Glands and types of secretion table. Anatomy of the human endocrine glands - information

Endocrine glands, or endocrine glands, are those glands that do not have excretory ducts and secrete physiologically active substances (hormones) directly into the internal environment of the body -. Together with the nervous endocrine system, it ensures that the body adapts to environmental conditions. But if the nervous system is structurally rigidly organized, then hormones, moving with the blood, act on all organs and where they can contact specific hormone receptors. If the nervous system exercises its influences almost instantly, then the endocrine system develops its effects on the body more slowly, but their duration, unlike the nervous ones, can be very significant.

Hormones are substances of various classes (amino acids and their derivatives, peptides, steroids, etc.), which are usually produced and secreted by specialized glands. Although, for example, many hormones are synthesized in the hypothalamic region of the diencephalon. So the hypothalamus is a neuroendocrine organ. All activities of the endocrine system are under the control of the nervous system, although the nervous system is constantly controlled by the endocrine system.

A substance that belongs to hormones must meet the following criteria: be isolated from living cells, and without violating their integrity; not serve as a source of energy; released into the blood in very small quantities; enter directly into the blood; act on target organs through specific receptors.

Some hormones have a direct regulatory effect on some organ, while others may have a programming effect, i.e. at a certain moment, they change the cells of any tissues for the entire subsequent time of their life.

Receptors for hormones are proteins. Some of them are located on the outer membrane of the cell, and when a hormone molecule binds to such a receptor, a whole cascade of chemical changes is triggered in the cell, and its state changes. Protein-peptide hormones usually have this mechanism of action. This type of reception is called membrane. Another type of reception is nuclear. Hormones with such a reception (for example, steroids) must get inside the cell, pass into its nucleus and there affect the genetic apparatus of the cell, inducing or inhibiting the synthesis of some proteins. The effects of hormones with nuclear reception develop slowly, but they persist for a very long time.

Pituitary

The pituitary gland is a lower cerebral appendage connected to the hypothalamus by a thin stalk. The mass of the pituitary gland is about 0.5 g. It is located in a special bone recess - the Turkish saddle. Anatomically and functionally, the pituitary gland is divided into three lobes: anterior, intermediate, and posterior. In the anterior lobe of the pituitary gland, peptide hormones are synthesized and released into the blood, which control the activity of other endocrine glands.

Hormones of the anterior pituitary gland. Adrenocorticotropic hormone (corticotropin, ACTH) stimulates the activity of the adrenal cortex. In turn, the release of ACTH is controlled by corticoliberin, a peptide produced in the hypothalamus. With an excess of ACTH, Cushing's syndrome develops: the adrenal cortex grows, obesity occurs, headaches, hysteria appear, etc.

Thyroid-stimulating hormone (TSH) stimulates the synthesis of thyroid hormones. The release of TSH is controlled by thyroliberin, a peptide that is produced in the hypothalamus.

Gonadotropins (luteinizing and follicle-stimulating hormones) control the activity of the gonads. They enhance the formation of male and female sex hormones in the testes and ovaries, stimulate the growth of the testes, the growth of follicles. The synthesis and release of gonadotropins is controlled by luliberin, a peptide that is produced in the hypothalamus.

Somatotropic hormone (growth hormone) does not act on any one endocrine gland, but stimulates the production of tissue growth factors in the cells of many tissues. In turn, these tissue factors stimulate the growth of all parts of the body. With a lack of somatotropic hormone, pituitary dwarfism develops in children, and with an excess, pituitary gigantism develops. If an excess of somatotropic hormone is observed in an adult, when normal growth has already stopped, then a disease occurs - acromegaly, in which the nose, lips, fingers and toes grow. The production of somatotropin is regulated by peptides of the hypothalamus: stimulated by somatoliberin, and inhibited by somatostatin.

Prolactin stimulates the production of milk in nursing mothers and is involved in organizing the activity of the gonads.

In the intermediate lobe of the pituitary gland, a melanocystimulating hormone is produced, the functions of which have not been studied enough, but it has been shown that its excess increases skin pigmentation and it noticeably darkens.

The hormones of the posterior pituitary gland - vasopressin (antidiuretic hormone - ADH) and oxytocin - are peptides and are similar in chemical structure. They are produced in the neurons of the hypothalamus, and then descend along the leg into the posterior lobe of the hypothalamus and from there can enter the bloodstream. The main function of vasopressin is to increase reabsorption in the renal tubules, which leads to a decrease in urine volume. This hormone takes an important part in the regulation of the constancy of the internal environment of the body, and when it is lacking, a person develops a disease - diabetes insipidus, in which the body loses a large amount of water and some salts. Oxytocin stimulates contraction of the smooth muscles of the vas deferens and oviducts, and also plays a critical role in childbirth by stimulating uterine muscle contraction.

