GROWTH

From Big Medical Encyclopedia

GROWTH — increase in the sizes and the body weight of an organism in the course of an ontogeny (ontogenesis). The term «growth» is applied also to designation of time history of number of cells in culture. A special form P. of bodies and parts of a body is regeneration (see).

R.'s processes a metaphyte (including and the person) consist of increase in number of cells (proliferative R.), their mass and volume, adjournment of various extracellular substances and educations. The relative role of these processes is not identical at different types of organisms during the different periods of development.

An indispensable condition for R. is receipt in an organism and assimilation of sources of substance and energy or from the stock which is saved up in an oogenesis (eggs of birds, reptiles, seeds of plants, etc.), or from an organism of mother, or from the environment (postembryonal R.). In turn R. is the integral component of an ontogenetic morphogenesis (see. Morphogenesis , Ontogenesis ). In particular, acquisition by bodies and parts of a body of a specific form is, as a rule, connected with topography of the centers of cellular divisions, with the arranged orientation of spindles of mitoses, i.e. with proliferative

R. R. features of an organism begins at the earliest stages of embryonic development and continues in the postembryonal period of development. At the same time nek-ry organisms grow to some extent all life (the majority of plants, mollusks, fishes, etc.), others, reaching a certain age, the sizes or a stage of development (e.g., polovozret awns), almost completely stop growing.

R.'s speed of the developing organism is not constant: the most intensive R. takes place in the embryonal and early postembryonal period. Age dynamics of R. can be characterized by curves of absolute and relative Ruble. Absolute R.'s curves show change of weight or razkhmer of a body with age. For the majority of animals, including mammals, absolute R.'s curves have the characteristic S-shaped form (so-called logistic curves) with the most steep slope in a middle part and slower increase of the weight (sizes) at the beginning and the end of this period. Relative R.'s curves (more precisely, a gain) show an increment of the weight (sizes) of a body (usually as a percentage) for certain (consecutive) intervals of time in relation to the weight (size) at the beginning of each piece. For exact determination of speed of relative R. consecutive measurements should be performed through equal short time terms (no more than 0,1 from the general duration of the period of R.). At the same time, considering nonlinearity of growth curves, the best estimates turn out during the use of a formula of Brody — Shmalgauzena:

With r = [(lgC t+1 - lgC t )/0,4343]*100%

where C r — relative growth, C t and C t+1 — sizes of a body in intervals of time of t and t+1, 0,4343 — coefficient (a constant divider, size to-rogo it is found in the empirical way). At animals relative R. is most intensive in the earliest embryogenesis then its speed steadily decreases, in the beginning quickly, then more slowly. At plants relative R.'s speed at first increases, reaches a maximum (big R.'s period), then decreases, being stabilized at the certain level.

In the general age dynamics of R. fluctuations are quite often observed — the periods of the accelerated and slowed down R. Odni from them are dated for certain stages of development and naturally repeat. Others can be manifestation of day-night, seasonal and other rhythms of growth processes. Year rhythms of R. of sinks of mollusks, scales of fishes and reptiles, perennial woody plants are most known. In these cases morphological expressiveness of layers of an annual gain allows to determine by them age of individuals.

In the course of ontogenesis the uniform (isometric) growth of all body and the developing bodies is observed seldom. Discrepancy of speeds of R. of laying of different bodies and body in general is more characteristic (allometric growth). Quantitatively communication between R. of body and all body is expressed by the equation of so-called allometric growth:

at — bx and ,

where at — the size of body, x — the size of a body — an empirical constant, and — an indicator of an allometriya: at and = 1 isometric growth takes place, at and> 1 speak about a positive allometriya (a part grows quicker than whole), and at and< 1 — about negative an allometrpa.

