Features of the endocrine system during puberty. Endocrine glands, their age characteristics

AGE FEATURES OF THE ENDOCRINE SYSTEM

Endocrine glands. The endocrine system plays an important role in the regulation of body functions. The organs of this system are endocrine glands- secrete special substances that have a significant and specialized effect on the metabolism, structure and function of organs and tissues. Endocrine glands differ from other glands that have excretory ducts (exocrine glands) in that they secrete the substances they produce directly into the blood. Therefore they are called endocrine glands (Greek endon - inside, krinein - to highlight).

The endocrine glands include the pituitary gland, pineal gland, pancreas, thyroid gland, adrenal glands, sex, parathyroid or parathyroid glands, thymus (goiter) gland.

Pancreas and gonads - mixed, since part of their cells performs an exocrine function, the other part - intrasecretory. The sex glands produce not only sex hormones, but also germ cells (eggs and sperm). Some cells of the pancreas produce the hormone insulin and glucagon, while other cells produce digestive and pancreatic juice.

The human endocrine glands are small in size, have a very small mass (from fractions of a gram to several grams), and are richly supplied with blood vessels. Blood brings to them the necessary building material and carries away chemically active secrets.

An extensive network of nerve fibers approaches the endocrine glands, their activity is constantly controlled by the nervous system.

The endocrine glands are functionally closely related to each other, and the defeat of one gland causes a dysfunction of other glands.

Thyroid. In the process of ontogenesis, the mass of the thyroid gland increases significantly - from 1 g in the neonatal period to 10 g by 10 years. With the onset of puberty, the growth of the gland is especially intense, during the same period the functional tension of the thyroid gland increases, as evidenced by a significant increase in the content of total protein, which is part of the thyroid hormone. The content of thyrotropin in the blood increases intensively up to 7 years.

An increase in the content of thyroid hormones is noted by the age of 10 and at the final stages of puberty (15-16 years). At the age of 5-6 to 9-10 years, the pituitary-thyroid relationship changes qualitatively; the sensitivity of the thyroid gland to thyroid-stimulating hormones decreases, the highest sensitivity to which was noted at 5-6 years. This indicates that the thyroid gland is especially important for the development of the organism at an early age.

Insufficiency of thyroid function in childhood leads to cretinism. At the same time, growth is delayed and the proportions of the body are violated, sexual development is delayed, mental development lags behind. Early detection of hypothyroidism and appropriate treatment has a significant positive effect.

Adrenals. The adrenal glands from the first weeks of life are characterized by rapid structural transformations. The development of adrenal measles proceeds intensively in the first years of a child's life. By the age of 7, its width reaches 881 microns, at the age of 14 it is 1003.6 microns. The adrenal medulla at the time of birth is represented by immature nerve cells. They quickly differentiate during the first years of life into mature cells, called chromophilic, as they are distinguished by the ability to stain yellow with chromium salts. These cells synthesize hormones, the action of which has much in common with the sympathetic nervous system - catecholamines (adrenaline and norepinephrine). Synthesized catecholamines are contained in the medulla in the form of granules, from which they are released under the action of appropriate stimuli and enter the venous blood flowing from the adrenal cortex and passing through the medulla. The stimuli for the entry of catecholamines into the blood are excitation, irritation of the sympathetic nerves, physical activity, cooling, etc. The main hormone of the medulla is adrenalin, it makes up about 80% of the hormones synthesized in this section of the adrenal glands. Adrenaline is known as one of the fastest acting hormones. It accelerates the circulation of blood, strengthens and speeds up heart contractions; improves pulmonary respiration, expands the bronchi; increases the breakdown of glycogen in the liver, the release of sugar into the blood; enhances muscle contraction, reduces their fatigue, etc. All these effects of adrenaline lead to one common result - the mobilization of all the forces of the body to perform hard work.

Increased secretion of adrenaline is one of the most important mechanisms of restructuring in the functioning of the body in extreme situations, during emotional stress, sudden physical exertion, and cooling.

The close connection of the chromophilic cells of the adrenal gland with the sympathetic nervous system causes the rapid release of adrenaline in all cases when circumstances arise in a person's life that require an urgent effort from him. A significant increase in the functional tension of the adrenal glands is noted by the age of 6 and during puberty. At the same time, the content of steroid hormones and catecholamines in the blood increases significantly.

Pancreas. In newborns, intrasecretory pancreatic tissue predominates over exocrine pancreatic tissue. The islets of Langerhans increase significantly in size with age. Islets of large diameter (200-240 microns), characteristic of adults, are found after 10 years. An increase in the level of insulin in the blood in the period from 10 to 11 years was also established. The immaturity of the hormonal function of the pancreas may be one of the reasons that diabetes mellitus is detected in children most often between the ages of 6 and 12, especially after acute infectious diseases (measles, chickenpox, mumps). It is noted that the development of the disease contributes to overeating, especially the excess of carbohydrate-rich foods.

9. AGE FEATURES OF THE GENERAL GLANDS The male and female gonads (testes and ovaries), having formed during fetal development, undergo slow morphological and functional maturation after birth. The mass of the testicle in newborns is 0.3 G, in 1 year - 1 G, at the age of 14 - 2 G, at 15-16 years old - 8 G, at 19 years old - 20 G . The seminiferous tubules in newborns are narrow, over the entire period of development their diameter increases by 3 times. The ovaries are laid above the pelvic cavity, and in the newborn the process of their lowering has not yet been completed. They reach the cavity of the small pelvis in the first 3 weeks after birth, but only by the age of 1-4 years is their position, characteristic of an adult, finally established. The mass of the ovary in a newborn is 5-6 g, and it changes little during subsequent development: in an adult, the mass of the ovary is 6-8 g. In old age, the mass of the ovary decreases to 2 g. In the process of sexual development, several periods are distinguished: children - up to 8 -10 years old, adolescent - from 9-10 to 12-14 years old, youthful - from 13-14 to 16-18 years old, puberty - up to 50-60 years old and menopause - the period of extinction of sexual function. During childhood in the ovary In girls, primordial follicles grow very slowly, in which in most cases the membrane is still absent. In boys, the seminiferous tubules in the testes are little convoluted. In, urine, regardless of gender, contains a small amount of androgens and estrogens, which are formed during this period in the adrenal cortex. The content of androgen in the blood plasma of children of both sexes immediately after birth is the same as in young women. Then it decreases to very low figures (sometimes to 0) and remains at this level until 5-7 years. During adolescence, graafian vesicles appear in the ovaries, follicles grow rapidly. The seminiferous tubules in the testes increase in size, along with spermatogonia, spermatocytes appear. During this period, in boys, the amount of androgens in the blood plasma and in the urine increases; girls have estrogen. Their number increases even more in adolescence, which leads to the development of secondary sexual characteristics. During this period, the periodicity inherent in the female body appears in the amount of secreted estrogens, which ensures the female sexual cycle. A sharp increase in estrogen secretion coincides in time with ovulation, after which, in the absence of fertilization, menstruation occurs, which is called the release of the decaying uterine mucosa along with the contents of the uterine glands and blood from the vessels that open at the same time. Strict cyclicity in the amount of estrogen released and, accordingly, in the changes that take place in the ovary and uterus, is not immediately established. The first months of sexual cycles may not be regular. With the establishment of regular sexual cycles, the period of puberty begins, lasting for women up to 45-50 years, and for men, on average, up to 60 years. The period of puberty in women is characterized by the presence of regular sexual cycles: ovarian and uterine.

Puberty

The concept of puberty. The gonads and related signs of sex, being laid in the prenatal period, are formed throughout the entire period of childhood and determine sexual development. Sex glands, their functions are inextricably linked with the holistic process of child development. At a certain stage of ontogenesis, sexual development accelerates sharply and physiological sexual maturity sets in. The period of accelerated sexual development and the achievement of puberty is called period of puberty. This period occurs mainly during adolescence. The puberty of girls is 1-2 years ahead of the puberty of boys, and there is also a significant individual variation in the timing and rate of puberty.

The timing of the onset of puberty and its intensity are different and depend on many factors: health status, diet, climate, living and socio-economic conditions. An important role is played by hereditary features.

Unfavorable living conditions, defective food, lack of vitamins in it, severe or repeated diseases lead to a delay in puberty. In big cities, puberty of adolescents usually occurs earlier than in rural areas.

During puberty, profound changes occur in the body. Changes in the relationship of the endocrine glands and, above all, the hypothalamic-pituitary system. The structures of the hypothalamus are activated, the neurosecretions of which stimulate the release of tropic hormones from the pituitary gland.

Under the influence of pituitary hormones, body growth in length increases. The pituitary gland also stimulates the activity of the thyroid gland, which is why, especially in girls, the thyroid gland noticeably increases during puberty. The increased activity of the pituitary gland leads to an increase in the activity of the adrenal glands, the active activity of the gonads begins, the increasing secretion of sex hormones leads to the development of the so-called secondary sexual characteristics - physique, body hair, voice timbre, development of the mammary glands. The gonads and the structure of the genital organs are classified as primary sexual characteristics.

Stages of puberty. Puberty is not a smooth process; certain stages are distinguished in it, each of which is characterized by the specifics of the functioning of the endocrine glands and, accordingly, of the whole organism as a whole. The stages are determined by the combination of primary and secondary sexual characteristics. Both in boys and girls, there are 5 stages of puberty.

