Proper metabolism and energy provide the vital activity of the human body. But people are prone to various diseases. Why this happens, and what does metabolism have to do with diseases, you will learn from this article.
What you need to know about metabolism
What is metabolism? This is the activity of the body, as a result of which tissues, organs and organ systems receive the necessary nutrients (fats, carbohydrates and proteins) and remove the decay products of the body (salts, unnecessary chemical compounds). If these processes work well in the body, a person does not have health problems, and, conversely, various diseases develop with metabolic disorders.
Why does the body need nutrients? In the human body, there is a continuous, intensive synthesis, that is, complex chemical compounds are formed from simpler ones in organs, tissues and at the cellular level. At the same time, the second process is uninterrupted - the process of decomposition and oxidation of organic compounds that are no longer needed by the body and are removed from it. This complex metabolic process ensures the vital activity, formation and growth of new cells, and nutrients are the building material of all organs and systems as a whole.
Nutrients are not only needed to build tissues and organs, but also for the intensive, well-established work of all systems - the cardiovascular, respiratory, endocrine, genitourinary systems and the gastrointestinal tract. This is the energy that enters the human body during the oxidation and decomposition of organic compounds in the metabolic process. Therefore, nutrients are a significant source of energy necessary for the smooth functioning of the whole organism.
Speaking of types nutrients, then proteins, namely their enzymes, are the main material for the structure and growth of organs. Fats and carbohydrates are designed to produce and cover energy costs. All types of nutrients, including minerals and vitamins, must be supplied to the body in a certain daily amount. Lack of vitamins or a norm that exceeds the allowable one leads to disorders in the work of the whole organism and provokes various diseases. Therefore, the role of metabolism is certainly significant for the body in every sense of the word.
When metabolism is disturbed and slowed down, there is often a problem excess weight. Many people ask: "Is it possible to speed up the metabolic process?". Of course, but it takes a lot of effort to achieve the desired result. So, dreaming of having an ideal weight and, many women resort to grueling workouts and sports exercises. Of course, physical activity can build muscle mass by destroying body fat, but here you need an integrated approach to losing weight, including a balanced diet. Regular consumption of green tea helps to speed up metabolism, which has been proven by well-known nutritionists.
Many people want to change their weight in extraordinary ways. Some even start smoking because they believe that smoking promotes fat burning. Indeed, the body spends fat reserves to restore the body from tobacco poisons. In this case, you need to think about whether it is worth sacrificing the health of the whole organism for the sake of the disappearance of a few kilograms.
Often, hereditary diseases provoke weight gain and a slowdown in the metabolic process. So, obesity is observed in patients with diabetes mellitus, due to disruption of the thyroid gland. In most cases, these diseases are passed down through the genes to children. Therefore, the most optimal diet option is prescribed by an endocrinologist.
Age-related features of metabolism
The nutritional requirements of a child's body are much higher than those of an adult. Therefore, there is an intensive metabolism, where the processes of anabolism (synthesis) and catabolism (decay) are much faster than in the body of an adult. Since there is an intensive growth of cells and the development of a young organism, protein as a building material is needed two or even more times than an adult. So if child under 4 years old a daily rate of 30 ... 50g is required, then a 7-year-old needs up to 80g of protein per day. Protein enzymes in the human body do not accumulate like fats. If you increase the daily dose of proteins, it threatens with digestive disorders.
Together with fats, hormones and vitamins necessary for life enter the body. They are divided into 2 main groups: those that are broken down with the help of fats and those that need only water. The younger the child, the more percentage of fat is needed for its development. Thus, an infant with mother's milk receives approximately 90%, the body of an older child absorbs 80%. The digestibility of fats directly depends on the amount of carbohydrates, the deficiency of which leads to various undesirable changes in digestion, an increase in acidity in the body. It is a sufficient daily intake of fat that helps to strengthen the immune system.
Carbohydrates are needed by the children's body in large quantities. With age, the need of a growing organism for them also increases. Exceeding the norm of carbohydrates raises blood sugar in a child only for a few hours after ingestion of carbohydrates, then the level is normalized. Therefore, the risk of getting sick with diabetes is practically excluded, in adults, the opposite is true.
The metabolism of older people changes significantly, as it is associated with hormonal changes in the body. 2 main stages of metabolism slow down: the processes of synthesis and decomposition of compounds. So, people over 60 need to limit the intake of proteins with food. Therefore, meat consumption should be limited, but not completely. Since the elderly are prone to frequent constipation and intestinal problems, it is useful for them to take sour-milk products, raw vegetables and fruits. It is better to use fats at a minimum, it is better - vegetable. Carbohydrates should also not be carried away (meaning sweets, but sweet fruits are allowed).
