After birth, the child grows rapidly, the mass and length increase, as well as the surface area of the body.

Human growth continues during the first 20-22 years of his life. Then, up to 60-65 years, the body length almost does not change. However, in the elderly and senile age (after 70 years), due to a change in body posture, thinning of the intervertebral discs, flattening of the arches of the feet, the body length decreases annually by 1.0-1.5 cm.

By the end of the first year of a child's life, the body length increases by 21-25 cm. The periods of early and first childhood (1 year - 7 years) are characterized by a rapid decrease in the growth rate.

At the beginning of the second childhood period (8-12 years), the growth rate is 4.5-5.5 cm per year, and then increases. In adolescence (12-16 years), the annual increase in body length in boys is on average 5.8 cm, in girls - about 5.7 cm. In girls, the most intensive growth is observed at the age of 10 to 13 years, and in boys - at 13-16 years old, then growth slows down.

The body weight of a person doubles by the 5-6th month, triples by the end of the 1st year and increases by about 4 times by 2 years after birth. The increase in body length and weight occurs at approximately the same rate. The maximum annual increase in body weight is observed in adolescents: in girls - at the 13th, and in boys - at the 15th year of life. Body weight increases up to 20-25 years, and then stabilizes and usually does not change until 40-46 years. It is considered important and physically justified to keep body weight within the digits of 19-20 years of age.

Over the past 100-150 years, there has been an acceleration of morphofunctional development and maturation of the whole organism in children and adolescents (acceleration). This acceleration is more pronounced in economically developed countries. Thus, the body weight of newborns over the century has increased by an average of 100-300 g, one-year-olds - by 1500-2000 g. The body length has increased by 5 cm. The length of the body of children during the periods of the second childhood and in adolescents increases by 10-15 cm, and in adult men - by 6-8 cm. The time during which the length of the human body increases has decreased. At the end of the XIX century. growth continued until 23-26 years old, at the end of the 20th century. in men, body growth in length occurs up to 20-22 years, and in women - up to 18-20 years. Accelerated eruption of milk and permanent teeth. Mental development and puberty occur faster. At the end of the XX century. compared with its onset, the average age of menarche has decreased from 16.5 years to 12-13 years, and the onset of menopause occurs not at 43 - 45 years, but at 48-50 years.

After birth, during the period of continuing growth of a person, morphofunctional features are noted in each age period.

The newborn's head is round, large, the neck and chest are short - the abdomen is long; legs are short, arms are long. The circumference of the head is 1-2 cm larger than the circumference of the chest, the cerebral region of the skull is relatively larger than the facial one. The chest is barrel-shaped. The spine is devoid of bends, the cape is only slightly pronounced. The bones that form the pelvic bone are not yet fused together. The internal organs are larger than those of an adult. The length of the intestine in a newborn is 2 times the length of the body, in an adult - 4-4.5 times. The mass of the brain in a newborn is 13-14%, and in an adult - about 2% of body weight. The adrenal glands and thymus differ in large sizes in a newborn.

In infancy (10 days-1 year), the child's body grows most rapidly. Approximately from the 6th month, the eruption of milk teeth begins. During the first years of life, the musculoskeletal system, digestive, and respiratory systems grow and develop rapidly.

In the period of early childhood (1-3 years), all milk teeth erupt and the first “rounding” occurs: an increase in body weight outstrips body growth in length. The mental development of the child, speech, memory are rapidly progressing. The child begins to navigate in space. During the 2-3rd year of life, the growth in length prevails over the increase in body weight. In connection with the rapid development of the brain, whose mass reaches 1100-1200 g by the end of this period, mental abilities and causal thinking develop rapidly, the ability to recognize, orientate in time, and days of the week is retained for a long time. In early and first childhood (4-7 years), sexual differences (except for primary sexual characteristics) are almost not expressed. From the age of 6-7 years, the eruption of permanent teeth begins.

In the period of the second childhood (8-12 years), the growth of the body in width again prevails. By the end of this period, the growth of the body in length increases, the rate of which is greater in girls. Progressive mental development. Orientation towards months and calendar days develops. Puberty begins, earlier in girls, which is associated with increased secretion of female sex hormones. In girls at the age of 8-9, the pelvis begins to expand and the hips become rounded, the secretion of the sebaceous glands increases, and pubic hair develops. In boys, at the age of 10-11, the growth of the larynx, testicles and penis begins, which by the age of 12 increases by 0.5-0.7 cm.

