The meaning of life lies in the constant reproduction of species. The growth of the organism and the development of the organism are the most important elements in the formation of a living individual. What are the characteristics of these processes? Do scientists single out separate patterns of development and growth? The answers to these and many other questions will be provided in the article.

What is growth?

By growth, biologists mean the process of increasing the mass of an organism in the process of its development. Already in the definition is the first relationship between the development of the organism and the growth of the organism.

Growth is the most important and necessary process. Without it, the body would have remained an unfertilized egg. The process under consideration is influenced by many of the most various factors. In particular, here it is worth highlighting:

• an increase in the number and size of cells;
• the growth of waste products - non-cellular substances.

A special shift takes place in the volume of substances. Conditions appear that favor the flow of water, synthesis, and deposition of intercellular substance. All of these factors also point to a growth process.

What are the features of the growth and development of the human body? Biologists distinguish two forms of growth: unlimited and limited. In the first case, growth does not stop until biological death. The limited process of growth is finite - however, each organism is different.

What is development?

If growth can be called a quantitative change in the body, in which the number of cells increases, then development is a qualitative change. There is a process of synthesis of new compounds, through differentiation various cells are formed.

One should not think that the growth of an organism and the development of an organism are exclusively incremental processes. In the animal world a large number of species can also be subject to negative processes, that is, degradation. It is important to understand that growth is, first of all, change. Separate parts of the body are lost and new ones are added. With positive developmental processes, synthesis is more active than decay. In this case, the predominance of the decay process over synthesis is called aging. For most of life in the body of a living being, the processes of decay and synthesis are balanced. However, only cell organelles are subject to constant renewal.

unicellular organisms

How do the growth of an organism and the development of an organism correlate in unicellular creatures? AT this case there is one interesting feature. A unicellular organism can live exactly as long as one cell can live. However, bacteria and protists are creatures that are too volatile, and therefore subject to mutation processes. Unicellular organisms exchange genetic material with each other. Because of this, the process of cell development becomes optional.

How long does one particular single-celled organism live? It all depends on the received hereditary information. The creature needs protein synthesis. A new protein is the guarantee of a new function. In this case, the function can lead both to an increase in viability and to harm to the body. In the latter case, the organism becomes less capable of life and dies.

Multicellular organisms

In the case of organisms containing many cells, the situation is somewhat more complicated. It is immediately worth noting that a multicellular creature is more adapted to life than a unicellular one. It has many more features, plus there is no isolation. The significance of the growth and development of the organism in this case is especially great. These are the most balanced processes, constantly complementing each other.

At the first stages of development and growth, one cell divides multiple times. The fetus of the body increases in size, after which it is born. The organism of a multicellular creature has a balanced growth and development up to a certain age period. All components and parameters are already embedded in the genome: here are the skin color, and physiological characteristics, and the maximum possible growth. Most living organisms stop developing in the first half of life. However, there are such multicellular organisms that are able to grow constantly. These are, for example, some types of reptiles or amphibians. The crocodile is a simple confirmation of this.

The Importance of Human Growth

The growth and development of the child's human body is maximally balanced, the processes are correlated with each other. However, there is also a small paradox here. It is connected with the social component. So, height is really important for a person. It affects the development of the body, its strengthening. This is the driving factor of reproduction, which has a truly positive evolutionary meaning. However, it contradicts the very existence of the society that man has built. In society, even the most physically undeveloped person is able to raise offspring - and all thanks to intellectual abilities. Therein lies the paradox. Society supports a person, and therefore almost everyone has the opportunity to reproduce.

The difference between man and other animal organisms is truly great. The phenomenon of society plays a particularly important role in this. Today, social processes of growth and development come to the fore, which, however, do not contradict physiological processes.

On the patterns of growth and development of the human body

Human growth factor is a group of protein-type molecules that contribute to the synthesis of cellular DNA. Growth and development are based on a number of patterns. The most important are the principles of continuity and unity. What are they?

The principle of unity of development and growth means that qualitative and quantitative changes in the body will always be balanced. A simple example is the increase in muscle strength when building muscle mass.

The continuity of the growth and development of the organism is an even more important regularity. During the entire period of ontogenesis (individual development), the processes of qualitative and quantitative changes continue uninterrupted. They can be less or more intense, more regressive or progressive. Growth and development can fade, or they can flourish. However, the complete cessation of these processes is possible only with the death of the organism.

Heterochronism and reliability

The principle of heterochrony of development and growth was formed by the famous physiologist Pyotr Kuzmich Anokhin. According to the concept of this scientist, the maturation of different functional systems occurs in a different order. This is necessary for the body to achieve an adaptive and maximally optimal result.

Heterochrony also implies systemogenesis. This is step by step process inclusion and change of different functional systems. Systemogenesis can always be observed in infants. Systems mature first functional type, then - vegetative, and only at the end motor. The newborn must learn to breathe, see and hear, digest food, etc. Only then does the ability to move appear.

Another important principle was formed by the physiologist Hakob Markosyan. It's called reliability. At the heart of a person are the mechanisms that ensure the development and growth of the body. All of them reliably protect a person from dangerous harmful factors. Such mechanisms promote duplication of functions (a pair of eyes, ears, kidneys, lungs, etc.), redundancy (for example, some nerve cells exist as spares), plasticity, etc.

Harmony and heterosensitivity

The principle of harmony of the body was formed by Nikolai Petrovich Gundobin. He argued that all stages of development and growth are interconnected. One stage sets the stage for another. This principle is somewhat similar to the theory of heterochrony. The functional system is the basis for the formation of vegetative organs, and the vegetative system is the basis for the development of movement. In turn, movement presupposes intellectual development. In all this, the physiologist Gundobin observed a certain harmony, and therefore named his principle accordingly.

Finally, many scientists call heterosensitivity, the sensitivity of emerging systems to external influences, the main pattern of growth and development of an organism. The presence or absence of sensitive periods significantly affects the development and growth of a person. A simple example is the lack of communication, which leads to the deterioration of speech.

Sensitive periods should not be confused with periods of crisis and critical. A crisis is a kind of restructuring of the body. The critical period marks the transition from one stage of development to another.

Development periods

There are many classifications by which scientists determine the periods of human development. Embryogenesis and fetogenesis are the stages from the moment of conception to the formation of a zygote. This whole stage takes 9 months. This is followed by the newborn period, lasting 10 days. Infancy takes a period from the first month to one year.

Breast age is replaced by early childhood. Its first period lasts from 1 to 7 years, and the second - from 8 to 12 years. Adolescence ends at age 15 for girls and 17 for boys. This is followed by adolescence, lasting up to 20 years for both sexes.

