The concept of growth, development and shaping of children. The concept of the growth and development of the child's body. Features of growth and development in periods of life

The biological meaning of life is reduced to the reproduction of species. Here, reproduction is considered as a barrier process leading from an adult organism to a newly formed one. At the same time, only a small part of organisms is able to reproduce almost immediately, as it appeared itself. These are the simplest bacteria that are able to divide after 20 minutes from the beginning of life. Others, in order to begin to multiply, need to grow and develop.

General concept of growth and development

So, living beings populate the planet and live on it. Their huge number, which cannot be counted, is reproduced within days, weeks, months and years. For reproduction, many do not need to acquire new functions, that is, additional to those that they received after their appearance. But most others need it. They just need to grow, that is, increase in size, and develop, that is, acquire new functions.

Growth is called the process of increasing the morphological size of an organism. A newly formed living being must grow in order to run its metabolic processes at the most active level. And only with an increase in body size is it possible for new structures to appear that guarantee the development of certain functions. Therefore, the growth of an organism and the development of an organism are related processes, each of which is a consequence of each other: growth ensures development, and further development increases the ability to grow.

Private understanding of development

The growth and development of the organism are connected by the fact that they proceed in parallel to each other. Previously, it was understood that the creature must first grow up, and new organs, which guarantee the emergence of new functions, will be located in the supposedly vacated place in the internal environment of the body. Approximately 150 years ago, there was an opinion that first there is growth, then development, then growth again, and so on through the cycle. Today, the understanding is completely different: the concept of the growth and development of an organism denotes processes that, although not identical, but flow together.

It is noteworthy that in biology two types of growth are distinguished: linear and volumetric. Linear is an increase in the length of the body and its sections, and volumetric is the expansion of the body cavity. Development also has its own differentiation. Allocate individual and species development. Individual implies the accumulation of certain functions and skills by one organism of the species. And species development is the improvement of a new species, capable, for example, of adapting a little better to living conditions or populating previously uninhabited areas.

The ratio of growth and development in unicellular organisms

The life span of unicellular organisms is the period that a cell can live. In multicellular organisms, this period is much longer, and that is why they develop more actively. But unicellular (bacteria and protists) are too volatile creatures. They actively mutate and can exchange genetic material with representatives of different strains of the species. Therefore, the process of development (in the case of gene exchange) does not require an increase in the size of the bacterial cell, that is, its growth.

However, as soon as the cell receives new hereditary information through the exchange of plasmids, protein synthesis is required. Heredity is information about its primary structure. It is these substances that are the expression of heredity, since a new protein guarantees a new function. If the function leads to an increase in viability, then this hereditary information is reproduced in subsequent generations. If it does not carry any value or even harms, then cells with such information die, because they are less viable than others.

The biological significance of human growth

Any one is more viable than a single-celled one. In addition, he has much more features than a single isolated cell. Therefore, the growth of an organism and the development of an organism are the most specific concepts for multicellular organisms. Since the acquisition of a certain function requires the appearance of a certain structure, the processes of growth and development are maximally balanced and are mutual "engines" of each other.

All information about the abilities to which development is possible is embedded in the genome. Each cell of a multicellular creature contains the same genetic set. On early stages growth and development one cell divides many times. Thus, growth occurs, that is, an increase in size necessary for development (the emergence of new functions).

Growth and development of multicellular different classes

As soon as the human body is born, the processes of growth and development are balanced among themselves until a certain period. It's called linear growth arrest. The size of the body is embedded in the genetic material, as is the color of the skin and so on. This is an example of polygenic inheritance, the patterns of which have not yet been sufficiently studied. However, normal physiology is such that body growth cannot continue indefinitely.

However, this is typical mainly for mammals, birds, amphibians and some reptiles. For example, a crocodile is able to grow throughout its life, and its body size is limited only by its lifespan and some of the dangers that may await it during its course. Plants do grow all their lives, although, of course, there are artificially grown species in which this ability is somehow inhibited.