Thyroid

The thyroid gland is located on the anterior wall of the larynx, consists of two lobes and an isthmus and has a mass of 25 to 40 g. Outside, the gland is covered with a connective tissue membrane. The gland itself is formed by special vesicles - follicles, in which hormones containing iodine are produced - thyroxine (tetraiodothyronine) and triiodothyronine. Thyroid hormones perform a number of functions. Firstly, they are programming, participating, for example, in the puberty of various animals and humans. If the tadpole of a frog is deprived of these hormones, it will grow to a gigantic size, but it will not be able to turn into a frog. Secondly, these hormones increase the metabolism, stimulating cellular respiration, increase the secretion of growth hormone from the pituitary gland. Thirdly, thyroid hormones increase the production of heat by the body - thermogenesis. Diseases associated with disorders of the thyroid gland can occur not only with changes in the gland itself, but also with a lack of iodine in the body, diseases of the anterior pituitary gland, etc.

With a decrease in thyroid function in childhood, cretinism develops, characterized by inhibition in the development of all body systems, short stature, and dementia. In an adult with a lack of thyroid hormones, myxedema occurs, in which edema, dementia, decreased immunity, and weakness are observed. This disease responds well to treatment with thyroid hormones administered externally. With an increase in the activity of the thyroid gland, Graves' disease occurs, in which excitability, metabolism, heart rate increase sharply, bulging eyes (exophthalmos) and weight loss are characteristic.

In those geographic areas where it contains little iodine (usually found in the mountains), the population often has goiter - a disease in which the secreting tissue of the thyroid gland grows, but cannot, in the absence of the required amount of iodine, synthesize full-fledged hormones. In such areas, the consumption of iodine by the population should be increased, which can be ensured, for example, by selling table salt with mandatory small additions of sodium iodide.

parathyroid glands

Parathyroid glands are small glands located on the surface or in the thickness of the thyroid gland, usually two on each side. They secrete parathyroid hormone, which regulates calcium metabolism in the body. When these glands are affected, there is a lack of calcium ions in the blood, convulsions, vomiting and death against the background of paralysis of the respiratory muscles. With increased function, the bones begin to lose Ca 2+, muscle weakness occurs. At the same time, the level of Ca 2+ in the blood plasma increases.

Pancreas

The pancreas has a mixed secretion: some of its cells secrete a number of digestive enzymes through the ducts into the duodenum (external secretion), while clusters of other cells, called the islets of Langerhans, secrete the hormones insulin and glucagon directly into the blood. The continuous release of insulin into the blood is necessary so that the main source of energy - glucose - can freely pass from the blood plasma to the tissues, and its excess is deposited in the liver in the form of a glycogen polymer. With a lack of insulin, diabetes mellitus develops - a disease in which glucose does not penetrate into the tissues, and its level in the blood plasma increases greatly, which entails the excretion of glucose from the body in large volumes of urine. If a diabetic patient is not administered insulin from outside, then depriving the brain of glucose leads to loss of consciousness, convulsions and rapid death. The second hormone of the pancreas - glucagon - is synthesized in special cells of the islets of Langerhans and is necessary for the formation of glucose from glycogen when there is a shortage of it in the blood plasma. Thus, insulin and glucagon, by having an opposite effect on carbohydrate metabolism, provide a precise regulation of the body's consumption of glucose.

adrenal glands

The adrenal glands are small paired glands located at the upper poles of the kidneys and consisting of two layers: cortical and medulla. The cells of the outer cortical layer produce three groups of hormones:

1) Glucocorticoids, the main of which is cortisol, stimulate the synthesis of glycogen from glucose, lower the level of glucose consumption by tissues, inhibit the immune response, and prevent inflammatory processes.

2) Mineralocorticoids (for example, aldosterone) regulate the content of Na + and K + in the body, increasing the reverse absorption of Na + in the renal tubules and stimulating the excretion of K + and H + in the urine.

3) The precursors of sex hormones, mainly male ones, are involved in the formation of secondary sexual characteristics as programming hormones.

With insufficient functioning of the adrenal cortex, Addison's disease occurs, which is characterized by carbohydrate metabolism disorders, low blood pressure, weight loss, nausea, and increased skin pigmentation.

The adrenal medulla produces adrenaline and norepinephrine and functionally enters into a single regulatory system with the sympathetic division of the autonomic nervous system. In those periods when the body must work under great stress (in case of injury, during danger, in conditions of increased physical and mental labor, etc.), these hormones enhance muscle work, increase blood glucose (to ensure increased energy costs brain), increase blood flow in the brain and other vital organs, increase systemic blood pressure, increase cardiac activity, etc. Thus, the hormones of the adrenal medulla serve to ensure the body's response to extreme exposure or stress response.

epiphysis

The pineal gland is a small reddish-brown gland weighing only 0.15-0.20 g, located between the upper tubercles of the quadrigemina of the midbrain in a special cranial cavity. The pineal gland is connected to the brain by a hollow stalk. So far, only one hormone of the pineal gland is known - melatonin, under the influence of which the release of gonadotropic hormones is inhibited, the rate of puberty changes, and in animals seasonal physiological cycles are regulated. The work of the pineal gland is sensitive to ambient light: the synthesis of melatonin in it is enhanced in the dark, it is increased in blind people.

