Each child has an individual rate of biological development, and his biological age may differ to a certain extent from the age of his peers on the birth certificate. We are talking about the individual biological clock of the organism, which have a specificity in speed. This is so important an individual characteristic that even such powerful external synchronizers as the Sun, the Moon, the change of seasons, the change of day and night are incapable of neutralizing it and subordinating it to the general rhythm of the current of time. Many indicators of the functional capabilities of the organism, its reactivity systems correlate primarily with biological age, but not with the calendar. Features of the biological age of the child are important for the adoption of an individual mode of life, health protection, the use of different approaches to his upbringing and learning. It is difficult to put on one desk and make the same demands for two friends of 6 years of age (according to the calendar), if the biological age of one of them is 4, and the second one is 8 years old. And this is often found in our schools.
Therefore, in the biology of childhood, attempts have been made to classify periods of childhood, not according to the calendar life span, but on the essential biological features of maturity. The periodizations of prof. IA Arshavsky and G. Grimm.
IA Arshavsky's classification for the postnatal period of life
- The neonatal stage of development is from birth to the end of feeding with milk.
- The period of lactotrophic nutrition - before the introduction of thick complementary foods.
- The period of combination of dairy nutrition and complementary foods - until the realization of the posture of standing.
- Preschool age - development of locomotion acts. Formation of walking and running.
- Preschool age - before the appearance of the first permanent teeth.
- Junior school - until the first signs of puberty.
- Senior school - until the end of puberty.
An interesting point of the classification is to emphasize the connection between developmental biology and the type of nutrition. In this case, not always the association is determined by the degree of maturity of the child. It can be created arbitrarily. There is also a clear tendency to determine the essence of the period, and not the criteria for its isolation.
Classification by G. Grimm
- The neonatal period is until the healing of the umbilical wound.
- Breast age - before the appearance of the first milk tooth.
- Nursery age - before mastering walking.
- Preschool age - before the appearance of the first permanent tooth or the end of the first stretching.
- Junior school age - to the first sign of puberty.
- The senior school age is until the end of puberty.
- The period of youth or maidenhood is until the optimum performance is reached.
This classification is much more focused on the delimiting criteria of biological age periods. The disadvantage is the relative rudeness of division with excessively large age blocks.
The variant of biological periodization can be and such:
- Pre-neonatal period (for premature or small) - up to a body weight of 2500 g and the formation of stable swallowing and sucking reflexes.
- The neonatal period is before the removal of the physiological hypertension of the flexors of the upper limbs.
- Early infancy - until complete removal of the physiological hypertension of the flexor of the extremities.
- Late breast age - to walk without support and support.
- Breastfeeding - until the full eruption of milk teeth.
- Pre-school - up to the obvious signs of the second period of milk bite (diastema - tremes).
- Preschool age - before the formation of a positive Philippine test.
- Junior school age, or pre-pubertal, - until the appearance of secondary signs of puberty.
- The pubertal first (I-II stage of maturation according to J. Tanner).
- The pubertal second (stage III-IV maturation by J. Tanner).
- The pubertal third (V stage of maturation according to J. Tanner).
- Age of maturity - from the completion of transverse growth (according to the measurement of bitrochamber and biacromial distances).
To determine the biological age of a child, an evaluation is used of the development of such traits that reflect new qualitative signs during the biological maturation process or have a high degree of correlation with biological maturation. The simplest markers of biological age in adolescent children may be signs or stages of puberty. In young children, the biological age can be judged by the development and disappearance of the basic reflexes of newborns, the formation of motor skills, the appearance of milk teeth. In the preschool age, the appearance of permanent teeth is an important sign of maturity. In special studies, the biological age is determined radiologically, according to the number of available points and ossification nuclei. It is wrong to believe that bone age is the reflection of the true biological age of a child's body. This is the age of the bone system, depending on the combination of factors or conditions of development of the musculoskeletal system. The remaining physiological systems can develop at a different pace and have other age characteristics.
Convenient guidelines for tracing the biological age can be the evolution of hemoglobins of peripheral blood, the cytometric formula of lymphocytes, the formation of the a-rhythm of the electroencephalogram, etc. All the anthropometric, physiological, metabolic, immunological signs of a healthy child, having a clear and sufficiently vivid age dynamics or functional evolution, can be used to judge the biological age relative to the age of the calendar. For this, it is necessary to have tables of age distributions of these characteristics, preferably presented in a centile or nonparametric form. The biological age of the examinee for this system (bone, cardiovascular, blood system, kidney tubule function, etc.) will most likely correspond to the calendar age period when the quantitative or dimensional characteristic of the organ (function) obtained falls within the interval between 25 and 75th centile distribution. This indicates the most typical characteristics or properties inherent in 50% of healthy children of the age-sexual group. In the absence of tables of distributions on biological age, it can be tentatively judged on the basis of the maximum approximation of the chosen quantitative characteristic to one of the average age values (arithmetic mean, median or mode).
The biological age of a child can be said with certainty only if, for a number of signs of maturity, it reveals similar trends in magnitude and direction. Thus, the biological age of the child is the dominance of certain biological ages of individual tissues, organs and systems of the body. It can be represented in the form of the most frequent age or average biological age and some description of the revealed oscillations. This is the basis for judging the degree of harmony or disharmony in the growth and maturation of a child, or, in the language of theoretical biology, about the degree of heterochrony of development.
Heterochrony is inherent to every child, it is an inalienable property of the development process. The pronounced disharmonization with retardation of development (retardation, or bradigenesis) of some systems or advance of development (acceleration, or tachygenez) of others creates critical states of functional adaptation and vital activity with an increased risk of diseases.
Of the anthropometric features most closely correlated with biological age, you can indicate the body weight, the circumference of the chest, the ratio of the upper and lower segments of the body. A set of characteristics that can be used to determine biological age is given in the chapter on physical development.
Very informative and valuable for the practice of pediatricians, the biological age diagnostics method is its integral evaluation for a large set of different and age-specific characteristics associated with different physiological systems. Such an approach has proved itself in perinatology, when there are significant differences between the terms of gestation, anthropometric data of newborns and the characteristics of their biological maturity or age. The latter is significantly more significant for the probability of survival and preservation of the vital functions of the child. The age in weeks of gestation is determined by the sum of scores for 22 clinical signs.
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