The first mature age lasts from 22 to 35 years. The second period of maturity ends at 60 years. This is followed by old age, ending at 74 years. Old age stops at the age of 90, after which we can talk about such a phenomenon as longevity.

The physical development of a person is a complex of morphological and functional properties of the body that determine the shape, size, body weight and its structural and mechanical qualities.

Introduction

Signs of physical development are variable. The physical development of a person is the result of the influence of hereditary factors (genotype) and environmental factors, and for a person - the whole complex of social conditions ( phenotype). With age, the value of heredity decreases, the leading role passes to individually acquired features.
The physical development of children and adolescents is associated with growth. Each age period - infancy, childhood, adolescence and youth - is characterized by specific features of the growth of individual parts of the body. In each age period, the child's body has a number of characteristic features that are unique to this age. Between the body of a child and an adult, there are not only quantitative differences (body size, weight), but, above all, qualitative ones.
Currently, there is an acceleration of human physical development. This phenomenon is called acceleration.
In my work, I will try to briefly characterize each of the main stages of individual development of a person.

The main stages of individual human development

When studying human development, its individual and age characteristics in anatomy and other disciplines, they are guided by scientifically based data on age periodization. The scheme of age periodization of human development, taking into account anatomical, physiological, and social factors, was adopted at the VII Conference on Problems of Age Morphology, Physiology, and Biochemistry (1965). It distinguishes twelve age periods (Table 1). Table 1

Individual development, or development in ontogeny, occurs in all periods of life - from conception to death. In human ontogenesis, two periods are distinguished: before birth (intrauterine, prenatal - from the Greek natos - born) and after birth (extrauterine, postnatal).

Prenatal ontogeny

To understand the individual structural features of the human body, it is necessary to get acquainted with the development of the human body in the prenatal period. The fact is that each person has his own individual characteristics of external appearance and internal structure, the presence of which is determined by two factors. This is heredity, traits inherited from parents, as well as the result of the influence of the external environment in which a person grows, develops, studies, works.
In the intrauterine period, from conception to birth, for 280 days (9 calendar months), the embryo (embryo) is located in the mother's body (from the moment of fertilization to birth). During the first 8 weeks, the main processes of the formation of organs and body parts take place. This period is called the embryonic (embryonic), and the body of the future person is the embryo (embryo). From the age of 9 weeks, when the main external human features begin to appear, the body is called a fetus, and the period is fetal (fetal - from the Greek fetus - fetus).
The development of a new organism begins with the process of fertilization (the fusion of sperm and egg), which usually occurs in fallopian tube. Merged sex cells form a qualitatively new unicellular embryo - a zygote that has all the properties of both germ cells. From this moment, the development of a new (daughter) organism begins.
The optimal conditions for the interaction of sperm and egg are usually created within 12 hours after ovulation. The union of the nucleus of the spermatozoon with the nucleus of the ovum leads to the formation in a unicellular organism (zygote) of a diploid set of chromosomes characteristic of a human being (46). The sex of the unborn child is determined by the combination of chromosomes in the zygote and depends on the father's sex chromosomes. If the egg is fertilized by a sperm with the sex chromosome X, then two X chromosomes appear in the resulting diploid set of chromosomes, which are characteristic of the female body. When fertilized by a sperm with a Y sex chromosome, a combination of XY sex chromosomes is formed in the zygote, which is characteristic of the male body.
The first week of embryo development is the period of crushing (division) of the zygote into daughter cells (Fig. 1). Immediately after fertilization, during the first 3-4 days, the zygote divides and simultaneously moves along the fallopian tube towards the uterine cavity. As a result of division of the zygote, a multicellular vesicle is formed - a blastula with a cavity inside (from the Greek blastula - sprout). The walls of this vesicle are formed by two types of cells: large and small. From the outer layer of small cells, the walls of the vesicle are formed - the trophoblast. Subsequently, trophoblast cells form the outer layer of the membranes of the embryo. Larger dark cells (blastomeres) form a cluster - an embryoblast (embryonic nodule, embryo rudiment), which is located medially from the trophoblast. From this accumulation of cells (embryoblast), the embryo and adjacent extraembryonic structures (except for the trophoblast) develop.

Fig.1. A - fertilization: 1 - sperm; 2 - egg; B; C - crushing of the zygote, D - morublastula: 1 - embryoblast; 2 - trophoblast; D - blastocyst: 1-embryoblast; 2 - trophoblast; 3 - amnion cavity; E - blastocyst: 1-embryoblast; 2-amnion cavity; 3 - blastocoel; 4 - embryonic endoderm; 5-amnionitic epithelium - F - I: 1 - ectoderm; 2 - endoderm; 3 - mesoderm.
A small amount of fluid accumulates between the surface layer (trophoblast) and the germinal nodule. By the end of the 1st week of development (6-7th day of pregnancy), the embryo enters the uterus and is introduced (implanted) into its mucous membrane; implantation lasts about 40 hours. The surface cells of the embryo that form the vesicle, the trophoblast (from the Greek trophe - nutrition), secrete an enzyme that loosens the surface layer of the uterine mucosa, which is prepared for the introduction of the embryo into it. The emerging villi (outgrowths) of the trophoblast come into direct contact with the blood vessels of the mother's body. Numerous trophoblast villi increase the surface of its contact with the tissues of the uterine mucosa. The trophoblast turns into a nutrient membrane of the embryo, which is called the villous membrane (chorion). At first, the chorion has villi on all sides, then these villi remain only on the side facing the wall of the uterus. In this place, a new organ develops from the chorion and the uterine mucosa adjacent to it - the placenta (children's place). The placenta is the organ that connects the mother's body with the fetus and provides its nutrition.
The second week of the life of the embryo is the stage when the embryoblast cells are divided into two layers (two plates), from which two vesicles are formed (Fig. 2). From the outer layer of cells adjacent to the trophoblast, an ectoblastic (amniotic) vesicle is formed. An endoblastic (yolk) vesicle is formed from the inner layer of cells (the rudiment of the embryo, the embryoblast). The bookmark ("body") of the embryo is located where the amniotic vesicle is in contact with the yolk sac. During this period, the embryo is a two-layer shield, consisting of two sheets: the outer germinal (ectoderm) and the inner germinal (endoderm).