thymus

Thymus (thymus gland) is a small lymphoid organ, consisting of two lobules and located behind the sternum in the mediastinum. The thymus is well developed only in childhood and practically disappears during puberty. The non-endocrine function of the thymus is that T-lymphocytes, which are necessary for providing immunity, mature in it, which, after maturation, populate other lymphoid organs. The endocrine function of the thymus is that it secretes into the blood the peptide hormones thymosin and thymopoietins, which stimulate the growth and formation of the immune system. If the thymus continues to function actively in an adult, autoimmune diseases can develop, in which, due to a pathological increase in immunity, the destruction of the body's own proteins by antibodies is observed. Such diseases include systemic lupus erythematosus, myasthenia, etc.

gonads

Sex glands (gonads) - are glands of mixed, that is, both external and internal, secretion. The sex glands of a woman - the ovaries - secrete eggs into the external environment, and the hormones estrogens and progestins into the internal environment. The sex glands of a man - the testes - secrete spermatozoa into the external environment, and hormones androgens into the internal environment.

The ovaries secrete estradiol into the blood, an ovulation inducer related to estrogen, which is also involved in the formation of secondary sexual characteristics according to the female type (development of the mammary glands, a certain type of physique, etc.). Progesterone, related to progestins, is produced in the corpus luteum, which is formed at the site of a burst follicle. Progesterone is a hormone of pregnancy, it is necessary for the attachment (implantation) of the embryo to the wall of the uterus, and also inhibits the maturation and ovulation of follicles during pregnancy.

The testicles secrete androgens into the blood, the main of which is testosterone, which performs a number of functions. It is necessary for the normal formation of the reproductive system in the embryo according to the male type, for the development of male secondary sexual characteristics (hair growth and muscle development according to the male type, deep voice, metabolic and behavioral features, etc.), ensures the constancy of spermatogenesis, etc.

The concept of endocrine glands and hormones. endocrine glands, or endocrine, called glands that do not have excretory ducts. Products of their vital activity - hormones - they secrete into the internal environment of the body, i.e. into the blood, lymph, tissue fluid.

Hormones- organic substances of various chemical nature: peptide and protein(protein hormones include insulin, somatotropin, prolactin, etc.), amino acid derivatives(adrenaline, norepinephrine, thyroxine, triiodothyronine), steroid(hormones of the gonads and adrenal cortex). Hormones have high biological activity (therefore, they are produced in extremely small doses), specificity of action, distant effect, i.e., they affect organs and tissues located far from the place where hormones are formed. Entering the bloodstream, they are carried throughout the body and carry out humoral regulation of functions organs and tissues, changing their activity, stimulating or inhibiting their work. The action of hormones is based on the stimulation or inhibition of the catalytic function of certain enzymes, as well as the impact on their biosynthesis by activating or inhibiting the corresponding genes.

The activity of the endocrine glands plays a major role in the regulation for a long time ongoing processes: metabolism, growth, mental, physical and sexual development, adaptation of the body to changing conditions of the external and internal environment, ensuring the constancy of the most important physiological indicators (homeostasis), as well as in the body's reactions to stress.

When the activity of the endocrine glands is disturbed, diseases called endocrine arise. Violations can be associated either with increased (compared to the norm) activity of the gland - hyperfunction, in which an increased amount of the hormone is formed and released into the blood, or with a reduced activity of the gland - hypofunction, accompanied by the opposite result.

Intrasecretory activity of the most important endocrine glands. The most important endocrine glands include the thyroid, adrenal glands, pancreas, sex, pituitary (Fig. 13.4). The hypothalamus (hypothalamic region of the diencephalon) also has an endocrine function. The pancreas and gonads are glands mixed secretion, since, in addition to hormones, they produce secrets that enter through the excretory ducts, that is, they also perform the functions of the external secretion glands.

Thyroid(weight 16-23 g) is located on the sides of the trachea just below the thyroid cartilage of the larynx. thyroid hormones (thyroxine and triiodothyronine) they contain iodine, the intake of which with water and food is a necessary condition for its normal functioning.

Thyroid hormones regulate metabolism, enhance oxidative processes in cells and the breakdown of glycogen in the liver, affect the growth, development and differentiation of tissues, as well as the activity of the nervous system. With hyperfunction of the gland develops Graves' disease. Its main signs are: proliferation of gland tissue (goiter), bulging eyes, rapid heartbeat, increased excitability of the nervous system, increased metabolism, weight loss. Hypofunction of the gland in an adult leads to the development myxedema(mucous edema), manifested in a decrease in metabolism and body temperature, an increase in body weight, swelling and puffiness of the face, mental disorders. Hypofunction of the gland in childhood causes growth retardation and the development of dwarfism, as well as a sharp lag in mental development (cretinism).

adrenal glands(weight 12 g) - paired glands adjacent to the upper poles of the kidneys. Like the kidneys, the adrenal glands have two layers: the outer one, the cortical layer, and the inner one, the medulla, which are independent secretory organs that produce different hormones with different patterns of action.