Stage I - pre-puberty (the period immediately preceding puberty). It is characterized by the absence of secondary sexual characteristics.

Stage II - the beginning of puberty. In boys, a slight increase in the size of the testicles. Minimal pubic hair. Hair is sparse and straight. Girls have swelling of the mammary glands. Slight hair growth along the labia. At this stage, the pituitary gland is sharply activated, its gonadotropic and somatotropic functions increase. The increase in the secretion of somatotropic hormone at this stage is more pronounced in girls, which determines the increase in their growth processes. The secretion of sex hormones increases, the function of the adrenal glands is activated.

Stage III - in boys, a further increase in the testicles, the beginning of an increase in the penis, mainly in length. Pubic hair becomes darker, coarser, begins to spread to the pubic joint. In girls, the further development of the mammary glands, hair growth spreads towards the pubis. There is a further increase in the content of gonadotropic hormones in the blood. The function of the sex glands is activated. In boys, increased secretion of somatotropin determines accelerated growth.

IV stage. In boys, the penis increases in width, the voice changes, juvenile acne appears, facial hair, axillary and pubic hair begin. In girls, the mammary glands intensively develop, hair growth is of an adult type, but less common. At this stage, androgens and estrogens are intensively released. Boys retain a high level of somatotropin, which determines a significant growth rate. In girls, the content of somatotropin decreases and the growth rate decreases.

Stage V - in boys, the genitals and secondary sexual characteristics finally develop. In girls, the mammary glands and sexual hairs correspond to those of an adult woman. At this stage, menstruation stabilizes in girls. The appearance of menstruation indicates the beginning of puberty - the ovaries are already producing mature eggs ready for fertilization.

Menstruation lasts 2 to 5 days on average. During this time, about 50-150 cm 3 of blood is released. If menstruation is established, then they are repeated approximately every 24-28 days. The cycle is considered normal when menstruation occurs at regular intervals, lasts the same number of days with the same intensity. At first, menstruation can last 7-8 days, disappear for several months, for a year or more. Only gradually is a regular cycle established. In boys, spermatogenesis reaches full development at this stage.

During puberty, especially at stages II-III, when the function of the hypothalamic-pituitary system, the leading link in endocrine regulation, is dramatically rebuilt, all physiological functions undergo significant changes.

For the intensive growth of the bone skeleton and muscular system in adolescents, the development of internal organs - the heart, lungs, and gastrointestinal tract - does not always keep pace. The heart outstrips the blood vessels in growth, as a result of which blood pressure rises and makes it difficult, first of all, the work of the heart itself. At the same time, the rapid restructuring of the whole organism, which occurs during puberty, in turn, makes increased demands on the heart. And insufficient work of the heart (“youthful heart”) often leads to dizziness, blueness and cold extremities in boys and girls. Hence the headaches, and fatigue, and periodic bouts of lethargy; often in adolescents there is a fainting state due to spasms of the cerebral vessels. With the end of puberty, these disorders usually disappear without a trace.

Significant changes at this stage of development in connection with the activation of the hypothalamus undergo the functions of the central nervous system. The emotional sphere is changing: the emotions of adolescents are mobile, changeable, contradictory: hypersensitivity is often combined with callousness, shyness with deliberate swagger, excessive criticism and intolerance towards parental care are manifested. During this period, there is sometimes a decrease in efficiency, neurotic reactions, irritability, tearfulness (especially in girls during menstruation).

CONCLUSION

In periods of development before reaching adulthood, it develops most intensively, a person grows and during these periods parents should especially closely monitor their children, if the necessary measures are not taken during these periods, then the consequences will be unpleasant, both for the child himself and for his parents . The most difficult periods for parents are the “newborn”, “breast” and “teenage”.

In the first two periods, the body is only becoming, and it is not known how it will develop - after all, it is still weakened and not ready for life.

In "teenage" the personality of a teenager is intensively formed, a feeling of growing up arises, attitudes towards members of the opposite sex change.

During the transitional period, children need a particularly sensitive attitude from parents and teachers. You should not specifically draw the attention of adolescents to complex changes in their body, psyche, however, it is necessary to explain the regularity and biological meaning of these changes. The art of the educator in these cases is to find such forms and methods of work that would switch the children's attention to various and diverse types of activity, distract them from sexual experiences. This is, first of all, increasing the requirements for teaching, work and behavior of schoolchildren.

At the same time, a tactful, respectful attitude of adults towards the initiative and independence of adolescents, the ability to direct their energy in the right direction is very important. After all, teenagers tend to overestimate their strengths and the measure of their independence. This is also one of the features of the transition period. 12. Literature:

1. Anatomy and physiology of the child's body: (Fundamentals of the doctrine of the cell and the development of the body, the nervous system, musculoskeletal apparatus): A textbook for students of ped. in-t on spec. "Pedagogy and psychology". / Ed. Leontyeva N.N., Marinova K.V. - 2nd ed. revised - M .: Education, 1986.

2. Anatomy and physiology of the child's body: (Internal organs) ” / Ed. Leontyeva N.N., Marinova K.V. - M.: Enlightenment, 1976

3. Age physiology and school hygiene: A guide for ped students. institutions” / Ed. Khripkova A.G. etc. - M.: Enlightenment, 1990

4. The endocrine system of a growing organism: Textbook for universities / Ed. Drzhevetskoy I.A - M .: Higher School, 1987.

LECTURE COURSE ON

Development and age-related features of the endocrine glands

Pituitary. In a newborn, the pituitary gland has a spherical or triangular shape with an apex directed towards the posterior surface of the Turkish saddle (Atl., Fig. 5, p. 21). In an adult, its dimensions are 1.5 x 2 x 0.5 cm. In newborns, the mass of the pituitary gland is 0.1-0.15 g, an increase in weight begins in the 2nd year of life and by the age of 10 it reaches 0.3 g The mass of the pituitary gland increases especially intensively during puberty, as a result of which by the age of 14 it becomes equal to 0.7 g in girls, and 0.66 g in boys.

During pregnancy, the mass of the pituitary gland increases to 1 g, which is associated with an increase in its functional activity. After childbirth, the mass of the pituitary gland decreases somewhat, but still the pituitary gland in women weighs more than in men of the same age.

The pituitary gland develops from two independent embryonic buds. The adenohypophysis is formed from the primary oral recess (pocket), which, as the embryo develops, separates from the oral cavity, the cells of its walls multiply and form glandular tissue (hence the name adenohypophysis, that is, the glandular pituitary gland).

The posterior lobe and the pituitary stalk are formed from the bottom of the third ventricle. The parenchyma of the posterior lobe consists of thin fibers of neuroglia and ependyma. Cells are located between the fibers and accumulations of neurosecretion are found, which descends into the posterior pituitary along the axons of neurosecretory cells from the supraoptic and paraventricular nuclei of the hypothalamus.

epiphysis. The rudiments of the epiphysis in the embryo appear at the 6-7th week of embryogenesis as a protrusion of the roof of the diencephalon. By the second half of pregnancy, it is already formed. The first signs of functioning of the pineal gland were found on the 2nd month of intrauterine development.

In a newborn, the pineal gland has a rounded shape, flattened, without a leg, it is located between the lobules of the midbrain and has a depression on its surface. At birth, it has the following dimensions; length 2-3 mm, width 2.5 mm, thickness - 2 mm. In an adult, respectively, 5-12 mm, 3-8 mm, 3-5 mm, weight 100-200 mg. Its weight increases in the first year of life and from 3 to 6 years old acquires its final value, and then undergoes age-related involution (reverse development). The cavity of the epiphyseal ventricle may sometimes still be open.

The pineal gland of a newborn contains small embryonic undifferentiated cells that disappear at the 8th month of life, and large cells with a vesicular nucleus. The existence of these two types of marks leads to the fact that dark and lighter islands are located inside the gland. The pigment is absent, but appears later in large numbers at about 14 years of age. At the age of 2 years, the form becomes like that of an adult.

Differentiation of the parenchyma begins in the 1st year of life, starting from the 3rd year, glia appears, and until 5-7 years of age, the differentiation of epiphyseal cells ends. Connective tissue develops rapidly at 6-8 years of age, but maximum development occurs after 14 years of age.

During the neonatal period and early childhood, the secretory activity of the pineal gland increases and reaches its maximum expression at the age of 10-40 years, after which a decline occurs. Level melatonin in the blood is subject to significant fluctuations due to the action of factors such as sleep, light, darkness, the change in the phases of the menstrual cycle in women, the season, etc. Melatonin is characterized by a circadian rhythm of fluctuations in blood levels: maximum values ​​during the night, and minimum during the day. Consequently, the pineal gland plays a significant role in the operation of the "biological clock" mechanism - the frequency of body functions at different times of the day.

Thyroid. In the process of embryogenesis, the thyroid gland is laid in the form of a thickening of the endoderm lining the bottom of the pharynx at the 3rd week of intrauterine development, and its two lateral lobes and isthmus are gradually formed (Atl., Fig. 8, p. 23).

In a newborn, it is enclosed in a thick capsule formed from two sheets. The outer leaf is rich in blood vessels, formed by short collagen fibers. The inner leaf is rich in cellular elements, formed by long collagen and ellastic fibers.