Fig.2. The position of the embryo and embryonic membranes at different stages of human development: A - 2-3 weeks; B - 4 weeks: 1 - amnion cavity; 2 - the body of the embryo; 3 - yolk sac; 4 - tropholast; B - 6 weeks; D - fetus 4-5 months: 1 - body of the embryo (fetus); 2 - amnion; 3 - yolk sac; 4 - chorion; 5 - umbilical cord.
The ectoderm faces the amniotic sac, and the endoderm is adjacent to the yolk sac. At this stage, the surfaces of the embryo can be determined. The dorsal surface is adjacent to the amniotic vesicle, and the ventral surface to the yolk sac. The trophoblast cavity around the amniotic and vitelline vesicles is loosely filled with strands of cells of the extraembryonic mesenchyme. By the end of the 2nd week, the length of the embryo is only 1.5 mm. During this period, the germinal shield thickens in its posterior (caudal) part. Here, in the future, axial organs (chord, neural tube) begin to develop.
The third week of the life of the embryo is the period of formation of a three-layer shield (embryo). The cells of the outer, ectodermal plate of the germinal shield are displaced towards its posterior end. As a result, a cell ridge (primary streak) is formed, which is elongated in the direction of the longitudinal axis of the embryo. In the head (front) part of the primary strip, cells grow and multiply faster, resulting in a slight elevation - the primary nodule (Hensen's nodule). The location of the primary nodule indicates the cranial (head end) of the body of the embryo.
Rapidly multiplying, the cells of the primary streak and the primary nodule grow to the sides between the ectoderm and endoderm, thus forming the median germ layer - the mesoderm. The cells of the mesoderm located between the sheets of the shield are called the intraembryonic mesoderm, and those that have moved beyond it are called the extraembryonic mesoderm.
Part of the mesoderm cells within the primary nodule grows especially actively forward from the head and tail ends of the embryo, penetrates between the outer and inner sheets and forms a cell strand - the dorsal string (chord). At the end of the 3rd week of development, active cell growth occurs in the anterior part of the outer germ layer - the neural plate is formed. This plate soon bends, forming a longitudinal groove - the neural groove. The edges of the groove thicken, approach and fuse with each other, closing the neural groove into the neural tube. In the future, from the neural tube, the entire nervous system. The ectoderm closes over the formed neural tube and loses contact with it.
In the same period, a finger-like outgrowth, the alantois, penetrates from the back of the endodermal plate of the germinal shield into the extraembryonic mesenchyme (the so-called amniotic stalk), which does not perform certain functions in humans. In the course of the allantois, blood umbilical (placental) vessels sprout from the embryo to the chorion villi. A cord containing blood vessels that connects the embryo to the extra-embryonic membranes (placenta) forms the ventral stalk.
Thus, by the end of the 3rd week of development, the human embryo looks like a three-layer plate, or a three-layer shield. In the region of the outer germ layer, the neural tube is visible, and deeper - the dorsal string, i.e. axial organs of the human embryo appear. By the end of the third week of development, the length of the embryo is 2-3 mm.
The fourth week of life - the embryo, which has the form of a three-layer shield, begins to bend in the transverse and longitudinal directions. The embryonic shield becomes convex, and its edges are delimited from the amnion surrounding the embryo by a deep furrow - the trunk fold. The body of the embryo from a flat shield turns into a three-dimensional one, the ectoderm covers the body of the embryo from all sides.
From the ectoderm, the nervous system, the epidermis of the skin and its derivatives, the epithelial lining of the oral cavity, the anal part of the rectum, and the vagina are further formed. The mesoderm gives rise to internal organs (except endoderm derivatives), the cardiovascular system, the organs of the musculoskeletal system (bones, joints, muscles), and the skin itself.
The endoderm, which is inside the body of the human embryo, rolls up into a tube and forms the embryonic rudiment of the future intestine. The narrow opening connecting the embryonic intestine with the yolk sac later turns into the umbilical ring. The epithelium and all glands are formed from the endoderm. digestive system and respiratory tract.
The embryonic (primary) intestine is initially closed in front and behind. In the anterior and posterior ends of the body of the embryo, invaginations of the ectoderm appear - the oral fossa (future oral cavity) and the anal (anal) fossa. Between the cavity of the primary intestine and the oral fossa there is a two-layer (ectoderm and endoderm) anterior (oropharyngeal) plate (membrane). Between the intestine and the anal fossa there is a cloacal (anal) plate (membrane), also two-layered. The anterior (oropharyngeal) membrane ruptures during the 4th week of development. At the 3rd month, the posterior (anal) membrane breaks.
As a result of bending, the body of the embryo is surrounded by the contents of the amnion - amniotic fluid, which acts as a protective environment that protects the embryo from damage, primarily mechanical (concussion).
The yolk sac lags behind in growth and at the 2nd month of intrauterine development looks like a small sac, and then it is completely reduced (disappears). The ventral stalk lengthens, becomes relatively thin and is later called the umbilical cord.
During the 4th week of development of the embryo, the differentiation of its mesoderm, which began on the 3rd week, continues. The dorsal part of the mesoderm, located on the sides of the chord, forms paired thickened protrusions - somites. Somites are segmented, i.e. divided into metameric regions. Therefore, the dorsal part of the mesoderm is called segmented. Segmentation of somites occurs gradually in the direction from front to back. On the 20th day of development, the 3rd pair of somites is formed, by the 30th day there are already 30 of them, and on the 35th day - 43-44 pairs. The ventral part of the mesoderm is not divided into segments. It forms two plates on each side (non-segmented part of the mesoderm). The medial (visceral) plate is adjacent to the endoderm (primary intestine) and is called the splanchnopleura. The lateral (outer) plate is adjacent to the wall of the body of the embryo, to the ectoderm, and is called the somatopleura.
The epithelial cover of the serous membranes (mesothelium), as well as the lamina propria of the serous membranes and the subserous base, develop from the splanchno- and somatopleura. The mesenchyme of the splanchnopleura also goes to the construction of all layers of the digestive tube, except for the epithelium and glands, which are formed from the endoderm. The space between the plates of the non-segmented part of the mesoderm turns into the body cavity of the embryo, which is subdivided into the peritoneal, pleural and pericardial cavities.