cells cortical layer hormones are synthesized that regulate mineral, carbohydrate, protein and fat metabolism. So, with their participation, the level of sodium and potassium in the blood is regulated, a certain concentration of glucose in the blood is maintained, the formation and deposition of glycogen in the liver and muscles increases. The last two functions of the adrenal glands are performed in conjunction with pancreatic hormones. At hypofunction the adrenal cortex develops bronze, or Addison's disease. Its signs: bronze skin tone, muscle weakness, increased fatigue, decreased immunity.

medulla adrenal glands produce hormones adrenalin and norepinephrine. They stand out with strong emotions - anger, fear, pain, danger. The entry of these hormones into the blood causes palpitations, narrowing of blood vessels (except for the vessels of the heart and brain), increased blood pressure, increased breakdown of glycogen in the cells of the liver and muscles to glucose, inhibition of intestinal motility, relaxation of the muscles of the bronchi, increased excitability of the receptors of the retina, auditory and vestibular apparatus. The result is a restructuring of body functions. under the conditions of action emergency stimuli and mobilization the body's ability to cope with stressful situations.

Pancreas has special islet cells, which produce the hormones insulin and glucagon, which regulate carbohydrate metabolism in the body. So, insulin increases the consumption of glucose by cells, promotes the conversion of glucose into glycogen, thus reducing the amount of sugar in the blood. Due to the action of insulin, the blood glucose content is maintained at a constant level, favorable for the flow of vital processes. With insufficient production of insulin, the level of glucose in the blood rises, which leads to the development of the disease. diabetes. Sugar not used by the body is excreted in the urine. Patients drink a lot of water, lose weight. Insulin is required to treat this disease. Another pancreatic hormone glucagon- is an insulin antagonist and has the opposite effect, i.e., it enhances the breakdown of glycogen to glucose, increasing its content in the blood.

The most important gland of the endocrine system of the human body is pituitary, or lower appendage of the brain (weight 0.5 g). It produces hormones that stimulate the functions of other endocrine glands. There are three lobes in the pituitary gland: anterior, middle, and posterior, and each of them produces different hormones. Yes, in anterior lobe the pituitary gland produces hormones that stimulate the synthesis and secretion of thyroid hormones (thyrotropin), adrenal glands (corticotropin), gonads (gonadotropin), as well as growth hormone (somatotropin). With insufficient secretion of somatotropin in a child, growth is inhibited and a disease develops. pituitary dwarfism(the height of an adult does not exceed 130 cm). With an excess of the hormone, on the contrary, it develops gigantism. Increased secretion of somatotropin in an adult causes disease acromegaly in which separate parts of the body grow - tongue, nose, hands. Hormones posterior lobe pituitary increase the reabsorption of water in the renal tubules, reducing urination (antidiuretic hormone), increase uterine smooth muscle contractions (oxytocin).

gonads - testicles, or testicles, in men and ovaries in women, they belong to the glands of mixed secretion. Testicles produce hormones androgens, and the ovaries -estrogens. They stimulate the development of reproductive organs, the maturation of germ cells and the formation of secondary sexual characteristics, i.e., structural features of the skeleton, muscle development, distribution of hairline and subcutaneous fat, larynx structure, voice timbre, etc. in men and women. The effect of sex hormones on shaping processes is especially evident in animals when the gonads are removed (castracin) or transplanted.

The exocrine function of the ovaries and testes is the formation and excretion of eggs and spermatozoa through the genital ducts, respectively.

Hypothalamus. The functioning of the endocrine glands, which together form endocrine system, carried out in close interaction with each other and the relationship with the nervous system. All information from the external and internal environment of the human body enters the corresponding zones of the cerebral cortex and other parts of the brain, where it is processed and analyzed. From them, information signals are transmitted to the hypothalamus - the hypothalamic zone of the diencephalon, and in response to them it produces regulatory hormones entering the pituitary gland and through it exert their regulatory effect on the activity of the endocrine glands. Thus, the hypothalamus performs coordinating and regulatory functions in the activity of the human endocrine system.

Endocrine system- a system for regulating the activity of internal organs by means of hormones secreted by endocrine cells directly into the blood, or diffusing through the intercellular space into neighboring cells.

The endocrine system is divided into the glandular endocrine system (or glandular apparatus), in which the endocrine cells are brought together to form the endocrine gland, and the diffuse endocrine system. The endocrine gland produces glandular hormones, which include all steroid hormones, thyroid hormones, and many peptide hormones. The diffuse endocrine system is represented by endocrine cells scattered throughout the body that produce hormones called aglandular - (with the exception of calcitriol) peptides. Almost every tissue in the body contains endocrine cells.

