Age-related features of metabolism. Age-related physiological characteristics of metabolism and energy

Metabolism is a complex set of processes that occur in the body from the moment these substances enter it until the moment they are released. In the process of metabolism, two opposing and interrelated processes occur: anabolism and catabolism. Anabolism is the reaction of biological synthesis of complex molecules from simple components. Energy is required for this reaction to occur. The energy required for anabolic processes is supplied by catabolic processes. Catabolism is the reaction of the breakdown of complex organic compounds with the release of energy. The end products of catabolism - water, carbon dioxide, ammonia, urea, uric acid - are removed from the body.

The relationship between the processes of anabolism and catabolism determines three states: dynamic equilibrium, growth, and partial destruction of body structures. In dynamic equilibrium, when the processes of anabolism and catabolism are balanced, the total amount of tissue does not change. An increase in anabolic processes leads to the accumulation of tissue - the body grows; the predominance of catabolism over anabolism leads to tissue destruction, that is, it leads to exhaustion of the body. In adults, the processes of anabolism and catabolism are usually balanced.

Chemical transformations of food substances begin in the gastrointestinal tract, where complex food substances are broken down into simple ones that can be absorbed into the blood and lymph. Simple substances are brought into cells where intracellular exchange occurs. They are acted upon by enzymes - special catalyst proteins. Enzymes themselves do not participate in reactions, but thanks to them, intramolecular chemical bonds are broken and energy is released. Of particular importance here are the processes of oxidation and reduction, phosphorylation reactions (transfer of a phosphoric acid residue), transamination (transfer of an amino group) and transmethylation (transfer of a methyl group - CH 3). The end products of intracellular metabolism are partially used for the construction of new chemical compounds in the cell, and unused substances are removed from the body by the excretory organs. Energy metabolism of cells (production and transformation of energy) occurs in mitochondria. The production of energy in mitochondria with the participation of oxygen is called aerobic. Energy can also be generated in the cytoplasm, but without the participation of oxygen. This reaction is called anaerobic. Anaerobic processes are most characteristic of muscle tissue. The main battery and energy carrier is ATP.

All food substances have a certain amount of energy. The body is called an energy transformer, because specific transformations of nutrients constantly occur in it, leading to the release of energy and its transition from one type to another. The relationship between the amount of energy received from food and the amount of energy expended is called the body's energy balance. To study it, it is necessary to determine the energy value of food.

Studies have shown that each gram of polysaccharides and proteins provides 17.2 kJ. When a gram of fat breaks down, 38.96 kJ is released. It follows that the energy value of different food products is not the same and depends on what nutrients the product contains. So, for example, the energy value of nuts turns out to be equal to 2723.5 kJ, butter - 3322.2 kJ, etc. The energy value of nutrients does not always coincide with their physiological value, because the latter is still determined by the ability to assimilate. Nutrients of animal origin are absorbed better than those of plant origin.

The amount of energy released in the body depends on the chemical transformations of substances in it, i.e., on metabolic processes. It follows that the amount of heat generated by the body can serve as an indicator of metabolism. Determining the amount of heat, i.e., the number of calories released by the body, gives the entire amount of energy transformations in the form of the final thermal result. This method of determining energy is called direct calorimetry. Determination of the number of calories by direct calorimetry is carried out using a calorimetric chamber, or calorimeter.

All these determinations can be made much more simply by studying gas exchange. Determining the amount of energy released by the body by studying gas exchange is called indirect calorimetry. Knowing that the entire amount of energy released in the body is the result of the breakdown of proteins, fats and carbohydrates, knowing also how much energy is released during the breakdown of these substances, and how much of them has undergone breakdown over a certain period of time, we can calculate the amount of energy released.

A distinction is made between general metabolism and basal metabolism. Basic metabolism is the energy expenditure of the body under resting conditions associated with maintaining the minimum level of metabolic processes necessary for the functioning of cells. Basal metabolism is determined in a state of muscle rest - lying down, 12 - 16 hours after eating at a temperature of 18 - 20°C. Under these conditions, energy is spent on heart function, breathing, maintaining body temperature, etc. But this energy expenditure is small. The main costs in determining basal metabolism are associated with biochemical processes that always take place in living cells. The basal metabolic rate ranges from 4,200 to 8,400 kJ per day for men and from 4,200 to 7,140 kJ for women. On average, in a middle-aged person, the basal metabolism is 4187 J per 1 kg of weight per hour or 7140 - 7560 thousand J per day. In children 8 - 9 years old, the basal metabolism is 2 - 2.5 times higher than in an adult.

The smaller the child, the more energy is spent on his growth. Thus, at the age of 3 months, energy consumption is 36%, at 6 months - 26%, 10 months - 21% of the total energy value of food.

In preschool and primary school age, there is a correspondence between the intensity of the decrease in basal metabolism and the dynamics of growth processes: the greater the rate of relative growth, the more significant the changes in resting metabolism.

The basal metabolic rate in girls is slightly lower than in boys. This difference begins to appear in the second half of the first year of life.

The second component of the body's energy expenditure after the main metabolism is the so-called regulated energy expenditure. They correspond to the need for energy used for work above the basal metabolism. Any type of muscular activity, even changing body position (from a lying position to a sitting position), increases the body's energy consumption. The change in energy consumption is determined by the duration, intensity and nature of muscle work. The more intense the muscle load, the more significant the increase in metabolism. In this regard, workers of different professions spend different amounts of energy per day (from 12,600 to 21,000 kJ). Mental work causes a slight increase in metabolism: only 2 - 3%. Any emotional excitement inevitably leads to an increase in metabolism. Metabolism also changes under the influence of food intake. After eating, metabolism increases by 10 - 40%. The effect of food on metabolism does not depend on the activity of the gastrointestinal tract; it is due to the specific effect of food on metabolism. In this regard, it is customary to talk about the specific dynamic effect of food on metabolism, meaning by this its increase after eating.

Metabolism and energy are the basis of the body’s vital processes. In the human body, in its organs, tissues, and cells, there is a continuous process of synthesis, i.e., the formation of complex substances from simpler ones. At the same time, the breakdown and oxidation of complex organic substances that make up the cells of the body occurs.

The work of the body is accompanied by its continuous renewal: some cells die, others replace them. In an adult, 1/20 of the skin epithelial cells, half of all digestive tract epithelial cells, about 25 g of blood, etc. die and are replaced within 24 hours. The growth and renewal of body cells is possible only if there is a continuous supply of oxygen and nutrients to the body. Nutrients are precisely the building and plastic material from which the body is built.

For continuous renewal, the construction of new cells of the body, the work of its organs and systems - the heart, gastrointestinal tract, respiratory system, kidneys and others, a person needs energy to perform work. A person receives this energy through decay and oxidation during the metabolic process. Consequently, nutrients entering the body serve not only as plastic building material, but also as a source of energy necessary for the normal functioning of the body.

Thus, metabolism is understood as a set of changes that substances undergo from the moment they enter the digestive tract and until the formation of final breakdown products excreted from the body.

Anabolism and catabolism. Metabolism, or metabolism, is a finely coordinated process of interaction between two mutually opposite processes occurring in a certain sequence. Anabolism is a set of biological synthesis reactions that require energy. Anabolic processes include the biological synthesis of proteins, fats, lipoids, and nucleic acids. Due to these reactions, simple substances entering cells, with the participation of enzymes, enter into metabolic reactions and become substances of the body itself. Anabolism creates the basis for the continuous renewal of worn-out structures.

Energy for anabolic processes is supplied by catabolic reactions, in which molecules of complex organic substances are broken down to release energy. The end products of catabolism are water, carbon dioxide, ammonia, urea, uric acid, etc. These substances are not available for further biological oxidation in the cell and are removed from the body.

The processes of anabolism and catabolism are inextricably linked. Catabolic processes supply energy and starting materials for anabolism. Anabolic processes ensure the construction of structures that go towards the restoration of dying cells, the formation of new tissues in connection with the growth processes of the body; provide the synthesis of hormones, enzymes and other compounds necessary for cell functioning; supply macromolecules to be broken down for catabolic reactions.

All metabolic processes are catalyzed and regulated by enzymes. Enzymes are biological catalysts that “start” reactions in the cells of the body.

Transformation of substances. Chemical transformations of food substances begin in the digestive tract, where complex food substances are broken down into simpler ones (most often monomers), which can be absorbed into the blood or lymph. Substances received as a result of absorption into the blood or lymph are brought into the cells, where they undergo major changes. Complex organic compounds formed from the incoming simple substances are part of the cells and take part in the implementation of their functions. The transformations of substances that occur inside cells constitute the essence of intracellular metabolism. A decisive role in intracellular metabolism belongs to numerous cell enzymes that break intramolecular chemical bonds with the release of energy.

Oxidation and reduction reactions are of primary importance in energy metabolism. With the participation of special enzymes, other types of chemical reactions are also carried out, for example, reactions of transfer of a phosphoric acid residue (phosphorylation), amino group NH2 (transamination), methyl group CH3 (transmethylation), etc. The energy released during these reactions is used to build new substances in the cell, to maintain the vital functions of the body.

The end products of intracellular metabolism are partially used for the construction of new cell substances; substances not used by the cell are removed from the body as a result of the activity of the excretory organs.

ATP. The main accumulating and energy-transferring substance used in the synthetic processes of both the cell and the whole organism is adenosine triphosphate, or adenosine triphosphate (ATP). The ATP molecule consists of a nitrogenous base (adenine), a sugar (ribose) and phosphoric acid (three phosphoric acid residues). Under the influence of the enzyme ATPase, the bonds between phosphorus and oxygen in the ATP molecule are broken and a water molecule is added. This is accompanied by the elimination of a phosphoric acid molecule. The cleavage of each of the two terminal phosphate groups in the ATP molecule occurs with the release of large amounts of energy. As a result, the two terminal phosphate bonds in the ATP molecule are called energy-rich bonds, or high-energy bonds.

10.2. Basic forms of metabolism in the body

Protein metabolism. The role of proteins in metabolism. Proteins occupy a special place in metabolism. They are part of the cytoplasm, hemoglobin, blood plasma, many hormones, immune bodies, maintain the constancy of the body’s water-salt environment, and ensure its growth. Enzymes that are necessarily involved in all stages of metabolism are proteins.

Biological value of food proteins. The amino acids used to build the body's proteins are unequal. Some amino acids (leucine, methionine, phenylalanine, etc.) are essential for the body. If an essential amino acid is missing from food, protein synthesis in the body is severely disrupted. Amino acids that can be replaced by others or synthesized in the body itself during metabolism are called non-essential.

Food proteins that contain the entire necessary set of amino acids for normal protein synthesis in the body are called complete. These include mainly animal proteins. Food proteins that do not contain all the amino acids necessary for protein synthesis in the body are called incomplete (for example, gelatin, corn protein, wheat protein). The highest biological value is found in the proteins of eggs, meat, milk, and fish. With a mixed diet, when the food contains products of animal and plant origin, the set of amino acids necessary for protein synthesis is usually delivered to the body.

The supply of all essential amino acids is especially important for a growing organism. For example, the absence of the amino acid lysine in food leads to stunted growth of a child and depletion of his muscular system. Valine deficiency causes vestibular disorders in children.

Of the nutrients, only proteins contain nitrogen, so the quantitative side of protein nutrition can be judged by nitrogen balance. Nitrogen balance is the ratio of the amount of nitrogen received during the day from food and the nitrogen excreted from the body during the day through urine and feces. On average, protein contains 16% nitrogen, i.e. 1 g of nitrogen is contained in 6.25 g of protein. By multiplying the amount of absorbed nitrogen by 6.25, you can determine the amount of protein received by the body.

In an adult, nitrogen balance is usually observed - the amounts of nitrogen introduced with food and excreted with excreted products coincide. When more nitrogen enters the body from food than is excreted from the body, we speak of a positive nitrogen balance. This balance is observed in children due to an increase in body weight during growth, during pregnancy, and during heavy physical activity. A negative balance is characterized by the fact that the amount of nitrogen introduced is less than that removed. It can occur during protein starvation or severe illness.

The breakdown of proteins in the body. Those amino acids that did not go into the synthesis of specific proteins undergo transformations, during which nitrogenous compounds are released. Nitrogen is split off from the amino acid as ammonia (NH3) or as the amino group NH2. An amino group, having split off from one amino acid, can be transferred to another, due to which the missing amino acids are built. These processes occur mainly in the liver, muscles, and kidneys. The nitrogen-free residue of the amino acid undergoes further transformations with the formation of carbon dioxide and water.

Ammonia, formed during the breakdown of proteins in the body (a toxic substance), is neutralized in the liver, where it turns into urea; the latter is excreted from the body in urine.

The end products of protein breakdown in the body are not only urea, but also uric acid and other nitrogenous substances. They are excreted from the body through urine and sweat.

Features of protein metabolism in children. In the child’s body, intensive processes of growth and formation of new cells and tissues occur. The protein requirement of a child's body is greater than that of an adult. The more intense the growth processes, the greater the need for protein.

In children, a positive nitrogen balance is observed when the amount of nitrogen introduced with protein foods exceeds the amount of nitrogen excreted in the urine, which ensures the growing body's need for protein. The daily protein requirement per 1 kg of body weight for a child in the first year of life is 4–5 g, from 1 to 3 years – 4–4.5 g, from 6 to 10 years – 2.5–3 g, over 12 years – 2–2.5 g, in adults – 1.5–1.8 g. It follows that, depending on age and body weight, children from 1 to 4 years old should receive 30–50 g of protein per day, from 4 to 7 years - about 70 g, from 7 years - 75–80 g. At these indicators, nitrogen is retained in the body to the maximum. Proteins are not stored in the body in reserve, so if you give them with food more than the body needs, then an increase in nitrogen retention and an increase in protein synthesis will not occur. Too little protein in food causes a decrease in the child’s appetite, disrupts the acid-base balance, and increases the excretion of nitrogen in the urine and feces. The child needs to be given the optimal amount of protein with a set of all the necessary amino acids, and it is important that the ratio of the amount of proteins, fats and carbohydrates in the child’s food is 1:1:3; under these conditions, nitrogen is retained in the body as much as possible.

In the first days after birth, nitrogen makes up 6–7% of the daily urine output. With age, its relative content in urine decreases.