Improper nutrition, age-related changes, aging of organs, tissues and cells makes it difficult and slows down the metabolism in the body. Therefore, older people should eat moderately and lead an active lifestyle.
The processes of metabolism and energy are especially intense during the growth and development of children and adolescents, which is one of the characteristic features of a growing organism. At this stage of ontogenesis, plastic processes significantly predominate over destruction processes, and only in an adult person a dynamic balance is established between these processes of metabolism and energy. Thus, in childhood, the processes of growth and development or assimilation predominate, in old age - the processes of dissimilation. This pattern can be violated as a result of various diseases and other extreme environmental factors.
Protein metabolism. The absence of any of the essential amino acids in food causes serious disturbances in the vital activity of the organism, especially when it is growing. Protein starvation leads to a delay, and then to a complete cessation of growth and physical development.
For a growing organism, protein requirements are much higher than for an adult. In the first year of postnatal development, a child should receive more than 4 g of protein per 1 kg of body weight, at 2-3 years old - 4 g, at 3-5 years old - 3.8 g, etc.
Metabolism of fats and carbohydrates. The needs of children and adolescents in fats have their own age characteristics. So, up to 1.5 years there is no need for vegetable fats, and the total need is 50 g per day, from 2 to 10 years the need for fats increases 80 g per day, and for vegetable fats - up to 15 g, during puberty the need for fat in boys is 110 g per day, and in girls - 90 g, and the need for vegetable fats in both sexes is the same - 20 g per day.
The carbohydrate requirements of children and adolescents are much less, especially in the first years of life. So, up to 1 year the need for carbohydrates is 110 g per day, from 1.5 to 2 years - 190 g, at 5-6 years old - 250 g, at 11-13 years old - 380 g and in young men - 420 g, and for girls - 370 g. In the children's body, there is a more complete and rapid absorption of carbohydrates and greater resistance to excess sugar in the blood.
Water-salt exchange. The water content in the child's body is much higher, especially in the early stages of development. The total water requirement of children and adolescents increases as the body grows. If a one-year-old child needs about 800 ml of water per day, then at 4 years old - 1000 ml, at 7-10 years old - 1350 ml, and at 11-14 years old - 1500 ml.
mineral exchange. The needs of an adult and a child for minerals differ significantly, a lack of minerals in a child's food more quickly leads to various metabolic disorders and, accordingly, to a violation of the growth and development of the body. By the end of puberty, the need for trace elements decreases slightly.
Vitamins. They are required for our body in negligible amounts, but their absence leads the body to death, and a lack of nutrition or a violation of their absorption processes leads to the development of various diseases called hypovitaminosis.
About 30 vitamins are known that affect various aspects of metabolism, both individual cells and the whole organism as a whole. This is due to the fact that many vitamins are part of enzymes. Consequently, the lack of vitamins causes the cessation of enzyme synthesis and, accordingly, metabolic disorders.
A person receives vitamins from food of plant and animal origin. For normal life, a person needs 16-18 out of 30 vitamins. A growing organism is highly sensitive to a lack of vitamins in food. The most common hypovitaminosis among children is a disease called rickets. It develops with a lack of vitamin D in baby food and is accompanied by a violation of the formation of the skeleton. Rickets occurs in children under 5 years of age.
It should also be noted that the intake of an excess amount of vitamins into the body can cause serious impairment of its functional activity and even lead to the development of diseases called hypervitaminosis. Therefore, one should not abuse vitamin preparations and include them in the diet only on the advice of a doctor.
Energy exchange. Metabolism in the body is closely related to the conversion of energy. One of the most important indicators of the intensity of metabolic processes in the body is the value of basal metabolism, which depends on age, sex and weight.
On average, the value of the basal metabolism in men is 7140-7560 kJ per day, and in women 6430-6800 kJ. The intensity of metabolic reactions in children in terms of 1 kg of body weight or 1 m 2 of its surface is much higher than in adults, although the absolute values are smaller. So, in boys of 8 years, the value of the main metabolism in terms of 1 m 2 of surface is 6190 kJ, and in girls - 5110 kJ. Further, with age, the value of the basal metabolism decreases and in boys of 15 years old it is 4800 kJ, in girls it is 4480 kJ.
Knowing the body's energy costs, it is possible to compose an optimal diet so that the amount of energy supplied with food fully covers the body's energy costs. For children and adolescents, the composition of food is especially important, since the child's body needs a certain amount of proteins, fats, carbohydrates, mineral salts, water and vitamins for normal development and growth.
7. Thermoregulation, its age-related features
thermoregulation (Greek thermē heat and Latin regulare to order)- a set of physiological processes in the human body aimed at maintaining a constant body temperature (normally 36.0-37.0 0 С).