Endocrine system. Main endocrine glands. (on the left - a man, on the right - a woman): 1. Epiphysis (refer to the diffuse endocrine system) 2. Pituitary gland 3. Thyroid gland 4. Thymus 5. Adrenal gland 6. Pancreas 7. Ovary 8. Testicle

Functions of the endocrine system

• It takes part in the humoral (chemical) regulation of body functions and coordinates the activity of all organs and systems.
• It ensures the preservation of the body's homeostasis under changing environmental conditions.
• Together with the nervous and immune systems, it regulates
  • growth,
  • body development,
  • its sexual differentiation and reproductive function;
  • takes part in the processes of formation, use and conservation of energy.
• Together with the nervous system, hormones are involved in providing
  • emotional
  • mental activity of a person.

glandular endocrine system

The glandular endocrine system is represented by separate glands with concentrated endocrine cells. Endocrine glands (endocrine glands) are organs that produce specific substances and secrete them directly into the blood or lymph. These substances are hormones - chemical regulators necessary for life. Endocrine glands can be both independent organs and derivatives of epithelial (border) tissues. The endocrine glands include the following glands:

Thyroid

The thyroid gland, whose weight ranges from 20 to 30 g, is located in the front of the neck and consists of two lobes and an isthmus - it is located at the level of the ΙΙ-ΙV cartilage of the windpipe and connects both lobes. On the back surface of the two lobes, there are four parathyroid glands in pairs. Outside, the thyroid gland is covered with neck muscles located below the hyoid bone; with its fascial sac, the gland is firmly connected to the trachea and larynx, so it moves following the movements of these organs. The gland consists of vesicles of an oval or round shape, which are filled with a protein iodine-containing substance such as a colloid; loose connective tissue is located between the vesicles. The vesicle colloid is produced by the epithelium and contains the hormones produced by the thyroid gland - thyroxine (T4) and triiodothyronine (T3). These hormones regulate the metabolic rate, promote the uptake of glucose by the cells of the body and optimize the breakdown of fats into acids and glycerol. Another hormone secreted by the thyroid gland is calcitonin (polypeptide by chemical nature), it regulates the content of calcium and phosphates in the body. The action of this hormone is directly opposite to parathyroidin, which is produced by the parathyroid gland and increases the level of calcium in the blood, increases its influx from the bones and intestines. From this point, the action of parathyroidin resembles that of vitamin D.

parathyroid glands

The parathyroid gland regulates calcium levels in the body within narrow limits so that the nervous and motor systems function normally. When the level of calcium in the blood falls below a certain level, the calcium-sensitive parathyroid glands become activated and secrete the hormone into the blood. Parathyroid hormone stimulates osteoclasts to release calcium from bone tissue into the blood.

thymus

The thymus produces soluble thymic (or thymic) hormones - thymopoietins, which regulate the processes of growth, maturation and differentiation of T cells and the functional activity of mature cells. With age, the thymus degrades, being replaced by a connective tissue formation.

Pancreas

The pancreas is a large (12-30 cm long) secretory organ of double action (secretes pancreatic juice into the lumen of the duodenum and hormones directly into the bloodstream), located in the upper part of the abdominal cavity, between the spleen and duodenum.

The endocrine pancreas is represented by the islets of Langerhans located in the tail of the pancreas. In humans, islets are represented by various types of cells that produce several polypeptide hormones:

• alpha cells - secrete glucagon (a regulator of carbohydrate metabolism, a direct antagonist of insulin);
• beta cells - secrete insulin (a regulator of carbohydrate metabolism, lowers blood glucose levels);
• delta cells - secrete somatostatin (inhibits the secretion of many glands);
• PP cells - secrete pancreatic polypeptide (suppresses pancreatic secretion and stimulates gastric juice secretion);
• Epsilon cells - secrete ghrelin ("hunger hormone" - stimulates appetite).

adrenal glands

At the upper poles of both kidneys are small triangular-shaped glands - the adrenal glands. They consist of an outer cortical layer (80-90% of the mass of the entire gland) and an inner medulla, the cells of which lie in groups and are entwined with wide venous sinuses. The hormonal activity of both parts of the adrenal glands is different. The adrenal cortex produces mineralocorticoids and glycocorticoids, which have a steroidal structure. Mineralocorticoids (the most important of them is amide oox) regulate ion exchange in cells and maintain their electrolytic balance; glycocorticoids (eg, cortisol) stimulate protein breakdown and carbohydrate synthesis. The medulla produces adrenaline, a hormone from the catecholamine group, which maintains sympathetic tone. Adrenaline is often referred to as the fight-or-flight hormone, as its secretion rises sharply only in moments of danger. An increase in the level of adrenaline in the blood entails corresponding physiological changes - the heartbeat quickens, blood vessels constrict, muscles tighten, pupils dilate. The cortex also produces small amounts of male sex hormones (androgens). If disorders occur in the body and androgens begin to flow in an extraordinary amount, the signs of the opposite sex increase in girls. The adrenal cortex and medulla differ not only in different hormones. The work of the adrenal cortex is activated by the central, and the medulla - by the peripheral nervous system.

DANIEL and human sexual activity would be impossible without the work of the gonads, or sex glands, which include the male testicles and female ovaries. In young children, sex hormones are produced in small quantities, but as the body grows older, at a certain point, a rapid increase in the level of sex hormones occurs, and then male hormones (androgens) and female hormones (estrogens) cause a person to develop secondary sexual characteristics.

