The human endocrine apparatus and its age-related characteristics. Course of lectures on

Endocrine glands. The endocrine system plays an important role in regulating body functions. The organs of this system are endocrine glands– secrete special substances that have a significant and specialized effect on 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. That's why they are called endocrine glands (Greek endon - inside, krinein - to secrete).

The endocrine glands include the pituitary gland, pineal gland, pancreas, thyroid gland, adrenal glands, reproductive glands, parathyroid or parathyroid glands, and thymus gland.

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

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 the necessary building material to them and carries away chemically active secretions.

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 damage to one gland causes disruption of the function of other glands.

Thyroid. During ontogenesis, the mass of the thyroid gland increases significantly - from 1 g during the newborn period to 10 g by the age of 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 rapidly until the age of 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-tropic hormones decreases, the greatest sensitivity to which is noted at 5-6 years. This indicates that the thyroid gland is especially important for the development of the body at an early age.

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

Adrenal glands. From the first weeks of life, the adrenal glands are characterized by rapid structural transformations. The development of adrenal measles occurs intensively in the first years of a child’s life. By the age of 7, its width reaches 881 microns, at 14 years it is 1003.6 microns. At birth, the adrenal medulla consists of immature nerve cells. During the first years of life, they quickly differentiate into mature cells called chromophilic cells, as they are distinguished by their ability to be stained yellow with chromium salts. These cells synthesize hormones whose action 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 influence of appropriate stimuli and enter the venous blood flowing from the adrenal cortex and passing through the medulla. Stimuli for the entry of catecholamines into the blood are excitement, irritation of the sympathetic nerves, physical activity, cooling, etc. The main hormone of the medulla is adrenalin, it makes up approximately 80% of the hormones synthesized in this part of the adrenal glands. Adrenaline is known as one of the fastest-acting hormones. It accelerates blood circulation, strengthens and increases heart rate; 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 influences of adrenaline lead to one common result - the mobilization of all the body’s forces 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 during cooling.

The close connection of the chromophilic cells of the adrenal gland with the sympathetic nervous system determines the rapid release of adrenaline in all cases when circumstances arise in a person’s life that require him to urgently exert his strength. A significant increase in functional tension of the adrenal glands is observed 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, the intrasecretory tissue of the pancreas predominates over the exocrine tissue. The islets of Langerhans increase significantly in size with age. Islands of large diameter (200-240 µm), characteristic of adults, are detected after 10 years. An increase in the level of insulin in the blood in the period from 10 to 11 years has also been established. The immaturity of the hormonal function of the pancreas may be one of the reasons that diabetes mellitus is most often diagnosed in children between the ages of 6 and 12 years, especially after acute infectious diseases (measles, chickenpox, mumps). It has been noted that overeating, especially excess carbohydrate-rich foods, contributes to the development of the disease.

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 nerve pathways and special organs called endocrine glands. Organs are called glands which produce and secrete certain substances: digestive juices, sweat, sebum, milk, etc. The substances secreted by the glands are called secretions. Secretions are released through the excretory ducts onto the surface of the body or onto the mucous membrane of internal organs.

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

As long as the endocrine glands function normally, they do not remind anyone of their existence, the human body works smoothly and balancedly. 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 in the functioning of the entire body of an adult and baby play endocrine glands, let's get acquainted with the main ones and with their features 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, when it is large in size, with the so-called goiter, there is a decrease in the function of the gland. This discrepancy between the large size and weak function of the gland is especially often noted in mountainous places and other areas, the nature of which (earth, water, plants) contains only insignificant amounts of iodine necessary for the formation thyroxine. By introducing iodine into the body, you can prevent the development of goiter and enhance the function of the gland. This is what they do in areas where goiter is common: iodine is added to the salt.

With a lack of thyroxine disorders occur in the body, characterized by slowed growth, dry and thickened skin, impaired bone development, muscle weakness and significant mental retardation, which usually manifests itself in childhood. The extreme degree of these disorders, observed in the absence of visible gland function, is called myxedema. In this case, the child is given thyroid medications.

Increased gland function also leads to severe symptoms. The stimulating effect of thyroxine on the central nervous system becomes excessive. This condition is called thyrotoxicosis. In severe forms of thyrotoxicosis (the so-called Basedow's disease), weight loss, rapid heartbeat, and nervous excitability sharply increase, 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 appendage of the brain) is a small, but plays a large role in the body endocrine gland. Pituitary hormones affect human growth, skeletal and muscle development. If its function is insufficient, growth is sharply delayed and the person may remain a dwarf; Sexual development is delayed and stopped. With increased activity of certain cells of the pituitary gland, giant growth occurs; if a person’s growth has already ended, there is an increase in individual bones (face, hands, feet), and sometimes other parts of the body (tongue, ears), 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 metabolism in the body and enhance the function of the gonads; It also produces the hormone adrenaline, which plays a large role in the proper functioning of the cardiovascular system and has a number of other functions.