Fig.3. Cross section through the body of the embryo (diagram): 1 - neural tube; 2 - chord; 3 - aorta; 4 - sclerotome; 5 - myotome; 6 - dermatome; 7 - primary intestine; 8 - body cavity (as a whole); 9 - somatopleura; 10 - splanchnopleura.
The mesoderm on the border between the somites and the splanchnopleura forms nephrotomes (segmental legs), from which the tubules of the primary kidney, the sex glands, develop. From the dorsal part of the mesoderm - somites - three rudiments are formed. The anteromedial section of the somites (sclerotome) goes to the construction of skeletal tissue, giving rise to cartilage and bones of the axial skeleton - the spine. Lateral to it lies the myotome, from which it develops skeletal muscle. In the posterolateral part of the somite there is a site - the dermatome, from the tissue of which the connective tissue base of the skin is formed - the dermis.
In the head section on each side of the embryo from the ectoderm on the 4th week, the rudiments of the inner ear (first the auditory pits, then the auditory vesicles) and the future lens of the eye are formed. At the same time, the visceral sections of the head are rebuilt, which form the frontal and maxillary processes around the mouth bay. Behind (caudal) of these processes, the contours of the mandibular and sublingual (hyoid) visceral arches are visible.
Elevations are visible on the anterior surface of the torso of the embryo: cardiac, and behind it - hepatic tubercles. The recess between these tubercles indicates the place of formation of the transverse septum - one of the rudiments of the diaphragm. Caudal to the hepatic tubercle is the ventral stalk, which contains large blood vessels and connects the embryo to the placenta (umbilical cord). The length of the embryo by the end of the 4th week is 4-5 mm.

Fifth to eighth weeks

In the period from the 5th to the 8th week of the life of the embryo, the formation of organs (organogenesis) and tissues (histogenesis) continues. This is the time of early development of the heart and lungs, the complication of the structure of the intestinal tube, the formation of visceral arches, the formation of capsules of the sense organs. The neural tube completely closes and expands in the head region (the future brain). At the age of about 31-32 days (5th week), the length of the embryo is 7.5 mm. At the level of the lower cervical and 1st thoracic segments of the body, fin-like rudiments (buds) of the hands appear. By the 40th day, the rudiments of the legs are formed.
At the 6th week (parietal-coccygeal length of the embryo - 12 - 13 mm), the laying of the outer ear is noticeable, from the end of the 6-7th week - the laying of the fingers, and then the toes.
By the end of the 7th week (the length of the embryo is 19-20 mm), eyelids begin to form. Thanks to this, the eyes are outlined more clearly. On the 8th week (the length of the embryo is 28-30 mm), the laying of the organs of the embryo ends. From the 9th week, i.e. from the beginning of the 3rd month, the embryo (parietal-coccygeal length 39-41 mm) takes the form of a person and is called a fetus.

third to ninth months

Starting from three months and throughout the entire fetal period, further growth and development of the resulting organs and body parts occur. At the same time, the differentiation of the external genitalia begins. Nails are laid on the fingers. From the end of the 5th month (length 24.3 cm), eyebrows and eyelashes become noticeable. At the 7th month (length 37.1 cm), the eyelids open, fat begins to accumulate in the subcutaneous tissue. On the 10th month (length 51 cm) the fetus is born.

Critical periods of ontogeny a

In the process of individual development, there are critical periods when the sensitivity of the developing organism to the effects of damaging factors of the external and internal environment is increased. There are several critical periods of development. These most dangerous periods are:
1) the time of development of germ cells - ovogenesis and spermatogenesis;
2) the moment of fusion of germ cells - fertilization;
3) implantation of the embryo (4-8 days of embryogenesis);
4) formation of rudiments of axial organs (brain and spinal cord, spinal column, primary intestine) and formation of the placenta (3-8 weeks of development);
5) the stage of enhanced brain growth (15-20 weeks);
6) formation of the functional systems of the body and differentiation of the urogenital apparatus (20-24th week of the prenatal period);
7) the moment of the birth of the child and the neonatal period - the transition to extrauterine life; metabolic and functional adaptation;
8) the period of early and first childhood (2 years - 7 years), when the formation of relationships between organs, systems and apparatuses of organs ends;
9) adolescence (puberty - in boys from 13 to 16 years, in girls - from 12 to 15 years).
Simultaneously with the rapid growth of the organs of the reproductive system, emotional activity is activated.

Postnatal ontogeny. Neonatal period

Immediately after birth, there is a period called the neonatal period. The basis for this allocation is the fact that at this time the child is fed with colostrum for 8-10 days. Newborns in the initial period of adaptation to the conditions of extrauterine life are divided according to the level of maturity into full-term and premature. Intrauterine development of full-term babies lasts 39-40 weeks, premature babies - 28-38 weeks. When determining maturity, not only these terms are taken into account, but also the mass (weight) of the body at birth.
Newborns with a body weight of at least 2500 g (with a body length of at least 45 cm) are considered full-term, and newborns with a body weight of less than 2500 g are considered premature. In addition to weight and length, other dimensions are taken into account, for example, chest girth in relation to body length and head circumference in relation to chest circumference. It is believed that the girth of the chest at the level of the nipples should be more than 0.5 body length by 9-10 cm, and the girth of the head - more than the girth of the chest by no more than 1-2 cm.

Breast period

The next period - chest - lasts up to a year. The beginning of this period is associated with the transition to feeding "mature" milk. During the breast period, the greatest intensity of growth is observed, in comparison with all other periods of extrauterine life. Body length increases from birth to a year by 1.5 times, and body weight triples. From 6 months milk teeth begin to erupt. In infancy, uneven body growth is pronounced. In the first half of the year, babies grow faster than in the second. In each month of the first year of life, new indicators of development appear. In the first month, the child begins to smile in response to the appeal of adults, at 4 months. persistently tries to stand on legs (with support), at 6 months. tries to crawl on all fours, at 8 - makes attempts to walk, by the year the child usually walks.

Period early childhood

The period of early childhood lasts from 1 year to 4 years. At the end of the second year of life, teething ends. After 2 years, the absolute and relative values ​​of annual body size increases rapidly decrease.

First childhood period

From the age of 4, the period of the first childhood begins, which ends at the age of 7. Starting from the age of 6, the first permanent teeth appear: the first molar (large molar) and the medial incisor on the lower jaw.
The age from 1 year to 7 years is also called the period of neutral childhood, since boys and girls almost do not differ from each other in size and body shape.

second childhood period

The period of second childhood lasts for boys from 8 to 12 years, for girls - from 8 to 11 years. During this period, sex differences in the size and shape of the body are revealed, and an increased growth of the body in length begins. Growth rates in girls are higher than in boys, since puberty in girls begins on average two years earlier. Increased secretion of sex hormones (especially in girls) causes the development of secondary sexual characteristics. The sequence of appearance of secondary sexual characteristics is fairly constant. In girls, the mammary glands first form, then pubic hair appears, then in the armpits. The uterus and vagina develop simultaneously with the formation of the mammary glands. To a much lesser extent, the process of puberty is expressed in boys. Only towards the end of this period do they begin to accelerate the growth of the testicles, scrotum, and then the penis.

