of glucagon and insulin by pancreatic islet cells	Hyperproduction of growth hormone (with eosinophilic pituitary adenoma, tumor and infectious-toxic damage to the brain and hypothalamus) leads to the development of gigantism (see) and acromegaly (see), impaired glucose tolerance and diabetes mellitus (see. Diabetes mellitus); (in violation of the function of the hypothalamic-pituitary system) in childhood leads to dwarfism (see)
	Thyrotropic hormone (TSH, thyrotropin); glycoprotein	Thyroid. Stimulates plastic and trophic processes, iodine uptake by thyrocytes, activates the processes of iodination of tyrosine and enzymatic breakdown of thyroglobulin, increasing the secretion of thyroxine and triiodothyronine.	Hyperproduction of the hormone causes hyperfunction of the thyroid gland; can be observed with acromegaly, Itsenko-Cushing's disease, less often with gigantism and pituitary obesity. Hypoproduction of TSH (with hypopituitarism, pituitary cachexia) causes hypothyroidism (see)
	Follicle stimulating hormone (FSH); glycoprotein	Ovary. Stimulates the growth and maturation of follicles (postmenstrual phase of the cycle). Testicle. Activates spermatogenesis. Acts in synergy with luteinizing hormone	Premature gonadotropic activity of the pituitary gland (with pathology of the hypothalamus and the epiphysis of the brain in children) leads to early puberty. Hyperproduction of FSH causes the development of hypergonadism (see), hypoproduction - hypogonadism (see)
intermediate	Sideshows (melanocyte-stimulating hormone, melanoform hormone); polypeptide	pigment cells (melanocytes). Promotes the biosynthesis and intracellular redistribution of the pigment and, thus, the pigmentation of the skin and mucous membranes. It has a stimulating effect on c. n. s., activates the rods and cones of the retina, improves the adaptation of the eyes to the dark	Hyperproduction of intermedin (with Addison's disease, acromegaly, Itsenko-Cushing's disease and other pituitary syndromes, pregnancy) causes hyperpigmentation of the skin and mucous membranes. Hypoproduction (with hypopituitarism, adiposogenital dystrophy, skull trauma with diencephalic phenomena) leads to skin depigmentation, increasing its sensitivity to sunlight
Thyroid	Calcitonin (thyreocalcitonin); polypeptide	Bone. Inhibits the processes of resorption, demineralization. Calcium metabolism regulator, parathyroid hormone antagonist	Paget's disease
	thyroxine (tetraiodothyronine); iodinated amino acid	Regulator of metabolism, processes of growth and development of the body. It enhances oxidative processes and heat production in tissues, promotes the synthesis or breakdown of protein (with varying degrees of protein saturation), stimulates the absorption of fats and their mobilization from the depot, the biosynthesis and breakdown of cholesterol, promotes glycogenolysis, increases the release of potassium and water as a result of activation of dissimilatory processes. Stimulates the activity of the adrenal glands, sex and mammary glands. A sufficient level of the hormone is necessary for the normal development of c. n. N of page, a skeleton, functioning of system of a hemopoiesis, cardiovascular system, went. - kish. tract	Hyperproduction of thyroxine causes thyrotoxicosis (see. Diffuse toxic goiter), hypoproduction - hypothyroidism (see.)
	Triiodothyronine; iodinated amino acid	The same, but the effect is 5-6 times higher	Hyperproduction of triiodothyronine causes thyrotoxicosis (see. Diffuse toxic goiter), hypoproduction - hypothyroidism (see.)
parathyroid glands	parathormone; polypeptide	Bone. It activates osteoclasts, causing depolymerization of mucopolysaccharides, bone decalcification and the entry of calcium and phosphorus ions into the blood. Kidneys. By weakening the reabsorption of phosphorus, it increases its excretion in the urine and reduces the content of phosphorus in the blood. The interaction of vitamin D, calcitonin and parathyroid hormone ensures the constancy of the level of calcium and phosphorus in the blood	Hyperproduction of parathyroid hormone causes a state of hyperparathyroidism (see), parathyroid osteodystrophy (see); hypoproduction - hypoparathyroidism (see), tetany (see)
Pancreatic islets (Islets of Langerhans):
basophilic insulocytes (beta cells)	Insulin; polypeptide	Regulates carbohydrate, fat, protein and water-mineral metabolism. Promotes the utilization of glucose by tissues, reduces blood sugar, inhibits gluconeogenesis, enhances lipogenesis, has an anabolic effect	Hyperproduction of insulin in insuloma leads to the development of hyperinsulinism (see); hypoproduction causes the development of diabetes mellitus (see Diabetes mellitus)
acidophilic insulocytes (alpha cells)	Glucagon; peptide	Participates in the regulation of carbohydrate metabolism. Enhances glycogenolysis in the liver, reduces tissue sensitivity to insulin, increases blood sugar	Hyperproduction of glucagon in glucagonoma leads to the development of diabetes mellitus (see Diabetes mellitus). Wedge, manifestations of hormone hypoproduction are unknown
Adrenals:
cortex:
a) glomerular zone	Aldosterone; C21-steroid with a cyclopentanoperhydrophenan-tren ring	Kidneys. Mineralocorticoid. Enhances sodium reabsorption in the distal tubules of the nephron, promotes the release of potassium, hydrogen and ammonium ions; regulates water-salt metabolism and acid-base balance (together with vasopressin)	Hyperproduction of aldosterone in aldosterone leads to the development of primary aldosteronism, in hypertension and a number of other diseases, to the development of secondary aldosteronism (see Hyperaldosteronism). Hypoproduction of aldosterone (with Addison's disease, removal of the adrenal gland) leads to the development of hypoaldosteronism (see)