Thymus or thymus gland (has nothing to do with goiter - an enlargement of the thyroid gland), is most active in childhood. Its 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 received 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. This is one of the most important digestive glands. In addition to the cells that secrete digestive juice, it also includes special island areas consisting of cells that secrete a hormone that is very important for normal metabolism. This is insulin, which promotes the absorption of sugar. When the hormonal function of the pancreas decreases, diabetes mellitus develops. Until insulin was discovered and a way to obtain it was found, it was difficult to help such patients; Currently, the administration of insulin restores their ability to metabolize carbohydrates, and at the same time increases their overall performance.

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

Normal function of the gonads is very important for the full development of a person. Gonadal hormones affect the child’s metabolism through the nervous system and activate the development of his physical and spiritual powers. The period of sexual development is also a period of active formation of a person’s personality.

This is a 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: developmental features

Endocrine glands guide child development from early years of life. They function with varying intensity at different periods of a person’s life. For each age period characterized by the predominance of the activities of one group or another child's endocrine glands.

The age of up to 3-4 years is characterized by the most intense function of the thymus gland, which regulates growth. Growth is also enhanced by the hormones of the thyroid gland, which functions 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 gland and thyroid gland remain active, the activity of the adrenal glands increases, and at the end of this period the gonads also become active. 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 by sometimes gradual, and sometimes rapidly increasing hormonal activity of the gonads, 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 and clumsiness, which is often observed in adolescents. The activity of the thyroid gland and adrenal glands also increases significantly. The thyroid gland, enlarging, 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 of the functioning 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 crucial transition period of a person’s life proceeds calmly. When proportionality in endocrine activity is disturbed, a kind of “crisis” often occurs. The child’s nervous system and psyche become vulnerable: irritability, lack of restraint in behavior, fatigue, and a tendency to cry appear. Gradually, with the appearance of secondary sexual characteristics, adolescence turns into adolescence, and balance is restored in the body.

It's important for parents 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 stimulation of the child’s nervous system, protect it from unnecessary stimuli. This, of course, does not mean that the child should be relieved of schoolwork or the necessary lesson preparation for him. Age-appropriate, involve children in helping with household chores 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 spend time in the fresh air and for sleep, which ensures complete rest of the nervous system. In the first grades of school, sleep is at least 10 hours, and later the sleep time gradually decreases to 8.5 hours a day.
Always go to bed and get up at the same time, but not too late.
Avoid excessive irritants before bedtime: do not read until late, especially while lying in bed, and resolutely avoid excessive use of TV and computer.
Greater value in prevention of endocrine diseases in children It also has food. The child's food should be complete, contain sufficient amounts of proteins and other nutrients, in particular vitamins.
Remember the leading role of the central nervous system in the functioning of the endocrine glands. Protect your child from mental trauma, which often leads to imbalance in the endocrine glands.
When making certain demands on your child, try to mobilize his will, instill in him how important a conscientious attitude to schoolwork and organization in everyday life are. It is essential that parents themselves be an example of such organization and that they show calm and restraint when dealing with teenagers.

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

In more severe cases of dysfunction of the endocrine glands, treatment with endocrine gland preparations or other treatment methods is required: medications, physiotherapy and even surgery. 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.

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Bibliography

General characteristics of the endocrine glands in children and adolescents

The endocrine glands form the endocrine system, which, along with the nervous system, has a regulatory effect on the human body. Endocrine glands are organs in which a secretion is formed that specifically affects various functions of the body. The secretion of the endocrine glands is called hormones (biologically active substances). Unlike other glands, endocrine glands do not have excretory ducts and their secretions are released into the blood or lymph. Based on this principle, endocrine glands are called endocrine glands. The endocrine glands (ECGs) include:

1) pituitary gland,

2) thyroid,

3) parathyroid,

4) thymus,

5) adrenal glands,

6) pineal gland,

7) pancreas and 8) genitals.

The pituitary gland, thyroid gland, parathyroid and adrenal glands have only internal secretion. The pancreas and genitals are characterized by mixed secretion: they not only produce hormones, but also secrete substances that do not have hormonal activity.

Hormones affect all body functions. They

1) regulate metabolism (protein, carbohydrate, fat, mineral, water);

2) maintain homeostasis (self-regulation of the constancy of the internal state);

3) influence the growth and formation of organs, organ systems and the entire organism as a whole;

4) tissue differentiation occurs under the influence of hormones;

5) they can change the intensity of functioning of any organ.

All hormones are characterized by specificity of action. Phenomena that occur when one of the glands is insufficient can disappear when treated with hormones of the same gland. Thus, carbohydrate metabolism disorders can be eliminated only by the hormones of the same gland, insulin. All hormones can act on certain organs located at a great distance from the place of release. For example, the pituitary gland is located in the cranial cavity, and its hormone acts on many organs, including the gonads located in the pelvic cavity. Hormones have an effect in very small concentrations, i.e. their biological activity is very high. Thus, hormones have a number of properties:

Formed in small quantities.