Fat metabolism. The importance of fats in the body. Fat received from food in the digestive tract is broken down into glycerol and fatty acids, which are absorbed mainly into the lymph and only partially into the blood. Through the lymphatic and circulatory systems, fats enter adipose tissue. There is a lot of fat in the subcutaneous tissue, around some internal organs (for example, kidneys), as well as in the liver and muscles. Fats are part of cells (cytoplasm, nucleus, cell membranes), where their quantity is constant. Accumulations of fat can serve other functions. For example, subcutaneous fat prevents increased heat transfer, perinephric fat protects the kidney from bruises, etc.

Fat is used by the body as a rich source of energy. With the breakdown of 1 g of fat in the body, more than two times more energy is released than with the breakdown of the same amount of proteins or carbohydrates. A lack of fat in food disrupts the activity of the central nervous system and reproductive organs, and reduces endurance to various diseases.

Fat is synthesized in the body not only from glycerol and fatty acids, but also from metabolic products of proteins and carbohydrates. Some unsaturated fatty acids needed by the body (linoleic, linolenic and arachidonic) must be supplied to the body in finished form, since the body is not able to synthesize them on its own. The main source of unsaturated fatty acids are vegetable oils. Most of them are in flaxseed and hemp oil, but there is a lot of linoleic acid in sunflower oil.

With fats, the body receives vitamins soluble in them (A, D, E, etc.), which are vitally important for humans.

For 1 kg of adult weight per day, 1.25 g of fat should be supplied from food (80-100 g per day).

The end products of fat metabolism are carbon dioxide and water.

Features of fat metabolism in children. In the child’s body, from the first six months of life, fats cover approximately 50% of the energy requirement. Without fats, it is impossible to develop general and specific immunity. Fat metabolism in children is unstable; if there is a lack of carbohydrates in food or with increased consumption, the fat depot is quickly depleted.

Fat absorption in children is intense. When breastfeeding, up to 90% of milk fats are absorbed, and when artificially fed, 85–90%. In older children, fats are absorbed by 95–97%.

For a more complete use of fat, carbohydrates must be present in children’s food, since when they are lacking in the diet, incomplete oxidation of fats occurs and acidic metabolic products accumulate in the blood.

The body's need for fat per 1 kg of body weight is higher, the younger the child's age. With age, the absolute amount of fat required for the normal development of children increases. From 1 to 3 years, the daily requirement for fat is 32.7 g, from 4 to 7 years – 39.2 g, from 8 to 13 years – 38.4 g.

Carbohydrate metabolism. The role of carbohydrates in the body. Over the course of a lifetime, a person eats about 10 tons of carbohydrates. They enter the body mainly in the form of starch. Having broken down into glucose in the digestive tract, carbohydrates are absorbed into the blood and absorbed by cells. Plant foods are especially rich in carbohydrates: bread, cereals, vegetables, fruits. Animal products (with the exception of milk) are low in carbohydrates.

Carbohydrates are the main source of energy, especially during intense muscle work. In adults, the body receives more than half of its energy from carbohydrates. The breakdown of carbohydrates with the release of energy can occur both in oxygen-free conditions and in the presence of oxygen. The end products of carbohydrate metabolism are carbon dioxide and water. Carbohydrates have the ability to quickly break down and oxidize. In case of severe fatigue or heavy physical exertion, taking a few grams of sugar improves the condition of the body.

In the blood, the amount of glucose is maintained at a relatively constant level (about 110 mg%). A decrease in glucose levels causes a decrease in body temperature, disruption of the nervous system, and fatigue. The liver plays a large role in maintaining constant blood sugar levels. An increase in the amount of glucose causes its deposition in the liver in the form of reserve animal starch - glycogen, which is mobilized by the liver when the blood sugar level decreases. Glycogen is formed not only in the liver, but also in the muscles, where it can accumulate up to 1–2%. Glycogen reserves in the liver reach 150 g. During fasting and muscular work, these reserves are depleted.

However, a persistent increase in blood sugar may occur. This occurs when the function of the endocrine glands is impaired. Impaired functioning of the pancreas leads to the development of diabetes mellitus. With this disease, the ability of body tissues to absorb sugar is lost, as well as convert it into glycogen and store it in the liver. Therefore, blood sugar levels are constantly elevated, which leads to increased excretion in the urine.

The importance of glucose for the body is not limited to its role as an energy source. It is part of the cytoplasm and is therefore necessary for the formation of new cells, especially during the growth period. Carbohydrates are also part of nucleic acids.

Carbohydrates are also important in metabolism in the central nervous system. With a sharp decrease in the amount of sugar in the blood, severe disturbances in the activity of the nervous system are observed. Convulsions, delirium, loss of consciousness, and changes in heart activity occur. If such a person is given glucose into the blood or given regular sugar to eat, then after a while these severe symptoms disappear.

Sugar does not completely disappear from the blood even if it is absent from food, since carbohydrates in the body can be formed from proteins and fats.

The glucose requirement of different organs is not the same. The brain retains up to 12% of the supplied glucose, the intestines - 9%, muscles - 7%, kidneys - 5%. The spleen and lungs almost do not retain it at all.

Metabolism of carbohydrates in children. In children, carbohydrate metabolism occurs with great intensity, which is explained by the high level of metabolism in the children's body. Carbohydrates in a child’s body not only serve as the main source of energy, but also play an important plastic role in the formation of cell membranes and connective tissue substances. Carbohydrates also participate in the oxidation of acidic products of protein and fat metabolism, which helps maintain acid-base balance in the body.

The intensive growth of a child's body requires significant amounts of plastic material - proteins and fats, therefore the formation of carbohydrates in children from proteins and fats is limited. The daily requirement for carbohydrates in children is high and in infancy is 10–12 g per 1 kg of body weight. In subsequent years, the required amount of carbohydrates ranges from 8–9 to 12–15 g per 1 kg of body weight. A child aged 1 to 3 years should be given an average of 193 g of carbohydrates per day with food, from 4 to 7 years - 287 g, from 9 to 13 years - 370 g, from 14 to 17 years - 470 g, for an adult - 500 G.

Carbohydrates are absorbed by the child's body better than by adults (in infants - by 98–99%). In general, children are relatively more tolerant of high blood sugar levels than adults. In adults, glucose appears in the urine if it is 2.5–3 g per 1 kg of body weight, and in children this occurs only when 8–12 g of glucose per 1 kg of body weight is received. Taking small amounts of carbohydrates with food can cause children to double their blood sugar, but after 1 hour the blood sugar level begins to decrease and after 2 hours it is completely normalized.

Water and mineral metabolism. Vitamins. The importance of water and mineral salts. All transformations of substances in the body take place in an aquatic environment. Water dissolves nutrients that enter the body and transports dissolved substances. Together with minerals, it takes part in the construction of cells and in many metabolic reactions. Water is involved in the regulation of body temperature: by evaporating, it cools the body, protecting it from overheating.

Water and mineral salts create mainly the internal environment of the body, being the main component of blood plasma, lymph and tissue fluid. Some salts dissolved in the liquid part of the blood are involved in the transfer of gases in the blood.

Water and mineral salts are part of digestive juices, which determines their importance for digestive processes. And although neither water nor mineral salts are sources of energy in the body, their normal intake and removal from the body is a condition for its normal functioning. Water makes up approximately 65% ​​of body weight in an adult, and about 80% in children.

Loss of water by the body leads to very serious disorders. For example, in case of indigestion in infants, dehydration poses a great danger; this entails convulsions and loss of consciousness. Depriving a person of water for several days is fatal.

Water exchange. The body is constantly replenished with water by absorbing it from the digestive tract. A person needs 2–2.5 liters of water per day with a normal diet and normal ambient temperature. This amount of water comes from the following sources: water consumed when drinking (about 1 l); water contained in food (about 1 l); water, which is formed in the body during the metabolism of proteins, fats and carbohydrates (300–350 cubic cm).

The main organs that remove water from the body are the kidneys, sweat glands, lungs and intestines. The kidneys remove 1.2–1.5 liters of water in urine from the body per day. The sweat glands remove 500–700 cubic meters through the skin in the form of sweat. cm of water per day. At normal temperature and air humidity per 1 sq. cm of skin, about 1 mg of water is released every 10 minutes. The lungs remove 350 cubic meters of water vapor. cm of water; this amount increases sharply with deepening and rapid breathing, and then 700–800 cubic meters can be released per day. cm of water. 100–150 cubic meters are excreted through the intestines with feces per day. cm of water; when intestinal activity is disrupted, more water may be excreted, which leads to depletion of the body in water.

For normal functioning of the body, it is important that the intake of water into the body completely covers its consumption. If more water is removed from the body than enters it, a feeling of thirst occurs. The ratio of the amount of water consumed to the amount released is the water balance.

In a child’s body, extracellular water predominates, this causes greater hydrolability of children, i.e. the ability to quickly lose and quickly accumulate water. The need for water per 1 kg of body weight decreases with age, and its absolute amount increases. A three-month-old child needs 150–170 g of water per 1 kg of body weight, at 2 years old – 95 g, at 12–13 years old – 45 g. The daily need for water for a one-year-old child is 800 ml, at 4 years old – 950-1000 ml, at 5 years old –6 years old – 1200 ml, at 7-10 years old – 1350 ml, at 11–14 years old – 1500 ml.

The importance of mineral salts in the process of child growth and development. The presence of minerals is associated with the phenomenon of excitability and conductivity in the nervous system. Mineral salts provide a number of vital functions of the body, such as the growth and development of bones, nerve elements, muscles; determine the blood reaction (pH), contribute to the normal functioning of the heart and nervous system; used for the formation of hemoglobin (iron), hydrochloric acid of gastric juice (chlorine); maintain a certain osmotic pressure.

In a newborn, minerals make up 2.55% of body weight, in an adult – 5%. With a mixed diet, an adult receives all the minerals he needs in sufficient quantities from food, and only table salt is added to human food during cooking. A growing child's body especially needs an additional supply of many minerals.

Minerals have an important impact on child development. Calcium and phosphorus metabolism are associated with bone growth, the timing of cartilage ossification and the state of oxidative processes in the body. Calcium affects the excitability of the nervous system, muscle contractility, blood clotting, protein and fat metabolism in the body. Phosphorus is needed not only for the growth of bone tissue, but also for the normal functioning of the nervous system, most glandular and other organs. Iron is part of blood hemoglobin.

The greatest need for calcium is observed in the first year of a child’s life; at this age it is eight times more than in the second year of life, and 13 times more than in the third year; then the need for calcium decreases, increasing slightly during puberty. Schoolchildren's daily requirement for calcium is 0.68-2.36 g, for phosphorus - 1.5-4.0 g. The optimal ratio between the concentration of calcium and phosphorus salts for preschool children is 1: 1, at the age of 8-10 years - 1: 1.5, in adolescents and older schoolchildren - 1: 2. With such ratios, skeletal development proceeds normally. Milk contains an ideal ratio of calcium and phosphorus salts, so the inclusion of milk in children's diet is mandatory.

The need for iron in children is higher than in adults: 1–1.2 mg per 1 kg of body weight per day (in adults – 0.9 mg). Children should receive 25–40 mg of sodium per day, 12–30 mg of potassium, and 12–15 mg of chlorine.

Vitamins. These are organic compounds that are absolutely necessary for the normal functioning of the body. Vitamins are part of many enzymes, which explains the important role of vitamins in metabolism. Vitamins contribute to the action of hormones, increasing the body's resistance to adverse environmental influences (infections, high and low temperatures, etc.). They are necessary to stimulate growth, tissue and cell restoration after injury and surgery.

Unlike enzymes and hormones, most vitamins are not produced in the human body. Their main sources are vegetables, fruits and berries. Vitamins are also contained in milk, meat, and fish. Vitamins are required in very small quantities, but their deficiency or absence in food disrupts the formation of the corresponding enzymes, which leads to diseases - vitamin deficiencies.

All vitamins are divided into two large groups: a) water-soluble; b) soluble in fats. Water-soluble vitamins include the group of vitamins B, vitamins C and P. Fat-soluble vitamins include vitamins A1 and A2, D, E, K.

Vitamin B1 (thiamine, aneurin) is found in hazelnuts, brown rice, wholemeal bread, barley and oatmeal, especially in brewer's yeast and liver. The daily requirement for the vitamin is 1 mg in children under 7 years old, 1.5 mg from 7 to 14 years old, 2 mg from 14 years old, and 2–3 mg in adults.

Without vitamin B1 in food, beriberi disease develops. The patient loses his appetite, quickly gets tired, and weakness gradually appears in the leg muscles. Then there is a loss of sensitivity in the muscles of the legs, damage to the auditory and optic nerves, cells of the medulla oblongata and spinal cord die, paralysis of the limbs occurs, and without timely treatment - death.

Vitamin B2 (riboflavin). In humans, the first sign of a lack of this vitamin is skin lesions (most often in the lip area). Cracks appear, become wet and become covered with a dark crust. Later, damage to the eyes and skin develops, accompanied by the falling off of keratinized scales. In the future, malignant anemia, damage to the nervous system, a sudden drop in blood pressure, convulsions, and loss of consciousness may develop.

Vitamin B2 is found in bread, buckwheat, milk, eggs, liver, meat, and tomatoes. The daily need for it is 2–4 mg.

Vitamin PP (nicotinamide) is found in green vegetables, carrots, potatoes, peas, yeast, buckwheat, rye and wheat bread, milk, meat, and liver. The daily need for it in children is 15 mg, in adults – 15–25 mg.

With vitamin deficiency RR, a burning sensation in the mouth, excessive salivation and diarrhea are noted. The tongue becomes crimson-red. Red spots appear on the arms, neck, and face. The skin becomes rough and rough, which is why the disease is called pellagra (from Italian pelle agra - rough skin). In severe cases of the disease, memory weakens, psychosis and hallucinations develop.

Vitamin B12 (cyanocobalamin) in humans is synthesized in the intestines. Contained in the kidneys, liver of mammals and fish. With its deficiency, the body develops malignant anemia associated with impaired formation of red blood cells.

Vitamin C (ascorbic acid) is widely distributed in nature in vegetables, fruits, pine needles, and liver. Ascorbic acid is well preserved in sauerkraut. 100 g of pine needles contain 250 mg of vitamin C, 100 g of rose hips - 150 mg. The requirement for vitamin C is 50-100 mg per day.