Thick partitions extend from the capsule, penetrating into the gland; in the gland, thinner septa separate the lobules and nodes of the gland from them. In a newborn, the nodes are in the form of vesicles (follicles) that contain colloid (Atl. Fig. 7, p. 22). The wall of each follicle consists of a single-layer epithelium that produces two iodine-containing hormones. The number of follicles that form the thyroid gland and their size increase with age.

So, in newborns, the diameter of the follicle is 60-70 microns, at the age of 1 year - 100 microns, 3 years old - 120-150 microns, 6 years old - 200 microns, at 12-15 years old - 250 microns. The follicular epithelium of the thyroid gland in newborns is cubic or cylindrical. As the body grows, it is replaced by a cubic or cylindrical one, which is characteristic of adult thyroid follicles. By the age of 15, the mass and structure of the thyroid gland become the same as in an adult.

The location of the thyroid gland in relation to other organs is almost the same as in an adult. The isthmus is attached to the cricoid cartilage by a short, strong ligament. The cranial half is located on the larynx, and the lower half is on the trachea, which does not completely cover, leaving a free area 6-9 mm high and 8 mm wide.

The cranial part of the thymus gland, which enters the upper opening of the chest cavity, can penetrate into this space. The lateral lobules can rise to the level of the upper edge of the thyroid cartilage near the greater horn of the hyoid bone. They may come into contact with the neurovascular bundle of the neck. The common internal carotid artery is covered by the thyroid gland, only the internal jugular vein remains free.

The gland penetrates between the trachea and the artery, reaching the prevertebral fascia, with which it connects through free connecting bridges (Atl., Fig. 9, p. 23). In the groove between the trachea and the esophagus is the laryngeal nerve adjacent to the gland; on the left, the gland is adjacent to the esophagus, to which it is attached by connective tissue fibers; on the right, it is at a distance of 1 - 2mm from the esophagus. Usually the contact surface between the thyroid gland, trachea and esophagus is smaller than in an adult.

In a newborn, the mass of the thyroid gland ranges from 1 to 5 g. It decreases somewhat by 6 months, and then a period of its increase begins, lasting up to 5 years. From the age of 6-7 years, the period of rapid increase in the mass of the thyroid gland is replaced by a slow one. During puberty, a rapid increase in the mass of the thyroid gland is again noted, its weight reaches 18-30 g, that is, the size of an adult.

At 11-16 years old, the thyroid gland grows faster in girls than in boys. In 10-20 years, her weight doubles or sometimes triples.

In an adult male, the average length of the lateral lobes is 5-6 cm, thickness is 1-2 cm. In women, the size of the thyroid gland is slightly larger than in men. After 50 years, the mass and size of the thyroid gland gradually decrease.

Parathyroid glands. By the end of fetal development, the parathyroid glands are fully formed anatomical structures surrounded by a capsule. In a newborn, they are located, as in an adult: the upper ones on the posterior surface of the thyroid gland, in its upper half; the lower ones are located on the lower pole of the thyroid gland. There are 4 types of parathyroid glands: compact(contains a small amount of connective tissue), reticular(has thick connective tissue crossbars), lobular, or alveolar(thin septa), and spongy. In a newborn and a child under 2 years of age, the first three types usually occur, and especially the compact type. The number of glands can vary: usually there are 4, but it can be 3.2 or even 1. The lower parathyroid glands are larger than the upper ones. In childhood, their rapid growth and slowdown after puberty are noted.

In the process of aging, the tissue of the parathyroid glands is partially replaced by adipose and connective tissue. In an adult, each gland is 6-8 mm long, 3-4 mm wide, about 2 mm thick, and weighs 20 to 50 mg. In the tissue of the parathyroid glands, two types of cells are distinguished: main and oxyphilic. The chief cells are small, with a large nucleus and a light-staining cytoplasm. Oxyphilic cells are larger, and oxyphilic (that is, stained with acidic colors) granularity is found in their cytoplasm. Recent studies suggest that oxyphilic cells are aging chief cells. Oxyphilic cells first appear after 5-7 years. Apparently, for the first time in 4-7 years of life, the parathyroid glands function especially actively.

Thymus. The thymus gland is laid on the 6th week of embryonic development. In a child, the thymus gland is located in front of the trachea, pulmonary artery, aorta, superior vena cava, behind the sternum (Atl., Fig. 12, p. 24). It has the appearance of a quadrangular pyramid, located mostly in the chest cavity (base), and the bifurcated top is in the cervical region. The thymus can be of three types: a) single lobe, rare, located entirely in the chest cavity at a distance from the thyroid gland, sometimes may have two small horns; b) shape c two shares occurs in 70% of cases. The gland has two lobes separated by a median line; c) third form multi-lobe, which is very rare. The gland is formed from 3-4 lobes. In a newborn, it has a pink color, and in a small child it is white-gray, at an older age the color becomes yellowish as a result of the process of rebirth.

The thymus gland is covered with a capsule, from which the interlobar septa extend. The lobes of the thymus gland have two zones: the cortical, formed from epithelial cells, and the brain, containing two layers, consisting of epithelial and reticular fibers. Lymphocytes are densely located in the cortical part, and Hassall's bodies are located in the brain part - concentrically arranged spindle-shaped epithelial cells with a large light nucleus. Gassall's bodies undergo cyclic development: they are formed, then disintegrate, and their remains are absorbed by lymphocytes and eosinophilic granulocytes. It is believed that Gassall's little bodies are secretory cells of the thymus gland.

In relation to body weight, the thymus is heavier in boys than in girls. In a newborn, its weight is 10-15 g, in an infant - 11-24 g, in a small child - 23-27 g, at 11-14 years old - an average of 35-40 g, at 15-20 years old - 21 g, in 20-25 years - about 19 g. The greatest weight is observed during puberty. After 13 years, age-related involution (reverse development) of the thymus gland gradually occurs, and by the age of 66-75 its mass is on average 6 g. Thus, the thymus gland reaches its greatest development in childhood.

The thymus plays an important role in the immunological defense of the body, in particular in the formation of immunocompetent cells, that is, cells capable of specifically recognizing an antigen and responding to it with an immune response ( Burnet, 1961).

Children with congenital underdevelopment of the thymus usually die at the age of 2-5 months. It is noted that the thymus gland plays an important role in the antitumor protection of the body.

It should be noted that the thymus gland is closely connected with other organs of internal secretion, in particular with the adrenal glands. For example, an increase in the secretion of glucocorticoids during stress leads to a rapid decrease in the size and mass of the thymus gland. At the same time, in the gland and other lymphoid organs, first there is a disintegration of lymphocytes, and then a new formation of Hassal's bodies. On the contrary, the introduction of thymus extracts inhibits the development and function of the adrenal cortex up to its significant atrophy. If a person has not undergone age-related involution of the thymus gland, he has an insufficiency of the function of the adrenal cortex and reduced resistance to the action of stress factors.

Pancreas refers to the glands of mixed secretion. Its main mass performs an exocrine function - it produces digestive enzymes secreted through the duct into the duodenal cavity (Atl., Fig. 13, p. 25). Endocrine functions are inherent in the islets of Langerhans. Islet tissue is no more than 3% in humans. The largest amount of it is in the caudal part of the gland: this section contains an average of 36.0 islets per 1 mm 3 of parenchyma, in the body - 22.4, in the head - 19.8 per 1 mm 3 of tissue. In general, there are up to 1800 thousand islets in the human pancreas. Their size is different - from small (diameter less than 100 microns) to large (diameter up to 500 microns). The shape of the islands is round or oval (Atl., Fig. 14, p. 25).

The human pancreas begins between the 4th and 5th weeks of embryonic development and separates from the protrusion of the intestinal tube. The islets of Langerhans appear at the 10-11th week of embryogenesis, and by the 4-5th month they reach sizes approaching those in an adult. There are suggestions that the secretion of insulin and glucagon begins already in the early stages of embryonic development ( falin, 1966).

The cells that make up the islet apparatus are called strokes and there are several types of these cells. Most of these cells are B cells that produce insulin. The second type of cells are A-cells, which are located either along the periphery of the islet or in small groups throughout the islet. They secrete glucagon.

The growth and development of the insular apparatus is especially active in the first months of life. Then, up to 45-50 years, the structure of the islets stabilizes, after 50 years, their formation is activated again ( Shevchuk, 1962). It should be noted that at a young age, large islets, which include B-cells, predominate, and in senile age, small-sized islets, consisting mainly of A-cells, predominate. This indicates that insulin secretion predominates in childhood and young age, while glucagon secretion predominates in senile age.

Adrenals. The adrenal glands are composed of two layers: the cortex and the medulla. The medulla is located in the center of the adrenal gland and makes up about 10% of the entire tissue of the gland, and the surrounding cortical layer is approximately 90% of the mass of this organ. The adrenal glands are covered with a thin capsule consisting of elastic fibers. The adrenal cortex consists of epithelial columns located perpendicular to the capsule. Three zones are distinguished in it: glomerular, fascicular and reticular (Atl., Fig. 16, p. 26).

Glomerular zone lies under the capsule and consists of glandular cells, forming, as it were, clusters. The widest area beam, which includes cells arranged in the form of strands running parallel to each other from the glomerular layer to the center of the adrenal gland. Deepest, next to the medulla, is located mesh zone. It consists of a loose network of intertwined cells.