They have high biological activity.

They have strict specificity of action.

They have a remote action.

Research in recent years has led to the creation of hypotheses regarding the mechanism of action of hormones. It is not the same for different hormones. It is believed that hormones act on target cells by changing the physical structure of enzymes, the permeability of the cell membrane and influencing the genetic apparatus of the cell. According to the first hypothesis, hormones, when joining enzymes, change their structure, which affects the rate of enzymatic reactions. Hormones can activate or inhibit the action of enzymes. This mechanism has been proven only for some of the hormones. Similarly, not all hormones have been proven to influence the permeability of the cell membrane. The effect of insulin, a pancreatic hormone, on the permeability of the cell membrane with respect to glucose has been well studied. It has now been proven that almost all hormones tend to act through the genetic apparatus.

All vital substances in the whole organism are in constant interaction. Pituitary hormones regulate the functioning of the thyroid gland, pancreas, adrenal glands, and gonads. Gonadal hormones affect the functioning of the thymus gland, and thymus hormones affect the gonads, etc. The interaction is manifested in the fact that the reaction of one or another organ is often carried out only under the sequential influence of a number of hormones. Interaction can also be carried out through the nervous system. Hormones of some glands affect the nerve centers, and impulses coming from the nerve centers change the nature of the activity of other glands.

Hormones are important in maintaining relative physico-chemical constancy the internal environment of the body, called homeostasis. The preservation of homeostasis is facilitated by humoral regulation of functions, which exhibits the ability to activate or inhibit the functional activity of organs and systems .

In the body, humoral and nervous regulation of functions are closely interrelated. On the one hand, there are many biologically active substances that can influence the vital activity of nerve cells and the functions of the nervous system, on the other, the synthesis and release of humoral substances into the blood is regulated by the nervous system. Thus, in the body there is a unified neuro-humoral regulation of functions, ensuring the ability to self-regulate life activity.

For example, male sex hormones androgens influence the occurrence of sexual reflexes associated with the activity of the nervous system. The nervous system, through the senses, in turn, sends signals about the production of sex hormones at the right moments.

The hypothalamus plays an important role in the integration of the nervous and endocrine systems. This property is due to the close connection between the hypothalamus and the pituitary gland. The hypothalamus has a very significant influence on the production of pituitary hormones. Large neurons of the hypothalamus are secretory cells, the hormone of which enters the posterior lobe of the pituitary gland along the axons. The vessels surrounding the nuclei of the hypothalamus, uniting in the portal system, descend to the anterior lobe of the pituitary gland, supplying the cells of this part of the gland. From both lobes of the pituitary gland, its hormones enter the vessels through the vessels. endocrine glands, the hormones of which, in turn, in addition to affecting peripheral tissues, also influence the hypothalamus and the anterior pituitary gland, thereby regulating the need for the release of various pituitary hormones in a given amount.

Endocrine influences change reflexively: impulses from proprioceptors, pain stimulation, emotional factors, mental and physical stress affect the secretion of hormones.

Age-related features of the endocrine glands

Weight pituitary gland a newborn child is 100 - 150 mg. In the second year of life, its increase begins, which turns out to be sharp at 4–5 years, after which a period of slow growth begins until the age of 11. By the period of puberty, the mass of the pituitary gland averages 200-350 mg, and by 18-20 years - 500-650 mg. Up to 3-5 years, the amount of growth hormone is released more than in adults. From 3-5 years of age, the rate of GH secretion is equal to that of adults. In newborns, the amount of ACTH is equal to that of adults. TSH is released sharply immediately after birth and before puberty. Vasopressin is maximally released in the first year of life. The greatest intensity of release of gonadotropic hormones is observed during puberty.

iron homeostasis internal secretion

The newborn has a mass thyroidglands ranges from 1 to 5 g. It decreases slightly by 6 months, and then a period of rapid increase begins, which lasts up to 5 years. During puberty, the increase continues and reaches the mass of the gland of an adult. The greatest increase in hormone secretion is observed during early childhood and puberty. Maximum activity of the thyroid gland is achieved at 21-30 years of age.

After the birth of a child, maturation occurs parathyroidglands, which is reflected in an increase in the amount of hormone released with age. The greatest activity of the parathyroid glands is observed in the first 4-7 years of life.

The newborn has a mass adrenal glands is approximately 7 years old. The growth rate of the adrenal glands is not the same at different age periods. A particularly sharp increase is observed at 6-8 months. and 2-4 g. The increase in the mass of the adrenal glands continues up to 30 years. The medulla appears later than the cortex. After 30 years, the amount of hormones in the adrenal cortex begins to decrease.