Hypothalamic-pituitary system

And their hormones (also called secrets) ensure the functioning of the endocrine system of the body. Secrets are secreted into the internal environment of the body, since these organs do not have ducts that allow secretions to be removed into the cavity or onto the surface of the skin.

Organs that secrete biologically active substances are divided into three large groups: external, internal and mixed secretion.

• The organs of external secretion include sweat, sebaceous, salivary and gastric glands. The released secret passes through the ducts to the surface of the skin, oral cavity or stomach.
• The group of endocrine organs of internal secretion includes the pituitary gland, adrenal glands, thyroid and parathyroid glands. Blood is the main transport of these secrets. Hormones secreted by glands with internal secretion come here.
• The thymus, pancreas and gonads are classified as mixed secretions. This also includes the placenta. They are traditionally referred to as the endocrine system, since the hormone can be released both outside and inside the body.

The main function of the endocrine system is the regulation of processes occurring in the body. The maturation of the egg or sperm, the onset of puberty or menopause, depression, insomnia and excessive activity - the consequences of the work of substances can be different, and their action is complex and balanced.

Anatomically, this area of ​​the brain is not an organ of secretion, as it is represented by neurons. But the latter can secrete substances that activate the work of the pituitary gland - the next representative of the organs of internal secretion.

The work is presented in this way. Hormones are synthesized in neurons and produced in the neurohypophysis, from which they enter the bloodstream and reach the target organ. The main secrets of the gland and those hormones that are produced under their action are vasopressin.

• Prolactin is responsible for the onset of the lactation period and the formation of milk in pregnant women.
• Oxytocin stimulates the work of smooth muscles, strengthens the muscles and contractile activity of muscle fibers. It is indicated for pregnant women with low activity of the muscle fibers of the uterus, as well as with muscle hypotrophy.
• Vasopressin regulates the excretion of water by the kidneys, increases the tone of the smooth muscles of the digestive tract, and with an excess of secretion, it increases blood pressure.

Pituitary

The apex of the endocrine glands is the pituitary gland. It is located in the center of the brain and its dimensions do not exceed 5x5 mm. There are several targets where they enter. It regulates the work of other glands, the reproductive system, metabolic processes and human growth.

The pituitary gland secretes corticotropin, thyrotropic and gonadotropic secretions.

• Corticotropin regulates the work of the adrenal glands, stimulates the release of hormones in them
• Thyrotropin stimulates the production of: thyroxine and triiodothyronine, which further regulate metabolic processes and the condition of the skin
• Follitropin is responsible for the formation of follicles, and lutropin is responsible for the rupture of the follicle membrane and the formation of the corpus luteum.
• Somatotropin is the most important hormone formed by the endocrine gland. Being released into the blood and cavities, it increases RNA synthesis, regulates carbohydrate metabolism, and stimulates growth processes. The lack of somatotropin in childhood leads to lifelong.

Thyroid

The organ in the form of a shield is located on the front wall of the neck and reaches a mass of 20-23 g. Under the action of the pituitary gland, the synthesis of secrets in the A-cells of the thyroid gland is activated, after which they are released into the blood, where they bind with carrier proteins and reach target organs.

The thyroid and parathyroid glands secrete thyroxine, calcitonin and triiodothyronine. The first two hormones are abbreviated as T4 and T3.

• - hormonal regulator of metabolism and peptide synthesis. Participates in the development and growth of the body. Excess T4 is a common endocrine disease, when the hormone produced is rejected by the body and is regarded by it as a foreign substance.
• Triiodothyronine, the production of which only a quarter occurs in the thyroid gland, is also involved in the regulation of metabolic processes and protein synthesis, being released from T4.
• takes an active part in strengthening bone tissue, reduces the concentration of phosphorus and calcium in the blood, activates the excretion of phosphates by the kidneys.

pancreas

Mixed glands produce hormones of both intra- and exocrine function. The last function is performed by small pancreatic islets, which are pierced by capillaries.

Hormones formed by islets enter these capillaries through the endothelial membranes and are carried by the blood throughout the body.

• - secretion of the hormone occurs in the A-cells of the islets. Its function is aimed at converting incoming glycogen into a more digestible form - glucose.
• - the most important hormone responsible for the regulation of blood glucose levels. Each time glucose enters the bloodstream, insulin binds it into animal starch, which is burned by muscle fibers. A decrease in insulin secretion leads to diabetes mellitus, and an increase leads to excessive consumption of glucose by tissues, the deposition of sugars and hypoglycemic coma.
• Pancreatic polypeptide and somatostatin are substances of the general hormonal background that are of little importance in clinical practice.

adrenal glands

This is a paired endocrine organ that forms the signaling hormonal systems of the body. It is located above the upper region of the kidneys and reaches a mass of no more than 8 g. The secretion occurs in the cortex of the organ.

The development and functioning of the cortex is completely dependent on the pituitary gland.