Features of growth and development in biological terms

The growth of the organism and the development of the organism are aimed at solving several problems that are related to the fundamental properties of all living things. First, these processes are necessary for the realization of hereditary material: organisms are born immature, grow, and acquire the function of reproduction during their life. Then they give offspring, and the reproduction cycle itself is repeated.

The second meaning of growth and development is the settlement of new territories. No matter how unpleasant it was to realize this, but nature in each species has a tendency to expand, that is, to populate as much as possible. more territories and zones. This gives rise to competition, which is the engine of species development. The human body also constantly competes for its habitats, although this is not so noticeable now. Basically, he has to deal with the natural defects of his body and with the smallest pathogens.

Fundamentals of Growth

The concepts of "growth of an organism" and "development of an organism" can be considered much deeper. For example, growth is not only an increase in size, but also an increase in the number of cells. Each body of a multicellular organism consists of many elementary components. And in biology, the elementary units of living things are cells. And although viruses do not have cells, but are still considered alive, should be revised.

So be it, but the cell is still the smallest of all balanced systems that can live and function. At the same time, an increase in the size of the cell and supracellular structures, as well as an increase in their number, is the basis of growth. This applies to both linear and volumetric growth. Development also depends on their number, because the more cells, the larger the body size, which means that the more spacious territories the body can inhabit.

The social significance of human growth

If we consider the processes of growth and development only on the example of a person, then a certain paradox appears here. Growth is important because the physical development of a person is the main driving factor in reproduction. Physically undeveloped individuals are often unable to give viable offspring. And this is the positive meaning of evolution, although, as a fact, it is negatively perceived by society.

It is the presence of society that is a paradox, because under its protection even a physically undeveloped person, due to enviable intellectual abilities or other achievements, is able to marry and give offspring. Of course, normal physiology does not change its principles in people who do not have diseases, but are physically less developed than others. But it is obvious that body size is a genetic dominant. Since they are smaller, it means that a person is less able than others to adapt to changing living conditions.

Human development in society

Although a person has adapted living conditions for himself, he still faces adverse factors. Survival in them is a matter of fitness. But here there is another biological paradox: today man survives in society. This is a conglomerate of people who equalizes the chances of everyone to survive in certain situations.

The biological instincts for the preservation of the species also work here, therefore, in the most horrific situations, few of the personalities care only about themselves. Therefore, since it is beneficial for us to stay in society, it means that the development of the human body without it is impossible. Man even developed a language for communication in society, and therefore one of the stages of personal and species development is its study.

From birth, a person is not able to speak: he only makes sounds that demonstrate his fear and irritation. Then, as he develops and stays in the language environment, he adapts, says the first word, then enters into full-fledged speech contact with other people. And this is an extremely important period of its development, because without society and without adaptation to living in it, a person is least of all adapted to life in the current conditions.

Periods of development of the human body

Each organism, especially multicellular, goes through a series of stages in its development. They can be considered on the example of a person. From the moment of conception and the formation of a zygote, it goes through fetogenesis. The whole process of growth and development from a single-celled zygote to an organism takes 9 months. After birth, the first stage of the life of the organism outside the mother's womb begins. It is called which lasts 10 days. The next one is infancy (from 10 days to 12 months).

After that, early childhood begins, which lasts up to 3 years, and from 4 to 7 years, the early childhood period begins. From 8 to 12 years old in boys, and in girls up to 11 years old, the period of late (second) childhood lasts. And from 11 to 15 for girls and from 12 to 16 for boys, adolescence lasts. Boys become young men from the age of 17 to 21, and girls - from 16 to 20 years. This is the time when children become adults.

Adolescence and adulthood

By the way, it is wrong to call heirs children already. They are young men who from 22 to 35 years old experience the first mature age. The second mature in men starts at 35 and ends at 60, and in women from 35 to 55 years. And from 60 to 74 years old, age-related physiology very revealingly reflects the changes that occur in the human body over the course of life, but geriatrics deals with diseases and life characteristics of older people.

Despite medical measures, mortality during this period is the highest. Since the physical development of a person stops here and tends to involution, there are more and more bodily problems. But development, that is, the acquisition of new functions, practically does not stop, if considered mentally. In terms of physiology, development, of course, also tends to involution. It reaches a maximum in the period from 75 to 90 years (senile) and continues in centenarians who have overcome the age barrier of 90 years.