In adolescence (12-16 years), the genital organs grow and develop rapidly, secondary sexual characteristics intensify. In girls, the amount of hair on the skin of the pubic region increases, hair appears in the armpits. The size of the genitals, mammary glands increase, the alkaline reaction of the vaginal secretion becomes acidic, menstruation appears, and the size of the pelvis increases. In boys, the testicles and penis grow rapidly. Initially, pubic hair develops according to the female type, the mammary glands swell. By the end of adolescence (15-16 years), hair growth begins on the face, body, in the armpits, and on the pubis - according to the male pattern. The skin of the scrotum is pigmented, the genitals increase even more, the first ejaculations occur (involuntary ejaculation).

In adolescence, mechanical and verbal-logical memory develops.

Adolescence (16-21 years) coincides with the period of maturation of the body. At this age, the growth and development of the organism is basically completed, all apparatuses and organ systems practically reach morphological and functional maturity.

The structure of the body in adulthood (22 years - 60 years) changes little, and in the elderly (61-74 years) and senile (75-90 years) there is a restructuring characteristic of these age periods, which is studied by the special science of gerontology (from the Greek. gerontos - old man). The time limits of aging have wide limits in different individuals. In old age, there is a decrease in the adaptive capabilities of the body, a change in the morphological and functional indicators of all apparatuses and organ systems, among which the most important role belongs to the immune, nervous and circulatory systems.

An active lifestyle, regular physical education slows down the aging process, but this is possible within the limits due to hereditary factors.

Men are distinguished from women by gender. They are divided into primary (genital organs) and secondary (development of pubic hair, mammary glands, voice change, etc.).

Breast age (1st year of life). The first month of life is called the neonatal period. Most of the day the baby sleeps, and his posture resembles the position of the fetus in the uterus. Caring for a newborn requires special cleanliness, maintaining an air temperature of at least 20 ° C and strict adherence to feeding times. Failure to comply with the feeding regime disrupts sleep, leads to indigestion. Harmonious development is ensured by breastfeeding. From the age of two months, vegetable and fruit juices and bait with easily digestible food are needed.
Movement changes. At the end of the first month of life, the child begins to straighten his legs, at the 6th week he raises and holds his head, at 6 months he sits, at the end of the 1st year he makes an attempt to walk.
Mental changes. At the 2nd month, the child begins to smile, by the 4th month he takes toys in his mouth and distinguishes between adults. After 6 months, the child reacts with complex behavior to the presence of the mother, begins to understand her speech.
In infancy, children are especially susceptible to environmental influences. During this period, they need active movements. They contribute to the development of muscles and bones, improve blood circulation, provide the body with oxygen and nutrients, normalize and train the activity of the nervous system. An effective means of hardening is fresh air and water procedures. They enhance metabolism, protective functions of the blood, regulate the functions of the nervous system. Good physical and mental development is ensured by a rational mode of life.
Early childhood - the period from 1 year to 3 years. At this time, the child grows rapidly, switches to eating ordinary food, he has a desire for independent knowledge of the world around him. The child begins to walk, talk, manipulate various objects. He has a lot of motor skills.
Preschool period - from 3 to 7 years. This is the period of maximum curiosity of the child, when he becomes a "pochemuchka". At this time, the child's brain still continues to grow intensively and speech is finally formed. His mental development occurs in the process of games. They
contribute to the development of imagination, fantasy, encourage him to creativity. Outdoor games improve the muscular system. 5-6 years is the age limit after which, if you start from scratch, you cannot achieve mastery of speech.
The school period - from 7 to 17 years - is the time of restructuring of all organs and systems of the developing organism. Entering school, the need to comply with school discipline, the process of mastering knowledge is a serious and hard work. At school, the child is exposed to the influence of the collective. All this contributes to its harmonious mental and physical development.
From the age of 11, a child is called a teenager. At this age, the production of sex hormones increases, which causes the process of restructuring. In boys, the muscles of the back and chest develop, body weight increases, the thickness of subcutaneous fat decreases, an abdominal type of breathing is formed due to the contraction of the muscles of the diaphragm, secondary sexual characteristics develop and nocturnal emissions occur - eruptions of semen from the urethra.
In girls during this period, along with the development of the muscular system, the subcutaneous fat layer increases, the chest type of breathing is formed due to the contraction of the intercostal muscles, secondary sexual characteristics develop and menstrual cycles begin - bleeding from the uterus that occurs at regular intervals. They are connected with the fact that in the female body one egg periodically matures and, if it is not fertilized, menstruation occurs.
During adolescence, the adrenal cortex secretes especially a lot of hormones, which maintains a state of high activity. The resulting tension is reduced by sports games and other activities. At this time, the formation of character and moral formation of the personality takes place.
At the age of 17, the development of the body does not end. Differentiate between physiological, psychological and social maturity. Physiological maturity is the stage of puberty of the body. The term of its achievement depends on hereditary factors, climate and characteristics of the organism.