Changes of speed of R. in ontogenesis usually connect with a differentsn-rovka of cells: the relative gain is maximum while all germ consists of unspecialized embryonic cells, to-rye intensively share; in process of a differentiation of cells their mitotic activity decreases, and at highly specialized cells (nervous, muscular, cells of a liver) is almost stopped. In fabrics, to-rye are characterized by mitotic activity during all life, cell population is usually subdivided into not sharing mature cells and intensively sharing (e.g., trunk hemopoietic) the cells forming the proliferative pool providing substitution of the died-off cells.

Despite such antagonism between processes of growth and a differentiation, they are the obligatory and coordinate interacting components of a morphogenesis of an organism as complete system. The disturbances of interaction of processes of growth and a differentiation induced by external factors (viruses, teratogens) or the internal reasons (hormonal, genetic disorders) can lead to excessive (giantism) or to insufficient (dwarfism) R., and also to emergence of the isolated and multiple inborn malformations (see).

The physiology of growth

Growth is one of important indicators of norm and pathology of development of a human body and the highest vertebrate animals. Its intensity and features at each stage of age development are defined by the complexes of the hereditary properties acquired in long process of evolution and also the conditions of development of an individual influencing rates of assimilatory and dissimilyatsionny processes put in the genetic device of cells.

At R.'s assessment as indicator of level physical development (see) consider two of its components — linear and weight, differing on rates of age development and in a uniform complex characterizing the constitution of this person.

Intensity of increase of live body weight and its biochemical structure significantly change in ontogenesis. It is known that in an organism of the child in early age (see) the increased content of intracellular water is observed (see. Homeostasis ); its fabrics contain high concentration of nucleic acids and rather low proteins, fats and mineral substances. At the same time a set of proteins in tissues of children differs from a set of proteins in fabrics of an adult organism. With age there is a gradual increase of fractions of globulins in a blood plasma, accumulation of collagen and falling of elastin in connecting tissue of skin and nek-ry other bodies, increase in concentration of sokratitelny proteins (a myosin, actin and tropomyosine) in muscles. By the period of achievement of a maturity in body tissues there is an accumulation lipids (see). In the course of R. in a human body there is a gradual mineralization of a bone tissue, to accumulation in it calcium (see) and phosphorus (see). According to dynamics of growth of an organism its requirements to food change. In particular, intensive R. demands enrichment of a diet complete proteins — to 2 — 4 g on 1 kg of body weight a day against 1,2 g for an adult organism (see Proteins). Requests of a children's organism to the main thing irreplaceable are especially high to amino acids (see).

The role of sufficient supply of the growing organism is very big mineral substances (see), especially salts of calcium and phosphorus, and also microelements (see), especially compounds of iron and copper (for formation of hemoglobin and tsitokhrom), zinc (for synthesis of a number of enzymes of an intermediate metabolism and activity of insulin), cobalt (for providing an erythrogenesis), etc.

Requirement of the growing organism is high and in vitamins (see). Their general dosage reaches in the period of the early childhood of the doubled and trebled doses in comparison with the adult organism which already finished the Ruble. Vitamins A, B12, E and D are necessary for R.'s optimization. Vitamin D (see. Calciferols ) it is especially important for a mineralization of a bone tissue and protein synthesis. Process of calcification is provided in an organism with difficult interaction of vitamin D and two hormones — calcitonin (see) and parathyroid hormone (see. Parathormone ); the calcitonin together with vitamin D stimulates process of a mineralization of a bone tissue, and parathyroid hormone, on the contrary, will mobilize removal of calcium and phosphorus from deep zones of a bone.

The river substantially depends on hormonal regulation. Especially are important for normal R.'s providing somatotropic hormone of a hypophysis (see. Somatotropic hormone ), iodinated hormones of a thyroid gland (see. Tiroksin , Triiodothyronine ), insulin (see) and sex hormones (see). The growth hormone directly stimulates activity genetic and protein - the synthesizing device of a cell; iodinated hormones of a thyroid gland (thyroxine, triiodothyronine) not only stimulate processes of bio-energetics with use of the released energy on formation of makroergichesky connections, but also directly influence the genetic device of a cell and increase in protein synthesis.