Features of growth and development in periods of life

Age physiology reflects the features of development and growth in different periods life. It focuses on the biochemical processes and important mechanisms of aging. Unfortunately, there is no way to effectively influence aging, so people still die due to damage accumulated over a lifetime. The growth of the body ends after 30 years, and, according to many physiologists, already at 25 years. At the same time, physical development also stops, which can be started again with hard work on oneself. In different periods of development, one should work on oneself, because this is the most effective evolutionary mechanism. After all, even strong genetic inclinations cannot be realized without training and practice.

Correlation between growth and development processes

Definition of concepts. Growth and development are usually used as identical concepts, inextricably linked. Meanwhile, the biological nature of these processes is different, their mechanisms and consequences are different.

Height- this is a quantitative increase in the biomass of an organism due to an increase in the geometric dimensions and mass of its individual cells or an increase in the number of cells due to their division. Development - these are qualitative transformations in a multicellular organism that occur due to differentiated processes (increase in the diversity of cellular structures) and lead to qualitative and quantitative changes in functions (of the body.

The relationship between growth and development is manifested, in particular, in the fact that certain stages of development can occur only when certain body sizes are reached. So, puberty in girls can only occur when body weight reaches a certain value (for representatives of the European race, this is about 48 kg). Active growth processes also cannot continue at the same stage of development indefinitely. differentiated processes, or differentiation, - this is the emergence of specialized structures of a new quality from poorly specialized progenitor cells. The meaning of differentiated processes. The least specialized can be considered a zygote - a germ cell, formed as a result of the fusion of the maternal egg with the paternal sperm. The genetic apparatus of the zygote contains a complete double set of chromosomes, and all further development is the activation or repression of one or another part of the genome, which from germ cell is completely and unchanged transmitted to all its descendants during each act of division.The first stages of development of the zygote are a simple increase in the number of cells indistinguishable from each other - first the zygote is divided into 2, then each of them by 2 more, i.e., is formed 4 cells, then - 8, 16, 32, etc. These embryonic cells are called blastomeres, they are like two drops of water.However, already at the stage of 32 blastomeres, some features of individual cells associated with their location begin to emerge. the number of blastomeres, these differences are increasing.Some of these cells, which together form a sphere, increase in size more than others, and, finally, the stage of gastrulation begins - the invagination of smaller cells inside the sphere with the formation of internal (coelomic) and external (gastric) cavities . The organism acquires a completely new form of an elongated tube closed at one end, which differs sharply from the recent spherical shape. The cells of the apical and caudal ends begin to differ more and more not only externally, but also in their properties: internal, metabolic. Moreover, the functions of the cells of the outer (ectodermal), inner (endodermal), and formed intermediate (mesoderm) layers of the gastrula, as well as the role of these cells in the further development of the organism, become different. So, the ectodermal layer of cells gives rise to the skin and nervous tissue. The mesodermal layer serves as the progenitor of all the muscles of the body. Endoderm cells form further parenchymal organs (liver, kidneys, spleen, endocrine glands) and the epithelium of the gastrointestinal tract. All these complex transformations, gradually leading to the formation of completely dissimilar cellular structures and tissues that are different in form and function, are manifestations of differentiation processes. This is precisely what development consists of - from a single germ cell to an organism with millions of cells of various specializations.

Terms of development and maturation of the child's body. For a long time there was a belief that differentiation processes basically end in the prenatal period, and further development is associated mainly with growth characteristics. individual bodies. In recent decades, it has been convincingly shown that this is not the case: many tissues of the body continue to develop, including through differentiation processes, until the completion of puberty. The period of maturation of excitable tissues - nervous and muscular - is especially long.