Teenage years

The next period - adolescence - is also called puberty, or puberty. It continues in boys from 13 to 16 years old, in girls - from 12 to 15 years old. At this time, there is a further increase in growth rates - the puberty jump, which applies to all body sizes. The greatest increase in body length in girls occurs between 11 and 12 years, in body weight - between 12 and 13 years. In boys, an increase in length is observed between 13 and 14 years, and an increase in body weight between 14 and 15 years. The growth rate of body length is especially high in boys, as a result of which at the age of 13.5-14 they overtake girls in body length. Due to the increased activity of the hypothalamic-pituitary system, secondary sexual characteristics are formed. In girls, the development of the mammary glands continues, there is growth of hair on the pubis and in the armpits. The most clear indicator of puberty of the female body is the first menstruation.
In adolescence, there is an intensive puberty of boys. By the age of 13, their voice changes (mutates) and pubic hair appears, and at 14, hair appears in the armpits. At the age of 14-15, boys have their first wet dreams (involuntary eruptions of sperm).
In boys, compared with girls, the pubertal period is longer and the pubertal growth spurt is more pronounced.

adolescence

Adolescence lasts for boys from 18 to 21 years old, and for girls - from 17 to 20 years old. During this period, the growth process and the formation of the body basically end, and all the main dimensional features of the body reach the definitive (final) value.
In adolescence, the formation of the reproductive system and the maturation of the reproductive function are completed. The ovulatory cycles in a woman, the rhythm of testosterone secretion and the production of mature sperm in a man are finally established.

Mature, elderly, senile age

In adulthood, the shape and structure of the body change little. Between 30 and 50 years, body length remains constant, and then begins to decrease. In the elderly and senile age, gradual involutive changes in the body occur.

Individual differences in the process of growth and development

Individual differences in the process of growth and development can vary widely. The existence of individual fluctuations in the processes of growth and development served as the basis for the introduction of such a concept as biological age, or developmental age (as opposed to passport age).
The main criteria for biological age are:
1) skeletal maturity - (the order and timing of ossification of the skeleton);
2) dental maturity - (terms of eruption of milk and permanent teeth);
3) the degree of development of secondary sexual characteristics. For each of these biological age criteria - "external" (skin), "dental" and "bone" - rating scales and normative tables have been developed to determine the chronological (passport) age by morphological features.

Factors affecting individual development

Factors affecting individual development (ontogenesis) are divided into hereditary and environmental (influence of the external environment).
The degree of hereditary (genetic) influence is not the same at different stages of growth and development. The influence of hereditary factors on the total body size increases from the period of the newborn (tm) to the second childhood, with a subsequent weakening by the age of 12-15.
The influence of environmental factors on the processes of morphofunctional maturation of the body is clearly seen in the example of the timing of menarche (menstruation). Studies of growth processes in children and adolescents in various geographical areas have shown that climatic factors have almost no effect on growth and development, if living conditions are not extreme. Adaptation to extreme conditions causes such a profound restructuring of the functioning of the whole organism that it cannot but affect the growth processes.

Dimensions and proportions, body weight

Among the body sizes, total (from French total - whole) and partial (from Latin pars - part) are distinguished. Total (general) body dimensions are the main indicators of human physical development. These include body length and weight, as well as chest circumference. Partial (partial) dimensions of the body are terms of the total size and characterize the size of individual parts of the body.
Body sizes are determined during anthropometric surveys of various contingents of the population.
Most anthropometric indicators have significant individual fluctuations. Table 2 shows some average anthropometric indicators in postnatal ontogeny.
The proportions of the body depend on the age and gender of the person (Fig. 4). body length and age-related changes are usually individual. So, for example, differences in the body length of newborns during normal pregnancy are in the range of 49-54 cm. The largest increase in the body length of children is observed in the first year of life and averages 23.5 cm. In the period from 1 to 10 years, this indicator gradually decreases by an average of 10.5 - 5 cm per year. From the age of 9, sex differences in growth rate begin to appear. Body weight from the first days of life until about 25 years of age in most people gradually increases, and then remains unchanged.

Fig. 4 Changes in the proportions of body parts in the process of human growth.
KM - the middle line. The numbers on the right show the ratio of body parts in children and adults, the numbers below show the age.
table 2
Length, mass and body surface area in postiatal orthogenesis



Table 2
After the age of 60, body weight usually begins to gradually decrease, mainly as a result of atrophic changes in tissues and a decrease in their water content. The total body weight consists of a number of components: the mass of the skeleton, muscles, fatty tissue, internal organs and skin. In men, the average body weight is 52-75 kg, in women - 47-70 kg.
In the elderly and senile age, characteristic changes are observed not only in the size and weight of the body, but also in its structure; these changes are studied by the special science of gerontology (gerontos - old man). It should be especially emphasized that active image life, regular physical education oh slow down the aging process.

Acceleration

It should be noted that over the past 100-150 years there has been a noticeable acceleration in the somatic development and physiological maturation of children and adolescents - acceleration (from Latin acceleratio - acceleration). Another term for the same trend is "epochal shift". Acceleration is characterized by a complex set of interrelated morphological, physiological, and mental phenomena. To date, morphological indicators of acceleration have been determined.
Thus, the length of the body of children at birth over the past 100-150 years has increased by an average of 0.5-1 cm, and the weight - by 100-300 g. During this time, the mass of the placenta in the mother has also increased. There is also an earlier alignment of the ratios of chest and head girths (between the 2nd and 3rd month of life). Modern one-year-old children are 5 cm longer and 1.5-2 kg heavier than their peers in the 19th century.
Children's body length preschool age over the past 100 years has increased by 10-12 cm, and for schoolchildren - by 10-15 cm.
In addition to an increase in body length and weight, acceleration is characterized by an increase in the size of individual parts of the body (segments of limbs, thickness of skin-fat folds, etc.). Thus, the increase in chest girth in relation to the increase in body length was small. The onset of puberty in modern adolescents occurs about two years earlier. The acceleration of development also affected motor functions. Modern teenagers run faster, jump further from a place, pull themselves up on the crossbar (horizontal bar) more times.
Epochal shift (acceleration) affects all stages of human life, from birth to death. For example, the length of the body of adults also increases, but to a lesser extent than in children and adolescents. So, at the age of 20-25 years, the body length of men increased by an average of 8 cm.
Acceleration covers the entire body, affecting the size of the body, the growth of organs and bones, the maturation of the sex glands and the skeleton. In men, changes in the process of acceleration are more pronounced than in women.
Men and women are distinguished by sexual characteristics. These are primary signs (genital organs) and secondary (for example, the development of pubic hair, the development of the mammary glands, a change in voice, etc.), as well as body features, proportions of body parts.
The proportions of the human body are calculated as a percentage according to the measurement of the longitudinal and transverse dimensions between the boundary points set on various protrusions of the skeleton.
The harmony of body proportions is one of the criteria for assessing the state of human health. With disproportion in the structure of the body, one can think of a violation of growth processes and the causes that caused it (endocrine, chromosomal, etc.). Based on the calculation of body proportions in anatomy, three main types of human physique are distinguished: mesomorphic, brachymorphic, dolichomorphic. The mesomorphic body type (normosthenics) includes people whose anatomical features approach the average parameters of the norm (taking into account age, gender, etc.). In people of the brachymorphic body type (hypersthenics), transverse dimensions predominate, muscles are well developed, they are not very tall. The heart is located transversely due to the high-standing diaphragm. In hypersthenics, the lungs are shorter and wider, the loops of the small intestine are located mainly horizontally. Persons of dolichomorphic body type (asthenics) are characterized by a predominance of longitudinal dimensions, have relatively longer limbs, poorly developed muscles and a thin layer of subcutaneous fat, and narrow bones. Their diaphragm is lower, so the lungs are longer, and the heart is located almost vertically. Table 3 shows the relative sizes of body parts in humans different types physique.
Table 3