By the end of 2 months of intrauterine development, rudiments appear in the form of outgrowths pancreasglands. The head of the pancreas in an infant is raised slightly higher than in adults and is located approximately at the 10-11 thoracic vertebrae. The body and tail go to the left and rise slightly upward. It weighs a little less than 100 g in an adult. At birth, iron weighs only 2-3 g in babies and is 4-5 cm long. By 3-4 months its weight doubles, by 3 years it reaches 20 g, and by 10-12 years - 30 g. Resistance to glucose load in children under 10 years of age is higher, and the absorption of dietary glucose occurs faster than in adults. This explains why children love sweets and consume them in large quantities without danger to their health. With age, the insular activity of the pancreas decreases, so diabetes most often develops after 40 years.

In early childhood thymusgland the cortex predominates. During puberty, the amount of connective tissue in it increases. In adulthood, there is a strong proliferation of connective tissue.

The weight of the pineal gland at birth is 7 mg, and in an adult it is 100-200 mg. The increase in the size of the epiphysis and its mass continues until 4-7 years, after which it undergoes reverse development.

Bibliography

1. Anatomy and age-related physiology, Educational and methodological manual. - Komsomolsk-on-Amur, 2004.

2. Badalyan L.O., Child neurology. - M, 1994.

3. Leontyeva N.N., Marinova V.V., Anatomy and physiology of the child’s body. - M, 1986.

4. Mamontov S.G., Biology. - M, 1991.

5. Mikheev V.V., Melnichuk P.V., Nervous diseases. - M, 1991

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Endocrine system - endocrine glands that secrete physiologically active substances into the body and do not have excretory ducts. Functions of hormones in the human body. The structure of the hypothalamus and pituitary gland. Diabetes insipidus. Epithelial body.

The endocrine glands include the pituitary gland, pineal gland, pancreas, thyroid gland, adrenal glands, reproductive glands, parathyroid or parathyroid glands, and thymus gland.

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 damage to one gland causes disruption of the function of other glands.

9. AGE FEATURES OF THE GENITAL GLANDS Male and female gonads (testes and ovaries), having formed during intrauterine development, undergo slow morphological and functional maturation after birth. Testicular weight in newborns is 0.3 G, in 1 year – 1 G, at 14 years old – 2 G, at 15-16 years old – 8 G, at 19 years old – 20 G . The seminiferous tubules in newborns are narrow, and over the entire period of development their diameter increases 3 times. The ovaries are laid above the pelvic cavity, and in the newborn the process of their descent is not yet complete. They reach the pelvic cavity 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 weight of the ovary in a newborn is 5-6 g, and it changes little during subsequent development: in an adult, the weight of the ovary is 6-8 g. In old age, the weight of the ovary decreases to 2 g. In the process of sexual development, several periods are distinguished: childhood - up to 8 -10 years, adolescence - from 9-10 to 12-14 years, youth - from 13-14 to 16-18 years, period of puberty - up to 50-60 years and menopause - the period of extinction of sexual function. During childhood in the ovary In girls, the primordial follicles grow very slowly, in which in most cases the membrane is still absent. In boys, the seminiferous tubules in the testes are slightly convoluted. Regardless of gender, urine contains a small amount of androgens and estrogens, which are formed during this period in the adrenal cortex. The androgen content 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 numbers (sometimes to 0) and remains at this level for up to 5-7 years. During adolescence, Graafian vesicles appear in the ovaries, and the follicles grow rapidly. The seminiferous tubules in the testes increase in size, and spermatocytes appear along with spermatogonia. During this period, the amount of androgens in the blood plasma and urine increases in boys; in girls - estrogens. Their number increases even more during adolescence, which determines the development of secondary sexual characteristics. During this period, a periodicity characteristic of the female body appears in the amount of secreted estrogens, which ensures the female reproductive cycle. A sharp increase in estrogen secretion coincides with ovulation, after which, in the absence of fertilization, menstruation occurs, which is called the release of the disintegrating uterine mucosa along with the contents of the uterine glands and blood from the vessels that open. Strict cyclicality in the amount of estrogen released and, accordingly, in the changes taking place in the ovary and uterus is not immediately established. During the first months, 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 associated sex characteristics, being formed in the prenatal period, are formed throughout the entire period of childhood and determine sexual development. The gonads and their functions are inextricably linked with the holistic process of child development. At a certain stage of ontogenesis, sexual development accelerates sharply and physiological puberty occurs. The period of accelerated sexual development and the achievement of puberty is called period of puberty. This period occurs mainly during adolescence. Puberty of girls is 1-2 years ahead of puberty of boys, and there is also significant individual variation in the timing and pace of puberty.

The timing of puberty and its intensity are different and depend on many factors: health, nutrition, climate, living and socio-economic conditions. Hereditary characteristics also play an important role.

Unfavorable living conditions, unhealthy food, lack of vitamins, severe or repeated illnesses lead to delayed puberty. In big cities, adolescents usually reach puberty earlier than in rural areas.