Body temperature depends on heat production and heat loss.
Heat production, i.e., the production of heat in the body, depends on the intensity of metabolism. Heat transfer from the surface of the body to the external environment is carried out in several ways: by changing the intensity of blood circulation, perspiration, heat release with exhaled air, as well as with urine and feces. In children, especially infants, heat transfer is increased due to the abundant blood supply to the skin, the thinness of the skin itself, and the immaturity of the thermoregulation center (when an adult organism cools due to a decrease in ambient temperature, the vessels of its skin narrow reflexively, which allows you to save heat).
Normally, thermoregulation is carried out reflexively. The thermoregulatory center is located in the hypothalamus.
If the process of heat production prevails over the process of heat transfer, the body overheats, up to heat stroke. If the process of heat transfer prevails over heat production, hypothermia of the body occurs.
Violation of thermoregulation is observed with fever accompanying inflammatory and infectious diseases, circulatory disorders, alcohol consumption, etc.
In newborns and infants, thermoregulation is not completely formed (heat transfer prevails over heat production).
Isothermia - equalization in the process of ontogeny of the body temperature of a child with an adult organism - develops gradually, only by the 5th year of life. The maturation of the thermoregulation system in postnatal ontogenesis is closely related to the maturation of the mechanisms of neuroendocrine regulation and the implementation of the standing posture, with the maturation of skeletal muscles. By the time of birth, thermoregulatory mechanisms, even in premature babies, can already be included in the work: increased heat generation of predominantly non-shivering origin, vascular reactions, sweating, behavioral reactions. Due to the fact that the mechanisms of thermoregulation function in a child from the moment of birth, his hardening must begin as early as possible.
Questions for self-examination:
1. What is metabolism and what processes does it include?
2. List the functions of proteins.
3. What are essential amino acids?
Metabolism is understood as a set of changes that substances undergo from the moment they enter the digestive tract to the formation of final decay products excreted from the body. That is, the metabolism of all organisms, from the most primitive to the most complex, including the human body, is the basis of life.
Characterization of anabolic and catabolic processes in the body
In the process of vital activity in the body, continuous restructuring takes place: some cells die, others replace them. In an adult, it dies within a day, others replace them. In an adult, 1/20 of the cells of the skin epithelium and half of all epithelial cells of the digestive tract, about 25 g of blood, etc. die and are replaced during the day.
In the process of growth, renewal of body cells is possible only when O 2 and nutrients are continuously supplied to the body, which are the building material from which the body is built. But for the construction of new cells of the body, their continuous renewal, as well as for the performance of some kind of work by a person, energy is needed. The human body receives this energy during decomposition and oxidation in the processes of metabolism (metabolism). Moreover, metabolic processes (anabolism and catabolism) are finely coordinated with each other and proceed in a certain sequence.
Anabolism is understood as a set of synthesis reactions. Under catabolism - a set of decay reactions. It must be taken into account that both these processes are continuously connected. Catabolic processes provide anabolism with energy and starting materials, 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.
During individual development, the most significant changes are experienced by the anabolic phase of metabolism and, to a lesser extent, 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 (proliferation), growth of the body 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) - protein synthesis in regenerating tissues after injuries or malnutrition.
4) the synthesis of self-renewal associated with the stabilization of the body - the constant replenishment of the components of the internal environment that are destroyed during dissimilation.
All these forms weaken, albeit unevenly, in the course of individual development. At the same time, especially significant changes are observed in the synthesis of growth. The intrauterine period is characterized by the highest growth rates. For example, the weight of a human embryo compared to the weight of a zygote increases by 1 billion. 20 million times, and for 20 years of progressive human growth increases no more than 20 times.
Protein metabolism in the developing organism
Growth processes, quantified by weight gain and a 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 organs of 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 disturbed. The intake of essential amino acids for a growing organism is especially important, for example, the lack of lysine in food leads to growth retardation, depletion of the muscular system, and a lack of valine - balance disorders in a child.
In the absence of non-essential amino acids in food, they can be synthesized from essential ones (tyrosine can be synthesized from phenylalanine).
Finally, proteins containing all the necessary set of amino acids that ensure normal synthesis processes are biologically complete proteins. The biological value of the same protein for different people is different depending on the state of the body, diet, age.
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 old - 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 that enter the body and are destroyed in it is judged by the magnitude 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.
Studies have shown that the progressive phase of development is characterized by intensive protein metabolism and a positive nitrogen balance. The younger the body, the higher the positive balance and the greater the ability to retain food nitrogen. With a decrease in growth rates, the ability to retain protein metabolism also decreases.