Between the cortex and the medulla is a thin, sometimes interrupted connective tissue capsule. The medulla consists of large cells that have a rectangular or prismatic shape.

In the process of embryogenesis, the laying of the cortical part of the adrenal gland in the embryo is found on the 22-25th day of intrauterine development. At the 6th week of embryogenesis, cells from the embryonic neural tube are introduced into the incipient adrenal gland, giving rise to the adrenal medulla. The sympathetic ganglia differentiate from the same cells. Therefore, the adrenal medulla is of nervous origin.

The adrenal glands of the fetus are very large: in an 8-week-old human fetus, they are equal in size to the kidneys. These glands actively secrete hormones even in the embryonic period of development. The amount of adrenaline at 1 year is 0.4 mg, at 2 years - 1.18 mg, at 4 years - 1.96 mg, at 5 years - 2.92 mg, at 8 years - 3.96 mg, at 10-19 years - 4.29 mg.

After birth, the mass of the adrenal gland is 6.98 g, then rapidly decreases, and at 6 months it is 1/4 of the original weight. After the 1st year of life, the mass of the adrenal glands increases again up to 3 years, and then the growth rate decreases and remains slow until 8 years, and then increases again (Atl., Fig. 17, p. 27). At the age of 11-13, the mass of the adrenal glands increases again, especially during puberty, and stabilizes by the age of 20.

It should be noted a significant change in the growth rate of the adrenal glands at 6 months for girls, at 8 months for boys, at 2 years for boys, at 3 years for boys (during this last period, the adrenal glands in boys grow faster than in girls), at 4 years for children both sexes.

Women have more adrenal glands than men. At the age of 60-70 years, senile atrophic changes in the adrenal cortex begin.

The location of the adrenal glands in relation to other organs differs from those in an adult. The right adrenal gland is located between the upper edge of the twelfth thoracic vertebra (it can rise to the tenth) and the lower edge of the first lumbar vertebra. The left adrenal gland is located by the upper edge of the eleventh thoracic vertebra and the lower edge of the first lumbar. In a newborn, the adrenal glands are located more laterally than in an adult. As a result of the growth of the kidneys, the adrenal glands change their position, this is observed at 6 months of age.

Paraganglia - these are the endocrine glands, as well as additional organs of the endocrine system. They are leftovers adrenal, or chromaffin, systems that produce mainly catelochomines. They originate from the sympathetic nerves or from the sympathetic branches of the cranial nerves and are located medially or dorsally from the nodes of the sympathetic trunk.

Paraganglia consist of secretory chromaffin cells, auxiliary (enveloping type neuroglia) cells and connective tissue; in embryogenesis, they arise and migrate along with the neuroblasts of the sympathetic nervous system. Other paraganglia are non-chromaffin (mainly at the branching points of the parasympathetic nervous system), including the orbital paraganglia, pulmonary, bone marrow, paraganglia of the meninges, carotid, and paraganglia along the vessels of the trunk and extremities.

The role of paraganglia is to mobilize body systems during stress, in addition, they regulate general and local physiological reactions.

Paraganglia usually develop in the first year of life, grow during the second year, and then reverse development. In the embryonic period appears lumbar-aortic paraganglion located on both sides of the aorta at the level of the adrenal glands. Nonpermanent paraganglia may appear at the level of the cervical and thoracic sympathetic chains. Paraganglia located on the aorta can be connected to each other, but after birth, their connection breaks. By birth, the lumbar-aortic paraganglia are well developed and have lymph nodes.

Paraganglia of the carotid artery develop and differentiate late. In a newborn, glandular cells are in large numbers, the connective tissue is poorly developed. In the first year of life, numerous capillaries develop that surround the cells. Specific cells are still found at the age of 23.

supracardiac paraganglia, there are two of them, the upper one is located between the aorta and the pulmonary artery. In a newborn, groups of cells of the upper suprapericardial paraganglia are surrounded by muscular arteries. At 8 years of age, they do not contain chromaffin cells, but continue to grow until puberty and remain in the adult.

There is hardly any complex mechanism that works as smoothly as the body of a healthy person. This coherence of the body's work is ensured by the central nervous system through the nerve pathways and special organs called endocrine glands. Organs are called glands which produce and secrete some substances: digestive juices, sweat, sebum, milk, etc. The substances secreted by the glands are called secrets. Secrets are secreted through the excretory ducts to the surface of the body or to the mucous membrane of internal organs.

Endocrine glands- these are glands of a special kind, they do not have excretory ducts; their secret, called a hormone, is secreted directly into the blood. That's why they called endocrine glands or, otherwise, endocrine glands. Getting into the blood, hormones are carried to all human organs and have their own special, characteristic for each gland or, as they say, specific effect on them.

As long as the endocrine glands function normally, they do not remind of their existence in any way, the human body works in a harmonious, balanced way. We notice them only when, due to significant deviations in the activity of one or another gland, and sometimes several glands, the balance in the body is simultaneously disturbed.

Functions of the endocrine glands and their disorders

To understand how important the role of the whole body of an adult and child play endocrine glands Let's get acquainted with the main ones and with their characteristics functions(see picture).

Thyroid - one of the most important endocrine glands. In the normal state, it is not visible, and only when enlarged does it form a protrusion on the front surface of the neck, noticeable to the eye, especially at the time of swallowing. Often, with its large size, with the so-called goiter, there is a decrease in the function of the gland. Especially often there is such a discrepancy between the large size and weak function of the gland in mountainous places and other areas, the nature of which (earth, water, plants) contains only negligible amounts of iodine, which is necessary for the formation thyroxine. The introduction of iodine into the body can prevent the development of goiter and enhance the function of the gland. This is what is done in the areas of goiter distribution: iodine is added to the salt.

With a lack of thyroxine disorders occur in the body, characterized by growth retardation, dryness and thickening of the skin, impaired bone development, muscle weakness and significant mental retardation, which usually manifests itself already in childhood. The extreme degree of these disorders, observed in the absence of the function of a prominent gland, is called myxedema. In this case, the child is injected with thyroid preparations.

An increase in the function of the gland also leads to severe phenomena. The excitatory effect exerted by thyroxin on the central nervous system becomes excessive. Such a state is called thyrotoxicosis. In severe forms of thyrotoxicosis (the so-called Basedow's disease), emaciation, palpitations are observed, nervous excitability sharply increases, violated sleep, bulging eyes appear. In these cases, treatment is aimed at suppressing the activity of the thyroid gland, sometimes resorting to its removal.

Pituitary(or an appendage of the brain) - a small, but playing a large role in the body of endocrine iron. Pituitary hormones affect human growth, the development of the skeleton and muscles. With its insufficient function, growth is sharply delayed and a person can remain a dwarf; delayed and stops sexual development. With increased activity of certain pituitary cells, giant growth occurs; if the growth of a person has already ended, there is an increase in individual bones (face, hands, feet), and sometimes other parts of the body (tongue, auricles), which is called acromegaly. Violations the activity of the pituitary gland can cause other changes.

adrenal glands - a pair of small glands located above the kidneys, hence their name. The adrenal gland secretes hormones that affect the metabolism in the body and enhance the function of the sex glands; It also produces the hormone adrenaline, which plays an important role in the proper functioning of the cardiovascular system and has a number of other functions.

Goiter, or thymus, gland (has nothing to do with goiter - enlargement of the thyroid gland), is most active in childhood. Her hormone promotes the growth of the child, with the onset of puberty, it decreases and gradually atrophies. This gland is located behind the sternum and partially covers the anterior surface of the heart.

Pancreas , which got its name due to its location slightly below the stomach and behind it in the bend of the duodenum, is not only an endocrine gland. It is one of the most important digestive glands. In addition to the cells that secrete digestive juice, it also includes special islands, consisting of cells that secrete a hormone that is very important for normal metabolism. This is insulin, which promotes the absorption of sugar. With a decrease in the hormonal function of the pancreas, diabetes develops. Until insulin was discovered and a way to obtain it was found, it was difficult for such patients to help; at present, the introduction of insulin restores their ability to absorb carbohydrates, and at the same time increases their overall performance.

gonads have both external and intrasecretory function. In addition to the formation of special germ cells necessary for reproduction, they also secrete hormones that determine the external, so-called secondary sexual characteristics characteristic of each sex (growth of hair on the pubis and armpits, and later - and only in boys - on the face, breast enlargement in girls, etc.) and a number of others age features characteristic of one gender or another. In the first period of childhood, these glands almost do not function. Their function sometimes begins to affect from the age of 7-8 and especially increases during puberty (in girls from 11-13, in boys from 13-15 years).

The normal function of the sex glands is very important for the full development of a person. The hormones of the gonads through the nervous system affect the metabolism of the child and activate the development of his physical and spiritual strength. The period of sexual development is also the period of active formation of a person's personality.

Such is the general characteristic of the functions of the human endocrine glands, their role in the physiological, normal activity of the body.

Endocrine glands of a child: features of development

Endocrine glands direct child development from early years of life. They function with different intensity in different periods of human life. For everybody age period characterized by the predominance of the activities of one group or another child's endocrine glands.

For the age of up to 3-4 years, the most intensive function of the thymus gland, which regulates growth, is characteristic. Growth is also enhanced by thyroid hormones, which function very actively in the period from 6 months to 2 years, and the pituitary gland, whose activity increases after 2 years.