• - a signaling substance that increases the heartbeat, constricts blood vessels and accelerates the synthesis of glucose. The excitability of the retina, vestibular and hearing aids increases - the body works in an "emergency" mode under the influence of external stimuli.
• - a harbinger of adrenaline. It is synthesized before adrenaline, and in case of extreme stimuli it is immediately transformed into its final form.
• - regulates salt metabolism, preventing hyperkalemia.

These include the testes and ovaries. Knowing where the hormones secreted by the endocrine glands go, it is easy to understand the principle of the sex glands.

The testicles produce male sex hormones (androgens) that affect the development and functioning of the reproductive system.

The ovaries produce - female sex hormones that are responsible for the onset of pregnancy, childbearing functions, as well as stimulating the production of breast milk.

Conclusion

It is impossible to say which glands are more important for the body, because their system of work is interconnected and dependent on each hormone. The hormones formed by the endocrine glands are constantly secreted, providing the vital functions of the body.

Violations in the work of one endocrine organ will entail changes not only in other glands, but in all organs. For this reason, most diagnosis begins with an analysis of the endocrine system to determine which hormones are found outside the normal range.

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6. Anosova L. N., Zefirova G. S., Krakov V. A. Brief endocrinology. – M.: Medicine, 1971.

Human endocrine glands produce hormones. This is what biologically active substances are called, which have an extremely strong effect on the tissues, cells and organs to which their activity is directed. The glands got their name due to the absence of excretory ducts: they release active substances into the blood, after which hormones spread throughout the body and control its work.

The endocrine glands are divided into two groups. The first group includes organs whose activity is under the control of the pituitary gland, the second group includes glands that act independently, according to the biorhythms and rhythms of the body.

The central organ of the endocrine system, which controls the activities of almost everyone, is the pituitary gland, which consists of two parts and produces a huge amount of different types of hormones. It is located in the bone pocket of the sphenoid bone of the skull, attached to the lower part of the brain and controls the activity of the thyroid gland, parathyroid gland, adrenal glands, sex glands.

The hypothalamus controls the work of the pituitary gland, one of the parts of the brain, closely connected not only with the endocrine, but also with the central nervous system. This gives him the opportunity to capture and correctly interpret all the processes occurring in the body, interpret them and give the pituitary a signal to increase or decrease the synthesis of certain hormones.

The hypothalamus controls the endocrine glands with hormones that are produced in the anterior pituitary gland. How exactly the pituitary hormones affect the endocrine organs can be seen in the following table:

In addition to those indicated in the table, the anterior part of the pituitary gland produces, accelerating the synthesis of proteins in cells, which affects the formation of glucose, the breakdown of fats, the growth and development of the body. Another hormone that is involved in reproductive function is prolactin.

Under its influence, milk is formed in the mammary glands, and during lactation, the onset of a new pregnancy is inhibited, since it inhibits the hormones responsible for preparing for conception. It also affects metabolism, growth, causes instincts aimed at caring for offspring.

In the second part of the pituitary gland (neurohypophysis), hormones are not produced: biologically active substances that are produced by the hypothalamus accumulate here. After the hormones accumulate in the neurohypophysis in sufficient quantities, they pass into the blood. The best known posterior pituitary hormones are oxytocin and vasopressin.

Vasopressin controls the excretion of water by the kidneys, protecting the body from dehydration, has a vasoconstrictive effect, stopping bleeding, increases blood pressure, as well as the tone of the smooth muscles of the internal organs. It regulates aggressive behavior, is responsible for memory.

Oxytocin stimulates contraction of the smooth muscles of the bladder, gallbladder, ureters, and intestines. The need for is especially great, since this hormone is responsible for contracting the smooth muscles of the uterus, and after the birth of the baby, the mammary glands, stimulating the supply of milk to the baby during sucking.

Epiphysis and thyroid gland

Another endocrine gland attached to the brain is the pineal gland (other names are the pineal gland, pineal gland). He is responsible for the production of neurotransmitters and hormones melatonin, serotonin, adrenoglomerulotropin.

Serotonin, as well as melatonin synthesized with its participation, are responsible for the mode of wakefulness and sleep. Melatonin slows down the aging process, serotonin has a calming effect on the nervous system. They also improve tissue regeneration, if necessary, suppress reproductive function, stop the development of malignant tumors.

The thyroid gland is located on the front side of the neck, under the Adam's apple, consists of two lobes, which are connected to each other by the isthmus and covers the trachea from three sides. The thyroid gland produces iodine-containing hormones thyroxine (T4) and triiodothyronine (T3), the synthesis of which is regulated by the pituitary gland. Another thyroid hormone is calcitonin, which is responsible for the condition of bone tissue and affects the kidneys, accelerating the removal of calcium, phosphates, and chlorides from the body.

Thyroxine is produced by the thyroid gland in much greater quantities than triiodothyronine, but it is a less active hormone and is subsequently converted to T3. Iodine-containing hormones are actively involved in almost all processes occurring in the body: in metabolism, growth, physical and mental development.