As can be seen, the ability to retain nitrogen and sulfur in children is subject to significant individual fluctuations and persists throughout the entire period of progressive growth. With the cessation of growth, there is a sharp decrease in the retention of nitrogen and sulfur from food, which is noted in adults and the elderly.
As a rule, adults do not have the ability to retain food nitrogen, their metabolism is in a state of nitrogen balance. This indicates that the potential for protein synthesis persists for a long time - for example, under the influence of physical activity, an increase in muscle mass occurs (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 self-renewal processes that occur throughout life and which, with old age, fade much more slowly than other types of synthesis. The intensity of self-renewal can be judged by the wear coefficient (Rubner), which characterizes those minimal expenses that are associated with the basic processes of life in the absence of proteins in food. This indicator is calculated by the minimum amount of nitrogen excreted in the urine, with a sufficient calorie, but protein-free diet, that is, by the level of "endogenous" urine nitrogen.
The amount of urine nitrogen under these conditions decreases with age, and in men it is slightly higher than in women, but in old age the sex differences are smoothed out. The data show that with age, the amount of self-renewal synthesis decreases.
Age-related changes affect not only protein, but also fat and carbohydrate metabolism.
AGE ANATOMY AND HUMAN PHYSIOLOGY
LECTURE 5
Topic: Metabolism and energy and their age-related features.
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 organism.
4. Features of hormonal regulation of body functions.
5. Hormones, their classification and significance.
6. The 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 psychology of man". - St. Petersburg - 2003;
2. Bezrukikh M.M. - "Age-related physiology: Physiology of child development." - M.-2002;
3. McDermott M.T. - "Secrets of Endocrinology" - M.-1998.
4. Prishchepa I.M. - "Age anatomy and physiology". - Minsk. - 2006;
5. Sapin M.R. - "Anatomy and physiology of man". - M.-1999;
1. Characteristics and types of metabolic processes in the body.
Metabolism is the intake of various substances from the external environment into the body, their assimilation and the release of the resulting decay products. Metabolism consists of two interrelated and opposite 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 that enter cells. Anabolism is the basis for the formation of new tissues in the process of growth, regeneration processes, synthesis of cellular compounds and requires energy. The latter is supplied by the reactions catabolism, at which the molecules of complex organic substances are split with the release of 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 ratio of the processes of anabolism and catabolism determines three states: growth, destruction of structures and dynamic balance. The latter state is typical for an adult healthy person: the processes of anabolism and catabolism are balanced, tissue growth does not occur. With the growth of the organism, anabolism prevails over catabolism; when tissue is destroyed, vice versa.
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 with food is not necessary, they can be synthesized in the body. Food proteins containing all the 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 (vegetable proteins). The highest biological value of the proteins of eggs, meat, milk, fish. With a mixed diet, the body receives all the set of amino acids necessary for protein synthesis. The intake of all essential amino acids for a growing organism is especially important. For example, the absence of rubber in food leads to a delay in the growth of the child, valine - to a balance disorder in children. Children need more protein than adults, as they have more intensive growth processes and the formation of new cells and tissues. Protein starvation of the child leads to a delay, and then a complete cessation of growth and physical development. The child becomes lethargic, there is a sharp weight loss, widespread swelling, diarrhea, inflammation of the skin, and a decrease in 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. Hormones of the adrenal cortex (hydrocortisone, corticosterone) increase the breakdown of proteins in the tissues, and in the liver, on the contrary, they stimulate. 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 the body fat synthesized from glycerol and fatty acids, as well as from the metabolic products of carbohydrates and proteins. The main function of fat is energy: during its decay, 2 times more energy is generated (9.3 kcal.) than during the decay of the same amount of proteins and carbohydrates, most of the fats are in adipose tissue and constitute a reserve energy reserve. In addition, fat also performs a plastic function: it goes 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. The diet should be dominated by vegetable fats. After 40 years, animal fats should be excluded from the diet, because, integrating into the cell membrane, they make it impermeable to various substances, as a result of which the cell ages. Regulation of fat metabolism occurs in a nervous and humoral way. Nervous regulation is carried out by the hypothalamus. Parasympathetic nerves contribute to the deposition of fat, and sympathetic nerves increase its decay; 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 energy 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 (1 g releases 4.1 kcal.) The rate of glucose breakdown and the ability to quickly extract and process its reserve - glycogen - create conditions for 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 to 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 content by almost 2 times. This is called food 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. The metabolism of carbohydrates is regulated by the nervous and humoral pathways. Nervous regulation is carried out by the hypothalamus. Humoral regulation is due to somatotropic hormone (pituitary gland), thyroxine and triiodothyronine (thyroid gland), glucagon (pancreas), adrenaline (adrenal medulla) and glucocopticoids (cortical layer under the kidneys). All of these hormones increase blood sugar, and only insulin (the pancreas) lowers it.