At the age of 4 to 11 years, the pituitary and thyroid glands remain active, the activity of the adrenal glands increases, and at the end of this period, the sex glands also turn on. This is a period of relative balance in the activity of the endocrine glands.

In the next period - adolescence - the balance is disturbed. This age is characterized sometimes gradually, and sometimes rapidly growing hormonal activity of the sex glands, a significant increase in the function of the pituitary gland; under the influence of the pituitary hormone, increased bone growth (stretching) occurs; violation of the proportionality of growth leads to angularity, clumsiness, often observed in adolescents. The activity of the thyroid gland and adrenal glands is also significantly enhanced. The thyroid gland, increasing, sometimes becomes noticeable to the eye; in the absence of significant disorders characteristic of thyrotoxicosis, a slight increase in the gland can be considered physiological, corresponding to the age-related characteristics of this period.

Restructuring in the work of the endocrine glands has a great influence on the development of the body and especially on its nervous system. If these processes develop proportionally, then the responsible transitional period of a person's life proceeds calmly. In violation of proportionality in endocrine activity, a kind of "crisis" often occurs. The nervous system and psyche of the child become vulnerable: irritability, incontinence in behavior, fatigue, and a tendency to tears appear. Gradually, with the appearance of secondary sexual characteristics, adolescence passes into adolescence, balance is restored in the body.

Parents need to know age-related features of the development of the endocrine apparatus (endocrine glands) of a child and adolescent in order to notice possible deviations in time and take the necessary measures. School age, the beginning of a person's independent working life, requires special attention. The coincidence of this period with a serious restructuring of the neuro-endocrine apparatus makes it even more responsible.

Prevention of endocrine diseases in children

Maintaining balance in the body, which ensures the child's normal development and performance, largely depends on the parents:

• Avoid unnecessary excitation of the child's nervous system, protect it from unnecessary stimuli. This, of course, does not mean that the child should be unloaded from schoolwork or the preparation of lessons necessary for him. According to age, involve children in helping with household services for the family. Make sure that work processes alternate correctly with rest, entertainment, sleep, and nutrition.
• It is very important to allocate sufficient time for the child to be outdoors and for sleep, which provides a complete rest of the nervous system. In the first grades of the school - sleep for at least 10 hours, and in the future, sleep time gradually decreases to 8.5 hours a day.
• Always go to bed and wake up at the same time, but not too late.
• Avoid excessive irritants before going to bed: do not read until late, especially while lying in bed, resolutely avoid excessive use of the TV and computer.
• Greater value in prevention of endocrine diseases in children also has food. The child's food should be complete, contain a sufficient amount of proteins and other nutrients, in particular vitamins.
• Remember the leading role of the central nervous system in the work of the endocrine glands. Protect the child from mental trauma, often leading to a breakdown in the balance in the endocrine glands.
• Making certain demands on the child, try to mobilize his will, instill in him how important a conscientious attitude to studies, organization in everyday life are. It is essential that parents themselves be an example of such organization and that they show calmness and restraint in dealing with adolescents.

In the event of the appearance of the endocrine disorders described above (especially if they appeared in the late period of childhood and are not pronounced), the regulation of the child’s diet and nutrition, the strengthening of his nervous system by physical education methods usually lead to the restoration of the normal functioning of the endocrine glands.

In more severe cases of dysfunction of the endocrine glands, treatment with endocrine gland preparations or other methods of treatment is required: medicinal, physiotherapeutic and even surgical. In such cases, contact your doctor, who will be able to give a correct assessment of the child's condition, prescribe treatment, and refer you to an endocrinologist.

According to the journal...

The endocrine system of the human body is represented by endocrine glands that produce certain compounds (hormones) and secrete them directly (without ducts leading out) into the blood. In this, the endocrine glands differ from other (exocrine) glands, which secrete the product of their activity only into the external environment through special ducts or without them. External secretion glands are, for example, salivary, gastric, sweat glands, etc. There are also mixed glands in the body, which are both exocrine and endocrine. The mixed glands include the pancreas and the gonads.

The hormones of the endocrine glands with the blood flow are carried throughout the body and perform important regulatory functions: they affect metabolism, regulate cellular activity, growth and development of the body, determine the change in age periods, affect the functioning of the respiratory, circulatory, digestion, excretion and reproduction. Under the action and control of hormones (in optimal external conditions), the entire genetic program of human life is also realized.

Glands with topography are located in different places of the body: in the head area there are the pituitary and pineal glands, in the neck and chest area there are the thyroid, parathyroid and thymus (thymus) glands. In the abdomen are the adrenal glands and pancreas, in the pelvic area - the sex glands. In different parts of the body, mainly along the large blood vessels, there are small analogues of the endocrine glands - paraganglia.

The functions and structure of the endocrine glands change significantly with age.

Pituitary It is considered the gland of all glands, since its hormones affect the work of many of them. This gland is located at the base of the brain in the deepening of the Turkish saddle of the sphenoid (main) bone of the skull. V newborn weight of the pituitary gland is 0.1-0.2 g, at 10 years old it reaches a mass of 0.3 g, and in adults - 0.7-0.9 g. During pregnancy in women, the mass of the pituitary gland can reach 1.65 g The gland is conditionally divided into three parts: anterior (adenohypophysis), posterior (nonhypophysis) and intermediate. In the region of the adenohypophysis and the intermediate pituitary gland, most of the hormones of the gland are synthesized, namely somatotropic hormone (growth hormone), as well as adrenocorticotropic (ACTA), thyrotropic (THG), gonadotropic (GTH), luteotropic (LTH) hormones and prolactin. In the region of the neurohypophysis, the hypothalamic hormones acquire an active form: oxytocin, vasopressin, melanotropin and Mizin factor.

The pituitary gland is closely connected by neural structures with the hypothalamus of the diencephalon, due to which the interconnection and coordination of the nervous and endocrine regulatory systems is carried out. The hypothalamic - pituitary nerve pathway (the cord connecting the pituitary to the hypothalamus) has up to 100,000 nerve processes of hypothalamic neurons that are capable of creating a neurosecrete (mediator) of an excitatory or inhibitory nature. The processes of neurons of the hypothalamus have terminal endings (synapses) on the surface of the blood capillaries of the posterior pituitary gland (neurohypophysis). Once in the blood, the neurotransmitter is then transported to the anterior lobe of the pituitary gland (adenohypophysis). The blood vessels at the level of the adenohypophysis are again divided into capillaries, wrap around the islets of secretory cells and, thus, through the blood they influence the activity of hormone formation (accelerate or slow down). According to the scheme, which is described, the interconnection in the work of the nervous and endocrine regulatory systems is carried out. In addition to communication with the hypothalamus, the pituitary gland receives neuronal processes from the gray tubercle of the pituitary part of the cerebral hemispheres, from the cells of the thalamus, which is at the bottom of the 111 ventricle of the brain stem and from the solar plexus of the autonomic nervous system, which are also able to influence the activity of the formation of pituitary hormones.

The main pituitary hormone is somatotropic hormone (GH) or growth hormone, which regulates bone growth, increase in body length and weight. With an insufficient amount of somatotropic hormone (hypofunction of the gland), dwarfism is observed (body length up to 90-100 ohms, low body weight, although mental development can proceed normally). An excess of somatotropic hormone in childhood (hyperfunction of the gland) leads to pituitary gigantism (body length can reach 2.5 meters or more, mental development often suffers). The pituitary gland produces, as mentioned above, ACTH (ACTH), gonadotropic hormones (GTG) and thyroid-stimulating hormone (TGT). A greater or lesser amount of the above hormones (regulated from the nervous system) through the blood affects the activity of the adrenal glands, sex glands and thyroid gland, respectively, changing, in turn, their hormonal activity, and therefore affecting the activity of those processes by which are regulated. The pituitary gland also produces melanophoric hormone, which affects the color of the skin, hair and other structures of the body, vasopressin, which regulates blood pressure and water metabolism, and oxytocin, which affects the processes of milk secretion, the tone of the walls of the uterus, etc.

Pituitary hormones also affect the higher nervous activity of a person. During puberty, gonadotropic hormones of the pituitary gland are especially active, which affect the development of the gonads. The appearance of sex hormones in the blood, in turn, inhibits the activity of the pituitary gland (feedback). The function of the pituitary gland stabilizes in the post-pubertal period (at 16-18 years). If the activity of somatotropic hormone persists even after the completion of body growth (after 20–24 years), then acromegaly develops, when individual parts of the body become disproportionately large in which ossification processes have not yet completed (for example, the hands, feet, head, ears and other parts of the body). During the period of growth of the child, the pituitary gland doubles in weight (from 0.3 to 0.7 g).

The pineal gland (weight to OD g) functions most actively up to 7 years, and then it degenerates into an inactive form. The pineal gland is considered the gland of childhood, since this gland produces the hormone gonadoliberin, which inhibits the development of the gonads until a certain time. In addition, the pineal gland regulates water-salt metabolism, forming substances similar to hormones: melatonin, serotonin, norepinephrine, histamine. There is a certain cyclicity in the formation of pineal hormones during the day: melatonin is synthesized at night, and serotonin is synthesized at night. Due to this, it is believed that the pineal gland acts as a kind of chronometer of the body, regulates the change of life cycles, and also ensures the ratio of a person’s own biorhythms with the rhythms of the environment.