During puberty, profound changes in the body occur. The relationships between the endocrine glands and, above all, the hypothalamic-pituitary system change. The structures of the hypothalamus are activated, the neurosecrets of which stimulate the release of tropic hormones of the pituitary gland.

Under the influence of pituitary hormones, body length growth increases. The pituitary gland also stimulates the activity of the thyroid gland, which is why, especially in girls, the thyroid gland noticeably enlarges during puberty. Increased activity of the pituitary gland leads to increased activity of the adrenal glands, active activity of the gonads begins, increasing secretion of sex hormones leads to the development of so-called secondary sexual characteristics - features of physique, hair growth, timbre of voice, 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; it is divided into certain stages, each of which is characterized by the specific functioning of the endocrine glands and, accordingly, the entire organism as a whole. The stages are determined by a combination of primary and secondary sexual characteristics. In both boys and girls, there are 5 stages of puberty.

Stage I – prepuberty (the period immediately preceding puberty). Characterized by the absence of secondary sexual characteristics.

Stage II – beginning of puberty. Boys experience a slight increase in testicular size. Minimal pubic hair. The hair is sparse and straight. In girls, 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 increased secretion of growth hormone at this stage is more pronounced in girls, which determines the increased growth processes in them. The release of sex hormones increases, the function of the adrenal glands is activated.

Stage III - in boys, further enlargement of the testicles, the beginning of enlargement of the penis, mainly in length. Pubic hair becomes darker, coarser, and begins to spread to the pubic symphysis. In girls, the mammary glands develop further, and 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.

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

Stage V - boys finally develop genital organs and secondary sexual characteristics. In girls, the mammary glands and genital hair correspond to those of an adult woman. At this stage, girls' periods stabilize. The appearance of menstruation indicates the onset of puberty - the ovaries are already producing mature eggs ready for fertilization.

Menstruation lasts on average from 2 to 5 days. During this time, about 50-150 cm 3 of blood is released. If menstruation is established, then it repeats approximately every 24-28 days. The cycle is considered normal when menstruation occurs at the same intervals, lasts the same number of days with the same intensity. At first, menstruation may last 7-8 days, disappear for several months, a year or more. Only gradually does a regular cycle become 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 restructured, all physiological functions undergo significant changes.

The intensive growth of the bone skeleton and muscular system in adolescents is not always kept up with the development of internal organs - the heart, lungs, and gastrointestinal tract. The heart outpaces the blood vessels in growth, as a result of which blood pressure rises and, first of all, complicates the work of the heart itself. At the same time, the rapid restructuring of the entire body that occurs during puberty, in turn, places increased demands on the heart. And insufficient work of the heart (“youthful heart”) often leads to dizziness, blueness and coldness of the extremities in boys and girls. Hence the headaches, fatigue, and periodic bouts of lethargy; Teenagers often experience fainting due to spasms of cerebral vessels. With the end of puberty, these disorders usually disappear without a trace.

The functions of the central nervous system undergo significant changes at this stage of development due to the activation of the hypothalamus. The emotional sphere is changing: the emotions of adolescents are mobile, changeable, contradictory: increased sensitivity is often combined with callousness, shyness with deliberate cheekiness, excessive criticism and intolerance towards parental care are manifested. During this period, decreased performance, neurotic reactions, irritability, and tearfulness are sometimes observed (especially in girls during menstruation).

CONCLUSION

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

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

During the “teenage” period, the teenager’s personality is intensively formed, a feeling of growing up arises, and attitudes toward members of the opposite sex change.

During the transition 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 and psyche, but it is necessary to explain the pattern and biological meaning of these changes. The art of the teacher in these cases is to find such forms and methods of work that would switch the attention of children to various and varied types of activities and distract them from sexual experiences. This is, first of all, increasing the requirements for learning, work and behavior of schoolchildren.

At the same time, it is very important for adults to have a tactful, respectful attitude towards the initiative and independence of teenagers, and the ability to direct their energy in the right direction. After all, teenagers tend to overestimate both their strengths and the extent 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 study of the cell and development of the body, nervous system, musculoskeletal system): Textbook for pedagogical students. Institute for specialties “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.: Education, 1976

3. Age-related physiology and school hygiene: A manual for pedagogical students. institutes” / Ed. Khripkova A.G. and others - M.: Education, 1990

4. Endocrine system of a growing organism: A textbook for universities” / Ed. Drzhevetskaya I.A - M.: Higher School, 1987.

LECTURE COURSE ON

Age physiology

Pituitary

The pituitary gland is of ectodermal origin. The anterior and middle (intermediate) lobes are formed from the epithelium of the oral cavity, the neurohypophysis (posterior lobe) - from the diencephalon. In children, the anterior and middle lobes are separated by a gap; over time, it closes and both lobes are closely adjacent to each other.