3. Metabolism of inorganic substances and its importance in the process of growth and development of the organism.
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 the internal organs its content is 76-86%, in the muscles - 70%, less in adipose tissue - 30% and in the bones - 22%. The daily water requirement of an adult is 2 - 2.5 liters. This amount is made up of water consumed when drinking (1l), contained in food (1l) and formed during metabolism (300-350 ml). The normal activity of the body is characterized by the preservation of water balance, i.e. The amount of water taken in is equal to the amount taken out. If the water is withdrawn. If more water is excreted from the body than it enters, there is a feeling of thirst. The body of the child quickly accumulates and quickly loses water. This is due to the intensive growth of physiological immaturity of the kidneys and neuroendocrine mechanisms of regulation of 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. Per day, the release of water can reach 50% of the amount of fluid taken, especially when the child overheats. Insufficient water can lead to "salt fever", that 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. The regulation of water metabolism is carried out by the neuro-humoral way. 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, it is necessary to receive 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 5%. Mineral salts are contained in food in an amount sufficient to maintain vital activity, only sodium chloride is added additionally. For a growing organism and during pregnancy, more mineral salts are required. It is necessary to additionally introduce salts of potassium, magnesium, sodium, chlorine and phosphorus. With excessive use 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. With a lack of salts in the body, they come from the depot. The study of the biological effects of mineral substances on the body was started in 1891. Russian scientist V.I. Vernadsky. He suggested that in the composition of living organisms there are elements of the earth's crust. Currently, they are divided into macro- and microelements. Macroelements are necessary for a person daily 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 abundant 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 implementation of the process of blood coagulation, 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 taken along with fats, digestibility decreases sharply. Calcium is well utilized from foods that are both 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. Especially a lot of calcium is found in cheeses as well as legumes, soy, peanuts. 20-30% of calcium is absorbed from dairy products, 50% from vegetable 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. For the development of the child, the ratio of calcium and phosphorus is most important. 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 the bone tissue leads to the development of osteoporosis with increased bone fragility, a tendency to fracture. With aging, bone tissue loses some of the calcium, which is called bone demineralization, which, with age, captures all parts of the skeleton. This contributes to the development of various skeletal diseases, including osteochondrosis, more frequent bone fractures, the total magnesium content in the body of an adult is 21-24g, of which 50-70% is in the bone tissue. With 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. Of particular importance is magnesium in the functioning of the nervous system and the conduction system of the heart. A good supply of magnesium to the body contributes to better tolerance of stressful situations, suppression of depression. Significantly increases the body's need for it during physical exertion, in athletes in the process of long training, as well as in stressful situations. The daily requirement for magnesium by the body of an adult 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 secrete 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, ensure the reproductive function, growth and development of the body, the formation, utilization and conservation (“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 20th 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 a secret - hormones. Hormones are organic compounds produced by certain cells and designed to control the functions of the body, their regulation and coordination. Higher animals have two regulatory systems by which the body adapts to constant internal and external changes. One is the nervous system, which rapidly 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 by the blood and have an effect on tissues and organs distant 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 biologically active substances that have a strictly specific and selective effect, capable of raising or lowering 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 derivatives of amino acids- adrenaline, norepinephrine, dopamine, etc.
Hormones derived from fatty acids- prostaglandins.
According to the physiological action, hormones are divided into:
Launchers(hormones of the pituitary gland, epiphysis, hypothalamus). Affect other endocrine glands;
Performers- affect individual processes in tissues and organs.
The physiological action of hormones is aimed at:
1) providing humoral, i.e. carried out through the blood, the 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 growth, maturation and reproduction processes.
Hormones regulate the activity of all body cells. They affect mental acuity and physical mobility, physique and height, determine hair growth, voice tone, sexual desire and behavior. Thanks to the endocrine system, a person can adapt to strong temperature fluctuations, excess or lack of food, 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, and also to answer the question why some people are tall and others short, some are full, 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. As a medical discipline, it appeared 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 a cow. In addition, for centuries, castration has been practiced both to tame and domesticate animals, and to turn a person into a submissive slave.
The organ that reacts to this hormone is the target organ (effector). The cells of this organ are equipped with receptors. Hormones, once in the bloodstream, must flow to the appropriate target organs. In the 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 affected). 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 (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 a bound form is higher than in a free one; the two forms are in dynamic equilibrium. It is 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 the protein binding of hormones in the blood is not entirely clear. It is assumed that such binding facilitates the transport of the hormone or protects the hormone from loss of activity.