Conclusion

What can be the conclusion of the above?
Human growth is uneven. Each part of the body, each organ develops according to its own program. If we compare the growth and development of each of them with a long-distance runner, then it is not difficult to find that during this many years of "running" the leader of the competition is constantly changing. In the first month of embryonic development, the head is in the lead. In a two-month-old fetus, the head is larger than the body. This is understandable: the brain is located in the head, and it is the most important organ that coordinates and organizes the complex work of organs and systems. The development of the heart also begins early, blood vessels and liver.
In a newborn baby, the head reaches half of its final size. Up to 5-7 years of age, there is a rapid increase in body weight and length. At the same time, the arms, legs and torso grow alternately: first, the arms, then the legs, then the torso. The size of the head during this period increases slowly.
At primary school age from 7 to 10 years, growth is slower. If earlier arms and legs grew more quickly, now the torso becomes the leader. It grows evenly, so that the proportions of the body are not violated.
In adolescence, the hands grow so intensively that the body does not have time to adapt to their new size, hence some clumsiness and sweeping movements. After that, the legs begin to grow. Only when they reach their final size does the torso join in the growth. First, it grows in height, and only then begins to grow in width. During this period, the physique of a person is finally formed.
If we compare the body parts of a newborn and an adult, it turns out that the size of the head has only doubled, the torso and arms have become three times larger, while the length of the legs has increased five times.
An important indicator of the development of the body is the appearance of menstruation in girls and wet dreams in boys, it indicates the onset of biological maturity.
Along with the growth of the body is its development. Human growth and development different people occur at different times, so anatomists, doctors, physiologists distinguish between calendar age and biological age. Calendar age is calculated from the date of birth, biological age reflects the degree of physical development of the subject. The last one is different for each person. It may happen that people who are at the same biological age may differ by 2-3 years on the calendar, and this is completely normal. Girls tend to develop faster.

Literature

1. Medical scientific and educational journal No. 28 [October 2005]. Section - Lectures. Title of the work - PERIODS OF CHILDHOOD. Author - P.D. Vaganov
2. Vygotsky L.S. Collected works in 6 volumes. Volume 4
3. Vygotsky L.S. article "Problems of age periodization of child development"
4. Obukhova L.F. textbook "Children's (age) psychology". Fundamental and clinical physiology / Ed.A.G. Kamkin and A.A. Kamensky. - M.: "Academy", 2004.
5. Schmidt R., Tews G. Human Physiology: Per. from English. - M.: Mir, 1996.
6. Dragomilov A.G., Mash R.D. Biology: Man. - 2nd ed., revised. - M.: Ventana-Graf, 2004.
7. Sapin. M.R., Bryksina Z.G. Anatomy and physiology of children and adolescents: Proc. allowance for students. ped. universities. - M.: Publishing center "Academy", 2002.
8. Chusov Yu.N. Human Physiology: Proc. allowance for ped. Schools (special No. 1910). - M.: Enlightenment, 1981.
9. Encyclopedia "Round the World"
10. "Rusmedservice"
11. Encyclopedia "Wikipedia"

Tasks
Physical culture, grade 6

In all matters only one correct answer.

Teacher physical culture Musin A.N.

The formation of the human body ends by:

14-15 years old

17-18 years old

19-20 years old

22-25 years old

Athletics - including:

running, walking, jumping, throwing

running, swimming, jumping

rhythmic gymnastics, football

volleyball basketball

Alina Kabaeva is famous:

figure skater

gymnast

swimmer

tennis player

Short distance running refers to:

sprint

sports games

weightlifting

bobsleigh

In what game is a volleyball used?

football

pioneer ball

basketball

handball

Name the winter Olympic sport, which is a downhill skiing from the mountains along specially equipped ice tracks on a controlled sleigh.

bobsled

luge

short track

curling

What is the name of the game of football on motorcycles?

motofoot

motoball

bikefoot

footmotoball

In 2006, he became the best football player according to the most authoritative sports publications in the country - the weekly "Football", the newspapers "Sport-Express" and "Soviet Sport". Who is it?

Evgeni Plushenko

Andrey Arshavin

Marat Safin

Alexander Ovechkin

In 2014 Minsk hosted the Ice Hockey World Championship. The team became world champions:

Sweden

Canada

Russia

Finland

It is believed that this man founded the Olympic Games after defeating King Augeus.

Hades

Poseidon

Hercules

Hermes

What is the name of the residential complex for athletes, participants in the Olympic Games?

Olimpic village

sports town

Championship village

Glade of champions

13. What color is the fabric of the Olympic flag?

White

yellow

Red

blue

14. At the Olympic Games in Sochi there were representatives from:

88 countries

50 countries

106 countries

37 countries

15. The total number of medals won by Russian athletes at the Olympic Games in Sochi was:

ANSWERS:

1. Answer: The formation of the human body ends by the age of 22-25. During periods of growth and development of the body, the mass and surface of the body increase, which is due to the development of tissues, organs and individual parts of the body. At the same time, the functions of organs and systems develop.

2. Answer: Athletics - including running, walking, jumping and throwing. Combines the following disciplines: , (road running) and (cross country running). One of the main and most popular sports.

3. Answer: Alina Kabaeva - gymnast, Honored Master of Sports. She is the only gymnast in the world listed in the Guinness Book of Records, since at the age of 15 she became the absolute champion of Europe among adults.

4. Answer: Golf (English golf) is a sports game in which individual participants or teams compete by driving a small ball into special holes with clubs, trying to cover the allotted distance in the minimum number of strokes.