Insulin has the systemic anabolic effect on proteinaceous, fatty and carbohydrate exchanges and «constrains» catabolic action of an adrenal hormone — cortisol on protein metabolism.

Sex hormones (first of all testosterone), stimulating proteinaceous synthesis in a number of bodies, most strongly affect R.'s acceleration during puberty (12 — 19 years), changing proportions of a body.

Special and a little still the found-out value for regulation of growth belongs to the specific substances defining biochemical interaction of cells and fabrics. In particular, are found: the factor stimulating growth of neurons (NgF), an epidermal growth factor (EgF), a renal factor of proliferation and growth of erythroidal cells — eritropoetnn (see. Erythropoetins ), specific fabric inhibitors of growth and cell fission — chalones (see).

Mobility and functional activity of an organism are very important for optimum R.

Growth of children

In ontogenesis of mammals and the person is allocated by so-called critical periods: implantation of egg, platsentatspya, the strengthened differentiation, an organogenesis, a neonatality, puberty.

Prenatal ontogenesis (i.e. the period of development from fertilization till the birth) is subdivided into the periods, each of to-rykh differs in structural features and a peculiar type of food, breath, allocation. It is the germentativny period of development — from the moment of fertilization before implantation of a germ in a wall of a uterus (the 1st week); the embryonal (germinal) period — from the moment of implantation (the 2nd and the 3rd weeks of development) and the embriofetalny (prefetal) period — transition to vitelline, and then — to placental blood circulation (the 4th — the 8th weeks), when food germ (see) it is provided at the expense of the substances delivered by fibers of chorion. Intensively there are processes organogenesis (see), leading to formation of rudiments of bodies and formation of a trunk, head, extremities; regular reduction of heart, then blood circulation begin, jaws, other bones of a skull, a bone of humeral and pelvic belts, rudiments of vertebrae and edges form top and bottom. The fetalis (fetal) period of development begins with the 8th week until the birth: end of placentation and transition of a germ to supply with oxygen and nutrients from blood of mother through a placenta. During this period R. and a thin structural differentiation of bodies and fabrics proceed, the nervous system is improved.

From the moment of the birth the human body passes into new living conditions with a new form of food through went. - kish. a path, pulmonary type of breath, the changed blood circulatory system. At the same time there is a further development and maturing of physiological and biochemical functions, change of chemical composition of fabrics and body organs. At the same time characteristics of partial functions of kidneys, activity of various digestive enzymes increase, levels of sugar and osmotic pressure of blood, body temperature are stabilized, protective mechanisms against infections operate more effectively. In the course of R. sense bodys, nervous and bone systems ripen and form, so — the static functions having a certain sequence of development taking into account individual distinctions.

Secretion of digestive glands begins to amplify after the birth owing to irritant action of feedstuffs went on a mucous membrane. - kish. a path that causes release of digestive juices.

Formation of a morphological basis of a sucking reflex is referred to the pre-natal period since the five-months fruit (see) already has sucking and deglutitory movements, and newborn (see) has ability to suck and swallow right after the birth. Under the influence of food irritants gradual strengthening of salivation is noted up to uslovnoreflektorny — by sight and a flavor of food, on situation during the feeding etc.

The stomach of newborns differs in a smoothness of lines in places of transition of one department in another, and also big rotundity and rather thin walls. Growth of a wall of a stomach and development of glands are promoted extension of a stomach at each meal.

Secretion of glands of a stomach at the newborn child is insignificant, the gastric juice contains all enzymes which are available for adults, however has the insignificant digesting force and is formed in a small amount.

In a gastric juice of the child there is more chymosin promoting a proteopepsis of milk, than pepsin. The general growth of a stomach, development of a mucous membrane with increase in quantity and secretion of gastric glands provides increase in acidity and consequently, increase in enzymatic activity of pepsin and parallel decrease of the activity of chymosin.