6. The structure and functions of the endocrine glands
The endocrine system of the human body combines small in size and different in structure and functions of the endocrine glands: the pituitary gland, the epiphysis, the thyroid and parathyroid glands, the pancreas, the adrenal glands and the gonads. All together, they weigh no more than 100 grams, and the amount of hormones they produce can be calculated in billions of grams. Nevertheless, the sphere of influence of hormones is exceptionally large. They have a direct impact on the growth and development of the body, on all types of metabolism, on puberty. There are no direct anatomical connections between the endocrine glands, but there is an interdependence of the functions of one gland from 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 Turkish saddle 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 upper-lower - 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 on the base of the brain (lower surface), in the pituitary fossa of the Turkish saddle of the sphenoid bone. The pituitary gland consists of two large lobes of different origin and structure: the anterior - adenohypophysis (makes up 70-80% of the mass of the pituitary gland) and the posterior - 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 production and in the process of childbirth.
The large anterior pituitary gland secretes six tropic hormones into the blood. One of them - growth hormone, or somatotropic (GH) - stimulates the growth of the skeleton, activates protein biosynthesis, and contributes to an increase in body size. If, as a result of any disorders, the pituitary gland begins to produce too much growth hormone, body growth increases dramatically, gigantism develops. In cases where an increased release of growth hormone occurs in an adult, this is accompanied by acromegaly - an increase not in the whole body, but only in its individual parts: nose, chin, tongue, arms and legs. With insufficient production of somatotropic hormone by the pituitary gland, the child's growth stops and pituitary dwarfism develops. The remaining five hormones: adrenocorticotropic (ACTH), thyrotropic (TSH), prolactin, follicle-stimulating (FSH) and luteinizing (LH) - direct and regulate the activity of other endocrine glands. Adrenocorticotropic hormone stimulates the activity of the adrenal cortex, forcing it, if necessary, to produce corticosteroids more intensively. Thyroid-stimulating hormone promotes the formation and secretion of the thyroid hormone thyroxine. Follicle-stimulating hormone in women promotes the maturation of the egg, and in men it stimulates spermatogenesis. In close contact with it, the luteinizing hormone acts. It is thanks to LH that the so-called corpus luteum is formed in women, without which the normal course of pregnancy is impossible.
Prolactin, or lactogenic hormone, also takes an active part in the processes of reproduction. The size and shape of the mammary glands largely depends on this hormone; through a complex system of interrelations of 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 itself obeys the central nervous system, and in particular the hypothalamus. Together with the neurosecretory nuclei of the hypothalamus, the pituitary gland forms the hypothalamic-pituitary system that controls the activity of the peripheral endocrine glands.
The 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 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, all internal organs. Heart rate, blood vessel tone, body temperature, the amount of water in the blood and tissues, the 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 pituitary gland necessarily passes through the median eminence of the hypothalamus and is enriched there with hypothalamic neurohormones. Neurohormones are substances of a peptide nature, which are parts of protein molecules. To date, seven neurohormones, the so-called liberins (that is, liberators), have been discovered that stimulate the synthesis of tropic hormones in the pituitary gland. And three neurohormones - prolactostatin, melanostatin and somatostatin - on the contrary, inhibit their production.
Other neurohormones include vasopressin and oxytocin. They are produced by the nerve cells of the nuclei of the hypothalamus, and then transported along their own axons (nerve processes) to the posterior lobe of the pituitary gland, and from here these hormones enter the bloodstream, having a complex effect on the body systems.
Oxytocin stimulates the contraction of the smooth muscles of the uterus during childbirth, 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 rises. Due to the fact that 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 the primary urine into the blood. When, as a result of disturbances in the activity of the hypothalamic-pituitary system, the production of ADH decreases sharply, 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, lowering the “guiding” hormones along the chain. They themselves sensitively analyze the 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 work of this gland, and a deficiency induces 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 by a long evolutionary development and is very reliable.
However, a failure in one link of this complex chain is enough to cause a violation of quantitative, and sometimes even qualitative, relationships in the whole system, resulting in various endocrine diseases.
The neurohypophysis is made up of nerve lobe and funnels, fundibulum connecting the nerve 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 they enter the bloodstream. The pituitary infundibulum joins with the hypothalamic infundibulum to form the pituitary stalk.
Adenohypophysis - consists of branched strands 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 the cut. 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 distinguished 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 pituitary gland produces protein hormones, six of which have been isolated in chemically pure form. Their structure is now fully deciphered. The exact number of hormones secreted by the anterior lobe has not been established; only well-known ones are considered below.
