The integrity of ontogeny is based on the relationship and interaction of ontogenetic differentiations. The stages of ontogenetic differentiation are interrelated, the previous stages serve as the basis for the subsequent ones. Thus, the formation of gastrula in vertebrates leads to the formation of ecto- and endoderm, their active interaction gives rise to the neural tube, notochord, etc.; the latter, in turn, play the role of inductors in the formation of other organs. Violation of one of the links of differentiation leads to violations of ontogenesis. Hence, it is clear that the previous stages of ontogenesis must proceed in order to realize its subsequent differentiations. The study of animal embryogenesis as an example shows that the developing embryo has both very sensitive and stable periods.
In general, the evolution of life was accompanied by a gradual strengthening of the integrity and stability of ontogeny. The integrity and stability of ontogenesis is determined by correlations and coordinations.
Ontogenetic differentiation is the occurrence in the body (or a separate part of it) in the process of development of morphological and functional differences.
The presence of functional and structural interdependence between the structures of a developing organism, in which changes in some organs lead to changes in others, is called correlation.
The integrity of an organism implies a coordinated change in its organs and parts not only in ontogenesis (correlation), but also in phylogeny. The concomitant changes in organs in historical development are called coordinations.
AUTONOMIZATION AND EMBRYONIZATION OF ONTOGENESIS
Autonomization of ontogeny – the acquisition of an increasing stability of ontogeny from random changes in the environment. Autonomization of ontogeny is carried out by replacing external factors that stimulate development with internal factors. Thus, the formation of pulmonary alveoli in lower tetrapods is stimulated by the expansion of the lung sacs by inhaled air (the external factor is the leading one). In reptiles and mammals, the lungs are fully formed during the embryonic period and are prepared for breathing immediately after the birth of offspring (external factors are gradually replaced by internal developmental factors).
Embryonization of ontogenesis is the emergence in the process of evolution of the ability to pass through part of the stages of development under the protection of the mother’s body or special shells. Embryonization contributes to strengthening the integrity of ontogeny in evolution, neoteny and fetalization.
Embryoization in animals can be traced by the example of the evolution of different types of embryonic development. In general, the embryonicization of ontogeny by many changes leads to an increase in the role of the internal environment in the development of the embryo and its independence from the external environment. One of the important results of embryonization is the supply of the embryo with the necessary food and the achievement of its rapid development. With increased embryonization, selection is directed towards a decrease in the number of eggs and embryos and an increase in the survival rate of embryos.
Neoteny – the ability of an organism to reproduce in the early (larval) stages of ontogenesis.
Fetalization is a method of evolutionary changes in organisms, characterized by a slowdown in the ontogenesis of individual organs, as a result of the preservation of the embryonic state of signs in an adult organism .
We managed to find out that in the course of ontogenesis, each organism naturally goes through successive phases, stages or periods of development , of which the main ones in sexually reproducing organisms are: embryonic (embryonic, or prenatal), post-embryonic (post-embryonic, or post-natal) and the period of development adult organism. Ontogeny is based on a complex process of implementation at different stages of the development of an organism of hereditary information embedded in each of its cells. The program of ontogenesis determined by heredity is carried out under the influence of many factors (environmental conditions, intercellular and intertissue interactions, humoral-hormonal and nervous regulation, etc.) and is expressed in interconnected processes of cell reproduction, their growth and differentiation. Patterns of ontogenesis, causal mechanisms and factors of cellular, tissue and organ differentiation are studied by a complex science – developmental biology, which uses, in addition to traditional approaches of experimental embryology and morphology, methods of molecular biology, cytology and genetics.
At all stages of ontogenesis , the human body remains an integral and open biological system. The action of regulators and developmental factors begins even before the moment of conception. Then, other mechanisms continue to control the process of development throughout the entire prenatal period and postnatal ontogenesis, determining expression, acting directly at the cellular and tissue levels.
Many of these mechanisms have the property of self-regulation, and most of them are complex intersystem complexes that are themselves formed during ontogenesis. They trigger and control the development of individual body systems. We get a good opportunity to structure this continuous process into conditional stages (ontogeny periods), the regulation within which is more or less strictly genetically determined (sensitive periods).
Although everything or almost everything ends up in genes, even endogenous growth regulators (the same neuroendocrine system designed to channel growth) find themselves interacting with a wide range of exogenous conditions (“developmental noises”), many of which are random. The implementation of the hereditary program, which occurs in the course of individual development, is largely influenced by the specific conditions of the environment in which the entire process takes place. Yet these conditions are constantly changing.
As a result, ontogeny is a holistic and dynamic picture of the change of stages characterized by different growth rates. Each such stage has its own age reaction rate, usually approaching the average group (population) characteristic.
By accelerating or, conversely, slowing down the growth rates of individual systems or the whole organism as a whole, that is, by the degree of its acceleration or retardation, we can judge the normal course of individual development. And this, on the one hand, is a direct way to the control, prevention and diagnosis of possible deviations, and on the other hand, an opportunity for a deeper understanding of the causes of biological (and not only) human variability.