Secretion of glands of intestines (small bowel), as well as glands of a stomach, functionally is not perfect. The composition of intestinal juice at the child is identical to that at the adult, but the digesting possibilities of enzymes it is much less and increase only in process of increase in activity of gastric glands and acidity of juice. The pancreas also excretes less active juice.

The peristaltics of intestines of the child differs in hyperactivity and the expressed instability, amplifies from receipt and fermentation of food, and also action of such external factors as overheating, sound irritation in the form of knock, shout. Children have rather big length of intestines and easily extensible, weak mesentery in this connection they to a thicket have a torsion of guts.

There is an interrelation between a functional state went. - kish. a path and a liver with R. and development of children. So, disturbances of splitting of feedstuffs in intestines or their transport through a wall of a gut are followed by R.'s delay and development of the child (see. Malabsorption syndrome ).

Communication between a functional condition of kidneys and R. of children most clearly is traced at metabolic canalicular syndromes. It is group of diseases and syndromes, the general for to-rykh is disturbance of homeostatic functions of renal tubules. The balance of calcium and amino acids at the same time is broken that leads to a delay of physical development and lag in growth (see. Osteopathy nephrogenic ).

The endocrine system exerts considerable impact on the growing organism from the first days of embryonic development before the end of the period of puberty. During various periods of development of an organism mutual influence takes place: on the one hand — many functions develop under the influence of hormones, and with another — development of functions of hemadens is traced. So, the placental period of development is characterized by differentiation of mesodermal elements, from to-rykh the intrarenalovy system forms further and the insulyarny device is put.

In the period of a neonatality influence of hormones of mother is still shown, to-rye arrive transplatsentarno in the last days of pregnancy, and also with breast milk. During feeding at baby (see) thymic and thyroid glands more intensively begin to function, the intrarenalovy system is exposed to involution. In the age period from 1 year to 7 years especially strongly the organism is influenced by hormones of a thyroid gland, and also anterior pituitary hormones (secretion of the somatotropic hormone regulating the linear growth of children — amplifies up to the period of puberty).

In the pubertal period diseases of a diabetes mellitus are most frequent, pathology of a thyroid gland is shown, activity of gonads is stirred up, function of a hypophysis amplifies. Considerable changes in work of endocrine and cardiovascular systems are shown. Time of approach of this period depends on living conditions, food, climate, an ethnic origin, etc. (see. Acceleration ).

Secondary influence of endocrine system on growth of children happens through regulation of a metabolism, mainly phosphorus-calcium exchange and exchange of vitamin D.

Almost all endocrine diseases at children's age are followed by disturbances of River. Among the diseases connected with narusheniyekhm R. at children and teenagers the following is most known: giantism (see), acromegalia (see), Itsenko's disease — Cushing (see. Itsenko — Cushing a disease ), a pituitary nanism (see. Dwarfism ).

Giantism (meets at males more often) often is a consequence of eosinophilic adenoma of a front share of a hypophysis. There is a point of view that giantism — a consequence of special reactivity of epiphyseal cartilages to influence of usual secretion of somatotropic hormone when there is excessive epiphyseal and periosteal growth of bones.

The acromegalia at children is observed seldom. It is shown by increase in tails of a body — hands, legs, a nose, jaws, periosteal growths, increase in mass of soft tissues and internals. The etiology is connected with influence of the increased release of hormone P. in the period of already closed zones P.; the found cases of an acromegalia at children at yet not closed epiphyseal lines indicate complexity of a question. Believe that at this disease different sensitivity of fabrics to hormone P. of a hypophysis matters.

It is necessary to differentiate an acromegalia with osteodystrophy (see), or Pedzhet's disease (see. Pedzheta disease ).

R. (nanism) is a lot of reasons of a delay therefore at diagnosis it is necessary to isolate the leading defect which led to R. Razlichayut's delay cerebral and pituitary, primordialny, hypothyroid and other kinds of a nanism (see Dwarfism).

R.'s delay is considered considerable in relation to age norm when, e.g., lag exceeds 20% of average indicators of R. for specific age.