A growth hormone. Many hormones affect the growth of the body, but the most important role in this complex process is apparently played by the pituitary growth hormone (somatotropin). After removal of the pituitary gland, growth practically stops. The introduction of this hormone in young animals accelerates growth, and in adults it can lead to its renewal, and the study of metabolism in these cases always reveals a decrease in the excretion (removal) of nitrogen from the body. Nitrogen retention is a necessary sign of true growth, indicating that new tissue formation is actually taking place, and not just an increase in body weight due to the accumulation of fat or water. In 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 disorders 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 maturation of the body is completed, growth increases proportionally; if this occurs after reaching maturity, a condition called acromegaly occurs, in which there is a 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: eyebrows, nose and lower jaw begin to protrude, hands, feet and chest increase, the back becomes motionless, the nose and lips thicken.
lactogenic hormone pituitary (prolactin) stimulates lactation - the formation of milk in the mammary glands. Persistent lactation in combination with amenorrhea (abnormal absence or suppression of menses) may occur with a pituitary tumor. This disorder is also associated with impaired secretory activity of the hypothalamus, which normally inhibits 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 females, but also males, and not only in mammals, but also in lower vertebrates. Little is known about its functions in the male body.
Thyroid-stimulating hormone pituitary (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. The introduction of thyrotropin can cause excessive activity of the thyroid gland. Thus, violations of its function can be the result of not only diseases of the gland itself, but also pathological processes in the pituitary gland and, accordingly, require different treatment.
adrenocorticotropic hormone pituitary gland (ACTH, corticotropin) stimulates the adrenal cortex in the same way that thyroid-stimulating hormone stimulates the thyroid gland. One difference, however, is that the function of the adrenal cortex does not stop completely in the absence of ACTH. When there is no stimulation from the pituitary gland, the adrenal cortex retains the ability to secrete the hormone aldosterone, which is necessary for life, which regulates the content of sodium and potassium 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 if necessary. Therefore, patients with insufficiency of pituitary function become very sensitive to various kinds of loads and stresses. 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 features include weight gain, a moon-shaped face, an increase in body fat in the upper body, increased blood pressure, and muscle weakness.
Gonadotropic hormones(gonadotropins). The anterior 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 - 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 occur similar to those that occur during castration.
regulation of metabolism. 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 belongs, apparently, 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, diabetes mellitus, develops. With the simultaneous removal of the pancreas and pituitary gland, most of the symptoms of diabetes are absent, so in this respect the influence of the hormones of the pituitary and pancreatic glands seems to be 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 the reduction (compression) of pigment cells. MSH is derived from the same precursor molecule as adrenocorticotropic hormone (ACTH). In the anterior pituitary gland, this precursor is converted to ACTH, and in the intermediate lobe, to MSH. MSH is also produced in the mammalian pituitary gland, 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 uterine contractions as during childbirth. This hormone is sometimes used in obstetrics to stimulate prolonged labor, but the significance of its normal concentrations in labor has not been established. Oxytocin also causes contractions in the muscular 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 (urination). However, under normal conditions, it has only one known action in the body - it regulates the amount of water excreted through the kidneys. Even under the influence of extremely low concentrations, the 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 through the kidneys a huge amount of water, sometimes exceeding 38 liters per day. There is a strong thirst, and to avoid dehydration, patients have to consume an appropriate amount of water.
epiphysis(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 the illumination. In some vertebrate species, both functions are combined. In humans, this formation resembles a pine cone in shape, from which it got its name (Greek epiphysis - bump, 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, 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 in the form of a mature structure is found only in certain groups of vertebrates, such as lampreys, lizards and frogs.
Where the pineal and parapineal glands function as a light-perceiving 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 some 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 a violation of the daily rhythm of the body in connection with the flight through several time zones, sleep disorders and, probably, “winter depressions”.
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). Behind 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, 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 an iodine-containing thyroglobulin protein. The follicles are closely adjacent to each other. The walls of the follicle are lined with a single layer of 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 the cells of the follicular epithelium vary depending on the functional state of the thyroid gland: the epithelium is normally cubic, with increased functional activity it is high cylindrical, and with reduced functional activity it is flat. The size of the Golgi complex, the number of mitochondria and secretory drops 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 cavity of the follicle 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.
Such basic biological processes as growth, development and differentiation of tissues depend on the normal function of the thyroid gland. The thyroid gland secretes 3 hormones - thyroxine and triiodothyronine and thyrocalcitonin.
thyroxine: Enhances the processes of oxidation 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 largely similar to thyroxine.
thyrocalcitonin: Regulates the exchange of calcium in the body, reducing its content in the blood, and increasing its content in the bone tissue (has an effect opposite to the parathyroid hormone of the parathyroid glands). A decrease in the level of calcium in the blood reduces the excitability of the central nervous system.