Lack of vitamin C causes scurvy. Usually the disease begins with general malaise and depression. The skin takes on a dirty gray tint, gums bleed, and teeth fall out. Dark spots of hemorrhage appear on the body, some of them ulcerate and cause sharp pain.

Vitamin A (retinol, axerophthol) in the human body is formed from the common natural pigment carotene, found in large quantities in fresh carrots, tomatoes, lettuce, apricots, fish oil, butter, liver, kidneys, and egg yolk. The daily requirement for vitamin A for children is 1 mg, for adults – 2 mg.

With a lack of vitamin A, the growth of children slows down, and “night blindness” develops, i.e., a sharp drop in visual acuity in dim lighting, leading in severe cases to complete but reversible blindness.

Vitamin D (ergocalciferol) is especially necessary for children to prevent one of the most common diseases of childhood - rickets. With rickets, the process of bone formation is disrupted, the bones of the skull become soft and pliable, and the limbs become bent. Hypertrophied parietal and frontal tubercles form on softened areas of the skull. Lethargic, pale, with an unnaturally large head and a short bow-legged body, a large belly, such children are sharply retarded in development.

All these severe disorders are associated with the absence or deficiency of vitamin D in the body, which is found in yolks, cow's milk, and fish oil.

Vitamin D can be formed in human skin from the provitamin ergosterol under the influence of ultraviolet rays. Fish oil, sun exposure or artificial ultraviolet irradiation are means of preventing and treating rickets.

10.3. Age-related characteristics of energy metabolism

Even in conditions of complete rest, a person spends a certain amount of energy: the body continuously spends energy on physiological processes that do not stop for a minute. The minimum level of metabolism and energy expenditure for the body is called the basal metabolism. Basal metabolism is determined in a person in a state of muscular rest - lying down, on an empty stomach, i.e. 12-16 hours after eating, at an ambient temperature of 18-20 ° C (comfort temperature). In a middle-aged person, the basal metabolism is 4187 J per 1 kg of weight per hour. On average, this is 7,140,000-7,560,000 J per day. For each person, the basal metabolic rate is relatively constant.

Features of basal metabolism in children. Since children have a relatively larger body surface per unit mass than an adult, their basal metabolism is more intense than that of adults. In children there is also a significant predominance of assimilation processes over dissimilation processes. The younger the child, the higher the energy costs for growth. Thus, energy consumption associated with growth at the age of 3 months is 36%, at the age of 6 months – 26%, at 9 months – 21% of the total energy value of food.

The basal metabolism per 1 kg of weight in an adult is 96,600 J. Thus, in children 8-10 years old, the basal metabolism is two or two and a half times higher than in adults.

The basal metabolic rate in girls is slightly lower than in boys. This difference begins to appear already in the second half of the first year of life. The work performed by boys entails higher energy consumption than by girls.

Determining the basal metabolic rate often has diagnostic value. The basal metabolism increases with excessive thyroid function and some other diseases. If the function of the thyroid gland, pituitary gland, or gonads is insufficient, the basal metabolism decreases.

Energy expenditure during muscle activity. The harder the muscular work, the more energy a person spends. For schoolchildren, preparing for a lesson and a lesson at school require energy 20–50% higher than the basal metabolic energy.

When walking, energy expenditure is 150–170% higher than the basal metabolism. When running or climbing stairs, energy expenditure exceeds basal metabolism by 3–4 times.

Training the body significantly reduces energy consumption for the work performed. This is due to a decrease in the number of muscles involved in work, as well as changes in breathing and blood circulation.

People of different professions have different energy expenditures. During mental work, energy costs are lower than during physical work. Boys have a higher total daily energy expenditure than girls.

AGE ANATOMY AND HUMAN PHYSIOLOGY

LECTURE 5

Topic: Metabolism and energy and their age-related characteristics.

Hormonal regulation of body functions and its age-related features.

1. Characteristics and types of metabolic processes in the body.

2. Metabolism of organic substances and its importance for the growth and development of the body.

3. Metabolism of inorganic substances and its importance in the process of growth and development of the body.

4. Features of hormonal regulation of body functions.

5. Hormones, their classification and significance.

6. Structure and functions of the endocrine glands. 7. Hormonal status of the body and diseases associated with hormonal imbalance.

1. Batuev A.S. - “Anatomy, physiology and human psychology.” - St. Petersburg - 2003;

2. Bezrukikh M.M. - “Age physiology: Physiology of child development.” - M. - 2002;

3. McDermott M.T. - “Secrets of endocrinology.” - M. - 1998.

4. Prishchepa I.M. - “Age-related anatomy and physiology.” - Minsk - 2006;

5. Sapin M.R. - “Human Anatomy and Physiology.” - M. - 1999;

1. Characteristics and types of metabolic processes in the body.

Metabolism is the entry into the body of various substances from the external environment, their absorption and the release of the resulting breakdown products. Metabolism consists of two interrelated and opposing processes - anabolism and catabolism. Anabolism- these are reactions of biological synthesis of complex molecules of basic biological compounds, specific to a given organism, from simple components entering cells. Anabolism is the basis for the formation of new tissues during growth, regeneration processes, synthesis of cellular compounds and requires energy expenditure. The latter is supplied by reactions catabolism, in which the breakdown of molecules of complex organic substances occurs, releasing energy. The end products of catabolism (water, carbon dioxide, ammonia, urea, uric acid) do not participate in biological synthesis and are removed from the body. The relationship between the processes of anabolism and catabolism determines three states: growth, destruction of structures and dynamic equilibrium. The latter condition is typical for a healthy adult: the processes of anabolism and catabolism are balanced, tissue growth does not occur. As the body grows, anabolism prevails over catabolism; with tissue destruction, the opposite is true.

2. Metabolism of organic substances and its importance for the growth and development of the body.

Squirrels- These are polymers consisting of amino acids that are linked together in a certain sequence. The specificity of proteins is determined by the number of amino acids and their sequence. Of the 20 amino acids, only 8 are essential (tryptophan, leucine, isoleucine, valine, threonine, lysine, methionine, phenylalanine) and enter the body from the outside with food. Other amino acids are non-essential; their intake into the body through food is not necessary; they can be synthesized in the body. Food proteins that contain the entire necessary set of amino acids for the normal synthesis of body proteins are called complete (animal proteins). Food proteins that do not contain all the amino acids necessary for protein synthesis in the body are called incomplete (plant proteins). The biological value of proteins from eggs, meat, milk, and fish is the highest. With a mixed diet, the body receives the entire set of amino acids necessary for protein synthesis. The supply of all essential amino acids is especially important for a growing organism. For example, the absence of rubber in food leads to stunted growth of a child, and valine leads to balance disorders in children. Children need more protein than adults, as their processes of growth and formation of new cells and tissues are more intense. Protein starvation of a child leads to a delay and then a complete cessation of growth and physical development. The child becomes lethargic, there is a sharp loss of weight, widespread swelling, diarrhea, inflammation of the skin, and decreased resistance to infections. Serious developmental disorders in children and adolescents occur because protein is the main plastic material of the body, from which various cellular structures are formed. In addition, proteins are part of enzymes, hormones, form hemoglobin and blood antibodies. Protein metabolism is regulated by the nervous and humoral pathways. Nervous regulation is carried out by the hypothalamus; humoral regulation is realized by the somatotropic hormone of the pituitary gland and thyroid hormones (thyroxine and triiodothyronine), which stimulate protein synthesis. Adrenal punishment hormones (hydrocortisone, corticosterone) increase the breakdown of proteins in tissues, and, on the contrary, stimulate them in the liver. The end products of protein metabolism are nitrogen-containing substances - urea and uric acid, from which glucose is first formed, and then carbon dioxide and water.

In organism fat synthesized from glycerol and fatty acids, as well as from metabolic products of carbohydrates and proteins. The main function of fat is energetic: its breakdown produces 2 times more energy (9.3 kcal) than the breakdown of the same amount of proteins and carbohydrates; most of the fat is located in adipose tissue and constitutes a reserve energy reserve. In addition, fat also performs a plastic function: it is used to build new membrane structures of cells and replace old ones. Fats, like proteins, have specificity, which is associated with the presence of fatty acids in them. The absence of fats with such acids in the diet leads to severe pathological disorders. Vegetable fats should predominate in the diet. After 40 years, animal fats should be excluded from the diet, since, being embedded in the cell membrane, they make it impermeable to various substances, as a result of which the cell ages. Regulation of fat metabolism occurs through the nervous and humoral pathways. Nervous regulation is carried out by the hypothalamus. Parasympathetic nerves promote fat deposition, and sympathetic nerves enhance its breakdown; humoral regulation is realized by the somatotropic hormone of the pituitary gland; hormones of the adrenal medulla (adrenaline and norepinephrine) (thyroid gland thyroxine and triiodothyronine) inhibit the mobilization of fat from adipose tissue; glucocorticoids and insulin.

Carbohydrates perform both plastic and energetic functions in the body. As a plastic material, they are part of the cell membrane and cytoplasm, nucleic acids and connective tissue. The energy function of carbohydrates is that they are able to quickly decompose and oxidize (1g releases 4.1 kcal). The rate of breakdown of glucose and the ability to quickly extract and process its reserve - glycogen - create conditions for the emergency mobilization of energy resources during emotional arousal and muscle stress. The largest amount of carbohydrates is found in bread, potatoes, vegetables and fruits. Carbohydrates are broken down into glucose and absorbed into the blood. Unused glucose is stored as glycogen in the liver and muscles and serves as a reserve of carbohydrates in the body. A large amount of carbohydrates in a child’s food increases the blood glucose level by almost 2 times. This is called dietary glycemia. In children it is associated with increased carbohydrate metabolism, in adults it is accompanied by glucosuria - the appearance of sugar in the urine. A persistent pathological increase in the concentration of carbohydrates in the blood, accompanied by the excretion of sugar in the urine, is called diabetes mellitus. Carbohydrate metabolism is regulated by the nervous and humoral pathways. Nervous regulation is carried out by the hypothalamus. Humoral regulation is determined by somatotropic hormone (pituitary gland), thyroxine and triiodothyronine (thyroid gland), glucagon (pancreas), adrenaline (adrenal medulla) and glucocopticoids (cortical layer under the renal glands). All these hormones increase blood sugar levels and only insulin (pancreas) lowers it.

3. Metabolism of inorganic substances and its importance in the process of growth and development of the body.

Water is not a source of energy, but its entry into the body is mandatory for its normal functioning. The amount of water in an adult is 65% of the total body weight, in a child – 75–80%. It is an integral part of the internal environment of the body, a universal solvent, and is involved in the regulation of body temperature. Most of the water in the blood is 92%, in internal organs its content is 76-86%, in muscles - 70%, less in adipose tissue - 30% and in bones - 22%. The daily water requirement of an adult is 2 – 2.5 liters. This amount consists of water consumed when drinking (1 l), contained in food (1 l) and formed during metabolism (300-350 ml). Normal activity of the body is characterized by maintaining water balance, i.e. the amount of water coming in is equal to the amount of water going out. If the water is removed. If more water is removed from the body than it enters, a feeling of thirst occurs. The child's body quickly accumulates and quickly loses water. This is due to the intensive growth of physiological immaturity of the kidneys and neuroendocrine mechanisms for regulating water metabolism. At the same time, water loss and dehydration in children are much higher than in adults, and largely depend on the release of water through the lungs and skin. The release of water per day can reach 50% of the volume of liquid taken, especially when the child is overheated. Not drinking enough water can lead to “salt fever,” which is an increase in body temperature. The need for water per 1 kg of body weight decreases with age. At 3 months, a child needs 150-170 g of water per 1 kg of weight, at 2 years - 95 g, at 13 years - 45 g. Regulation of water metabolism is carried out through the neurohumoral pathway. The thirst center is located in the hypothalamus. Water balance is regulated by mineralocorticosteroids (adrenal cortex) and antidiuretic hormone (hypothalamus).

For the normal functioning of the body, intake is necessary minerals which determine the structure and functions of many enzymatic systems and processes, ensure their normal course and participate in plastic metabolism. In a newborn child, minerals make up 2.5% of body weight, in an adult it is 5%. Mineral salts are contained in food in quantities sufficient to maintain vital functions; only sodium chloride is added additionally. A growing body and during pregnancy require more mineral salts. It is necessary to additionally introduce potassium, magnesium, sodium, chlorine and phosphorus salts. With excessive consumption of mineral salts, they can be stored in reserve: sodium chloride - in the subcutaneous tissue, calcium salts - in the bones, potassium salts - in the muscles. When there is a lack of salts in the body, they come from the depot. The study of the biological effects of minerals on the body began in 1891. Russian scientist V.I. Vernadsky. He suggested that living organisms contain elements of the earth's crust. Currently, they are divided into macro- and microelements. Macroelements are necessary for a person every day in gram quantities; the need for microelements does not exceed milligrams or even micrograms, and their content in the body is less than 0.005%.

Macroelements include calcium, magnesium, sodium, potassium, phosphorus, sulfur, vanadium, each of which performs several functions in the body. Calcium is the most common macronutrient in the human body. Its total content is 1 kg. 99% of calcium is part of the skeleton, 1% is part of the teeth. Calcium is necessary for the process of blood clotting, nerve conduction, contraction of skeletal and cardiac muscles, the absorption of calcium is greatly influenced by its combination with other food components. For example, when it is consumed along with fats, digestibility decreases sharply. Calcium is well utilized from foods that are also rich in phosphorus. The optimal ratio of calcium and phosphorus is 2:1, which occurs in milk and dairy products, which are the main food sources of calcium. There is especially a lot of calcium in cheeses, as well as legumes, soybeans, and peanuts. 20-30% of calcium is absorbed from dairy products, and 50% from plant products. The need for calcium increases in childhood due to the growth of bone tissue in pregnant and lactating women after injuries and bone fractures. The ratio of calcium and phosphorus is most important for the development of a child. The metabolism of these substances is associated with bone growth, cartilage ossification and oxidative processes in the body. In women, the need for calcium increases during menopause. At this time, its deficiency in bone tissue leads to the development of osteoporosis with increased bone fragility and a tendency to fracture. With aging, bone tissue loses some calcium, which is called bone demineralization, which affects all parts of the skeleton with age. This contributes to the development of various skeletal diseases, including osteochondrosis, more frequent bone fractures; the total magnesium content in the adult body is 21-24g, of which 50-70% is in bone tissue. When there is a deficiency of magnesium, it is partially released from the bones. Magnesium is a universal regulator of biochemical and physiological processes in the body, as it participates in energy and plastic metabolism. It is involved in more than 300 biochemical reactions. Magnesium is of particular importance in the functioning of the nervous system and the conduction system of the heart. A good supply of magnesium in the body helps to better tolerate stressful situations and suppress depression. The body's need for it increases significantly during physical activity, among athletes during long-term training, as well as during stressful situations. The daily requirement for magnesium by the adult human body is 300-400 mg. In persons engaged in heavy physical labor, in athletes, pregnant and lactating women, it increases by 150 mg per day.