5. Answer: Sprint is a type of running performed at a very fast pace and only for short distances (up to 400 meters).

6. Answer: Pioneerball is a sports ball game similar in rules to. The game is played from to .

7. Answer: A winter Olympic sport, which is a downhill from the mountains along specially equipped ice tracks on a controlled bobsled. The birthplace of bobsleigh is Switzerland.

8. Answer: Motoball - one of the types of motorsport, is a game in on. The game is played on a field the size of a football field, but with slight differences in layout: there is no central circle, the goal area has the shape of a semicircle. The surface of the field is usually not dirt, but asphalt. They play with a ball, the size of which is much larger than a football. Each team has 5 people - a goalkeeper and 4 field players on motorcycles., second . In 2006, he became the best football player according to the most authoritative sports publications in the country - the weekly "Football", the newspapers "Sport-Express" and "Soviet Sport".

10. Answer: In 2014 Minsk hosted the Ice Hockey World Championship. The Russian team became the world champion, having beaten the Finnish team in the final match with a score of 5:2.

11. Answer: It is believed that the Olympic Games were founded by Hercules after completing his sixth feat - cleansing the barnyard of Avgeas, king of Elis. Augeas possessed incalculable riches. His herds were especially numerous. Hercules agreed to cleanse the entire huge courtyard of Avgius in one day if he would give him a tenth of his herds. Avgiy accepted the offer of help, believing that it was simply impossible to complete such work in one day. When Hercules completed the task and came to Avgiy to demand a reward, the king did not give him anything, and even kicked him out. Hercules took terrible revenge on the king of Elis. With a large army, he invaded Elis, defeated Augeas in a bloody battle and killed him with a deadly arrow. After the victory, Hercules gathered the army and all the booty, made sacrifices to the Olympic gods and established the Olympic Games, which have been held since then every four years on the sacred plain planted by Hercules himself with olives dedicated to the goddess Pallas Athena.

12. Answer: The Olympic Village is a complex of buildings where members of the delegations of the countries participating in the Olympic Games are located.

13. Answer: The Olympic flag is a white silk cloth with five interlaced rings of blue, black, red (top row), yellow and green (bottom row) embroidered on it.

14. Answer: There were representatives from 88 countries at the Olympic Games in Sochi.

15. Answer: The Russian team finished their performance at the Sochi Olympics, winning a total of 33 medals: 13 gold, 11 silver and 9 bronze; this result allowed the hosts of the Games to win the team event both in terms of the number of gold medals and the total number of medals.

lesson type- combined

Methods: partially exploratory, problematic presentation, reproductive, explanatory and illustrative.

Goals:

Awareness of life as the highest value, the ability to build one's relationship with nature and society based on respect for life, for all living things as a unique and priceless part of the biosphere;

Versatile development of the personality of students: observation, sustainable cognitive interest, the desire for self-education and the application of acquired knowledge in practice;

Formation of sanitary and hygienic culture, their ecological thinking and morality.

Tasks:

Educational: to have certain eco-logical knowledge and hygienic knowledge - an important component of the culture of each person;

Educational: develop cognitive and practical orientation, freedom and creative thought, general educational skills of working with popular science literature and Internet sources

Educational: to educate students by means of this lesson for the development of a physically and morally healthy human society.

Regulatory: organize your workplace under the guidance of a teacher; determine the plan for the implementation of tasks in the lesson, evaluate the result of their activities.

Communicative: participate in the dialogue in the classroom; answer the questions of the teacher, classmates; listen and understand the speech of others; work in a small group.

Cognitive: navigate in the textbook; to find the necessary information in the text of the educational article.

Planned results

subject

the influence of man on individual components of nature and the influence of nature on all aspects of human activity;

preparing schoolchildren for practical activities in the field of biology, ecology and medicine;

Establishing harmonious relations with nature, with all living things, as the main value on Earth.

basic bioecological terminology and symbols

Personal:

the formation of interest in the global problem, which received the name: "environmental problem", which is associated with the deterioration of the qualitative characteristics of the human environment.

Interdisciplinary: links with such academic disciplines as biology, chemistry, physics, geography - will contribute to a higher level of skills in this course and the implementation of the tasks of pre-profile training for schoolchildren.

Lesson Form- traditional

Technology - problem learning

Basic concepts: zygote, blastula, gastrula, fetus, newborn, breast and toddler period, placenta, uterus, oviduct, ovary, umbilical cord, egg, egg, sperm.

Learning new material

The development of the human body

The process of fertilization in higher vertebrates, including humans, occurs in the genitals. This is due to the fact that one or more male spermatozoa introduced into female body, merge with the egg formed in the ovary (sex Gland). Fertilization occurs in the oviduct, where the sperm and egg enter. The oviduct connects the ovary to the uterus, in which further development germ.

The initial stage of development of the human body is characterized by the formation of a zygote of a fertilized egg, which carries a diploid (double) set of chromosomes: one from the egg and the other from the sperm. Each pair of chromosomes is homologous.

I stage of development of the embryo - the blastula is a single-layer multicellular vesicle, which is formed in the oviduct as a result of crushing the zygote.

The 2nd stage of embryo development - gastrula - is characterized by the fact that the fertilized egg moves into the uterus and penetrates into its wall, after which a two-layer embryo is formed from it, which already has two germ layers (layers cells) - endoderm (inner layer) and ectoderm (outer layer). Then comes the mesoderm (layer of cells between the ectoderm and endoderm). From these three sheets, all organ systems are formed. On the side where the dividing egg contacts the wall of the uterus, the embryonic membranes (placenta, bladder) are formed, and on the opposite side, the embryo itself.

In the process of fetal development, the bubble is filled with a watery liquid, the placenta with its villi is introduced into the walls of the uterus. The umbilical cord connects the placenta to the fetus. The fetus develops one circle of blood circulation. "Gill slits, tail, as well as hairline in the early stages of fetal development testify to the common origin of all chordates and confirm the position of the biogenetic law, which states that the individual development of an organism is a brief repetition of the development of a given species by 9 months, the fetus has completely acquired - melts all the features of the human body. Developing in an aquatic environment, it is protected from impacts, moves freely. Through the placenta, the embryo receives oxygen and nutrients from the mother and returns decay products to her. This ends the embryonic stage of development of the human body.

postpartum period characterized by two stages: newborn and breastfeeding

The physiological features of the newborn stage of fetal development are characterized by the presence of non-united bones, which overlap each other, reducing the volume of the head and pelvis, which helps with the birth of a child. When the umbilical cord is ligated, an excess of carbon dioxide is created in the blood, which has a humoral effect on the respiratory center of the medulla oblongata, and as a result, the first reflex movement occurs - inhalation and crying, and then the next innate reflex appears - sucking.