Quantitative and qualitative changes in the activities of fi biological systems. Growth processes inevitably lead to changes in volumetric characteristics in the activity of almost all physiological systems of the body. So, it is quite obvious that in order to maintain the required level of supply of tissues of a growing organism with oxygen and nutrients, with a twofold increase in body weight, approximately the same increase in the mass of circulating blood, the size of the heart, blood-forming organs, etc. is necessary. The same proportions add up in other functional systems Oh. But all this is true only if the principles of organization of the physiological process do not change. If we assume that tissues undergo such qualitative changes that allow them to more fully extract oxygen and nutrients from the blood (which actually happens in the process of ontogenesis), then the need for blood circulation per unit body weight will decrease with age.

All physiological functions are somehow related to the size of the body. But at the same time, some of them change in ontogenesis in proportion to changes in body weight, while others change in proportion to changes in body surface area. If, in the course of development, one or another function demonstrates a change that is disproportionate to the mass or surface area, then this indicates a qualitative transformation of the mechanisms for implementing this function. Growth processes lead, as a rule, to quantitative, proportional changes. Differentiation processes can lead to the appearance of qualitative, disproportionate changes in the activity of the physiological systems of the body. This simple consideration underlies the widespread use of relative indicators in age physiology, i.e. expression of the activity of one or another physiological function in relation to body weight or its surface area. This technique makes it possible to visually see and distinguish between the stages of a quantitative increase in the capabilities of physiological systems and the stages of their qualitative transformations.

Energy costs in the process of growth and development. It is widely believed that growth processes require large amounts of energy. With this, some researchers associated an increased level of metabolism in the tissues of the child's body. However, accurate measurements carried out in the 1970-1980s showed that even during the period of the most intensive growth, no more than 4-5% of daily energy consumption is spent on this. Thus, the change in the size and proportions of the body that is visible to the eye is actually a fairly easy (from the point of view of the energy of the body) process to be implemented. The situation is quite different with the differentiation processes that determine the dynamics of the qualitative development of the organism. The number of syntheses that occur in the process of differentiation may not be so large, but their energy "price" is much higher. This is due to the fact that in the process of growth syntheses, ready-made, well-established metabolic pathways are used,

while differentiation processes require the organization of new metabolic pathways and a wide range of enzyme systems, which are necessary only at narrowly defined stages of the process. It has been experimentally shown that during periods when the growth of the organism slows down, which means that differentiation processes are activated, the intensity of basal metabolism increases significantly, i.e., those energy costs that are not associated with the implementation of any specific functions.

The concept of "growth spurt". In cases where growth processes are simultaneously observed in many different tissues of the body, phenomena of the so-called "growth spurts" are noted. First of all, this is manifested in a sharp increase in the longitudinal dimensions of the body due to an increase in the length of the trunk and limbs. In human postnatal ontogenesis, such “jumps” are most pronounced in the first year of life (1.5-fold increase in length and 3-4-fold increase in body weight per year, growth mainly due to body lengthening), at the age of 5-6 years ( the so-called "half-height spurt", as a result of which the child reaches approximately 70% of the adult's body length, growth is mainly due to elongation of the limbs), as well as at 13-15 years old (pubertal growth spurt due to both the lengthening of the body and the lengthening of the limbs ).

For the first time, the growth spurt became known from the studies of Count F. de Montbeilard, who in 1759-1777. observed the development of his son, weighing him every six months. These results were first published by Buffon in an appendix to his Natural History. On fig. 1 clearly shows a sharp increase in the growth rate in the period from 12 to 16 years (pubertal jump), and also shows a slowdown in the decrease in the rate of growth processes in the period from 6 to 8 years (half-growth jump). Subsequently, numerous researchers confirmed the reality of these two key moments in development, when the growth rate increases in contrast to the age-related tendency to decrease it.

As a result of each growth spurt, body proportions change significantly, more and more approaching adults. In addition, quantitative changes, expressed in an increase in body length and a change in its proportions, are necessarily accompanied by qualitative changes in the functioning of the most important physiological systems, which must be “tuned” to work in a new morphological situation. A number of qualitative age-related changes in the functioning of organs and systems is an inevitable consequence of an increase in the size and changes in the proportions of the body in ontogenesis: the organization of function that has developed at the previous stage of ontogenesis is not able to provide a stable process under new conditions, therefore, its more or less significant restructuring is required.