The thyroid gland (weight up to 30 grams) is located in front of the larynx on the neck. The main hormones of this gland are thyroxine, tri-iodothyronine, which affect the exchange of water and minerals, the course of oxidative processes, the processes of fat burning, growth, body weight, physical and mental development of a person. The gland functions most actively at 5-7 and at 13-15 years. The gland also produces the hormone thyrocalcitonin, which regulates the exchange of calcium and phosphorus in the bones (it inhibits their leaching from the bones and reduces the amount of calcium in the blood). With hypofunction of the thyroid gland, children are stunted, their hair falls out, their teeth suffer, their psyche and mental development are disturbed (myxedema disease develops), their mind is lost (cretinism develops). With hyperfunction of the thyroid gland, Graves' disease occurs, the signs of which are an increase in the thyroid gland, withdrawn eyes, a sharp weight loss and a number of autonomic disorders (increased heartbeat, sweating, etc.). The disease is also accompanied by increased irritability, fatigue, decreased performance, etc.

The parathyroid glands (weight up to 0.5 g) are located at the back of the thyroid gland in the form of small four destinies. The hormone of these glands is parathormone, which maintains the amount of calcium in the blood at a constant level (even, if necessary, by washing it out of the bones), and together with vitamin D affects the exchange of calcium and phosphorus in the bones, namely, it contributes to the accumulation of these substances in bone tissue. Hyperfunction of the gland leads to superstrong mineralization of bones and ossification, as well as to increased excitability of the cerebral hemispheres. With hypofunction, tetany (convulsions) is observed and softening of the bones occurs.

The thymus gland (thymus), like the bone marrow, is the central organ of immunogenesis. Separate stem cells of the red bone marrow enter the thymus with the blood flow and in the structures of the gland go through the stages of maturation and differentiation, turning into T-lymphocytes (thymus - dependent lymphocytes). The latter again enter the bloodstream and spread throughout the body and create thymus-dependent zones in the peripheral organs of immunogenesis (spleen, lymph nodes, etc.). The thymus also creates a number of substances (thymosin, thymopoietin, thymus humoral factor, etc.), which most likely affect the differentiation of G-lymphocytes. The processes of immunogenesis are described in detail in section 4.9.

The thymus is located in the sternum and has two destinies, covered with connective tissue. The stroma (body) of the thymus has a reticular retina, in the loops of which thymus lymphocytes (thymocytes) and plasma cells (leukocytes, macrophages, etc.) are located. The body of the gland is conventionally divided into darker (cork) and cerebral parts. On the border of the cortical and brain parts, large cells with high activity for division (lymphoblasts) are isolated, which are considered to be points of sprouts, because it is here that stem cells get to mature.

The thymus gland is active until the age of 13-15 - at this time it has the largest mass (37-39g). After the puberty period, the mass of the thymus gradually decreases: at 20 years old it averages 25 g, at 21-35 years old - 22 g (V. M. Zholobov, 1963), and at 50-90 years old - only 13 g (W. Kroeman , 1976). Completely lymphoid tissue of the thymus does not disappear until old age, but most of it is replaced by connective (adipose) tissue: if a newborn child has connective tissue up to 7% of the mass of the gland, then at 20 years old it reaches 40%, and after 50 years - 90% . The thymus gland is also able to restrain the development of the gonads in children by the time, and the hormones of the gonads themselves, in turn, can cause the reduction of the thymus.

The adrenal glands are located above the kidneys and have a birth weight of 6-8 g, and in adults - up to 15 g each. These glands grow most actively during puberty, and finally mature at 20-25 years. Each adrenal gland has two layers of tissues, outer (cork) and inner (brain). These glands produce many hormones that regulate various processes in the body. In the cortex of the glands, corticosteroids are formed: mineralocorticoids and glucocorticoids, which regulate protein, carbohydrate, mineral and water-salt metabolism, affect the rate of cell reproduction, regulate the activation of metabolism during muscle activity and regulate the composition of blood cells (leukocytes). Gonadocorticoids (analogues of androgens and estrogens) are also produced, which affect the activity of sexual function and the development of secondary sexual characteristics (especially in childhood and old age). In the brain tissue of the adrenal glands, the hormones adrenaline and norepinephrine are formed, which are able to activate the work of the whole organism (similar to the action of the sympathetic division of the autonomic nervous system). These hormones are extremely important for mobilizing the body's physical reserves during times of stress, while performing physical exercises, especially during hard work, strenuous sports training or competition. With excessive excitement during sports performances, children can sometimes experience muscle weakness, inhibition of body position support reflexes, due to overexcitation of the sympathetic nervous system, and also due to excessive release of adrenaline into the blood. Under these circumstances, there may also be an increase in the plastic tone of the muscles, followed by a numbness of these muscles, or even a numbness of the spatial posture (the phenomenon of catalepsy).

It is important to balance the formation of corticosteroids and mineralocorticoids. When glucocorticoids are not formed enough, the hormonal balance shifts towards mineralocorticoids and this, among other things, can reduce the body's resistance to the development of rheumatic inflammation in the heart and joints, to the development of bronchial asthma. An excess of glucocorticoids suppresses inflammatory processes, but if this excess is significant, it can contribute to an increase in blood pressure, blood sugar (the development of the so-called steroid diabetes) and can even contribute to the destruction of heart muscle tissue, the occurrence of stomach ulcers, etc.

Pancreas. This gland, like the sex glands, is considered mixed, as it performs exogenous (production of digestive enzymes) and endogenous functions. As an endogenous pancreas, it mainly produces the hormones glucagon and insulin, which affect carbohydrate metabolism in the body. Insulin reduces blood sugar, stimulates the synthesis of glycogen in the liver and muscles, promotes the absorption of glucose by muscles, retains water in tissues, activates protein synthesis and reduces the formation of carbohydrates from proteins and fats. Insulin also inhibits the production of the hormone glucagon. The role of glucagon is opposite to the action of insulin, namely: glucagon increases blood sugar, including due to the transition of tissue glycogen to glucose. With hypofunction of the gland, the production of insulin decreases and this can cause a dangerous disease - diabetes mellitus. The development of pancreatic function continues until about 12 years of age in children and, thus, congenital disorders in its work most often appear during this period. Among other hormones of the pancreas, lipocaine (promotes the utilization of fats), vagotonin (activates the parasympathetic division of the autonomic nervous system, stimulates the formation of red blood cells), centropein (improves the use of oxygen by the cells of the body) should be distinguished.

In the human body, in different parts of the body, there can be separate islands of glandular cells that form analogues of the endocrine glands and are called paraganglia. These glands usually form local hormones that affect the course of certain functional processes. For example, enteroenzyme cells of the walls of the stomach produce hormones (hormones) Gastrin, secretin, cholecystokinin, which regulate the processes of food digestion; the endocardium of the heart produces the hormone atriopeptide, which acts by reducing the volume and pressure of the blood. In the walls of the kidneys, the hormones erythropoietin (stimulates the production of red blood cells) and renin (acts on blood pressure and affects the exchange of water and salts) are formed.

The sex glands in both the female and male bodies are mixed glands, therefore they are able to produce sex hormones (endogenous function) and germ cells (exogenous function). One of the most important functions of the body is associated with the activity of the gonads - the physiology of sex and reproduction.

Reproduction is one of the most important qualities of living matter, which is designed to ensure the preservation and increase of life on earth. The complex function of reproduction in humans includes the following processes:

The formation of sex hormones and germ cells;

Sexual intercourse leads to fertilization;

The development of the embryo and fetus in the womb;

After childbirth rearing a child.

The regulation of the passage and alternation of these processes is provided by gonadotropic hormones of the pituitary gland, sex hormones, and adrenal hormones. The main condition for the implementation of the function of reproduction is the presence of the gonads and genital organs of the male and female type, sufficiently developed, functioning normally and healthy. These glands and organs determine the primary sexual characteristics. The development of male and female glands and reproductive organs is accompanied by significant general changes throughout the body and leads to the manifestation of secondary sexual characteristics.

The gonads are laid down in the prenatal period, are formed during the entire period of childhood and determine the sexual development of the child. The gonads are mixed glands. their external secretion consists in the formation and release of germ or germ cells, namely spermatozoa (in men) and eggs (in women). The internal secretion of the sex glands is associated with the formation and release into the blood of sex hormones: male - androgens and female - estrogens. In terms of functional significance, male and female sex hormones differ significantly from each other, although they are based on similar chemical structures. In addition, it should be noted that male and female sex hormones are constantly formed in the gonads of both men and women, and only their quantitative ratio is decisive for determining sex. In men, the gonads produce from 3 to 10 mcg1 of androgens per day and 5-15 mcg of estrogen; in women, respectively, from 3 to 10 mcg of androgens, but 18-36 mcg of estrogens.