According to the most common classification, the life and development of a child does not begin after birth, but from the moment of conception.

There are seven age stages of child development:

intrauterine stage - from conception to birth;
neonatal period - from birth to the end of the first month;
the period of infancy - from the first month to 1 year;
early age stage of development - from 1 year to 3 years;
preschool age stage - from 3 to 7 years;
junior school age stage of development - from 7 to 12 years;
stage of senior school age - from 12 to 16-18 years.

At each of these stages of development, the child's body has features that require a different approach to caring for him and educating him.

Stages of development of a child in the womb

There are three main stages in the development of a child in the womb: initial, embryonic and fetal. The initial stage lasts from the moment of fertilization to two weeks of pregnancy. At this stage, the egg and sperm join and the zygote is formed, which then attaches to the wall of the uterus. The embryonic period of intrauterine development lasts from 3 to 12 weeks of pregnancy. At this time, the formation of the organs and systems of the unborn child takes place. Starting from the 12th week, the fetal period of development begins, during which the fetus will actively grow and gain weight, and its organs will actively develop.

Neonatal and infancy periods

In the first month of his life, the baby is very vulnerable, and therefore requires special care. During infancy, the child gradually learns to control his body and explores the world around him: he learns to raise his head, sit, crawl, walk. At the age of 6 months, he begins to distinguish colors quite well, in addition, he develops a perception of space. At this stage, the development of a child’s speech occurs gradually: at about 3–4 months, he unconsciously pronounces vowel sounds, training his speech apparatus, by 8 months he learns to consciously repeat sounds, and at 10 months he is already able to pronounce several identical syllables together.

Early age stage of child development

From the age of one to three years, the child continues to improve the skills that allow him to interact with the outside world: his speech and thinking develop, he learns to communicate with peers and adults. From about a year old, an important stage in the development of a child’s speech begins: usually a one-year-old child can repeat syllables and individual words after adults, and by the age of 2.5–3 years, he already knows how to make simple sentences of 3–4 words. Toward the end of this period, the baby begins to show a desire for independence and independence. At this age, the normal development of the child is best promoted by active communication and play. At the age of 3, a child has a crisis period during which he can behave aggressively and be stubborn. Each baby experiences the crisis of three years in different ways. In this difficult time, parents are advised to support the child and try not to show negative emotions in response to his aggression and whims.

Preschool period

It is believed that from the age of three, the formation of the character of the child, as well as personal mechanisms of behavior, begins. During this period, the further development of the child is strongly influenced by his relationship with loved ones and the atmosphere in the family. A three-year-old baby is already aware of himself as a separate person, but at the same time copies the behavior of adults, therefore, at this age, a positive example is very important for the development of positive qualities in a child and the correct mechanisms of behavior. The main way of learning for the baby is the game. From 3 to 6 years old, the child actively develops thinking, attention, memory, imagination, as well as social skills. At the age of 6, the formation of speech is completely completed. The child should be taught the basics of counting, reading and writing, as well as developing his vocabulary and instilling the correct norms of behavior in society.