The alternation of periods of growth and differentiation serves as a natural biological marker of the stages of age development, at each of which the organism has specific features never found in the same combination at any of the other stages. This implies the need to always correlate the analysis of the state of the body (both morphologically and functionally with a specific stage of age development. In other words, the stages of ontogenesis are not an abstraction invented by scientists to facilitate analysis; but a completely real sequence of events that invariably repeats itself in the development of each individual.

The processes of growth and development are general biological properties of living matter. The growth and development of a person, starting from the moment of fertilization of the egg, is a continuous progressive process that takes place throughout his life. The process of development proceeds in leaps and bounds, and the difference between individual stages, or periods of life, is reduced not only to quantitative, but also to qualitative changes.

Availability age features in the structure or activity of certain physiological systems can in no way be evidence of the inferiority of the child's body at certain age stages. This or that age is characterized by a complex of similar features.

Development in the broad sense of the word should be understood as the process of quantitative and qualitative changes occurring in the human body, leading to an increase in the complexity of the organization and interaction of all its systems. Development includes three main factors: growth, differentiation of organs and tissues, shaping (the acquisition by the body of characteristic, inherent forms). They are closely interconnected and interdependent.

One of the main physiological features of the developmental process, which distinguishes a child's body from an adult's body, is height, i.e., a quantitative process characterized by a continuous increase in the mass of an organism and is accompanied by a change in the number of its cells or their size.

In the process of growth, the number of cells, body mass and anthropometric indicators increase. In some organs and tissues, such as bones, lungs, growth is carried out mainly due to an increase in the number of cells, in others (muscles, nervous tissue), the processes of increasing the size of the cells themselves predominate. This definition of the growth process excludes those changes in body weight and size that may be due to fat deposition or water retention. A more accurate indicator of the growth of an organism is an increase in its total amount of protein and an increase in bone size.

Growth is quantitative changes in the body, which have a measure of measurement (kg, m, cm)

Development - these are qualitative changes in the body that do not have a measure of measurement (estimated or measured) relative to the group in which the child is).

Differentiation processes, or differentiation, are the emergence of specialized structures of a new quality from poorly specialized progenitor cells. The least specialized can be considered a zygote - a germ cell formed as a result of the fusion of the mother's egg with the father's sperm. The first stages of zygote development are a simple increase in the number of cells indistinguishable from each other - first the zygote is divided into 2, then each of them by 2 more, i.e. 4 cells are formed, then 8, 16, 32, etc. These embryonic cells are called blastomeres, they look like two drops of water. However, already at the stage of 32 blastomeres, some features of individual cells associated with their location begin to be revealed.

In recent decades, it has been convincingly shown that differentiation processes do not end in the prenatal period: many tissues of the body continue to develop, including through differentiation processes, until the completion of puberty. Especially long is the period of maturation of excitable tissues - nervous and muscular.

Growth processes lead, as a rule, to quantitative, proportional changes.

Differentiation processes can lead to the appearance of qualitative, disproportionate changes in the activity of the physiological systems of the body.

Energy costs in the process of growth and development. Even during the period of the most intensive growth, no more than 4–5% of daily energy consumption is spent on growth processes. Visible to the eye, a change in the size and proportions of the body is actually a fairly easy (from the point of view of the energy of the body) process to be implemented. The situation is quite different with the differentiation processes that determine the dynamics of the qualitative development of the organism. The number of syntheses that occur in the process of differentiation may not be so large, but their energy "price" is much higher. This is due to the fact that in the process of growth syntheses, ready-made, well-established metabolic pathways are used, while differentiation processes require the organization of new metabolic pathways.

Quantitative and qualitative changes in the activity of physiological systems. All physiological functions, one way or another, are related to the size of the body. But at the same time, some of them change in ontogenesis in proportion to changes in body weight, while others change in proportion to changes in body surface area. If, in the course of development, one or another function demonstrates a change that is disproportionate to the mass or surface area, then this indicates a qualitative transformation of the mechanisms for implementing this function.

The alternation of periods of growth and differentiation serves as a natural biological marker of the stages of age development, at each of which the organism has specific features. In other words, the stages of ontogenesis are not an abstraction, but a completely real sequence of events, invariably repeating in the process of development of each individual.