Excess, as well as lack of iodine-containing hormones, negatively affects the body, provokes a change in body weight, pressure, increases nervous excitability, causes lethargy and apathy, deterioration of mental abilities, memory. Often it is the cause of the development of malignant and benign tumors, goiter. Lack of T3 and T4 in childhood can provoke cretinism.

Parathyroid and thymus glands

Parathyroid or parathyroid glands are attached to the back of the thyroid gland, two to each lobe, they synthesize parathyroid hormone, which ensures that calcium in the body is within normal limits, ensuring the proper functioning of the nervous and motor systems. It affects the bones, kidneys, intestines, has a positive effect on blood clotting, is involved in the exchange of calcium and phosphorus.

Lack of parathyroid hormone, and also if the parathyroid glands have been removed, causes frequent and very strong convulsions, and nervous excitability increases. A severe illness can lead to death.

The thymus (another name is the thymus gland) is located in the middle of the upper part of the human chest. It is classified as a mixed gland, since the thymus not only synthesizes hormones, but is also responsible for immunity. T-cells of the immune system are formed in it, the task of which is to suppress the auto-aggressive cells that the body, for some reason, begins to produce to destroy healthy cells. Another task of the thymus gland is to filter the blood and lymph passing through it.

Also, under the control of cells of the immune system and the adrenal cortex, the thymus synthesizes hormones (thymosin, thymalin, thymopoietin, etc.), which are responsible for immune and growth processes. Damage to the thymus gland entails a decrease in immunity, the development of cancerous tumors, autoimmune or serious infectious diseases.

Pancreas

It is not only an organ of the digestive system that secretes pancreatic juice containing digestive enzymes, but is also considered an endocrine gland, since it produces hormones to regulate fat, protein, and carbohydrate metabolism. Among the biologically active substances that the pancreas produces, hormones that are synthesized in the islets of Langerhans are of the greatest importance.

Alpha cells produce glucagon, which converts glycogen into glucose. Beta cells secrete the hormone insulin, whose task is to control the amount of glucose: when its level begins to exceed the norm, it converts it into glycogen. Thanks to insulin, cells have the ability to evenly absorb glucose, while glycogen accumulates in the muscles and liver.

If the pancreas does not cope with its duties and does not produce insulin in the right amount, sugar ceases to be converted into glycogen and diabetes mellitus develops. As a result, the metabolism of proteins and fats is disturbed, the digestibility of glucose worsens. If the disease is not treated, a person can fall into a hypoglycemic coma and die.

An excess of the hormone is no less dangerous, since the cells are oversaturated with glucose, which leads to a decrease in the amount of sugar in the blood, to which the body reacts accordingly and sets in motion mechanisms aimed at increasing glucose, contributing to the development of diabetes.

The role of the adrenal glands in the body

The adrenal glands are two glands located above the kidneys, each of which consists of a cortex and a medulla. , which are synthesized in the medulla, are adrenaline and norepinephrine, which are required to ensure a timely reaction of the body to a dangerous situation, bring all body systems into full readiness and overcome the obstacle.

The adrenal cortex consists of three layers, and the hormones it produces are controlled by the pituitary gland. The influence of biologically active substances that the cortex produces on the body can be seen in the following table:

Violations in can provoke the development of a variety of diseases, ranging from bronze disease to malignant tumors. The characteristic signs of the disease of the endocrine glands are a bronze shade (pigmentation) of the skin, constant fatigue, weakness, problems with blood pressure, and the digestive system.

Functions of the sex glands

The main purpose of biologically active substances that are produced in the sex glands is to stimulate the development of the reproductive organs, the maturation of eggs and sperm in them. They also play an important role in the formation of secondary sexual characteristics that distinguish women from men (the structure of the skull, skeleton, voice timbre, subcutaneous fat, psyche, behavior).

The testicles or seminal glands in men are a paired organ, inside which spermatozoa develop. Here, male sex hormones are synthesized, primarily testosterone. Inside the female ovaries are follicles. When the next menstrual cycle begins, the largest of them, under the influence of the FSH hormone, begins to grow, and inside it, the egg begins to mature.

During growth, the follicle begins to actively produce the main sex hormones responsible for preparing the female body for conception and childbirth - estrogens (estradiol, estrone, estriol). After ovulation, a corpus luteum forms at the site of the ruptured follicle, which begins to actively produce progesterone. To prepare the body for pregnancy, the female sex glands produce androgens, inhibin, and relaxin.

The relationship of the endocrine glands

All endocrine glands are closely related to each other: the hormones that one gland produces have a very strong influence on the biologically active substances that the other synthesizes. In some cases, they enhance their activity, in others they work on the principle of feedback, reducing or increasing the amount of hormones in the body.

This means that if one organ is damaged, for example, the pituitary gland, this will certainly be displayed on the glands under its control. They will begin to produce an insufficient or excessive amount of hormones, which will provoke the development of serious diseases.

Therefore, the doctor, suspecting the presence of problems in the endocrine system, prescribes a blood test for hormones in order to determine the cause of the disease and develop the correct treatment regimen.