The endocrine cells of the anterior lobe differentiate in the embryonic period, and at 7-9 weeks they are already capable of synthesizing hormones.

The mass of the pituitary gland in newborns is 100-150 mg, and the size is 2.5-3 mm. In the second year of life, it begins to increase, especially at the age of 4-5 years. After this, until the age of 11, the growth of the pituitary gland slows down, and from the age of 11 it accelerates again. By the period of puberty, the mass of the pituitary gland averages 200-350 mg, by 18-20 years old - 500-600 mg. The diameter of the pituitary gland reaches 10-15 mm by adulthood.

Pituitary hormones: functions and age-related changes

The anterior lobe of the pituitary gland synthesizes hormones that control the function of peripheral endocrine glands: thyroid-stimulating, gonadotropic, adrenocorticotropic, as well as somatotropic hormone (growth hormone) and prolactin. The functional activity of the adenohypophysis is completely regulated by neurohormones; it does not receive nervous influences from the central nervous system.

Somatotropic hormone (somatotropin, growth hormone) - growth hormone determines growth processes in the body. Its formation is regulated by the hypothalamic GH-releasing factor. This process is also influenced by the hormones of the pancreas and thyroid glands, and the hormones of the adrenal glands. Factors that increase the secretion of GH include hypoglycemia (lowering blood glucose levels), fasting, certain types of stress, and intense physical work. The hormone is also released during deep sleep. In addition, the pituitary gland occasionally secretes large amounts of GH in the absence of stimulation. The biological effect of GH is mediated by somatomedin, which is produced in the liver. STH receptors (i.e. structures with which the hormone directly interacts) are built into cell membranes. The main role of growth hormone is stimulation of somatic growth. Its activity is associated with the growth of the skeletal system, an increase in the size and mass of organs and tissues, protein, carbohydrate and fat metabolism. HGH acts on many endocrine glands, kidneys, and on the functions of the immune system. As a growth stimulator at the tissue level, growth hormone accelerates the growth and division of cartilage cells, the formation of bone tissue, promotes the formation of new capillaries, and stimulates the growth of epiphyseal cartilage. Subsequent replacement of cartilage with bone tissue is ensured by thyroid hormones. Both processes are accelerated under the influence of androgens; growth hormone stimulates the synthesis of RNA and proteins, as well as cell division. There are gender differences in the content of growth hormone and indices of muscle development, skeletal system and fat deposition. Excessive amounts of GH disrupt carbohydrate metabolism, reducing the use of glucose by peripheral tissues, and contributes to the development of diabetes mellitus. Like other pituitary hormones, GH promotes the rapid mobilization of fat from the depot and the entry of energy material into the blood. In addition, retention of extracellular water, potassium and sodium may occur, and calcium metabolism may also be impaired. Excess of the hormone leads to gigantism (Fig. 3.20). At the same time, the growth of skeletal bones accelerates, but the increase in the secretion of sex hormones upon reaching puberty stops it. Increased secretion of growth hormone is also possible in adults. In this case, growth of the extremities of the body (ears, nose, chin, teeth, fingers, etc.) is observed. Bone growths may form, and the size of the digestive organ (tongue, stomach, intestines) may increase. This pathology is called acromegaly and is often accompanied by the development of diabetes.

Children with insufficient secretion of growth hormone develop into dwarfs of a “normal” physique (Fig. 3.21). Growth retardation appears after 2 years, but intellectual development is usually not impaired.

The hormone is determined in the pituitary gland of a 9-week fetus. Subsequently, the amount of growth hormone in the pituitary gland increases and by the end of the intrauterine period increases 12,000 times. GH appears in the blood at the 12th week of intrauterine development, and in 5- to 8-month-old fetuses it is approximately 100 times more than in adults. The concentration of GH in the blood of children continues to remain high, although during the first week after birth it decreases by more than 50%. By 3-5 years of age, the level of growth hormone is the same as in adults. In newborns, growth hormone is involved in the immunological defense of the body, influencing lymphocytes.

HGH ensures the normal physical development of the child. Under physiological conditions, hormone secretion is episodic. In children, GH is secreted 3-4 times during the day. The total amount released during deep night sleep is significantly greater than in adults. In connection with this fact, the need for adequate sleep for the normal development of children becomes obvious. With age, the secretion of GH decreases.

The growth rate in the prenatal period is several times higher than in the postnatal period, but the influence of the endocrine glands on this process is not decisive. It is believed that fetal growth is mainly influenced by placental hormones, factors of the maternal body and depends on the genetic development program. The cessation of growth occurs probably because the general hormonal situation changes in connection with the achievement of puberty: estrogens reduce the activity of growth hormone.