A newborn child has a disproportionate body structure - a very large head and short limbs. The bones of the skull are not fused, between them there are skin films - fontanelles, the pelvic bones are also not fused, the spine has no bends.

The postpartum period of development lasts up to 12 months and is called the thoracic. During this period, the child masters the movements, raises his head, lies on his stomach, stands on his feet, this contributes to the formation of curves on the spine: cervical, thoracic, lumbar. Milk teeth appear. The physiological features of this period are associated with the formation of muscles in a child. Movements become diverse, the skeleton is strengthened, there is a need to walk. In the first period baby mother feeds breast milk, to feed the child food containing vitamins. At this time, the child has an intensive development of higher nervous activity and he begins to pronounce the first words.

nursery child development covers a period of 1 to 3 years. At this time, the proportions of the body change: the volume of the head decreases, the limbs lengthen. In the process of brain development, furrows and convolutions are formed. The physiological features of this period are characterized by the child's need for independence. He switches to eating regular food. Fontanelles in the skull overgrow, articulate speech develops.

Preschool lasts from 3 to 6 years. At this time, milk teeth are replaced by permanent ones, the development of the brain continues. The physiological features of this period are associated with the coordination of the movement of the child, speech is os-mental and is associated with the development of thinking. The conditioned reflex centers of speech and writing are formed.

school period from 6 to 16 years old. In it time runs enhanced development of the musculoskeletal system, body growth, character formation, which ends by the age of 20-25. After 10 years of life, the pelvic bones fuse in a child. In accordance with the peculiarities of the structure of the body, children, adolescents and youthful stages of development are distinguished. Physiological features of the teenage stage (13-15 years) are associated with the presence of restructuring of the body in connection with puberty. The activity of the glands of internal and external secretion changes. This causes psychological changes (the predominance of excitation over inhibition) and physiological changes in the body (secondary sexual characteristics appear: in girls the shape of the body, the timbre of the voice changes, and in boys - the proportions of the body, physical development increases, the voice breaks, hair appears on the face). However, sexual formation ends only by the age of 20-25.

Think and answer. 1. Which of the methods of reproduction appeared later in living organisms (vegetative, sexual, asexual)? 2. How does reproduction of an organism differ from reproduction? 3. What stages of development does the embryo go through and what are their features? 4. What is the role of the placenta and umbilical cord? 5. What characterizes the structure and formation of a child in different periods of its development? 6. What role does labor education, physical development, spiritual growth play in the formation young man?

Explain the meaning of the terms Key words: zygote, blastula, gastrula, fetus, newborn, infancy and toddlerhood, placenta, uterus, oviduct, ovary, umbilical cord, egg, egg, sperm.

Embryogenesis: Developmentgerm

Preschoolperioddevelopmentchild

Agepeculiaritiesschoolage

How do children change from 11 to 16 years old?

Resources:

Anastasova L.P. etc. Man and Environment. Textbook for differentiated learning grade 9. Moscow "Enlightenment" 1997. 320s

Presentation Hosting

The formation of the human body continues after birth (postnatal period) and ends by the age of 22-25. During periods of body growth, the mass and surface of the body increase, which is due to the development of tissues, organs and individual parts of the body. At the same time, the functions of organs and systems develop. Each period is characterized by its own characteristics. There are several schemes of periodization of human development. The most common of them are given in Table. 2.1.

Table 2.1

Age periods of ontogenetic development

Main title	Other names
Intrauterine development (antenatal, prenatal ontogeny)
Embryonic period	embryo development
fetal period	Fetal development
Extrauterine development	Postnatal ontogeny
Neonatal period	neonatal period	Birth to 4 weeks
Breast age	Infancy	4 weeks - 1 year
Early childhood	toddler age
First childhood	preschool age
Second childhood	Adolescence, primary school age	Boys 8-12 years old, girls 8-11 years old
Teenage years	Puberty, senior school age	Boys 13-16 years old, girls 12-15 years old
adolescence
Mature age	Maturity
	Maturity	Men 22-35 years old, women 21-35 years old
		Men 36-60 years old, women 36-55 years old
Elderly age
Senile age
centenarians		90 years and older

This scheme takes into account not only the morphological and physiological characteristics of a person, but also social factors focused on the system of institutions associated with the education of children and the retirement of an adult.

The growth and development of an organism includes the processes during which an adult individual develops from a fertilized egg. Growth - this is an increase in the size of the body and its parts; under the term " development» understand the various functional changes that occur as a result of the growth and improvement of the structure of organs. An increase in the mass and surface of the body is due to the development of tissues (cells and intercellular substance), organs and individual parts of the body. Growth and development is not just an increase in body weight, but also the formation of various functions of the body. At this time, a significant part of the physiological parameters approaches the level characteristic of an adult. For example, the activity of digestive enzymes increases, the sense organs and the nervous system improve, defense mechanisms against infection develop, etc.

The growth and development of the body, its organs and systems from the moment of birth to the onset of maturity proceed heterochronously: periods of growth acceleration alternate with its slowdown. Those organs or their systems that are necessary for the body to grow and develop faster this stage development. So, at the time of birth, a newborn's nutrition system is formed with liquid food - milk (at the same time, the development functional system eating solid food). In the process of growth and development, physiological functions adapt to the characteristics of the existence of the organism, i.e. its individual adaptation to environmental conditions occurs.

Achieving maturity is a long process. Among the higher mammals, a person has the longest childhood, during which the development of the brain and the formation of mental functions - speech, thinking, consciousness; This requires communication with other people. The development of a child is influenced by nutrition, care, climatic and geographical factors, family, school, objects around him, people (children and adults), life events, etc. All this is important not only for the physical development of the child, but also extremely important for the mental development adequate to his age. A child needs not only a favorable environment in the family, the children's team, but also the love of the people closest to him - parents, friends. For him, both excessive attention and abandonment are equally harmful.

The phenomenon has a positive effect on the growth and development of the organism. heterosis(gr. heterosis- transformation), or "hybrid power", which manifests itself in a greater body length, accelerated development, longer life expectancy and a longer reproductive period, and greater resistance to infections. The reasons for the successful combination of genes and their interaction, mainly in first-generation hybrids, have not yet been established. It is known that heterosis is especially common in people whose parents belong to different nationalities and were geographically separated before marriage. From this it is clear that at the present time, when the improvement of means of communication makes it possible to overcome geographical isolation, heterosis begins to play a particularly important role in the evolutionary development of human society.

In related marriages, the opposite phenomenon often occurs: children are poorly developed physically, susceptible to infectious diseases, hereditary disorders often appear, and a short life expectancy is characteristic.