The role of sex hormones is easy to check when the gonads are damaged or removed, called castration. If castration is carried out in childhood, then puberty and the development of secondary sexual characteristics do not occur at all, and sexual desire does not even appear later. Castration carried out after puberty leads to the reverse development of primary sexual characteristics and to a partial loss of secondary sexual characteristics (the nature of hair changes, the mammary glands degrade, etc.). If at an early age an insufficient amount of the pineal hormone ganadoliberin is produced (which should restrain the puberty of children until a certain period), or there is hyperfunction of the gonads, then premature puberty, rapid body growth and accelerated development of secondary sexual characteristics occur. Violation of the function of the gonads can also lead to a number of diseases, among which are: infertility eunuchoidism (deficiency of male sex hormones in men) intersexuality (the appearance in the male body of signs of the female body and vice versa); hermaphrodism (simultaneous development in one organism of male and female gonads and the corresponding primary and secondary sexual characteristics).

The reproductive system of the male and female body has internal and external genital organs.

In men, the internal genital organs include: sex glands (testes), represented by paired testicles from the epididymis; seven "clear straits; seven drunken vesicles (pukhirtsi) pidmihurova gland (prostate) bulbous gland and vas deferens (urinary) canal.

The external genital organs of the male body are the penis and scrotum. The last mass form of a bag is a thermos, inside of which the testicles and epididymis are located and is designed to maintain a temperature in its cavity lower than in the body by 1.5-3 ° C (a necessary condition for spermatogenesis).

Sex cells (spermatozoa) develop in the testicles and sex hormones (androgens) are formed (in the so-called Leydig cells), which include: testosterone (synthesized from acetyl cholesterol), androstandione (an isomer of testosterone, but b times less active from it) , androsterone (has the properties of male and female sex hormones, testosterone is 100 times less active) and estrogen. Testosterone acts on metabolism, causes the development of secondary sexual characteristics and inhibits the action of estrogen.

The development of germ cells in men (spermatogenesis) is continuous, but for each individual germ cell, the male reproductive cycle can be conditionally distinguished, it occurs in the testes according to the scheme: spermatogonia, spermatocytes, spermatids, spermatozoa (the latter mature in the epididymis within 62-64 days) . The formation of spermatozoa begins with the period of puberty (15-17 years) and ends with atrophy of the gonads at the age of 50-60 years, when the male menopause begins. If we take into account that 1 mm 3 of seminal fluid (sperm) contains up to 100 million spermatozoa, and only up to 3 mm 3 of sperm is released during one sexual intercourse, it is clear that an astronomical number of germ cells is formed in men over the entire period of life. Each human sperm cell has a head with an acrosome, a neck and a tail (flagellum) and carries a single (haploid) set of chromosomes (genetic information). With the help of a flagellum, spermatozoa are capable of independent movement at a speed of up to 3.5 mm / sec. (up to 20 cm can go in an hour!). In the cavity of the genital organs of a woman, spermatozoa retain the ability to move for 6-7 days. The acrosome contains the enzyme hyaluronidase, which is able to break down the membrane of the female egg, which is necessary for fertilization.

Each epididymis is an accumulation of coiled tubules up to 6 m long, moving along which each of the spermatozoa undergoes final formation and maturation within 62-64 days. The vas deferens are up to 15-20 cm long and connect the epididymis with the seminal vesicles (vesicles) located under the lower edge of the bladder and where spermatozoa accumulate before they are ejected from the body. The walls of the seminal vesicles produce a protein secret and mucus, is a solvent for spermatozoa, and together with the rest forms seminal fluid - sperm and serves as a source of nutrition for the sex cells themselves. The pidmihurov gland (prostate) is a bunion-muscular formation, in its function it resembles a three-way valve, which is able to switch the urinary or vas deferens to the common urinary canal of the penis. Pidmihurova gland also forms a secret of prostaglandins, which activates the spermatozoa of the sperm and stimulates the excitation of the genital organs during intercourse. The bulbous gland produces a secret that lubricates the urinary canal and facilitates the ejection of semen during intercourse.

The internal genital organs of women include: paired sex glands (ovaries) fallopian tubes; uterus; and vagina. The external genital organs of the female body are the front door of the vagina, the clitoris, the large and small pudendal lips and the pubis.

Sex cells (eggs) develop in the ovary and sex hormones (estrogens) are formed, which include: estrone, estriol, estradiol and androgens (the latter delays the onset of menstruation in women by a certain period). The ovary itself is a paired formation located in the pelvic cavity and has a cortical and medulla layers. In the cortical layer are follicles (vesicles) with immature eggs. In both ovaries of a healthy woman, there are up to 600 thousand primary follicles, however, over the entire period of sexual activity, only 200-550 follicles mature capable of fertilizing the egg. The medulla contains a large number of blood vessels and nerves.

Female sex hormones are derivatives of cholesterol and deoxycorticosterone and are synthesized in the granular layer of the follicles. In addition, in the yellow bodies of the ovary, which are formed at the site of exit from the follicle of a mature egg, the hormone of pregnancy, progesterone, is formed. Follicular hormones influence the development of the reproductive organs and secondary sexual characteristics. their action is due to the periodic appearance of menstruation, as well as the development and growth of the mammary glands. Progesterone Influences the processes associated with the onset and normal course of pregnancy. If at the beginning of pregnancy the corpus luteum is destroyed, then the pregnancy ends and the fetus is removed from the body. Under the influence of progesterone, the walls of the uterus loosen and prepare for the arrival of a fertilized egg, which can then easily be fixed in its loosened wall. The presence of progesterone in the blood (when pregnancy occurs) prevents the further maturation of the follicles, and hence the maturation of a new egg. During pregnancy, progesterone also activates additional growth of the mammary glands, helps prepare the body for feeding the unborn child. Acting on the muscles of the walls of the uterus, progesterone prevents their contraction, which is important for the normal course of pregnancy, since the contraction of the walls of the uterus caused by various reasons (for example, the hormone of the posterior pituitary gland oxytocin leads to termination of pregnancy and miscarriage.

The development of germ cells in women (oogenesis) is called the female reproductive cycle and is a process of periodic maturation and release of an egg capable of fertilization into the uterus. Such periodic cycles in a healthy woman during sexual activity (from 13-15 years to 45-55 years) are repeated every 24-28 days. The female sexual cycle (ovulation) is divided into the following periods:

Peredovulyatsionny, during which the woman's body is preparing for pregnancy. This process is triggered by the intensive formation of pituitary follicle hormones that act on the ovarian glands, sewing up an increased production of estrogens. Estrogens, in turn, cause an increase in the size of the uterus, contribute to the growth of its mucosa (myometrium), trigger periodic contractions of the fallopian tubes, and most importantly, stimulate the maturation of one or more follicles, the largest and most mature of which is called the Graaffian vesicle (a transparent formation filled with fluid). ). The maturation of the follicle lasts an average of 28 days and by the end of this period it moves to the surface of the ovary. Due to the increase in the fluid inside the Graaffian vesicle, its walls cannot withstand, burst and the mature egg is ejected from it by the current of fluid into the abdominal cavity - ovulation begins.

The ovulation period is characterized by the fact that in the abdominal cavity, the egg is directed by a fluid flow into the uterine (fallopian) tube (uterine) and first begins to move quickly along it under the action of contractions of the muscles of the walls and flickering of the villi of the epithelium (this process is controlled by an increased amount of estrogen). At this moment, in place of the bursting Graafian vesicle, a corpus luteum is formed, which begins to intensively produce the hormone progesterone. Saturation of the blood with progesterone begins to inhibit the action of estrogens, from which the activity of the oviducts decreases and the egg begins to move slowly and then it goes all the way to the uterus (12-16 cm) in about 3 days. If in the fallopian tube the egg meets the spermatozoa, then fertilization occurs and such a fertilized egg, when it enters the uterus, is fixed (implanted) in its wall - pregnancy occurs. In this case, the sexual cycle is interrupted, the corpus luteum is preserved and inhibits the next ovulation, and the uterine mucosa is even more loosened. If fertilization does not occur, then the corpus luteum disappears, and the egg is excreted from the body and conditions are created for the maturation of the next follicle - the ovulation period begins.

The ovulatory period in women is manifested by the removal of unfertilized eggs from the body, the uterine mucosa and the outflow of blood, called menstruation. Menstruation occurs from the moment of puberty and regularly repeats until the age of 45-55, when a woman's sexual life ends and the female menopause begins.

An unfertilized egg enters the uterus, lives in it for 2-3 days, and then dies without attaching to the wall of the uterus. At this time, the active activity of the corpus luteum continues and progesterone actively acts on the pituitary gland, thereby inhibiting the formation of follicle hormones, and automatically reduces the synthesis of estrogens in the ovaries. Since nerve impulses from the walls of the uterus about the implantation of the egg do not enter the hypothalamus, this reduces the formation of luteinizing hormones of the pituitary gland and, as a result, atrophy (resorption, rebirth) of the corpus luteum begins, the formation of progesterone stops and regression of pre-ovulatory rearrangements begins (the blood supply to the uterus decreases, layers of myometrium die off, etc.). A small amount of estrogen leads to the appearance of tonic contractions of the walls of the uterus, leads to the rejection of the mucous membrane, which, together with the blood, forms menstrual flow. Menstruation lasts an average of 3-5 days with each menstruation losing 50 to 250 ml of blood.

After menstruation, a period of mizhovulational calm begins, which, at 27-28 days of the sexual cycle, lasts 12-14 days, after which all periods of the sexual cycle repeat again.