Thyroid-stimulating hormone (TSH) regulates the activity of the thyroid gland according to the body's needs. The mechanism of the effect of TSH on the thyroid gland is still not fully understood, but its administration increases the mass of the organ and increases the secretion of thyroid hormones. The effect of TSH on protein, fat, carbohydrate, mineral and water metabolism is carried out through thyroid hormones.

TSH-producing cells appear in 8-week embryos. During the entire intrauterine period, the absolute content of TSH in the pituitary gland increases and in a 4-month fetus it is 3-5 times higher than in adults. This level persists until birth. TSH begins to affect the fetal thyroid gland in the second third of pregnancy. however, the dependence of thyroid function on TSH in the fetus is less pronounced than in adults. The connection between the hypothalamus and the pituitary gland is established only in the last months of intrauterine development.

In the first year of a child's life, the concentration of TSH in the pituitary gland increases. A significant increase in synthesis and secretion is observed twice: immediately after birth and in the period preceding puberty (prepuberty). The first increase in TSH secretion is associated with the adaptation of newborns to living conditions, the second corresponds to hormonal changes, including increased function of the gonads. The maximum secretion of the hormone is achieved between the ages of 21 and 30 years; at 51-85 years, its value is halved.

Adrenocorticotropic hormone (ACTH) acts indirectly on the body by stimulating the secretion of adrenal hormones. In addition, ACTH has direct melanocyte-stimulating and lipolytic activity, so an increase or decrease in ACTH secretion in children is accompanied by complex dysfunctions of many organs and systems.

With increased secretion of ACTH (Cushing's disease), growth retardation, obesity (fat deposition mainly on the trunk), moon-shaped face, premature development of pubic hair, osteoporosis, hypertension, diabetes, trophic skin disorders (stretch marks) are observed. With insufficient secretion of ACTH, changes characteristic of a lack of glucocorticoids are detected.

During the prenatal period, ACTH secretion in the fetus begins at the 9th week, and at the 7th month its content in the pituitary gland reaches a high level. During this period, the fetal adrenal glands respond to ACTH - the rate of formation of hodrocortisone and testosterone increases in them. In the second half of intrauterine development, not only direct, but also feedback connections between the pituitary gland and the adrenal glands of the fetus begin to operate. In newborns, all parts of the hypothalamus-pituitary-adrenal cortex system function. From the first hours after birth, children already react to stressful stimuli (associated, for example, with prolonged labor, surgical interventions, etc.) increased levels of corticosteroids in the urine. These reactions, however, are less pronounced than in adults due to the low sensitivity of the hypotadamic structures to changes in the internal and external environment of the body. The influence of the hypothalamic nuclei on the function of the adenohypophysis increases. which, under stress conditions, is accompanied by an increase in ACTH secretion. In old age, the sensitivity of the hypothalamic nuclei decreases again, which is associated with a less pronounced adaptation syndrome in old age.

Gonadotropins (gonadotropins) are called follicle-stimulating and luteinizing hormones

Follicle-stimulating hormone (FSH) in the female body causes the growth of ovarian follicles and promotes the formation of estrogens in them. In the male body, it affects spermatogenesis in the testes. FSH release depends on stage and age

Luteinizing hormone (LH) causes ovulation, promotes the formation of the corpus luteum in the ovaries of the female body, and in the male body it stimulates the growth of the seminal vesicles and prostate gland, as well as the production of androgens in the testes.

Cells that produce FSH and LH develop in the pituitary gland by the 8th week of intrauterine development, at which time LH appears in them. and at the 10th week - FSH. Gonadotropins appear in the blood of the fetus from 3 months of age. In the blood of female fetuses, especially in the last third of intrauterine development, their concentration is higher than in males. The maximum concentration of both hormones occurs in the period 4.5-6.5 months of the prenatal period. The significance of this fact is still not fully understood

Gonadotropic hormones stimulate the endocrine secretion of the fetal gonads, but do not control their sexual differentiation. In the second half of the intrauterine period, a connection is formed between the hypothalamus, the gonadotropic function of the pituitary gland and the hormones of the gonads. This occurs after fetal sex differentiation under the influence of testosterone.

In newborns, the concentration of LH in the blood is very high, but during the first week after birth it decreases and remains low until 7-8 years of age. During puberty, the secretion of gonadotropins increases, by the age of 14 it increases 2-2.5 times. In girls, gonadotropic hormones cause the growth and development of the ovaries, cyclical secretion of FSH and LH appears, which causes the onset of new sexual cycles. By the age of 18, FSH and LH levels reach adult values.

Prolactin, or luteotropic hormone (LTP. stimulates the function of the corpus luteum and promotes lactation, i.e. the formation and secretion of milk. The formation of the hormone is regulated by the prolactin-inhibiting factor of the hypothalamus, estrogens and thyrotropin-releasing hormone (TRH) of the hypothalamus. The last two hormones have a stimulating effect on the secretion of the hormone. An increase in the concentration of prolactin leads to an increase in the release of dopamine by the cells of the hypothalamus, which inhibits the secretion of the hormone. This mechanism works during the absence of lactation; excess dopamine inhibits the activity of cells that form prolactin.