4. Features of hormonal regulation of body functions.

The endocrine system is a system of glands that produce hormones and release them directly into the blood. These glands, called endocrine or endocrine glands, do not have excretory ducts; they are located in different parts of the body, but are functionally closely interconnected. The endocrine system of the body as a whole maintains the constancy of the internal environment of the body, which is necessary for the normal course of physiological processes. In addition, the endocrine system, together with the nervous and immune systems, ensures reproductive function, growth and development of the body, formation, utilization and storage (“in reserve” in the form of glycogen or fatty tissue) of energy.

The endocrine system was discovered by scientists only at the beginning of the twentieth century. True, a little earlier, researchers drew attention to strange inconsistencies in the structure of some organs. In appearance, such anatomical formations resembled glands that produced secretions - hormones. Hormones are organic compounds produced by certain cells and designed to control, regulate and coordinate body functions. Higher animals have two regulatory systems with the help of which the body adapts to constant internal and external changes. One of them is the nervous system, which quickly transmits signals (in the form of impulses) through a network of nerves and nerve cells; the other is endocrine, which carries out chemical regulation with the help of hormones that are carried in the blood and have an effect on tissues and organs remote from the place of their release. All mammals, including humans, have hormones; they are also found in other living organisms.

5. Hormones, their classification and significance

Hormones are biological active substances that have a strictly specific and selective effect, capable of increasing or decreasing the level of vital activity of the body. All hormones are divided into:

Steroid hormones- are produced from cholesterol in the adrenal cortex, in the gonads.

Polypeptide hormones- protein hormones (insulin, prolactin, ACTH, etc.).

Hormones derived from amino acids- adrenaline, norepinephrine, dopamine, etc.

Hormones derived from fatty acids- prostaglandins.

According to their physiological effects, hormones are divided into:

Launchers(hormones of the pituitary gland, pineal gland, hypothalamus). Affect other endocrine glands;

Performers- influence individual processes in tissues and organs.

The physiological action of hormones is aimed at:

1) providing humoral, i.e. carried out through the blood, regulation of biological processes;

2) maintaining the integrity and constancy of the internal environment, harmonious interaction between the cellular components of the body;

3) regulation of the processes of growth, maturation and reproduction.

Hormones regulate the activity of all cells in the body. They affect mental acuity and physical mobility, physique and height, determine hair growth, tone of voice, sex drive and behavior. Thanks to the endocrine system, a person can adapt to strong temperature fluctuations, excess or lack of food, and physical and emotional stress. The study of the physiological action of the endocrine glands made it possible to reveal the secrets of sexual function and the mechanism of childbirth, as well as answer the question of why some people are tall and others are short, some are plump, others are thin, some are slow, others are agile, some are strong, others are weak.

Endocrinology studies the role of hormones in the life of the body and the normal and pathological physiology of the endocrine glands. It appeared as a medical discipline only in the 20th century, but endocrinological observations have been known since antiquity. Hippocrates believed that human health and temperament depend on special humoral substances. Aristotle drew attention to the fact that a castrated calf, growing up, differs in sexual behavior from a castrated bull in that it does not even try to climb on a cow. In addition, castration has been practiced for centuries both to tame and domesticate animals and to transform humans into obedient slaves.

The organ that responds to this hormone is the target organ (effector). The cells of this organ are equipped with receptors. Hormones, once in the bloodstream, must travel to the appropriate target organs. In a normal state, there is a harmonious balance between the activity of the endocrine glands, the state of the nervous system and the response of target tissues (tissues that are targeted). Any violation in each of these links quickly leads to deviations from the norm. Excessive or insufficient production of hormones causes various diseases, accompanied by profound chemical changes in the body.

The transport of high molecular weight (protein) hormones has been little studied due to the lack of accurate data on the molecular weight and chemical structure of many of them. Hormones with a relatively small molecular weight quickly bind to plasma proteins, so that the content of hormones in the blood in the bound form is higher than in the free form; these two forms are in dynamic equilibrium. It is the free hormones that exhibit biological activity, and in a number of cases it has been clearly shown that they are extracted from the blood by target organs. The significance of protein binding of hormones in the blood is not entirely clear. It is believed that such binding facilitates the transport of the hormone or protects the hormone from loss of activity.

6. Structure and functions of the endocrine glands

The endocrine system of the human body combines endocrine glands, small in size and different in structure and function: pituitary gland, pineal gland, thyroid and parathyroid glands, pancreas, adrenal glands and gonads. All taken together, they weigh no more than 100 grams, and the amount of hormones they produce can be calculated in billionths of a gram. Nevertheless, the sphere of influence of hormones is extremely large. They have a direct effect on the growth and development of the body, on all types of metabolism, and on puberty. There are no direct anatomical connections between the endocrine glands, but there is an interdependence of the functions of one gland on the others. The endocrine system of a healthy person can be compared to a well-played orchestra, in which each gland confidently and subtly leads its part. And the main, supreme endocrine gland, the pituitary gland, acts as the conductor of this “orchestra”.

Pituitary, lat. hypophysis, or lower cerebral appendage - a rounded formation located on the lower surface of the brain in the pituitary fossa of the sella turcica of the sphenoid bone. The pituitary gland belongs to the central organs of the endocrine system and to the diencephalon. The dimensions of the pituitary gland are quite individual: the anteroposterior size ranges from 5 to 13 mm, the supero-inferior - from 6 to 8 mm, the transverse - from 12 to 15 mm; weight 0.4-0.6 g, and in women the pituitary gland is usually larger.

The pituitary gland is located at the base of the brain (lower surface), in the pituitary fossa of the sella turcica of the sphenoid bone. The pituitary gland consists of two large lobes of different origin and structure: the anterior one - the adenohypophysis (accounts for 70-80% of the mass of the pituitary gland) and the posterior one - the neurohypophysis. The adenohypophysis is the site of formation of tropic and some other protein hormones that control peripheral endocrine glands, anabolic and growth processes, metabolism and reproduction. Hormones deposited in the neurohypophysis are involved in the regulation of water balance, vascular tone, milk formation and during childbirth.

The large anterior lobe of the pituitary gland secretes six tropic hormones into the blood. One of them - growth hormone, or somatotropic hormone (GH) - stimulates skeletal growth, activates protein biosynthesis, and promotes an increase in body size. If, as a result of any disturbances, the pituitary gland begins to produce too much growth hormone, body growth increases sharply, and gigantism develops. In cases where increased secretion of growth hormone occurs in an adult, this is accompanied by acromegaly - an increase not in the entire body, but only in its individual parts: the nose, chin, tongue, arms and legs. If the pituitary gland does not produce enough growth hormone, the child’s growth stops and pituitary dwarfism develops. The remaining five hormones: adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), prolactin, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) - direct and regulate the activity of other endocrine glands. Adrenocorticotropic hormone stimulates the activity of the adrenal cortex, causing it, if necessary, to more intensively produce corticosteroids. Thyroid-stimulating hormone promotes the formation and release of the thyroid hormone thyroxine. Follicle-stimulating hormone promotes egg maturation in women, and stimulates spermatogenesis in men. Luteinizing hormone acts in close contact with it. It is thanks to LH that women develop the so-called corpus luteum, without which a normal pregnancy is impossible.

Prolactin, or lactogenic hormone, also takes an active part in reproduction processes. The size and shape of the mammary glands largely depend on this hormone; through a complex system of relationships between various hormones, it stimulates the production of breast milk in a woman after childbirth.

However, being the supreme gland of the endocrine system, the pituitary gland itself is subordinate to the central nervous system, and in particular to the hypothalamus. Together with the neurosecretory nuclei of the hypothalamus, the pituitary gland forms the hypothalamic-pituitary system, which controls the activity of the peripheral endocrine glands.

Hypothalamic-pituitary system. The pituitary gland is functionally and anatomically connected with the hypothalamus into a single hypothalamic-pituitary system, which is the center of integration of the nervous and endocrine systems. The hypothalamic-pituitary system controls and coordinates the activity of almost all the endocrine glands of the body.

The hypothalamus is the highest autonomic center that constantly coordinates and regulates the activity of various parts of the brain and all internal organs. Heart rate, tone of blood vessels, body temperature, amount of water in the blood and tissues, accumulation or consumption of proteins, fats, carbohydrates, mineral salts - in a word, the existence of our body, the constancy of its internal environment is under the control of the hypothalamus.

The hypothalamus controls the pituitary gland using both nerve connections and the blood vessel system. The blood that enters the anterior lobe of the pituitary gland necessarily passes through the median eminence of the hypothalamus and is enriched there with hypothalamic neurohormones. Neurohormones are substances of peptide nature, which are parts of protein molecules. To date, seven neurohormones have been discovered, the so-called liberins (that is, liberators), which stimulate the synthesis of tropic hormones in the pituitary gland. And three neurohormones - prolactostatin, melanostatin and somatostatin - on the contrary, inhibit their production.

Neurohormones also include vasopressin and oxytocin. They are produced by the nerve cells of the hypothalamic nuclei, and then transported along their own axons (nerve processes) to the posterior lobe of the pituitary gland, and from here these hormones enter the blood, having a complex effect on the body's systems.

Oxytocin stimulates the contraction of the smooth muscles of the uterus during childbirth and the production of milk by the mammary glands. Vasopressin is actively involved in the regulation of the transport of water and salts through cell membranes; under its influence, the lumen of blood vessels decreases and, consequently, blood pressure increases. Because this hormone has the ability to retain water in the body, it is often called antidiuretic hormone (ADH). The main point of application of ADH is the renal tubules, where it stimulates the reabsorption of water from primary urine into the blood. When, as a result of disturbances in the activity of the hypothalamic-pituitary system, the production of ADH sharply decreases, diabetes insipidus develops - diabetes. Its main symptoms are intense thirst and increased urine output. However, one should not think that the hypothalamus and pituitary gland only give orders, sending “guiding” hormones down the chain. They themselves sensitively analyze signals coming from the periphery, from the endocrine glands. The activity of the endocrine system is carried out on the basis of the universal principle of feedback. An excess of hormones of one or another endocrine gland inhibits the release of a specific pituitary hormone responsible for the functioning of this gland, and a deficiency prompts the pituitary gland to increase the production of the corresponding triple hormone.

The mechanism of interaction between the neurohormones of the hypothalamus, the triple hormones of the pituitary gland and the hormones of the peripheral endocrine glands in a healthy body has been worked out over a long evolutionary development and is very reliable.

However, a failure in one link of this complex chain is enough for a violation of quantitative, and sometimes qualitative, relationships in the whole system to occur, leading to various endocrine diseases.

Neurohypophysis - consists of nerve lobe And funnels, infundibulum connecting the neural lobe with the median eminence. The nerve lobe is formed by ependymal cells (pituicytes) and axon endings of neurosecretory cells paraventricular And supraoptic nuclei of the hypothalamus of the diencephalon, in which vasopressin (also known as antidiuretic hormone) and oxytocin are synthesized, transported along the nerve fibers that make up the hypothalamic-pituitary tract to the neurohypophysis. In the posterior lobe of the pituitary gland, these hormones are deposited and from there enter the blood. The pituitary infundibulum connects with the hypothalamic infundibulum to form the pituitary stalk.

Adenohypophysis - consists of branched cords formed by three types of glandular cells. Due to the large number of capillaries, the anterior lobe of the pituitary gland has a red-brown color on section. The anterior part of the adenohypophysis produces tropic hormones: corticotropin (adrenocorticotropic hormone), thyrotropin (thyroid-stimulating hormone), gonadotropic hormones - follitropin (follicle-stimulating hormone) and luteotropin (luteinizing hormone); somatotropin (growth hormone) and prolactin (lactotropic hormone).

The intermediate part, which has a cavity (pituitary fissure), is clearly visible during pregnancy, as well as in the fetus and in children under 5 years of age; produces melanotropin (melanocyte-stimulating hormone) and lipotropin (lipotropic hormone).

Pituitary hormones. The anterior lobe of the pituitary gland produces protein hormones, six of which are isolated in chemically pure form. Their structure has now been completely deciphered. The exact number of hormones secreted by the anterior lobe has not been established; only well-known ones are discussed below.

A growth hormone. Many hormones influence the growth of the body, but the pituitary growth hormone (somatotropin) seems to play the most important role in this complex process. After removal of the pituitary gland, growth virtually stops. The administration of this hormone to young animals accelerates growth, and in adults it can lead to its resumption, and metabolic studies in these cases always reveal a decrease in the excretion (removal) of nitrogen from the body. Nitrogen retention is a necessary sign of true growth, indicating that new tissue is actually being formed and not simply an increase in body weight due to the accumulation of fat or water. With pathological processes leading to a decrease in the function of the pituitary gland, in some cases pituitary dwarfism occurs; such dwarfs have small body sizes, but otherwise remain normal people. Other dysfunctions of the pituitary gland may be accompanied by excessive secretion of growth hormone, causing gigantism. If large amounts of growth hormone are produced before the body's maturation is complete, height increases proportionately; if this occurs after adulthood, a condition called acromegaly occurs, in which there is disproportionate growth of certain parts of the body, since in adults some bones lose the ability to further lengthen. With acromegaly, the patient acquires a characteristic appearance: the eyebrows, nose and lower jaw begin to protrude, the hands, feet and chest become enlarged, the back becomes motionless, the nose and lips thicken.