b) beam zone	Cortisol (hydrocortisone); C21-steroid with the presence of a cyclopentane-perhydrophenanthrene ring	Liver, blood-forming organs, muscles, kidneys, connective tissue. Stimulates gluconeogenesis, protein catabolism, fat mobilization from the depot, excretion of potassium and water from the body and sodium retention. It suppresses lymphopoiesis and the formation of antibodies, causes lympho- and eosinopenia, activates erythro- and granulopoiesis in the bone marrow. It inhibits the formation of the intercellular substance of the connective tissue by fibroblasts, reduces the activity of hyaluronidase, reduces the permeability of blood capillaries (anti-inflammatory mechanisms). Raises BP. Plays an important role in the development of the adaptation syndrome (see)	Hyperproduction of glucocorticoids leads to the development of hypercorticism (see Itsenko-Cushing's disease), hypoproduction - to the development of hypocorticism (see Addison's disease)
b) beam zone	Corticosterone; C21-steroid with a ring	Glucocorticoid. Biol, action on a metabolism is less expressed, than at a cortisol; more actively affects water-salt metabolism
c) mesh zone	Androgens	see testicle
c) mesh zone	Estrogens	see ovary
medulla	Adrenalin; catecholamine, a derivative of the amino acid tyrosine	beta-adrenergic receptors of target organs. Cardiovascular system - increases the contractility and excitability of the myocardium, heart rate and cardiac output, changes the tone of blood vessels, increases blood pressure. Reduces the tone of the muscles of the bronchi, gallbladder, uterus, reduces intestinal motility, causes contraction of the sphincters. Excites c. n. N of page, the centers of a hypothalamus. It has hyperglycemic, glycogenolytic (liver, muscles), lipolytic action. Increases oxygen consumption by tissues. Participates in the development of the adaptation syndrome (see)	Hyperproduction of catecholamines is observed in tumors of the adrenal medulla (see Pheochromocytoma); hypoproduction leads to hypoadrenalemia (see Adrenalinemia)
medulla	norepinephrine; catecholamine, a derivative of the amino acid tyrosine	alpha-adrenergic receptors of target organs. Cardiovascular system - increases the contractility and excitability of the myocardium, slightly lowers the heart rate and cardiac output, has a predominantly vasoconstrictive effect, increases systolic and diastolic blood pressure. Increases the tone of the muscles of the bronchi, the smooth muscles of other organs have little effect. It has a similar effect on adrenaline, but 4-8 times less pronounced effect on metabolism; participates in the development of the adaptation syndrome
	Progesterone (yellow body hormone); C21-steroid with the structure of cyclopentanoper-hydrophenanthrene	Sexual system. It inhibits proliferative and stimulates secretory processes in the endometrium (estrogen antagonist), reduces the excitability and contractility of the myometrium and its sensitivity to oxytocin, thereby preparing the uterus for egg implantation and nutrition of a fertilized egg, ensures the normal development of pregnancy. In the ovary, it prevents (large doses) or promotes (small doses) ovulation. Stimulates the development of the mammary glands. Has mineralocorticoid and protein catabolic action	Violations of the secretion of progesterone cause disorders of the menstrual cycle (see), prevent the development of pregnancy
	Estradiol (estrogen hormone); C18-steroid with the presence of a cyclopent-noperhydrophenanthrene ring	Sexual system. Stimulates the growth and development of female genital organs, proliferative processes in the myometrium and vaginal mucosa, increases the excitability of the uterus, its sensitivity to oxytocin, causes hyperemia, proliferation of the epithelium and contraction of the fallopian tubes. In the ovaries, it promotes the growth and maturation of follicles. Regulates the formation of secondary sexual characteristics. In men, it has an antimasculin effect. Has a pronounced anabolic effect, inhibits the growth of limb bones	Hyperproduction of estrogens in girls leads to early puberty, in women - to hypergonadism (see), in men - to the development of feminization. Hypoproduction causes disturbances in the ovarian menstrual cycle, hypogonadism (see)
	Estriol; C18-steroid with the presence of a cyclopentane-perhydrophenanthrene ring (estradiol metabolism product)	Less active than estradiol and estrone
	Estrone; C18-steroid with the presence of a cyclopentane-perhydrophenanthrene ring (metabolic product of estradiol)	Same; less active than estradiol
	Testosterone; C19-steroid with the structure of cyclopentanoper-hydrophenanthrene	Sexual system. Stimulates the development of primary (genital organs) and secondary male sexual characteristics, activates spermatogenesis (small doses). In women, it has a virilizing effect. Affects the development of the skeleton, the rate of closure of the epiphyseal zones. It has anabolic and glucostatic effects; affects fat and water-salt metabolism	Hyperproduction of androgens in boys leads to early puberty, in men - to hypergonadism, in women (with virilizing hypertrophy and tumors of the adrenal cortex) - to the development of adrenogenital syndrome (see), pseudohermaphroditism (see)
Placenta	Chorionic gonadotropin (CG, choriogonadotropin); glycoprotein	It has an action similar to follicle-stimulating hormone and pituitary prolactin. It is of great importance for the normal development of pregnancy, prolonging the functioning of the corpus luteum of the ovaries (corpus luteum of pregnancy)	Insufficient secretion of the hormone leads to a violation of the course of pregnancy
Placenta	Chorionic lactosomatotropic hormone (placental lactogen, choriomammotropin); protein	It has a pronounced anabolic effect, similar to the action of growth hormone. It is important for the normal course of pregnancy, the development of the mammary glands. It is excreted by the placenta from the 8th week. pregnancy	Wedge, manifestations associated with impaired secretion are not described