The secretion of prolactin begins from the 4th month of intrauterine development and increases significantly in the last months of pregnancy. It is believed that it is also involved in the regulation of metabolism in the fetus. At the end of pregnancy, prolactin levels become high in both the mother's blood and amniotic fluid. In newborns, the concentration of prolactin in the blood is high. It decreases during the first year of life. and increases during puberty. and it is stronger in girls than in boys. In teenage boys, prolactin stimulates the growth of the prostate gland and seminal vesicles.

The middle lobe of the pituitary gland influences the processes of hormone formation in the adenohypophysis. It is involved in the secretion of melanostimulating hormone (MSH) (melanotropin) and ACTH. MSH is important for skin and hair pigmentation. In the blood of pregnant women, its content is increased, and therefore pigment spots appear on the skin. In fetuses, the hormone begins to be synthesized at 10-11 weeks. but its function in development is still not completely clear.

The posterior lobe of the pituitary gland, together with the hypothalamus, functionally forms a single whole. Hormones synthesized in the nuclei of the hypothalamus - vasopressin and oxytocin - are transported to the posterior lobe of the pituitary gland and are stored here until released into the blood

Vasopressin, or antidiuretic hormone (ADH). The target organ of ADH is the kidneys. The epithelium of the renal collecting ducts becomes permeable to water only under the influence of ADH. which ensures passive reabsorption of water. Under conditions of increased salt concentration in the blood, the concentration of ADH increases and, as a result, urine becomes more concentrated and water loss is minimal. When the concentration of salts in the blood decreases, the secretion of ADH decreases. Alcohol consumption further reduces the secretion of ADH, which explains the significant diuresis after drinking fluids with alcohol.

When large amounts of ADH are introduced into the blood, a clearly expressed constriction of the arteries is due to the stimulation of vascular smooth muscle by this hormone, resulting in an increase in blood pressure (vasopressor effect of the hormone). A sharp drop in blood pressure due to blood loss or shock sharply increases the secretion of ADH. As a result, blood pressure increases. A disease that occurs when the secretion of ADH is impaired. called diabetes insipidus. This produces a large amount of urine with a normal sugar content in it.

The antidiuretic hormone of the pituitary gland begins to be released in the 4th month of embryonic development, the maximum of its release occurs at the end of the first year of life, then the antidiuretic activity of the neurohypophysis begins to fall to fairly low values, and at the age of 55 years it is approximately 2 times less than in a one-year-old child .

The target organ for oxytocin is the muscular layer of the uterus and myoepithelial cells of the mammary gland. Under physiological conditions, the mammary glands begin to secrete milk on the first day after birth, and at this time the baby can already suck. The act of sucking serves as a strong stimulus for the nipple's tactile receptors. From these receptors, impulses are transmitted along nerve pathways to the neurons of the hypothalamus, which are also secretory cells that produce oxytocin. The latter is transported in the blood to myoepithelial cells. lining the mammary gland. Myoepithelial cells are located around the alveoli of the gland, and during contraction, milk is squeezed into the ducts. Thus, to extract milk from the gland, the baby does not require active sucking, since the “milk ejection” reflex helps him.

Activation of labor is also associated with oxytocin. With mechanical irritation of the birth canal, nerve impulses that enter the neurosecretory cells of the hypothalamus cause the release of oxytocin into the blood. Towards the end of pregnancy, under the influence of the female sex hormones estrogen, the sensitivity of the muscles of the uterus (myometrium) to oxytocin sharply increases. At the beginning of labor, the secretion of oxytocin increases, which causes weak contractions of the uterus, pushing the fetus towards the cervix and vagina. Stretching of these tissues causes the excitation of numerous mechanoreceptors in them. From which the signal is transmitted to the hypothalamus. Neurosecretory marks of the hypothalamus respond by releasing new portions of oxytocin, due to which uterine contractions intensify. This process eventually progresses to labor, during which the fetus and placenta are expelled. After expulsion of the fetus, irritation of mechanoreceptors and the release of oxytocin stop.

The synthesis of hormones of the posterior lobe of the pituitary gland begins in the nuclei of the hypothalamus in the 3rd-4th month of the intrauterine period, and in the 4th-5th month they are found in the pituitary gland. The content of these hormones in the pituitary gland and their concentration in the blood gradually increase by the time the child is born. In children in the first months of life, the antidiuretic effect of vasopressin does not play a significant role; only with age does its importance in retaining water in the body increase. In children, only the antidiuretic effect of oxytocin is manifested; its other functions are weakly expressed. The uterus and mammary glands begin to respond to oxytocin only after the completion of puberty, that is, after prolonged action on the uterus of the sex hormones estrogen and progesterone, and on the mammary gland - the pituitary hormone prolactin.