Lactogenic hormone pituitary gland (prolactin) stimulates lactation - the formation of milk in the mammary glands. Persistent lactation combined with amenorrhea (abnormal absence or suppression of menstrual flow) can occur with a pituitary tumor. This disorder is also associated with disturbances in the secretory activity of the hypothalamus, which normally suppresses the release of prolactin. In females of some mammals, prolactin also affects other processes; in particular, it can stimulate the secretion of the hormone progesterone by the corpus luteum of the ovary. Prolactin is present in the pituitary gland of not only female but also male individuals, not only in mammals, but also in lower vertebrates. Little is known regarding its functions in the male body.

Thyroid-stimulating hormone pituitary gland (thyrotropin) stimulates the growth of the thyroid gland and its secretory activity. After removal of the pituitary gland, the function of the thyroid gland completely stops and it decreases in size. Administration of thyrotropin may cause overactivity of the thyroid gland. Thus, disturbances in its function can be a consequence not only of diseases of the gland itself, but also of pathological processes in the pituitary gland and, accordingly, require different treatments.

Adrenocorticotropic hormone pituitary gland (ACTH, corticotropin) stimulates the adrenal cortex in the same way as thyroid-stimulating hormone stimulates the thyroid gland. One difference, however, is that adrenal function is not completely shut down in the absence of ACTH. When there is no stimulation from the pituitary gland, the adrenal cortex retains the ability to secrete the vital hormone aldosterone, which regulates sodium and potassium levels in the body. However, without ACTH, the adrenal glands produce insufficient amounts of another vital hormone, cortisol, and lose the ability to increase its secretion when necessary. Therefore, patients with insufficiency of pituitary gland function become very sensitive to various types of stress and stress. Excessive amounts of ACTH, which can be produced by pituitary tumors, lead to the development of a potentially fatal disease, the so-called. Cushing's syndrome. Its characteristic signs include weight gain, a moon-shaped face, increased fat deposits in the upper body, increased blood pressure, and muscle weakness.

Gonadotropic hormones(gonadotropins). The anterior lobe of the pituitary gland secretes two gonadotropic hormones. One of them, follicle-stimulating hormone, stimulates the development of eggs in the ovaries and sperm in the testes. The second is called luteinizing hormone; in the female body it stimulates the production of female sex hormones in the ovaries and the release of a mature egg from the ovary, and in the male body it stimulates the secretion of the hormone testosterone. The introduction of these hormones or their excess production due to disease causes premature sexual development of the immature organism. When the pituitary gland is removed or destroyed by a pathological process, changes similar to those that occur during castration occur.

Metabolism regulation. Hormones secreted by the anterior pituitary gland are necessary for the proper use of dietary carbohydrates in the body; in addition, they perform other important functions in metabolism. A special role in the regulation of metabolism appears to belong to growth hormone and adrenocorticotropic hormone, which are functionally closely related to the pancreatic hormone, insulin. It is well known that in the absence of insulin, a chronic disease develops – diabetes mellitus. With the simultaneous removal of the pancreas and pituitary gland, most symptoms of diabetes are absent, so in this respect the influence of the hormones of the pituitary gland and pancreas is, as it were, opposite.

Intermediate share The pituitary gland secretes melanocyte-stimulating hormone (MSH, intermedin), which increases the size of some pigment cells in the skin of lower vertebrates. For example, tadpoles deprived of this hormone acquire a silvery color due to contraction (compression) of pigment cells. MSH is formed from the same precursor molecule as adrenocorticotropic hormone (ACTH). In the anterior lobe of the pituitary gland, this precursor is converted into ACTH, and in the intermediate lobe into MSH. MSH is also produced in the pituitary gland of mammals, but its function remains unclear.

Posterior lobe The pituitary gland contains two hormones, both of which are produced in the hypothalamus and from there enter the pituitary gland. One of them, oxytocin, is the most active of the factors present in the body, causing the same strong contractions of the uterus as during childbirth. This hormone is sometimes used in obstetrics to stimulate prolonged labor, but the significance of its normal concentrations during labor has not been established. Oxytocin also causes contractions of the muscle walls of the gallbladder, intestines, ureters and bladder. The second hormone, vasopressin, causes numerous effects when introduced into the body, including an increase in blood pressure due to vasoconstriction and a decrease in diuresis (urine output). However, under normal conditions it has only one known effect in the body - it regulates the amount of water excreted through the kidneys. Even under the influence of extremely low concentrations, water filtered in the renal glomeruli is absorbed back into the renal tubules (reabsorbed), and concentrated urine is formed. When the posterior lobe of the pituitary gland is destroyed by tumors or other pathological processes, a condition called diabetes insipidus develops. With this disease, the body loses a huge amount of water through the kidneys, sometimes exceeding 38 liters per day. There is intense thirst, and to avoid dehydration, patients have to consume an appropriate amount of water.

Pineal gland(pineal, or pineal, gland), a small formation located in vertebrates under the scalp or deep in the brain; located on the midline of the body, like the heart, it functions either as a light-perceiving organ or as an endocrine gland, the activity of which depends on illumination. In some vertebrate species both functions are combined. In humans, this formation is shaped like a pine cone, which is where it got its name (Greek epiphysis - cone, growth).

The pineal gland develops in embryogenesis from the fornix (epithalamus) of the posterior part (diencephalon) of the forebrain. One, located on the right side of the brain, is called the pineal gland, and the second, on the left, is the parapineal gland. The pineal gland is present in all vertebrates, with the exception of crocodiles and some mammals, such as anteaters and armadillos. The parapineal gland as a mature structure is present only in certain groups of vertebrates, such as lampreys, lizards and frogs.

Where the pineal and parapineal glands function as a light-sensing organ, or “third eye,” they are only able to distinguish between different degrees of illumination, and not visual images. In this capacity, they can determine certain forms of behavior, for example, the vertical migration of deep-sea fish depending on the change of day and night.

In humans, the activity of the pineal gland is associated with such phenomena as disruption of the body’s circadian rhythm due to flying across several time zones, sleep disorders and, probably, “winter depression.”

Thyroid(glandula thyreoidea), a specialized endocrine organ in vertebrates and humans; produces and accumulates iodine-containing hormones involved in the regulation of metabolism and energy in the body.

In humans, the thyroid gland is fully formed by 8-9 months. fetal development; consists of 2 lateral lobes and a transverse isthmus connecting them near the lower ends. Sometimes the pyramidal lobe extends upward from the isthmus. It is located on the neck in front of the windpipe and on the side walls of the larynx, adjacent to the thyroid cartilage (hence the name). At the back, the lateral lobes are in contact with the walls of the pharynx and esophagus. The outer surface of the thyroid gland is convex, the inner surface, facing the trachea and larynx, is concave. The diameter of the thyroid gland is about 50-60 mm, at the level of the isthmus 6-8 mm. Weight about 15-30 G(women have slightly more). The thyroid gland is abundantly supplied with blood vessels; the superior and inferior thyroid arteries approach it.

The main structural and functional unit of the thyroid gland is the follicle (spherical or geometrically irregular in shape), the cavity of which is filled with a colloid consisting of iodine-containing protein, thyroglobulin. The follicles are closely adjacent to each other. The walls of the follicle are lined with single-layer glandular epithelium. The structure of the thyroid gland is also formed by the connective tissue stroma, adjacent to the wall of the follicle and consisting of collagen and elastic fibers, with vessels and nerves passing through it. The shape, volume and height of follicular epithelial cells vary depending on the functional state of the thyroid gland: normally the epithelium is cubic, with increased functional activity it is high cylindrical, with decreased functional activity it is flat. The size of the Golgi complex, the number of mitochondria and secretory droplets contained in thyroid cells increase during the period of active secretory activity. The number and length of microvilli located on the apical surface of the epithelium and directed into the follicle cavity also increase with increased activity of the thyroid gland. The density, size, number and localization of cytoplasmic granules characterize both the processes of biosynthesis and the release of specific products.

7. Hormonal status of the body and diseases associated with hormonal imbalance.

Basic biological processes such as growth, development and tissue differentiation depend on the normal function of the thyroid gland. The thyroid gland secretes 3 hormones: thyroxine and triiodothyronine and thyrocalcitonin.

Thyroxine: Strengthens the oxidation processes of fats, carbohydrates and proteins in cells, thus accelerating the metabolism in the body. Increases the excitability of the central nervous system.

Triiodothyronine: The action is in many ways similar to thyroxine.

Thyrocalcitonin: Regulates calcium metabolism in the body, reducing its content in the blood and increasing its content in bone tissue (has the opposite effect of parathyroid hormone of the parathyroid glands). A decrease in calcium levels in the blood reduces the excitability of the central nervous system.

The biological effects of thyroid hormones in physiological doses are manifested in maintaining energy and biosynthetic processes in the body at an optimal level. The effect of hormones on biosynthesis processes, and consequently on the growth and development of the body, is mediated through the regulation of tissue respiration. Hormones in high doses enhance all types of metabolism with a predominance of catabolic processes, consumption of substances and energy in the form of heat, products of incomplete and perverted metabolism. The mechanism of action of thyroid hormones appears to be the stages of “recognition” and perception of the signal by the cell and the generation of mol. processes that determine the nature of the response. Specific receptor proteins are found in the cells of various tissues that “recognize” the hormone and trigger biochemical reactions. The function of the thyroid gland is regulated by the central nervous system. The thyroid gland interacts with other endocrine glands.

Diseases of the thyroid gland in humans (inflammatory, tumors, injuries, congenital anomalies, etc.) can be accompanied by an enlargement of the thyroid gland and disruption of its function: decreased production of hormones (hypothyroidism) or increased formation.

Parathyroid glands, four small glands located in the neck next to the thyroid gland. They are reddish-brown in color, and the total weight of all four glands is 130 mg. Like other endocrine glands, they are abundantly supplied with blood. The hormone they secrete into the bloodstream - parathyroid hormone, or parathyroid hormone - is a protein consisting of 84 amino acid residues connected into one chain. The activity of the parathyroid glands depends on the level of calcium in the blood: when it decreases, the secretion of parathyroid hormone increases. Diseases associated with low calcium levels in the blood, in particular rickets and renal failure, are characterized by increased activity of the parathyroid glands and an increase in their size. The main function of these glands is to maintain an almost constant, normal level of calcium in the blood, despite fluctuations in its intake from food. The action of parathyroid hormone is aimed at increasing the concentration of calcium and decreasing the concentration of phosphorus in the blood (there are reciprocal relationships between these indicators.) This action is ensured by the influence of parathyroid hormone on the excretion of calcium (inhibits) and phosphorus (accelerates) by the kidneys, as well as by stimulating the release of calcium and phosphorus from bones to blood. The main amount (99%) of all calcium in the body is found in bones and teeth. Hyperparathyroidism. Overactivity of the parathyroid glands, which may be caused by a small tumor, is called primary hyperparathyroidism. It is characterized by the loss of calcium and phosphorus from bone tissue, causing bones to become brittle, painful, and prone to breakage. Fractures of the vertebrae in this disease can lead to a shortening of the patient’s height by as much as 15 cm. Sometimes there is loosening of the teeth in the sockets, but the teeth themselves are not destroyed. Calcium and phosphorus lost from the bones during hyperparathyroidism pass through the kidneys into the urine, which often leads to the formation of stones in the kidneys and bladder (from fine sand to fist-sized stones). It has been established that primary hyperparathyroidism causes 5–10% of cases of kidney stones. Treatment of hyperparathyroidism involves surgical removal of the overactive glands. Hypoparathyroidism. When the parathyroid glands are destroyed due to a pathological process or after their surgical removal, hypoparathyroidism occurs - a deficiency of parathyroid hormone. At the same time, the level of calcium in the blood falls, and the phosphorus content increases. For the normal functioning of tissues, primarily nervous and muscle tissues, a stable, normal level of calcium in the blood is necessary. Its decrease in hypoparathyroidism causes attacks of increased nerve and muscle activity, leading to tetany, a condition characterized by muscle cramps in the arms and legs, a tingling sensation, anxiety and fear. The main treatment for hypoparathyroidism is currently vitamin D, large doses of which normalize the concentration of calcium in the blood. Pseudohypoparathyroidism, a disease caused by the insensitivity of the bones and kidneys to the action of parathyroid hormone, occurs occasionally. It also leads to tetany, which would seem to indicate hypoparathyroidism, but all four parathyroid glands in this case turn out to be normal.

Thymus(thymus, or goiter, gland) is an endocrine gland that plays a critical role in the formation of immunity. It stimulates the development of T (“thymus”) cells both in its own tissue and in the lymphoid tissue of other parts of the body. T cells “attack” foreign substances that enter the body, control the production of antibodies against pathogenic agents, and influence other protective reactions of the body. The thymus is present in all vertebrates, but its shape and location may vary. In humans, the thymus consists of two lobes located in the upper part of the chest just behind the sternum.

In humans, the thymus is formed in the 6th week of intrauterine life, developing, as in other mammals, from two segments that combine to form a single organ consisting of two lobes. In Australian marsupials, the two halves of the thymus remain separate organs. The human thymus reaches its largest size in relation to body weight at the time of birth (about 15 g). It then continues to grow, although much more slowly, and at puberty it reaches its maximum weight (about 35 g) and size (about 75 mm in length). After this, a gradual decrease in the gland begins, which continues for the rest of life. This process occurs at different rates in different animal species, and in some (for example, guinea pigs) the relatively large thymus gland remains throughout life.

In humans, the two lobes of the thymus are held together by connective tissue. A dense connective tissue capsule covers both lobes, penetrating inside and dividing them into smaller lobules. Each lobule consists of an outer zone (cortex), which is divided into superficial and deep cortical layers, and a central inner zone - the medulla. It contains bundles of flat cells, the so-called. Hassall's bodies, which probably serve as a site of cell destruction.

The thymus secretes only one hormone - thymosin. This hormone affects the metabolism of carbohydrates and calcium. In the regulation of calcium metabolism, the action is close to parathyroid hormone of the parathyroid glands. Regulates skeletal growth, participates in the management of immune reactions (increases the number of lymphocytes in the blood, enhances immune responses) during the first 10-15 years of life.