The physiology of fertilization and pregnancy is as follows. In a woman, fertilization of an egg is possible only in the first 1-2 days after ovulation, since from the third day the egg is usually covered with a protein coat that prevents sperm from penetrating into its middle. Spermatozoa in the cavity of the female genital organs retain their viability, as indicated, for 7 days, but their ability to fertilize lasts only 4-5 days. Spermatozoa that enter the vagina during intercourse are activated by its acidic environment and begin to move against the flow of fluid that is released from the female genital organs at a speed of 3-4 mm / sec. Thus, they gradually pass the cervix, its body and penetrate into the upper sections of the oviducts where, on occasion, one of them connects with the egg and fertilizes it (this can even happen on the surface of the ovary). To fertilize an egg, it is necessary that 1 spermatozoon gets into its middle, but this is possible only with the help of millions of other spermatozoa, called polyspermy. The fact is that only if the egg is surrounded by a thick layer of a large number of spermatozoa, each of which releases a drop of the hyaluronidase enzyme from its acrosome, they manage to dissolve the gelatinous shell of the egg and allow one of these spermatozoa to enter its cavity, which induce fertilization. When the head of one of the sperm enters the egg, the latter is instantly covered with a dense protein shell, isolating it from the rest of the sperm (sometimes, when two or more sperm enter the egg, the development of several identical twins is possible in the future). If there is little sperm in the woman's genitals, then fertilization may not take place at all.

The process of fertilization consists in the merging of a haploid set of 23 chromosomes of female and male germ cells into a diploid set (23 + 23 = 46) of the chromosomes of the future organism. After fertilization, a zygote is formed and the rapid and continuous division of the egg begins, and a dense villous membrane grows around it. From this moment, the development of the future organism begins (blastulation, gastrulation, and then all other stages of the embryonic and fetal periods of a child's life). Approximately on the 8th day after fertilization, the egg descends into the uterine cavity, its shell begins to produce a substance that destroys the uterine mucosa and allows the egg to sink into its loosened by this moment thickness, gain a foothold in it and begin to grow. This process is called egg implantation. Sometimes a fertilized egg does not reach the uterus and is attached to the wall of the fallopian tube; in this case, an ectopic pregnancy occurs.

If the implantation of the egg has taken place, then the flow of the corresponding nerve impulses is adjusted from the walls of the uterus to the hypothalamus and pituitary gland, as a result of which the activity of the formation of gonadotropic hormones of the pituitary gland does not decrease, the corpus luteum continues to grow, which increases the formation of progesterone and activates the restructuring of the woman's body, which are associated with her pregnancy . The corpus luteum hormone contributes to the preservation of the fetus in the uterus, prevents the maturation of the next follicle throughout pregnancy and affects the growth of the mammary glands, preparing them for feeding the baby. Under the influence of progesterone during the first pregnancy, the development of the mammary glands begins with the growth of the ducts, and then the glandular lobules of the breast gradually grow, increasing the overall size of the latter.

In the second half of pregnancy, which normally lasts 260-280 days, the corpus luteum and placenta (the membrane around the fetus) begin to synthesize the hormone relaxin, which acts on the pelvic bones, contributing to their difference during childbirth. The fetal placenta also produces a large amount of estrogens (up to 50 mg per day, while before pregnancy their total amount in the blood does not exceed 0.4 mg), progesterone and human chorionic gonadotropin

(the latter protects the corpus luteum from degeneration during the entire period of pregnancy). These hormones together also block the maturation of new follicles until a certain time, stimulate the growth of the size of the uterus and mammary glands. After childbirth, when the placenta and its hormones disappear, the formation of the pituitary hormone - prolactin, is sharply activated, "turns on" the secretion of milk.

The mammary gland begins to act from the day the child is born, but the release of real milk occurs only on the 3rd day of feeding. The liquid secreted in the first 2-3 days differs significantly from milk in composition (may does not contain casein protein) and is called colostrum.

Mother's milk is a necessary and the only product for the nutrition of a newborn, since the ratio of its quantitative and qualitative components better meets the needs of the growing one. The white color and opacity of milk are due to the fact that small droplets of fat are in suspension in its composition (up to 4-6 million such drops in 1 ml of milk). Mother's milk consists of water, organic and inorganic substances. Of the total volume, it contains: fat 2-4%; proteins (casein, milk albumin and globulin) - up to 4-5%, carbohydrates (lactose sugar) - up to 3-6%, mineral salts (phosphate, sulphate and chloride compounds of sodium, potassium, calcium and other elements) - up to 0, 75%. Milk also contains vitamin A, vitamins B, C and E. The value of mother's milk also lies in the fact that it contains antibodies that protect young children from certain infectious diseases. As the baby grows, the composition of mother's milk changes according to the needs of the body.

Endocrine glands. The endocrine system plays an important role in the regulation of body functions. The organs of this system are endocrine glands- secrete special substances that have a significant and specialized effect on the metabolism, structure and function of organs and tissues. Endocrine glands differ from other glands that have excretory ducts (exocrine glands) in that they secrete the substances they produce directly into the blood. Therefore they are called endocrine glands (Greek endon - inside, krinein - to highlight).

The endocrine glands include the pituitary gland, pineal gland, pancreas, thyroid gland, adrenal glands, sex, parathyroid or parathyroid glands, thymus (goiter) gland.

Pancreas and gonads - mixed, since part of their cells performs an exocrine function, the other part - intrasecretory. The sex glands produce not only sex hormones, but also germ cells (eggs and sperm). Some cells of the pancreas produce the hormone insulin and glucagon, while other cells produce digestive and pancreatic juice.

The human endocrine glands are small in size, have a very small mass (from fractions of a gram to several grams), and are richly supplied with blood vessels. Blood brings to them the necessary building material and carries away chemically active secrets.

An extensive network of nerve fibers approaches the endocrine glands, their activity is constantly controlled by the nervous system.

The endocrine glands are functionally closely related to each other, and the defeat of one gland causes a dysfunction of other glands.

Thyroid. In the process of ontogenesis, the mass of the thyroid gland increases significantly - from 1 g in the neonatal period to 10 g by 10 years. With the onset of puberty, the growth of the gland is especially intense, during the same period the functional tension of the thyroid gland increases, as evidenced by a significant increase in the content of total protein, which is part of the thyroid hormone. The content of thyrotropin in the blood increases intensively up to 7 years.

An increase in the content of thyroid hormones is noted by the age of 10 and at the final stages of puberty (15-16 years). At the age of 5-6 to 9-10 years, the pituitary-thyroid relationship changes qualitatively; the sensitivity of the thyroid gland to thyroid-stimulating hormones decreases, the highest sensitivity to which was noted at 5-6 years. This indicates that the thyroid gland is especially important for the development of the organism at an early age.

Insufficiency of thyroid function in childhood leads to cretinism. At the same time, growth is delayed and the proportions of the body are violated, sexual development is delayed, mental development lags behind. Early detection of hypothyroidism and appropriate treatment has a significant positive effect.

Adrenals. The adrenal glands from the first weeks of life are characterized by rapid structural transformations. The development of adrenal measles proceeds intensively in the first years of a child's life. By the age of 7, its width reaches 881 microns, at the age of 14 it is 1003.6 microns. The adrenal medulla at the time of birth is represented by immature nerve cells. They quickly differentiate during the first years of life into mature cells, called chromophilic, as they are distinguished by the ability to stain yellow with chromium salts. These cells synthesize hormones, the action of which has much in common with the sympathetic nervous system - catecholamines (adrenaline and norepinephrine). Synthesized catecholamines are contained in the medulla in the form of granules, from which they are released under the action of appropriate stimuli and enter the venous blood flowing from the adrenal cortex and passing through the medulla. The stimuli for the entry of catecholamines into the blood are excitation, irritation of the sympathetic nerves, physical activity, cooling, etc. The main hormone of the medulla is adrenalin, it makes up about 80% of the hormones synthesized in this section of the adrenal glands. Adrenaline is known as one of the fastest acting hormones. It accelerates the circulation of blood, strengthens and speeds up heart contractions; improves pulmonary respiration, expands the bronchi; increases the breakdown of glycogen in the liver, the release of sugar into the blood; enhances muscle contraction, reduces their fatigue, etc. All these effects of adrenaline lead to one common result - the mobilization of all the forces of the body to perform hard work.

Increased secretion of adrenaline is one of the most important mechanisms of restructuring in the functioning of the body in extreme situations, during emotional stress, sudden physical exertion, and cooling.

The close connection of the chromophilic cells of the adrenal gland with the sympathetic nervous system causes the rapid release of adrenaline in all cases when circumstances arise in a person's life that require an urgent effort from him. A significant increase in the functional tension of the adrenal glands is noted by the age of 6 and during puberty. At the same time, the content of steroid hormones and catecholamines in the blood increases significantly.

Pancreas. In newborns, intrasecretory pancreatic tissue predominates over exocrine pancreatic tissue. The islets of Langerhans increase significantly in size with age. Islets of large diameter (200-240 microns), characteristic of adults, are found after 10 years. An increase in the level of insulin in the blood in the period from 10 to 11 years was also established. The immaturity of the hormonal function of the pancreas may be one of the reasons that diabetes mellitus is detected in children most often between the ages of 6 and 12, especially after acute infectious diseases (measles, chickenpox, mumps). It is noted that the development of the disease contributes to overeating, especially the excess of carbohydrate-rich foods.