The diagnosis of a disease is made on the basis of the anamnesis (a growth inhibition from 2 — 3 years), delays in emergence of the centers of ossification, outward of the patient. At differential diagnosis it is necessary to remember cases family low-dews-losti, a possibility of overdue pubertal development with signs of a delay of linear R. etc.

The problem of treatment of a nanism is not solved yet. For this purpose widely apply a steroid retabolil, to-ry has the expressed anabolic effect and the prolonged action. Anabolic steroids at their prolonged use can cause virilescence in girls (see). In these cases it is necessary or to replace anabolic steroids, either to reduce a dose, or to appoint a break in their use.

Additional purpose of small doses of Thyreoidinum and chorionic gonadotrophin yield good result at a sharp delay of sexual development.

Itsenko's disease — Cushing arises at defeat of mezhutochnogipofizarny area (H. M. Itsenko, 1925) or as a result of development of basphilic adenoma of a front share of a hypophysis (X. Cushing, 1932). Pathogeny of a disease of Itsenko — Cushing is connected with the strengthened allocation in AKTG blood and its impact on cortical substance (bark) of adrenal glands. A proximate cause of a disease consider the excess maintenance of biologically active cortisol that can be connected with the increased stimulation of bark of adrenal glands of AKTG, with disturbance of a rhythm of products of a hydrocortisone, decrease in the connecting ability of serum proteins in relation to a cortisone.

Clinic of a disease at children: obesity, trophic changes of skin, osteoporosis, a hypertension, premature pilosis of a pubis at a growth inhibition and sexual development, disorder of carbohydrate metabolism (this disease is more often from 6 to 11 years are observed).

Treatment of a disease of Itsenko — Cushing — difficult and completely yet not solved problem. Methods of treatment are conditionally subdivided on conservative and operational. Treat conservative the roentgenotherapy of interstitial and pituitary area directed to decrease in secretion of AKTG and, thereby, to reduction of hyperfunction of bark of adrenal glands. X-ray radiation is considered effective: from 1 to 3 courses of treatment on 4000 — 4500 r on everyone, bucketed between courses in 6 — 8 months. According to T. N. Volkova (1967), improvement occurred in the form of normalization of the ABP, disappearance of headaches, reduction of osteoporosis, weight reduction, resuming of processes of growth and sexual development at considerable redistribution of fat. The roentgenotherapy is recommended to be combined with a dietotherapy, use of anabolic hormones.

Surgical treatment — a total bilateral adrenalectomy at an interval of 4 weeks between operations on one and other party. However at such treatment the chronic hypocorticoidism in this connection during all life patients shall receive replacement hormonal therapy develops. Surgical treatment normalizes the general state, outward of the child improves. Dispensary observation at the endocrinologist since any stressful situation after a total adrenalectomy can cause acute adrenal insufficiency in children is recommended.

Studying of features of physical development provides registration not only growth rates, the weight (weight) of the child and correctness of a constitution, but also the accounting of dynamics of sexual development in comparison to age norms.

Detection of initial symptoms of endocrine diseases at mass routine maintenances of children allows to reveal and eliminate timely the endocrine diseases in particular influencing R.

Zaderzhk R. can be one of displays of endocrine pathology and to serve as the test for allocation of such children in risk group for the subsequent profound inspection directed to clarification of the actual reason which caused R.'s delay for corrective therapy further.

Special attention should be paid on inspection of healthy children in families with the burdened heredity.

Children with the endocrine diseases breaking R. and development (a pituitary nanism, Itsenko's disease — Cushing, etc.), shall be on the dispensary account, as well as children with high-tallness and low-tallness, obesity etc. Medical examination (see) assumes obligation of participation in inspections of children of oculists, neuropathologists, gynecologists, urologists as early detection of endocrine diseases prevents development of severe forms of pathology.

Timely treatment of such patients is provided with creation of specialized medical aid in the country.



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V. I. Ivanov; S. A. Zhdanova (ped.), V. N. Nikitin (fiziol.).

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