Blood delivers immature bone marrow stem cells (lymphoblasts) to the thymus, where they come into contact with epithelial cells (“educators” or “nurses”) of the superficial cortical layer of the lobules and, under the influence of thymic hormones, are transformed into white blood cells (lymphocytes) - cells lymphatic system. As these small lymphocytes (also called thymocytes) mature, they move from the cortex to the medulla of the lobules. Some lymphocytes die here, while others continue to develop and, at various stages, up to fully mature T cells, leave the thymus into the blood and lymphatic system to circulate throughout the body.

T cell deficiency. In humans, T-cell deficiency can be congenital or acquired. An extremely low number of lymphocytes - up to their complete absence - is observed with such congenital anomalies as dysplasia (disorder of the structure) of the thymus, its insufficient development and Di George syndrome (partial or complete absence of the gland). The congenital absence of both T and B cells (another type of immune system cell) is called severe combined immunodeficiency. This condition, in which the child remains completely defenseless against disease-causing microbes, can sometimes be treated with a bone marrow transplant, fetal thymus transplant, or the introduction of antibodies.

Pancreas-digestive and endocrine gland. Available in all vertebrates with the exception of lampreys, hagfishes and other primitive vertebrates. Elongated in shape, the outline resembles a bunch of grapes. Only the inner part of the pancreas belongs to the endocrine system. In humans, the pancreas weighs from 80 to 90 g, is located along the posterior wall of the abdominal cavity and consists of several sections: head, neck, body and tail. The head is located on the right, in the bend of the duodenum - part of the small intestine - and is directed downward, while the rest of the gland lies horizontally and ends next to the spleen. The pancreas is made up of two types of tissue that perform completely different functions. The actual tissue of the pancreas consists of small lobules - acini, each of which is equipped with its own excretory duct. These small ducts merge into larger ones, which in turn flow into the Wirsungian duct, the main excretory duct of the pancreas. The lobules consist almost entirely of cells secreting pancreatic juice (pancreatic juice, from lat. pancreas- pancreas). Pancreatic juice contains digestive enzymes. From the lobules, through small excretory ducts, it enters the main duct, which flows into the duodenum. The main pancreatic duct is located near the common bile duct and connects with it before emptying into the duodenum. Interspersed between the lobules are numerous groups of cells that do not have excretory ducts - the so-called. islets of Langerhans. Islet cells secrete the hormones insulin and glucagon.

The pancreas has both endocrine and exocrine functions, i.e. carries out internal and external secretion. The exocrine function of the gland is participation in digestion.

Endocrine functions. The islets of Langerhans function as endocrine glands, releasing glucagon and insulin, hormones that regulate carbohydrate metabolism, directly into the bloodstream. These hormones have the opposite effect: glucagon increases and insulin decreases blood sugar levels.

Insufficient secretion of insulin leads to a decrease in the ability of cells to absorb carbohydrates, i.e. to diabetes mellitus.

Diabetes mellitus is a chronic disease in which the human body produces too little or no insulin. If there is not enough of it, disorders of all types of metabolism develop because the body tissues do not receive enough nutrients to obtain energy. Men and women are equally susceptible to this disease, and the risk of getting the disease increases with age. One of the reasons for the development of the disease is systematic overeating. It is also believed that hereditary predisposition and stress play an important role. The most important symptom of diabetes is an increase in blood sugar levels and its excretion in the urine. A person begins to complain first of constant strong thirst and copious urine output (up to 6 liters per day), itching of the skin, especially in the perineal area, may also occur; pustular diseases and sexual dysfunction are also possible. Metabolic disorders are steadily progressing and there is a decrease in appetite, even greater thirst, weakness, dry skin and mucous membranes, nausea, and vomiting. A person’s well-being, if he still has not sought the help of a specialist, worsens, and lethargy turns into an unconscious state - the most severe complication of diabetes mellitus develops - diabetic coma. Prevention of diabetes mellitus is a balanced diet, maintaining normal body weight and timely treatment of inflammatory diseases of the biliary tract and pancreas. And if there is a hereditary predisposition, periodic examination is necessary in order to recognize the disease in time and begin treatment.

Adrenal glands - small flattened paired yellowish glands located above the upper poles of both kidneys. The right and left adrenal glands differ in shape: the right is triangular, and the left is crescent-shaped. These are endocrine glands, i.e. The substances they secrete (hormones) enter directly into the bloodstream and participate in the regulation of the body’s vital functions. The average weight of one gland is from 3.5 to 5 g. Each gland consists of two anatomically and functionally different parts: the outer cortical and inner medulla. The cortex comes from the mesoderm (middle germ layer) of the embryo. The sex glands, the gonads, also develop from the same leaf. Like the gonads, the cells of the adrenal cortex secrete (release) sex steroids - hormones that are similar in chemical structure and biological action to the hormones of the gonads. In addition to the sex hormones, the cortex cells produce two more very important groups of hormones: mineralocorticoids (aldosterone and deoxycorticosterone) and glucocorticoids (cortisol, corticosterone, etc.). Decreased secretion of hormones from the adrenal cortex leads to a condition known as Addison's disease. Hormone replacement therapy is indicated for such patients. Excessive production of cortical hormones underlies the so-called. Cushing's syndrome. In this case, surgical removal of the overactive adrenal tissue is sometimes performed, followed by replacement doses of hormones. Increased secretion of male sex steroids (androgens) is the cause of virilism - the appearance of male characteristics in women. This is usually a consequence of a tumor of the adrenal cortex, so the best treatment is to remove the tumor. The medulla comes from the sympathetic ganglia of the embryonic nervous system. The main hormones of the medulla are adrenaline and norepinephrine. Adrenaline was isolated by J. Abel in 1899; it was the first hormone obtained in chemically pure form. It is a derivative of the amino acids tyrosine and phenylalanine. Norepinephrine, the precursor of adrenaline in the body, has a similar structure and differs from the latter only in the absence of one methyl group. The role of adrenaline and norepinephrine is to enhance the effects of the sympathetic nervous system; they increase heart and breathing rates, blood pressure, and also affect the complex functions of the nervous system itself.

Today, doctors have studied the endocrine system well enough to prevent disorders of hormonal functions and cure them.

Metabolism and energy, its age-related features.

Metabolism refers to the set of changes that substances undergo from the moment they enter the digestive tract to the formation of final breakdown products excreted from the body. That is, metabolism in all organisms, from the most primitive to the most complex, including the human body, is the basis of life.

In the process of life, continuous changes occur in the body: some cells die, others replace them. In an adult, 1/20 of the skin epithelial cells and half of all epithelial cells of the digestive tract, about 25 g of blood, etc. die and are replaced within 24 hours.

During the process of growth, renewal of the body's cells is possible only when the body continuously receives oxygen and nutrients, which are the building materials from which the body is built. But for the construction of new cells of the body, their continuous renewal, as well as for a person to perform some kind of work, energy is needed. The human body receives this energy through decay and oxidation in metabolic processes (metabolism). Moreover, metabolic processes (anabolism and catabolism) are finely coordinated with each other and occur in a certain sequence.

Under anabolism understand the set of synthesis reactions. Under catabolism- a set of decomposition reactions. It must be taken into account that both of these processes are continuously connected. Catabolic processes provide anabolism with energy and starting substances, and anabolic processes provide the synthesis of structures, the formation of new tissues in connection with the growth processes of the body, the synthesis of hormones and enzymes necessary for life.

Throughout individual development, the most significant changes are experienced by the anabolic phase of metabolism and, to a lesser extent, by the catabolic phase.

According to their functional significance in the anabolic phase of metabolism, the following types of synthesis are distinguished:

1) growth synthesis - an increase in the protein mass of organs during a period of increased cell division, growth of the organism as a whole.

2) functional and protective synthesis - the formation of proteins for other organs and systems, for example, the synthesis of blood plasma proteins in the liver, the formation of digestive tract enzymes and hormones.

3) synthesis of regeneration (recovery) - synthesis of proteins in regenerating tissues after injury or malnutrition.

4) synthesis of self-renewal associated with stabilization of the body - constant replenishment of components of the internal environment that are destroyed during dissimilation.

All these forms weaken, although unevenly, throughout individual development. In this case, especially significant changes are observed in growth synthesis. The intrauterine period has the highest growth rates. For example, the weight of a human embryo increases by 1 billion compared to the weight of a zygote. 20 million times, and over 20 years of progressive human growth it increases no more than 20 times.

Throughout postnatal life, there is a further decline in the level of anabolism.

Protein metabolism in a developing organism. Growth processes, the quantitative indicators of which are an increase in body weight and the level of positive nitrogen balance, are one side of development. Its second side is the differentiation of cells and tissues, the biochemical basis of which is the synthesis of enzymatic, structural and functional proteins.

Proteins are synthesized from amino acids that come from the digestive system. Moreover, these amino acids are divided into essential and non-essential. If essential amino acids (leucine, methionine and tryptophan, etc.) are not supplied with food, then protein synthesis in the body is disrupted. The supply of essential amino acids is especially important for a growing organism, for example, the lack of lysine in food leads to growth retardation, depletion of the muscular system, and a lack of valine leads to balance disorders in a child.

In the absence of essential amino acids in food, they can be synthesized from essential ones (tyrosine can be synthesized from phenylalanine).

And finally, proteins that contain the entire necessary set of amino acids that ensure normal synthesis processes are classified as biologically complete proteins. The biological value of the same protein varies for different people depending on the state of the body, diet, and age.

The daily protein requirement per 1 kg of weight in a child: at 1 year - 4.8 g, 1-3 years - 4-4.5 g; 6-10 years - 2.5-3 g, 12 and more - 2.5 g, adults - 1.5-1.8 g. Therefore, depending on age, children under 4 years old should receive 50 g of protein, up to 7 years - 70 g, from 7 years - 80 g per day.

The amount of proteins entering the body and destroyed in it is judged by the value of the nitrogen balance, that is, the ratio of the amounts of nitrogen that enters the body with food and is excreted from the body with urine, sweat and other secretions.

The ability to retain nitrogen in children is subject to significant individual fluctuations and persists throughout the entire period of progressive growth.

As a rule, adults do not have the ability to retain dietary nitrogen; their metabolism is in a state of nitrogen equilibrium. This indicates that the potential for protein synthesis remains for a long time - thus, under the influence of physical activity, muscle mass increases (positive nitrogen balance).

During periods of stable and regressive development, upon reaching maximum weight and cessation of growth, the main role begins to be played by the processes of self-renewal, which occur throughout life and which fade into old age much more slowly than other types of synthesis.

Age-related changes affect not only protein, but also fat and carbohydrate metabolism.

Age-related dynamics of fat and carbohydrate metabolism.

The physiological role of lipids - fats, phosphatides and sterols in the body is that they are part of cellular structures (plastic metabolism), and are also used as rich sources of energy (energy metabolism). Carbohydrates in the body are important as energy material.

With age, fat and carbohydrate metabolism changes. Fats play a significant role in the processes of growth and differentiation. Fat-like substances are especially important, primarily because they are necessary for the morphological and functional maturation of the nervous system, for the formation of all types of cell membranes. That is why the need for them in childhood is great. With a lack of carbohydrates in food, fat depots in children are quickly depleted. The intensity of synthesis largely depends on the nature of nutrition.

The phases of stable and regressive development are characterized by a peculiar reorientation of anabolic processes: a switch of anabolism from protein synthesis to fat synthesis, which is one of the characteristic features of age-related changes in metabolism during aging.

The age-related reorientation of anabolism towards fat accumulation in a number of organs is based on a decrease in the ability of tissues to oxidize fat, as a result of which, with a constant and even reduced rate of fatty acid synthesis, the body is enriched with fats (thus, the development of obesity was observed even with 1-2 meals a day). It is also undeniable that in the reorientation of synthesis processes, in addition to nutritional factors and nervous regulation, changes in the hormonal spectrum are of great importance, in particular changes in the rate of formation of somatotropic hormone, thyroid hormones, insulin, and steroid hormones.

Restructures with age and carbohydrate metabolism. In children, carbohydrate metabolism occurs with greater intensity, which is explained by a high metabolic rate. In childhood, carbohydrates perform not only an energy function, but also a plastic function, forming cell membranes and connective tissue substances. Carbohydrates participate in the oxidation of protein and fat metabolism products, which helps maintain acid-base balance in the body. The daily requirement for carbohydrates in children is high and in infancy is 10-12 g per 1 kg of body weight. In subsequent years, at the age of 8-9 years, it increases to 12-15 g per 1 kg of body weight. From 1 to 3 years, a child needs to receive about 193 g of carbohydrates per day from food, 4-7 years - 287, 9-13 - 370, 14-17 years - 470, and adults - 500 g.

Carbohydrates are absorbed better by children's bodies than by adults. One of the significant indicators of age-related changes in carbohydrate metabolism is a sharp increase in old age in the time it takes to eliminate hyperglycemia caused by the administration of glucose during sugar load tests.

An important part of metabolism in the body is water-salt metabolism.

The transformation of substances in the body takes place in an aquatic environment; together with minerals, water takes part in the construction of cells and serves as a reagent in cellular chemical reactions. The concentration of mineral salts dissolved in water determines the osmotic pressure of blood and tissue fluid, thus being of great importance for absorption and excretion. changes in the amount of water in the body and shifts in the salt composition of body fluids and tissue structures entail a violation of the stability of colloids, which can result in irreversible damage and death of individual cells and then the body as a whole. That is why maintaining a constant amount of water and mineral composition is a necessary condition for normal life.

In the progressive growth phase, water participates in the processes of creating body weight. It is known, for example, that out of a daily increase in body weight of 25 g, water accounts for 18, protein - 3, fat - 3 and mineral salts - 1 g. The younger the body, the greater the daily need for water. In the first six months of life, a child’s need for water reaches 110-125 g per 1 kg of weight, by 2 years it decreases to 115-136 g, at 6 years - 90-100 g, 18 years - 40-50 g. Children are able to quickly lose and also quickly deposit water.

A general pattern of individual evolution is a decrease in water in all tissues. With age, a redistribution of water in tissues occurs - the volume of water in the intercellular spaces increases and the volume of intracellular water decreases.

The balance of many mineral salts depends on age. In youth, the content of most inorganic salts is lower than in adults. The exchange of calcium and phosphorus is of particular importance. Increased requirements for the supply of these elements in children under one year of age are explained by increased formation of bone tissue. But these elements are no less important in old age. Therefore, older people need to introduce foods containing these elements (milk, dairy products) into their diet to avoid wasting these elements from bone tissue. The content of sodium chloride, on the contrary, should be reduced in the diet due to the weakening of the production of mineralocorticoids in the adrenal glands with age.