Growth and development proceed more intensively, the younger the child: growth at birth doubles by 4.5-5 years; triples by 14-15 years; at primary school age, the body length increases by an average of 4-5 cm. During puberty, the annual length increase is 6-8 cm.

It is based on the pattern of spasmodic development, when the gradual accumulation of quantitative changes at a certain moment passes into a new qualitative state (the appearance of perfect coordination of movements, more increased attention, interest in the environment).

Ontogeny - it is the process of individual development of an organism from the moment of its inception to death. Ontogeny is divided into two periods: embryonic and postembryonic.

Phylogeny - it is a process of historical development of wildlife and individual groups of its constituent organisms.

The growth and development of a person, starting from the moment of fertilization of the egg, is a continuous progressive process that takes place throughout his life. The process of development proceeds spasmodically, and the difference between the individual stages, or periods of life, is reduced not only to quantitative, but also to qualitative changes.

Under development in the broad sense of the word, one should understand the process of quantitative and qualitative changes occurring in the human body, leading to an increase in the levels of complexity of the organization and the interaction of all its systems. Development includes three main factors: growth, differentiation of organs and tissues, shaping (the acquisition by the body of characteristic, inherent forms). They are closely interconnected and interdependent.

In the process of growth, the number of cells, body mass and anthropometric indicators increase. In some organs and tissues, such as bones, lungs, growth is carried out mainly due to an increase in the number of cells, in others (muscles, nervous tissue), the processes of increasing the size of the cells themselves predominate. This definition of the growth process excludes those changes in body weight and size that may be due to fat deposition or water retention. A more accurate indicator of body growth is an increase in the total amount of protein in it and an increase in bone size.

Important patterns of growth and development of children include unevenness and continuity of growth and development, heterochrony, phenomena of advanced maturation of vital functional systems, reliability of a biological system.

Under the reliability of a biological system, it is customary to understand such a level of regulation of processes in the body, when their optimal flow is ensured with emergency mobilization of reserve capabilities and interchangeability, which guarantees adaptation to new conditions, and with a quick return to the initial state. According to this concept, the entire path of development from conception to the natural end takes place with a supply of life opportunities. These reserve capabilities ensure the development and optimal course of life processes under changing environmental conditions.

PK Anokhin put forward the doctrine of heterochrony (uneven maturation of functional systems) and the doctrine of systemogenesis that follows from it. According to his ideas, a functional system should be understood as a broad functional association of variously localized structures on the basis of obtaining the final adaptive effect that is necessary at the moment (for example, the functional system of the act of sucking, the functional system that ensures the movement of the body in space, etc.).

Functional systems mature unevenly, turn on in stages, change, providing the body with adaptation in different periods of ontogenetic development.

Systemogenesis as a general pattern of development is especially clearly revealed at the stage of embryonic development. However, heterochronous maturation, gradual inclusion and change of functional systems are also characteristic of other stages of individual development.

1.4. Age periodization
and characteristics of the age periods of the child

Age periodization includes the following steps:

I - newborn - 1-10 days;

II - infancy - 10 days - 1 year;

III - early childhood - 1-3 years;

IV - the first childhood - 4-7 years;

V - second childhood - 8-12 years old boys, 8-11 years old girls;

VI - adolescence - 13-16 years old boys, 12-15 years old girls;

VII - adolescence - 17-21 years old boys, 16-20 years old girls;

VIII - the period of maturity: the first mature - 21-35 for men, 20-35 for women, the second mature - 35-60 for men, 35-55 for women;

IX- elderly age- 55-75 for women, 60-75 for men.

X - senile age - 75-90 years;

XI - the age of centenarians after 90 years.

In the neonatal period, in infancy and in the first year of early childhood, the child undergoes accelerated shaping and maturation of the nervous structures of the brain. The improvement of the structure leads to a functional leap: the growth of the child's cognitive abilities both in the period of early and first childhood.

By the time the child enters school, the period of the first childhood ends. Morphological and functional prerequisites are being created for familiarization with new, complex forms of worldview and learning. school period turns out to be the most saturated with age-related jumps in the development of the child.