Bibliography: Aleshin BV About some topical issues of modern endocrinology, Arkh. patol., t. 31, No. 5, p. 3, 1969, bibliography; he, Histophysiology of the hypothalamic-pituitary system, M., 1971, bibliogr.; he, Endocrine system and homeostasis, in the book: Homeostasis, ed. P. D. Horizontova, p. 60, M., 1976; And r t and sh e sun to and y A. A. Adrenal glands (structure, function, development), Minsk, 1977, bibliogr.; Biochemistry of hormones and hormonal regulation, ed. Edited by N. A. Yudaeva. Moscow, 1976. Volkova O. V. Structure and regulation of function of ovaries, M., 1970, bibliogr.; In at N of e r P. A. Processes of self-regulation in endocrine system, M., 1965, bibliogr.; Kirshenblat Ya. D. General endocrinology, M., 1971, bibliogr.; it, Comparative endocrinology of ovaries, M., 1973, bibliogr.; Levina S. E. Formation of the endocrine system in the prenatal development of a person, M., 1976, bibliogr.; Naumenko E. V. iPopova N.K. Serotonin and melatonin in the regulation of the endocrine system, Novosibirsk, 1975, bibliogr.; Polenov A. L. Hypothalamic neurosecretion, L., 1968, bibliogr.; Guide to endocrinology, ed. B. V. Aleshina et al., M., 1973; Thyroid hormones, ed. I. X. Turakulova, Tashkent, 1972, bibliogr.; Chazov E. I. and Isachenko in V. A. Epiphysis, place and role in the system of neuroendocrine regulation, M., 1974, bibliogr.; Bargmann W. Neurosecretion, Int. Rev. Cytol., v. 19, p. 183, 1966, bibliogr.; Harris G. W. Neural control of the pituitary gland, Physiol. Rev., v. 28, p. 139, 1948; Leak D. The thyroid and the autonomic nervous system, L., 1970; S ch arrer E. The final common path in neuroendocrine integration, Arch. Anat. micr. Morph, exp., t. 54, p. 359, 1965; Textbook of endocrinology, ed. by R. H. Williams, Philadelphia, 1974.