An important indicator of energy transformations in the body is o main exchange.

Age dynamics of basal metabolism

The basal metabolic rate is understood as the minimum level of metabolism and energy expenditure for the body under strictly constant conditions: 14-16 hours before a meal, in a lying position in a state of muscular rest at a temperature of 8-20 C. In a middle-aged person, the basal metabolic rate is 4187 J per 1 kg of mass per 1 hour. On average, this is 7-7.6 MJ per day. Moreover, for each person the basal metabolic rate is relatively constant.

The basal metabolism in children is more intense than in adults, since they have a relatively large body surface per unit of mass, and the processes of dissimilation rather than assimilation are predominant. The younger the child, the higher the energy costs for growth. So the energy expenditure associated with growth at 3 months of age is 36%, at 6 months of age. - 26%, 9 months. - 21% of the total energy value of food.

In old age (the phase of regressive development), a decrease in body weight is observed, as well as a decrease in the linear dimensions of the human body, and the basal metabolism drops to low values. Moreover, the degree of decrease in basal metabolism at this age correlates, according to various researchers, with the extent to which signs of frailty and loss of performance are expressed in old people.

As for gender differences in the level of basal metabolism, they are detected in ontogenesis from 6-8 months. At the same time, the basal metabolic rate in boys is higher than in girls. Such relationships persist during puberty, and in old age they smooth out.

In ontogenesis, not only the average value of energy metabolism varies, but also the possibilities of increasing this level under conditions of intense, for example, muscle activity, change significantly.

In early childhood, insufficient functional maturity of the musculoskeletal, cardiovascular and respiratory systems limits the adaptive capabilities of the energy metabolism reaction during physical activity. In adulthood, adaptive capacity, as well as muscle strength, reach their maximum. In old age, the possibilities for a compensatory increase in the level of respiration and energy exchange under stress are exhausted due to a decrease in the vital capacity of the lungs, the coefficient of oxygen utilization by tissues, and a decrease in the functions of the cardiovascular system.

Various assumptions have been made and various mathematical expressions have been proposed to establish the dependence of energy production on parameters characterizing the structural features of the organism. Thus, Rubner believed that age-related changes in metabolism are the result of a decrease in the size of the relative surface of the body with age.

An attempt was made to explain the decline in metabolic processes in old age by the accumulation of subcutaneous fat and a decrease in skin temperature at this age.

Noteworthy are the works in which changes in energy metabolism are considered in connection with the formation of thermoregulation mechanisms and the participation of skeletal muscles in it (Magnus, 1899; Arshavsky, 1966-71).

An increase in skeletal muscle tone with insufficient activity of the vagus nerve center during the first year of life helps to increase energy metabolism. The role of age-related restructuring of skeletal muscle activity in the dynamics of energy metabolism is especially clearly highlighted in the study of gas exchange in people of different ages at rest and during physical activity. For progressive growth, an increase in resting metabolism is characterized by a decrease in the level of basal metabolism and improved energy adaptation to muscle activity. During the stable phase, a high functional rest metabolism is maintained and the metabolism during work increases significantly, reaching a stable, minimum level of basal metabolism. And in the regressive phase, the difference between the functional rest metabolism and the basal metabolism continuously decreases, and the rest time lengthens.

Many researchers believe that the decrease in the energy metabolism of the whole organism during ontogenesis is due, first of all, to quantitative and qualitative changes in metabolism in the tissues themselves, the magnitude of which is judged by the relationship between the main mechanisms of energy release - anaerobic and aerobic. This makes it possible to determine the potential capabilities of tissues to generate and use the energy of high-energy bonds.

In the human body there is a constant renewal of cellular structures,
various chemical compounds are synthesized and destroyed. Totality
all chemical reactions occurring in the body are called metabolism
(metabolism). ■-);■

In the process of individual development of a person, metabolism and energy undergoes a number of quantitative and qualitative changes, first of all, the relationship between the two phases of metabolism changes significantly: assimilation and dissimilation. Assimilation- the process of assimilation by the body of external substances, as a result of this process the substances become an integral part of living structures and are deposited as reserves in the body.

Dissimilation- the process of decomposition of organic compounds into simple substances, resulting in the release of energy, which is necessary for the life of the body.

Metabolism occurs in close connection with the environment. For life to function, the body must receive proteins, fats, carbohydrates, vitamins, mineral salts and water from the external environment. The quantity, properties and ratio of these elements must correspond to the state of the organism and the conditions of its existence. For example, if more food is received than necessary, a person gains weight; if less, he loses weight.

The main features of metabolism in children are: ■ the predominance of assimilation processes over dissimilation processes; high basal metabolic rate; increased need for proteins; positive nitrogen balance.

Protein metabolism

Squirrels, or proteins, are the main component of all organs and tissues of the body, all life processes are closely connected with them - metabolism, contractility, irritability, the ability to grow, reproduce and think.

Proteins make up 15-20% of the total human body weight (fats and carbohydrates together - only 1-5%). Proteins come from food and are among the essential components

Nentam diet. You exhibit biological activity of other nutrients only in the presence of proteins.

Main functions of proteins:

■ plastic - participation in the construction of new cells and tissues, ensuring
growth and development of young growing organisms and regeneration of worn-out
spent cells in adulthood;

“protective - antibodies are synthesized from food proteins that provide immunity to infections;

■ enzymatic - all enzymes are protein compounds;

■ hormonal - insulin, growth hormone, thyroxine, testosterone, estrogens and many other hormones are proteins;

■ contractile - the proteins actin and myosin provide muscle contraction;

■ transport - the protein hemoglobin contained in erythrocytes carries oxygen, blood serum proteins are involved in the transport of lipids, carbohydrates, some vitamins, hormones;

■ energy - provide the body with the necessary energy.
An indicator of the level of protein metabolism is nitrogen balance, he defines
is based on the results of comparing the amount of nitrogen taken in with food and excreted
from the body. Nitrogen balance is the difference between consumed and
food nitrogen and nitrogen excreted from the body (with urine, feces and microsweat
ryami). There are three types of nitrogen balance: nitrogen balance, positive
low and negative nitrogen balance.

Nitrogen balance- equality of the amount of nitrogen received from food and excreted from the body.

Positive nitrogen balance means that more nitrogen comes in from food than is excreted from the body; it characterizes the accumulation of protein (nitrogen) in the body. Nitrogen retention is physiological for children, pregnant and lactating women, after fasting, etc.

Negative nitrogen balance- the predominance of nitrogen excreted from the body over nitrogen that came from food; indicates the loss of the body's own proteins. In this case, proteins from the blood plasma, liver, intestinal mucosa, and muscle tissue become the source of free amino acids, which makes it possible to maintain the renewal of proteins in the brain and heart for a sufficiently long time. A negative nitrogen balance is observed during fasting, a lack of complete proteins in food, a number of diseases, injuries, burns, after operations, etc. A long-term negative nitrogen balance leads to death.

The early stage of development of the body is characterized by a positive nitrogen balance, mature age is characterized by a nitrogen balance, and old age is characterized by a predominantly negative nitrogen balance.

In the child’s body, processes of growth and formation of new cells and tissues occur intensively. Therefore, the need for proteins in a child is much higher than in an adult.

Depending on the age and body weight, the amount of protein in a child’s diet should be: 1-3 years - 55 g, 4-6 years - 72 g, 7-9 years - 89 g, 10-15 years -100-1 About g (adult norm).

About 10-15% of the total daily calories should be covered by food proteins.

The balance and retention of nitrogen in the body in a child’s body depends on his individual characteristics, determined by the type of GNI. In children with a predominance of excitation processes over inhibition processes, nitrogen retention is less pronounced than in children with a predominance of inhibition processes. The highest rates of nitrogen retention are observed in children with balanced VNI processes. Not only the quantity, but also the quality of the injected protein matters.

The ratio of proteins, fats and carbohydrates in a child’s food should be 1:1:4; under these conditions, nitrogen is retained in the body as much as possible.

In the urine of a newborn, there is less urea nitrogen, more ammonia nitrogen and uric acid nitrogen. During the neonatal period, amino acids make up 10% of the total urine nitrogen, while in adults it is only 3-4%. A feature of the protein metabolism of children is the constant presence of creatine in their urine.

One of the indicators of protein metabolism disorders in children is the accumulation of residual nitrogen in the blood. In healthy children, from 3 months. up to 3 years, residual nitrogen in the blood ranges from 17.69 to 26.15 mg (12.63-18.67 mmol/l).

8.5.2. Carbohydrate metabolism

Carbohydrates They constitute the main part of the diet and provide 50-60% of its energy value. Carbohydrates are found mainly in plant foods.

In the human body, carbohydrates can be synthesized from amino acids and fats, so they are not essential nutritional factors. The minimum carbohydrate intake corresponds to approximately 150 g/day. Carbohydrates are deposited in the body to a limited extent and human reserves are small.

The main functions of carbohydrates: “energy - when 1 g of digestible carbohydrates are oxidized, 4 kcal are released in the body;

plastic - they are part of the structures of many cells and tissues, participate in the synthesis of nucleic acids (a constant level of glucose is maintained in the blood serum, glycogen is in the liver and muscles, galactose is part of brain lipids, lactose is found in human milk, etc.) ; regulatory - participate in the regulation of acid-base balance in the body, prevent the accumulation of ketone bodies during fat oxidation; protective - hyaluronic acid prevents the penetration of bacteria through the cell wall; Liver glucuronic acid combines with toxic substances to form non-toxic esters, soluble in water, which are excreted in the urine; pectins bind toxins and radionuclides and remove them from the body.

In addition, carbohydrates tone the central nervous system and have biological activity. in combination with proteins and lipids, they form some enzymes, hormones, mucous secretions of glands, etc. Dietary fibers are physiological stimulants of the motor function of the gastrointestinal tract.

Carbohydrates in the child’s body not only perform an energy function, but also play an important plastic role in the creation of the basic substance of connective tissue, cell membranes, etc. The metabolism of carbohydrates in the child’s body is characterized by a much greater intensity than the metabolism of carbohydrates in the body of an adult. Required amount of blood sugar in children on an empty stomach in mg%:

Newborns 30-50

Chest 70-90

Older 80-100

12-14 years 90-120

Carbohydrate metabolism in children is characterized by high digestibility of carbohydrates (98-99%), regardless of the method of feeding. In a child’s body, the formation of carbohydrates from proteins and fats is weakened, since growth requires increased consumption of the body’s protein and fat reserves. Carbohydrates are deposited in a child's body in smaller quantities than in an adult's body. Young children are characterized by rapid depletion of liver carbohydrate reserves.

The daily requirement for carbohydrates in children is high and in infancy is 10-12 g per 1 kg of body weight per day. In subsequent years, the amount of carbohydrates, depending on the constitutional characteristics of the child, ranges from 8-9 g to 12-15 g per 1 kg of body weight per day. In the first half of life, the child receives the required amount of carbohydrates in the form of disaccharides. From 6 months there is a need for polysaccharides.

The daily amount of carbohydrates that children should receive from food increases significantly with age:

■ from 1 year to 3 years - 193 g;

■ 4-7 years - 287.9 ​​g;

■ 8-13 years -370 g;

■ 14-17 years -470 g.

Fat metabolism

Fats, or lipids, belong to the basic nutrients and are an important component of nutrition. Fats are divided into neutral (triglycerides) and fat-like substances (lipoids).

Fats in the human body perform the following main functions:

■ serve as an important source of energy, superior in this regard to all food
high substances - the oxidation of 1 g of fat produces 9 kcal (37.7 kJ);

» are part of all cells and tissues;

■ are solvents for vitamins A, D, E, K;

■ supply biologically active substances - PUFAs, phosphatides, sterols, etc.;

■ create protective and thermal insulating covers - the subcutaneous fat layer protects a person from hypothermia;

■ improve the taste of food;

■ cause a feeling of prolonged satiety. "■:

)Kirs can be formed from carbohydrates and proteins, but cannot be fully replaced by them.

Fats in the child’s body perform energy and plastic functions.< кцию. Обмен жира у детей характеризуется неустойчивостью, быстрым истоще­нием жировых депо при недостатке в пище углеводов или их усиленном расходе.

A number of fatty acids enter the body with dietary fats, including three bio
logically valuable fatty acids: linoleic, linolenic and arachidonic. These
acids are necessary to ensure normal growth and function
skin. With fats, the body receives soluble vitamins A, D, E, K,
necessary for the growth and development of the child. G ■

When compiling a children's diet, it is necessary to take into account not only the quantity, but also the quality of the fats included in it. Without fats, it is impossible to develop general and specific immunity.

Fat requirements change with age. Infants should consume more fat. During this period, 50% of the total calorie requirement is covered by fat. Breastfed children absorb 96% of fat, children on mixed and artificial nutrition - 90%.

With age, the daily amount of fat increases, which is necessary for the normal development of children. From 1-3 years old, a child should receive 32.7 g per day, 4-7 years old - 39.2 g, 8-13 years old - 38.4 g, 14-17 years old - 47 g, which approximately corresponds to the norm for an adult - 50 G.

Proper breakdown of fats is possible when fats are properly correlated with other nutritional ingredients. When feeding young children, the ratio between fats and carbohydrates should be maintained at 1:2.

Water exchange

Water is part of all cells and tissues of the body, serves as the best solvent for many biologically important substances, ensures the course of metabolic processes, participates in thermoregulation, dissolves the final products of metabolism and promotes their removal by the excretory organs.

A child's body is different from an adult's hydrolability, i.e., the ability to quickly lose and quickly accumulate water. There is a connection between energy

14 Age anatomy

Growth rate and water content in tissues. Daily weight gain in infants< го возраста составляет 25 г, на долю воды приходится 18 г, белка - 3 г, жира - 3 и 1 г приходится на долю минеральных солей.

The younger the child and the faster he grows, the greater his need for water | Water requirement per 1 kg of body weight:

Age Amount of water, ml
Newborns 150-200

Chest 120-130

12-13 years 40-50

Daily water requirement:

Age, years Amount of water, ml

800 950 1200 1350 1500

At an early age, even with small changes in any part of water metabolism, its regulation is disrupted, which can result in pathological phenomena. For example, children experience a “thirst fever” due to increased protein breakdown due to lack of water in the body.