During the period of the second childhood (primary school age), the morphological differentiation of the cells of the cerebral cortex is completed, conditions are created for the higher forms of the analytical-synthetic function of the brain. From 8-9 years old in girls and from 10-11 years old in boys, prepubertal changes begin, preceding the period of puberty.

Puberty in girls it lasts from 12 to 15, in boys - from 13 to 16 years. The pubertal period is accompanied by the most intensive rates of development of the organism, complex morphofunctional rearrangements associated with the preparation for the reproductive function. In this period, the highest growth rates and an increase in body weight are also noted.

In the pubertal period, there is an abrupt change in both the structure and function of individual organs and systems (pubertal leap). In boys, the puberty jump is observed between 12.5-15.5 years; in girls - between 10.5-13.5 years. The maximum growth spurt in boys in this period is about 10 cm, in girls - 8-9 cm. The growth spurt occurs mainly due to the lengthening of the torso. Three months after the growth spurt, there is a sharp increase muscle mass, and after six months - an increase in body weight. Spasmodic changes are also noted in the size of internal organs - the heart, liver, stomach.

Pubertal jumps are associated with the intensive development of the reproductive system. From the age of 12.5, there is an accelerated growth of the external genital organs in boys. At the same time, they also have pronounced secondary sexual characteristics (growth of pubic hair). Two years later, hair appears in the armpit and on the face, the cartilage of the larynx grows and the voice breaks down.

In girls, the first signs of puberty are characterized by swelling of the nipple area, although the appearance of pubic hair may precede this. The first menstruation coincides with the end of the maximum rate of body growth in length. Within a year after the first menstruation, a period of relative infertility is observed, since menstruation is not always preceded by the release of an egg from the ovary. The puberty jump is the result of an increase in hormonal function in the hypothalamus - pituitary gland - adrenal glands - gonads. Before the onset of puberty, the hypothalamus inhibits the production of gonadotropic hormones from the pituitary gland. Enhanced synthesis of gonadotropins occurs under the influence of the hypothalamic factor, which disinhibits the secretion of gonadotropic hormones (releasing factor). In puberty, girls experience a decrease in the sensitivity of the hypothalamus to sex hormones. Their level becomes insufficient to contain the production of gonadotropic releasing factor. The increase in its production results in an increase in the level of sex hormones in the blood until their excess inhibits the gonadotropic activity of the pituitary gland through the hypothalamus.

Male sex hormones appear in noticeable quantities only in adolescence. In boys during puberty, the sensitivity of the adrenal glands to corticotropic hormones of the pituitary gland increases. As a result, the production of androgenic hormones of the adrenal glands increases.

With the completion of puberty, however, the processes of growth and development do not end. In adolescence, the body continues to grow in length (by 1-2 cm per year), the structural and functional maturation of somatic and vegetative systems is completed.

The period of maturity, when the formation and progressive development of the body practically ends, occurs in women only by the age of 20, in men by the age of 21. Mature age is the age of men from
21 to 60 years of age and women from 20 to 55 years of age. The very name of the period of maturity contains the idea of the completion of functional and morphological rearrangements.

In adulthood, two periods are distinguished: the period of prosperity and stability of body functions (from 20–21 years to 35 years) and the period of initial involution (35–60 years for men and 35–55 years for women).

The elderly (from 60 to 75 years for men and from 55 to 75 years for women) are characterized by an accelerated development of involutional rearrangements and a decrease in adaptation reserves. One of the main signs of aging of the body is a decrease in the level of basic metabolism. In humans, by about the age of 60, a decrease in basal metabolism leads to starvation of cells and tissues. The morphological prerequisite for a decrease in basal metabolism is a decrease in the absolute number of mitochondria. So, in a person aged 50 to 70 years, it decreases by 30-35% in liver cells.

After 75 years, old age sets in. The level of all physiological functions decreases sharply, the body's resistance decreases, typical diseases of old age - atherosclerosis, coronary and hypertension diseases - receive a favorable morphological basis.

The age after 90 years is called the age of centenarians. In this period, the phenomena of aging become aggravated, the probability of sudden death sharply increases.