Junior school stage of child development

At this age, the child learns to plan his activities, follow the rules, take responsibility, and also accept social norms of behavior. During this period, it is necessary to engage in his upbringing with special attention, since the developing abilities of the child to study as a whole largely depend on acquaintance with the educational process. All children, upon entering the first grade, go through a period of psychological and physical stress, which usually lasts for one to one and a half months. Parents need to be attentive to the daily regimen and nutrition of the child, since many schoolchildren at this time worsen sleep and appetite. You should also provide moral support to the little student, which will help him quickly adapt to new conditions. 4.6 out of 5 (7 votes)

Summary: Age periods of human development. The main stages of individual human development

Ministry of Education of the Russian Federation

Bryansk State University

"Age periods of human development"

Bryansk, 2007

Introduction. 3

1. The main stages of individual human development. four

2. Prenatal ontogeny. 5

First week. 6

Second week. 7

Third week. 9

Fourth week. ten

2.1 Fifth-eighth weeks. 13

2.2 Third-ninth months.. 14

2.3 Critical periods of ontogeny. fourteen

3. Postnatal ontogenesis. 16

3.1 Neonatal period. 16

3.2 Breast period. 16

3.3 The period of early childhood. 17

3.4 The period of the first childhood. 17

3.5 The period of the second childhood. 17

3.6 Adolescence. eighteen

3.6 Adolescence. 19

3.7 Mature, elderly, senile age. 19

4. Individual differences in the process of growth and development. twenty

4.1 Factors affecting individual development. twenty

4.2 Dimensions and proportions, body weight. 21

5. Acceleration. 24

Conclusion. 27

Literature and Internet sources. 29

Introduction

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.

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.

1. 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

Period	Age
1. Intrauterine embryonic	9 weeks - 9 months
2. Newborn	1 - 10 days
3. Breast age	10 days - 1 year
4. Early childhood	1-3 years
5. First childhood	4-7 years old
6. Second childhood	8-12 years old (boys) 8-11 years old (girls)
7. Adolescence	13-16 years old (boys) 12-15 years old (girls)
8. Youthful age	17-21 years old (boys) 16-20 years old (girls)
9. Mature age 1st period 2nd period	22-35 (men) 21-35 (women) 36-60 (men) 36-55 (women)
10. Old age	61-74 years (men) 56-74 years (women)
11. Old age	75-90 years (men and women)
12. Centenarians	90 years and older

Individual development, or development in ontogenesis, 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).

2. 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 (fusion of sperm and egg), which usually occurs in the 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.

First week development of the embryo 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. Cleavage of the zygote and the formation of germ layers 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 trophē - 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.

Second week 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. In 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 germinal 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.

Third week 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, the entire nervous system develops from the neural tube. 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.

Fourth week 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. From the endoderm, the epithelium and all the glands of the digestive system and respiratory tract are formed.

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 (Fig. 3). 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 divided into peritoneal, pleural and

pericardial cavity.

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 neuphrotomes (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 the skeletal muscles develop. 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 - the dermis - is formed.

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.

2.1 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.

2.2 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.

2.3 Critical periods of ontogeny

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 genitourinary 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.

3. Postnatal ontogeny

3.1 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.

3.2 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.

3.3 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.

3.4 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.

3.5 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.

3.6 Adolescence

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.

3.6 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.

3.7 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.

4. 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.

4.1 Factors affecting individual development

Factors influencing individual development (ontogenesis) are divided into hereditary and environmental factors (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 neonatal period 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.

4.2 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 ontogenesis.

The proportions of the body depend on the age and gender of the person (Fig. 4). Body length and its age-related changes, as a rule, are 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.

KM - the middle line. The numbers on the right show the proportions of body parts in children and adults, the numbers below show age.

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 emphasized that an active lifestyle, regular physical education slows down the aging process.

5. 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.

The body length of preschool children 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 people of different body types.

Table 3

Body proportions (according to P.N. Bashkirov)

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, blood vessels and liver also begins early.

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. The growth and development of a person in 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.

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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.

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Introduction

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.

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

Table 1


1. Intrauterine embryonic	9 weeks - 9 months
2. Newborn
3. Breast age	10 days - 1 year
4. Early childhood
5. First childhood
6. Second childhood	8-12 years old (boys) 8-11 years old (girls)
7. Adolescence	13-16 years old (boys) 12-15 years old (girls)
8. Youthful age	17-21 years old (boys) 16-20 years old (girls)
9. Mature age 1st period 2nd period	22-35 (men) 21-35 (women) 36-60 (men) 36-55 (women)
10. Old age	61-74 years (men) 56-74 years (women)
11. Old age	75-90 years (men and women)
12. Centenarians	90 years and older