Loss of 10% of water by the body negatively affects vital functions and leads to thickening of the blood, impaired blood flow, changes in mental state, and convulsions. Reducing the amount of water by 20% leads to death.

8.5.5. Mineral metabolism

Minerals are vital components of nutrition and ensure the maintenance of homeostasis. Minerals perform the following main functions:

■ form tissues, their role is especially great in the construction of bone tissue, where phosphorus and calcium predominate (plastic function);

■ participate in all types of metabolism;

■ maintain osmotic pressure in cells and intercellular fluids; * provide acid-base balance (condition) in the body;

■ strengthen immunity;

■ activate hormones, vitamins, enzymes;

■ promote hematopoiesis.

Without minerals, the normal function of the nervous, cardiovascular, digestive, excretory and other systems is impossible.

As a rule, substances of animal and plant origin consumed in food contain sufficient quantities of all the mineral substances necessary for a growing organism. Only table salt is added during rational cooking.

In children, the balance of mineral metabolism is positive, this is associated with the growth of the body and, first of all, bone tissue. In a newborn, the amount of minerals is 2.55% of body weight, in an adult - 5%.

The balance of individual minerals depends on the child’s age, his or her
individual characteristics and time of year. TO""""

For a growing organism plays an important role calcium. Optimal environment
The body needs calcium throughout its entire life. Oso
Calcium is especially important during periods of intensive growth, as it is necessary
a condition for normal development of the skeleton, achieving the necessary strength
and safety. , -v

Inadequate calcium intake during childhood and adolescence prevents the achievement of optimal bone mass and strength, thereby increasing the risk of osteoporosis. Calcium deficiency increases the risk of rickets in children, disrupts the development of the skeleton and teeth, and increases the risk of cardiovascular diseases.

The thyroid and parathyroid glands regulate calcium metabolism, maintaining a constant level in the blood and providing the body with the necessary amounts in case of possible fluctuations.

For normal bone development it is also necessary phosphorus. This element is needed not only for the growth of bone tissue, but also for the normal functioning of the nervous system, most glandular cells and other organs. With age, the relative need for phosphorus decreases. The optimal ratio between the concentration of calcium and phosphorus salts for preschool children is 1:1; at the age of 8-10 years - 1:1.5; in adolescence -1:2. With such ratios, skeletal development proceeds normally. In the absence or deficiency of vitamin D, phosphatase activity decreases, the deposition of calcium phosphate salts in the bones decreases, and rickets develops.

Excess phosphorus is most dangerous for children in the first months of life, whose kidneys cannot cope with its excretion. This leads to an increase in phosphorus in their blood and a decrease in calcium, and subsequently to the development of urolithiasis.

Potassium is important for intracellular metabolism. It is necessary for normal muscle activity, in particular, it enhances the work of the heart, and takes part in the metabolism of carbohydrates, fats, and proteins. Children receive less potassium from food than adults and excrete less of it. Potassium deficiency in the body is accompanied by lethargy, apathy, drowsiness, decreased muscle tone, arrhythmia of the heart, and decreased blood pressure.

Iron is part of hemoglobin. Children have a greater need for iron than adults. Due to iron deficiency, the body develops iron deficiency anemia, fatigue, muscle weakness, and reduced mental and physical performance.

For the normal development of a child, all necessary microelements must enter his body with food: copper, zinc, manganese, magnesium, fluorine, etc. An infant receives them with mother's milk.

Norms and diet for children

When compiling food rations, the quantitative and qualitative selection of nutrients should be taken into account. It is important that the food contains all the necessary substances: proteins, fats, carbohydrates, water, mineral salts and vitamins. For children of primary school age, the best ratio of proteins, fats and carbohydrates is 1:1:6, for younger children - 1:2:3, for adults - 1:1:4. In table Table 8.1 shows the daily norms of proteins, fats and carbohydrates, which are necessary for organizing a balanced diet for children. Food must be sufficient in volume and calorie content, that is, it must cause a feeling of satiety and cover all the energy costs of the body.

The diet of children is of great importance. Schoolchildren should have
four meals a day with the following distribution of total quantities:
breakfast - 30%, lunch - 40-45%, afternoon snack - 10%, dinner - 20%. The younger the re
baby, the meals should be more frequent: for an infant 6-7 times a day,
for preschoolers - 5 times. i

Table 8.1 Daily norms of proteins, fats And carbohydrates in food of children and adolescents (in g)

Eating protein-rich foods before bedtime has an adverse effect on children's digestion, since such food stays longer in the stomach and for her processing requires more digestive juices. It increases the excitability of the nervous system, and this in turn prevents the rapid onset of deep sleep. Therefore, dinner for children should be small, consisting of light vegetables and dairy dishes, 1.5-2 hours before bedtime.

Violation of adequate balanced nutrition leads to various
diseases. The basics of rational nutrition are developed by specialists in
food hygiene and dietetics. S

D.5.7. Energy exchange

Energy exchange- conversion of potential energy of nutrients into heat and work. About 15% of a child's total energy expenditure is spent on growth and deposition of substances. He spends less energy on muscular work than an adult (15%) and the child loses slightly more energy with excrement. At an early age, energy expenditure on screaming and crying is especially high, during which energy expenditure can increase by 100 and even 200%. The total energy expenditure in children is presented in Table D8.2.

The basal metabolic rate in children is greater than in adults. This is due to:

■ intensity of growth, intensity of synthesis processes;

■ properties of young tissues, which have a more intense metabolism compared to adult tissues;

■ relatively larger body surface in children.

Newborns have a low metabolism due to insufficient functioning of the thyroid gland. However, already from the second half of the first year of life, the basal metabolism gradually increases and by 1-2.5 years reaches its maximum value, after which it begins to gradually decrease, approaching the basal metabolism of an adult.

The intensity of the basal metabolic rate in a child depends on age, gender, weight, height, the functioning of the endocrine glands, constitution, living conditions, etc. During the first six months of life in girls and boys, the basal metabolic rate is

Table 8.2. Distribution of daily energy expenditure in children (in%)

Ti is the same, but already in the second half of life the daily basal metabolic rate v of boys is slightly higher than that of girls. At 12-13 years old, girls are energetically... basal metabolic rate are ahead of boys. In adulthood, the basal metabolic rate in men is higher than in women. The basal metabolism in each individual subject is constant and fluctuates within ±10%.

Basic metabolism per 1 kg of body weight per day:

Total energy consumption, calculated per 1 kg of body weight, undergoes age-related changes. Daily energy expenditure in children of the first year of life:

Daily energy expenditure within a certain age group is subject to large individual fluctuations, both at rest and during various types of activity. This is due to differences in the physical development of children, the state of their endocrine and nervous systems, the intensity of movements, labor, etc. The daily energy expenditure of the same child on individual days is not the same and depends on the general condition of the child, the time spent on muscle activity.

8.5.8. Features of thermoregulation in children

Thermoregulation- a set of physiological processes in the human body that are aimed at maintaining a constant body temperature.

The main feature of the thermoregulation system in children is the insufficiency of its regulatory processes. The mechanisms of thermoregulation in children are imperfect due to:

"an undeveloped center of chemical thermoregulation;

■ imperfect mechanisms of heat transfer - vascular-motor reactions that regulate blood supply to the skin - and, consequently, heat transfer are not sufficiently developed;

■ large specific surface area of ​​the child’s body - the younger the child, the larger the body surface area per unit mass. Since the amount of heat

return depends on the size of the body surface, then in children this process occurs more intensively compared to adults, therefore, the need for heat formation in children is higher than in adults; structural features of the skin as a peripheral apparatus of physical thermoregulation - abundant blood supply, thin epidermal and stratum corneum, poorly developed sweat glands.

An increase in heat production during cooling or a weakening during heating (chemical thermoregulation) is already observed in infants. With an increase in heat production in infants, there is no thermoregulatory reaction of trembling. Increased muscle heat production during cooling is achieved by increasing the so-called thermoregulatory tone. In newborns, brown adipose tissue is an important source of heat.

The mechanism of heat transfer (physical thermoregulation) in a newborn and
the infant is not sufficiently developed, therefore, it is very easy for such
overheating is dangerous for the child. "^

In newborns, reflex regulation of the lumen of skin vessels is already carried out: skin vessels narrow when exposed to cold, both at the site of cooling and in a symmetrical area of ​​the skin. However, the latent period of the reaction is quite long, and its intensity is low.

Thus, at an early age, the main mechanism that maintains a constant body temperature is chemical thermoregulation. With age, the role of physical thermoregulation increases. Nine years of age is the boundary of the transition from one type of maintaining a constant body temperature to another.

After 1-1.5 years, up to 4-5 years, there is a large flow of heat through a unit of body surface: the growth rate of the child’s body slows down, but the intensity of the basal metabolic rate is still high. The high level of heat production at this age compensates for the weak capabilities of physical thermoregulation. At 6-7 years of age, the possibilities of physical thermoregulation increase and the role of chemical thermoregulation decreases.

In the prepubertal period (10 years for girls and 11-12 years for boys), as a result of hormonal changes, the possibilities of physical thermoregulation decrease and the role of chemical thermoregulation increases. Physical thermoregulation improves more intensively the earlier hardening activities begin.

Due to the imperfection of thermoregulation mechanisms, the child’s body is characterized by thermolability (temperature instability), which is pronounced in young children. Thus, eating, restlessness, movement, sleep, hunger, and occasional cooling affect their temperature curve. From 6-10 months, body temperature fluctuations become smaller.

The fetus is capable of independent heat production, so the body temperature of newborns is usually 0.1-0.6 ° C higher than the mother's rectal temperature. Che-

30-60 minutes after birth, the baby’s body temperature decreases noticeably ts after 2-3 hours it drops by 2.0-2.5 °C. In healthy children, the temperature rises again. It rises after 12-24 hours (sometimes after 2-3 days) and reaches 36.0-37.0 °C. For several more days, the temperature in newborns is somewhat erratic. The reasons for the initial decrease in body temperature in newborns are a sharp change in ambient temperature, as well as physical thermoriulation that has not yet established itself.

Monothermy is not typical for an infant. The average fluctuations in the difference between the maximum and minimum temperatures during the day in newborns are approximately 0.4 "WITH, and in older children, temperature fluctuations can reach up to 1 "C.

A newborn easily tolerates a decrease in body temperature by 3-4 "WITH, but it’s hard - promotion. Overheating occurs quickly in a child. If the temperature rises by more than 2 °C, this not only causes a painful condition, but also poses a danger to life, since vascular reactions occur both to warming and to local cooling of the skin.

Gradually, vascular reactions become more perfect - their latent period, duration, and rate of return to the original level are reduced. But even by the age of 12 they do not reach the level of development of adults.

There are certain age-related characteristics of physical regulation. There is an inverse relationship between the value of skin temperature and age: the younger a person’s age, the higher the skin temperature. Females aged 8-12 and 18-25 years old have a higher skin temperature than males. At the ages of 1-3 years, 4-7 years, gender differences in skin temperature do not appear. The rate of skin temperature recovery after local cooling in younger people is higher than in older people.

In adaptation to temperature influences, hardening plays an important role, i.e. exercise, training of vascular and neurohumoral processes (cold rubbing, bathing, air baths, etc.).

CONTROL QUESTIONS

1. The meaning of the cardiovascular system, its structure and functions.

2. The main ontogenetic directions in the development of the cardiovascular system: changes in structure, functional parameters, heart rate, blood pressure, etc.

3. Features of the fetal cardiovascular system.

4. Features of the CVS of a newborn.

5. Features of the CVS of children.

6. Features of the CVS of adolescents.

7. Structure and functions of the human respiratory organs.

8. Peculiarities of breathing of the fetus and newborns.

9. The main ontogenetic directions in the development of the respiratory system: from
changes in the frequency and depth of breathing, vital capacity of the lungs depending on
depending on gender and the level of training of children.

10. Age-related features of breathing regulation.

11. The importance of the digestive system, its structure and functions.

12. Features of digestion in the oral cavity in children and adolescents.

13. Features of digestion in the stomach in children and adolescents.

14. Features of digestion in the intestines in children and adolescents.

15. Features of absorption in children. ?"">"

16. Norms and diet for children.

17. The importance of the urinary system, its structure and functions.

18. Age-related morphofunctional changes in the urinary system.

19. Regulation of urinary tract, enuresis in children. ; "

20. The concept of assimilation and dissimilation. "-v*

21. Features of protein, carbohydrate and fat metabolism in children and adolescents.

22. Age-related changes in basal metabolism. Sex differences in total daily energy expenditure.

23. Formation of sweat and sebaceous glands in ontogenesis.

24. Thermoregulation in children.

INDIVIDUAL-TYPOLOGICAL (CONSTITUTIONAL) FEATURES OF A CHILD

Constitution- this is a set of morphological and functional characteristics of an organism, formed on the basis of hereditary and acquired properties and determining its capacity and reactivity, i.e. the nature of its response to various influences. Since the body is an integral structure, it is necessary to identify all intersystem relationships to establish consistency with each other of the morphological, physiological, biochemical, immunological, mental and other parameters of the body. The human constitution is an integral biopsychic characteristic of the body, which reflects its individuality. Moreover, each personality goes through a certain path in its development, realizing hereditary potentials in the specific conditions of the surrounding world.

Each type of constitution has characteristic features not only in anthropological indicators, but also in the activity of the nervous and endocrine systems, metabolism, structure and functions of internal organs. Specific types of constitution are characterized by different features of immunity, predisposition to infectious and non-infectious diseases.

In the process of historical development of society, as a result of natural selection and constant adaptation to changing environmental conditions, certain constitutional types were formed.

The approach to the study of constitutional types should not be evaluative, since none of the types is either good or bad. Each type is justified both biologically and socially. Society must have representatives of various constitutional types, which is a guarantee of sustainable development of society.

The constitutional type indicates what kind of life nature has provided for a particular individual. Understanding the strengths and weaknesses of different types makes it possible to choose the appropriate approach to regimen, nutrition, behavior, prevention and treatment of diseases, professional and sports guidance, educational program and lifestyle for each individual person.