Chapter 2. AGE ANATOMY
AND PHYSIOLOGY OF THE NERVOUS SYSTEM

The human body is a complex system of numerous and closely interconnected elements, united in several structural levels. The processes of growth and development are general biological properties of living matter. The growth and development of a person, starting from the moment of fertilization of the egg, is a continuous progressive process that takes place throughout his life.

The development process proceeds in leaps and bounds. The difference between individual stages, or periods of life, comes down not only to quantitative, but also to qualitative changes.

The presence of age-related features in the structure or activity of certain physiological systems can in no way be evidence of the inferiority of the child's body at certain age stages. This or that age is characterized by a complex of similar features.

Under development understand the qualitative changes in the child's body, which consist in the complication of its organization, ᴛ.ᴇ. in the complication of the structure and function of all tissues and organs, the complication of their relationships and the processes of their regulation.

Development includes three basic factors:

differentiation of organs and tissues

shaping (the acquisition by the body of characteristic, inherent forms.)

One of the basic physiological features of the developmental process that distinguishes a child's body from an adult's body is height , ᴛ.ᴇ. , a quantitative process characterized by a continuous increase in the length, volume and body weight of children and adolescents, associated with an increase in the number of cells and their number.

In the process of growth, the number of cells, body mass and anthropometric indicators increase. In some organs and tissues, such as bones, lungs, growth is carried out mainly due to an increase in the number of cells, in others (muscles, nervous tissue) the process of increasing the size of the cells themselves predominates. This definition of the growth process excludes those changes in body weight and size that are due to fat deposition or water retention. A more accurate indicator of the body's growth is an increase in the total amount of protein in it and an increase in bone size.

Height- these are quantitative changes in the body that have a measure of measurement (kg, m, cm)

Development- these are qualitative changes in the body that do not have a measure of measurement (estimated or measured) relative to the group in which the child is).

The growth and development of the child, ᴛ.ᴇ. Quantitative and qualitative changes are closely interconnected with each other. Gradual quantitative and qualitative changes that occur during the growth of the organism lead to the appearance of new qualitative features in the child.

Along with the harmony of development, there are special stages of the most abrupt spasmodic physiological transformations.

In postnatal development, there are three such ʼʼcritical periodsʼʼ or ʼʼage crisisʼʼ.

An important biological feature in the development of a child is that the formation of their functional systems occurs much earlier than they need.

The principle of advanced development of organs and functional systems in children and adolescents is a kind of "insurance" that nature gives to a person in case of unforeseen circumstances.

Development leads to morphological and functional changes, and growth leads to an increase in the mass of tissues, organs and the whole body. In the normal development of the child, both these processes are closely interrelated.

Important patterns of growth and development of children include uneven and continuous growth and development, heterochrony, and the phenomena of advanced maturation of vital functional systems.

The main patterns of growth and development:

Continuity

Unevenness (variability)

Heterochronism.

Individual pace of development / taking into account individual and age characteristics of development.

Based on the richest factual material of age-related morphology and physiology, which is the natural scientific basis for the physiology and hygiene of children and adolescents, the laws of growth and development of the child's body have been established. These patterns apply both to the organism as a whole and to the development of its individual organs and tissues.

The younger the child's body, the more intense the processes of growth and development proceed in it.

‣‣‣ A feature of the modern generation is heterochronous development.

‣‣‣ Heterochrony is the uneven development of a person's mental functions throughout life. For example, in the period of early adulthood (18-21 years), the level of some functions increases (the volume of the visual field, the eye, the constancy of recognition, differentiated recognition, spatial representation, attention), while others decrease (visual acuity, short term memory), the level of thirds remains stable (observation). After 30-35 years, there is a gradual decrease in non-verbal functions, as for verbal ones, it is from this period that they progress most intensively, reaching high level after 40-45 years.

Heterochronism manifests itself in three forms:

‣‣‣ a) Retardation is a process of slow development or lagging behind in the pace of development compared to their peers.

‣‣‣ b) The average rate of development.

‣‣‣ c) Acceleration is a process of advancing or accelerated development in comparison with their peers.