B. V. Aleshin; tabular compilers. P. S. Zavadsky, A. G. Mazovetsky.

Hormones are substances of an organic nature that affect metabolic processes, the functioning of tissues and organs, and the growth of the body. They are produced in humans by endocrine glands, enter the blood or lymph and are delivered to target cells, which are affected.

glands

They are called endocrine (internal secretion), because they do not have ducts to the outside, their secret (hormones) remains inside the body. They regulate each other's work and are able to speed up or slow down the rate of hormone production, thereby affecting the work of all organs and tissues. We can say that they support the entire vital activity of the body. The endocrine glands include:

They perform various functions.

Pituitary and hypothalamus

This system is located in the back of the brain, despite its small size (only 0.7 grams), it is the "head" of the entire endocrine system. Most of the hormones produced by the pituitary gland regulate the work of other glands. The hypothalamus acts as a "sensor", capturing brain signals about fluctuating levels of other hormones, and sending a "command" to the pituitary gland that it is time to start working. Previously, it was also considered a full-fledged gland that affects the functioning of the body, but thanks to research, it was found that hormones are secreted by the pituitary gland, and the hypothalamus regulates these functions through releasing hormones. There are two types of them: some start the secretion process (release), others slow down (stop). The pituitary hormones include:

Thyroid and parathyroid glands

The thyroid gland is located in the region of the upper third of the trachea, attached to it by connective tissue, has two lobes and an isthmus, resembling an inverted butterfly in shape. Its average weight is about 19 grams. The thyroid gland secretes thyroid hormones: thyroxine and triiodothyronine, which are involved in cell metabolism and energy metabolism. Maintaining the temperature of the human body, maintaining the body during stress and physical exertion, obtaining cells of water and nutrients, the formation of new cells - all this is the activity of thyroid hormones.

Small (no more than 6 g) parathyroid glands are located on the back wall of the thyroid gland. Most often, a person has two pairs of them, but sometimes it happens less, which is considered a variant of the norm. They produce hormones that regulate the level of calcium in the blood - paratin. They act in tandem with calcitonin, a thyroid hormone that lowers calcium levels, and they increase it.

This is an unpaired small organ located between the hemispheres in the center of the brain. Its shape resembles a pine cone, for which it received its second name - the pineal gland. Weight is only 0.2 g. The activity of this gland depends on the illumination of the place where the person is located. His leashes are attached to the optic nerves, through which he receives signals. It produces serotonin in the light and melatonin in the dark.

Serotonin also plays the role of a neurotransmitter - a substance that promotes the transmission of impulses between neurons, thanks to this property it improves a person's mood, restrains pain impulses, and is responsible for muscle activity.

Once in the blood, it performs the functions of a hormone: it affects the development of inflammatory processes and blood clotting, slightly on allergic reactions and regulates the hypothalamus.

Melatonin - a hormone derived from serotonin, is responsible for blood pressure, falling asleep and sleep depth, activates the immune system, inhibits the synthesis of somatotropic hormone, reducing the risk of developing tumors, controls puberty and sexual arousal. During sleep, it restores damaged cells and slows down the aging process. That is why healthy good sleep is so important for a person.

The pineal gland produces another hormone - adrenoglomerulotropin, its functions are not yet clear, scientists managed to find out that it affects the secretion of hormones by the adrenal medulla, but the whole process remains a mystery to them.

It is located behind the sternum, is a paired organ weighing about 20 grams. It grows until puberty, then begins to slowly atrophy, in older people it is almost indistinguishable from adipose tissue. The thymus gland is an important organ of the immune system in which T cells mature, differentiate and immunologically "learn". It produces hormones

Timalin;
Thymosin;
Thymopoietin;
IGF-1;

Its role for the body is still not well understood. But its most important function is to prevent a person from dying from infections in childhood. It works hard in babies, producing T-lymphocytes, endowing them with T-cell receptors and co-receptors (markers), forming acquired immunity. It is thanks to the thymus that a person does not get sick twice with diseases caused by measles, chicken pox, rubella and many others.

They are located above each of the human kidneys, the weight of one is about 4 g, 90% of the gland is the adrenal cortex, the remaining 10% is the medulla. They produce different groups of hormones:

Mineralocorticoids (water-salt balance);
Glucocorticoids (glucose formation, anti-shock effect, immunoregulation, anti-allergic effect);
Androgens (synthesis and breakdown of proteins, utilization of glucose, lowering the level of cholesterol and lipids in the blood, reducing the amount of subcutaneous fat);
Catecholamines (support the body during fear, rage, physical exertion, giving a signal to the hypothalamus, enhance the work of other glands);
Peptides (cell regeneration, removal of toxins, increases the wear resistance of tissues).

It is located in the epigastric region, behind the stomach. Endocrine functions are performed only by a small part of it - the pancreatic islets. They are not located in one place, but are scattered unevenly throughout the gland. They secrete several hormones:

Glucagon (increases blood glucose levels);
Insulin (transportation of glucose into cells).

Most of the pancreas produces gastric juices, performing an exocrine function.

gonads

The sex glands include the testes and ovaries, they, like the pancreas, are mixed glands, performing intrasecretory and exocrine functions.

The ovaries are paired female glands located in the pelvic cavity, weighing about 7 grams. They produce steroid hormones: estrogens, gestagens, androgens. They provide ovulation and the formation of the corpus luteum after conception. Their concentration is not constant, one of the hormones dominates, then another and a third, which creates a cycle.

The testicles are also a paired organ, male, glands are located in the scrotum. The main testicular hormone is testosterone.

The gonads are responsible for the development of the reproductive organs and the maturation of the egg and sperm. They form secondary sexual characteristics: the timbre of the voice, the structure of the skeleton, the location of body fat and hairline, affect mental behavior - everything that distinguishes men from women.