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|Periods and stages||Borders||Main characteristic|
|1. Prenatal period (intrauterine period 3 stages||0-9 months of intrauterine development||Formation of a biological human organism capable of surviving in the air.|
|1.1. Pre-embryonic stage||0-2 weeks after fertilization||The development of a fertilized egg before its introduction into the wall of the uterus and the formation of the umbilical cord|
|1.2. Germinal (embryonic stage)||From the 3rd week to the end of the 2nd month of development||Anatomical and physiological differentiation of various organs. From the 3rd week, the formation of the nervous system, spinal cord and brain begins, after the 8th week the nervous system begins to function. From the 6th week, sexual differentiation begins|
|1.3. Fetal stage||From the 3rd month of pregnancy to 9 months. and childbirth||By the end of the 3rd month, the sex of the child is determined. At the beginning of the 7th month the fetus is capable of surviving in the air and is called a child; the reflexes of sucking, blinking, and responding to sound are already functioning. By the time of birth, all brain cells are formed and more during life are not formed.|
|2. Childhood period (4 stages)|
|2.1. Neonatal and infancy stage||From the moment of birth to the 1st year of life. Crisis 1st year||The rapid growth of body weight, physical development: the formation of walking, hand movements, fingers. Formation of perception, figurative memory, visual-effective thinking, understanding of speech, emotional development|
|2.2. Early childhood (first childhood)||From 1 to 3 years Crisis 3 years||Development of functional independence and speech of the child, visual-figurative thinking. Mastering household skills, actions with objects|
|2.3. Preschool childhood (second childhood)||From 3 to 6-7 years Crisis 7-8 years||The development of the child’s personality, the development of cognitive processes, the formation of conscience, morality, initiative|
|2.4. Primary school age (third childhood) peripubertal||From 7 to 12 years old (boys) From 7 to 11 years old (girls) Teen crisis 13 years old||Inclusion of the child in a social group, going beyond the family. Development of intellectual skills and knowledge. Maturation at the age of 7-8 years of the androgenic zone of the adrenal cortex, which produces male sex hormones – androgens, increased growth and initial puberty|
|3. Adolescence (2 stages)||From 13 to 21-23 years old|
|3.1. Adolescence (puberty)||13-16 years old (boys) 12-15 years old (girls) Crisis 17-18 years old||The most important stage in human development is puberty. There is a maturation of the reproductive system of reproduction – the hypothalamus – the pituitary gland – sex hormones – sex glands – germ cells, the development of primary and secondary sexual characteristics, shifts in morphofunctional parameters, and a high probability of deviations in health indicators. A sharp peak in the growth of body size (at 13-15 years old in boys, at 11-13 years old in girls) under the influence of sex hormones and growth hormone, muscle development in men, hormonal and emotional changes. There is a development of logical thinking and the formation of self-awareness|
|3.2. Adolescence (juvenile)||17-21 years (boys) 16020 years (girls)||Sexual and biological maturation is completed, the body reaches the peak of its physical development, the full functional maturity of the brain by the age of 18, the peak of intellectual and cognitive capabilities by the age of 18-20. There is a formation of a worldview and stabilization of character, the development of professional abilities and skills, the choice of a life position, the adoption of responsible life decisions. Achievement of social maturity, independence, material and social self-sufficiency|
|4. The period of adulthood, maturity|
|4.1. Stage of youth or early maturity||22-33 years old Crisis 33-35 years old||Physical growth, intellectual growth ceases, full physiological maturity is reached. Personal development and social development continues. The stage of self-assertion in society, family, profession, sex, love, career, children, etc.|
|4.2. Mature age||35-60 years old (men) 35-55 years old (women)||From 35 to 40-43 years old – a period of stabilization, consolidating one’s success in a career, family, sex, material support, children, etc. The critical decade is 45-55 years (there are signs of deterioration in health, loss of youth and beauty, attempts to “prove” one’s youth through love affairs or a career, business, depressive moods appear, hormonal changes – a period of menopause begins in women). From 55 to 50-65 years – a period of physiological and psychological balance|
|5.1. Old age (first old age)||61-74 (men) 56-74 (women)||The crisis of old age: the loss of a social role, expressed by the aging of the body, the consciousness of the inevitability of imminent death, understanding one’s life: acceptance of one’s life or awareness of the fallacy, meaninglessness of one’s life. Aging is a natural biological process leading to a decrease in the adaptive capacity and viability of a person. Manifestations: decrease in growth by 1 cm in 5 years after 60 years, loss of teeth, skin elasticity, graying, disturbance at the cellular and molecular level, various diseases, weight loss, decrease in EEG brain bioactivity, decrease in hearing, vision, decrease in hormones, metabolism substances in the blood, an increase in the frequency of chromosomal abnormalities and in genes|
|5.2. Senile age||75-90 years old|
|centenarians||90 years and older|