The biological effects of thyroid hormones in physiological doses are manifested in maintaining the energy and biosynthetic processes in the body at an optimal level. The action of hormones on the processes of biosynthesis, 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 catabolism processes, the consumption of substances and energy in the form of heat, products of incomplete and perverted metabolism. The mechanism of action of thyroid hormones is represented by the stages of "recognition" and perception of the signal by the cell and the generation of a pier. processes that determine the nature of the response. In the cells of various tissues, specific receptor proteins have been found that "recognize" the hormone and turn on biochemical reactions. The function of the thyroid gland is regulated by the central nervous system. The thyroid gland is in interaction with other endocrine glands.
Diseases of the thyroid gland in humans (inflammatory, tumors, injuries, congenital anomaly, etc.) may be accompanied by an increase in the thyroid gland and a violation of its function: a decrease in hormone production (hypothyroidism) or their increased formation.
| Parathyroid glands, four small glands located in the neck near the thyroid gland. They have a reddish-brown color, the total weight of all four glands is 130 mg. Like other endocrine glands, they are richly supplied with blood. The hormone they secrete into the bloodstream - parathyroid, or parathormone - is a protein, consisting of 84 amino acid residues connected in 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. For diseases associated with a low content of calcium in the blood, in particular rickets and renal failure, an increase in the activity of the parathyroid glands and an increase in their size are characteristic. 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 reducing 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 by the kidneys (inhibits) and phosphorus (accelerates), 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 can be caused by a small tumor, is called primary hyperparathyroidism. It is characterized by the loss of calcium and phosphorus from the bone tissue, causing the bones to become brittle, painful, and often break. Vertebral fractures 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 holes, but the teeth themselves are not destroyed. Calcium and phosphorus lost from the bones in 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 stones the size of a fist). It has been established that primary hyperparathyroidism is the cause of 5-10% of cases of nephrolithiasis. Treatment of hyperparathyroidism is reduced to the surgical removal of overactive glands. Hypoparathyroidism. With the destruction of the parathyroid glands 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 content of phosphorus increases. For the normal functioning of tissues, primarily nervous and muscular, a stable, normal level of calcium in the blood is necessary. Its decrease in hypoparathyroidism causes bouts 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. Occasionally, pseudohypoparathyroidism occurs - a disease caused by the insensitivity of the bones and kidneys to the action of parathyroid hormone. It also leads to tetany, which would seem to indicate hypoparathyroidism, but all four parathyroid glands in this case are normal. |
thymus(thymus, or goiter, gland) is an endocrine gland that plays a crucial 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 have entered the body, control the production of antibodies against disease-causing 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 at the 6th week of intrauterine life, developing, like 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 by the time of birth (about 15 g). Then it continues to grow, although much more slowly, and at puberty 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. In different animal species, this process proceeds at different rates, and in some (for example, in guinea pigs), a relatively large thymus 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 little bodies, which probably serve as a site of cell destruction.
The thymus secretes only one hormone, thymosin. This hormone affects the metabolism of carbohydrates as well as calcium. In the regulation of calcium metabolism, the action is close to parathyroid hormone. Regulates the growth of the skeleton, participates in the management of immune responses (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 (“caregivers” or “nannies”) of the superficial cortical layer of the lobules and, under the influence of the thymus hormone, 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 for circulation throughout the body.
T-cell failure. 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 (structural disturbance) of the thymus, its insufficient development and Di George's 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 is completely defenseless against pathogenic microbes, can sometimes be treated with bone marrow transplantation, transplantation of the fetal thymus, or the introduction of antibodies.
Pancreas- Digestive and endocrine glands. Found in all vertebrates except lampreys, hagfish and other primitive vertebrates. Elongated shape, in outline resembles a bunch of grapes. The endocrine system refers only to the inner part of the pancreas. 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: the head, neck, body and tail. The head is 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 with completely different functions. Actually, the pancreatic tissue is made up 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 duct of Wirsung, the main excretory duct of the pancreas. The lobules are almost entirely composed of cells that secrete pancreatic juice (pancreatic juice, from lat. pancreas- pancreas). Pancreatic juice contains digestive enzymes. From the lobules through the 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 flowing 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 (endocrine glands), releasing directly into the bloodstream glucagon and insulin, hormones that regulate carbohydrate metabolism. These hormones have the opposite effect: glucagon raises and insulin lowers blood sugar levels.
Insufficient secretion of insulin leads to a decrease in the ability of cells to absorb carbohydrates, i.e. to diabetes.
Diabetes mellitus is a chronic disease in which the body produces too little or no insulin. If it is not enough, all kinds of metabolic disorders develop, because the tissues of the body do not receive enough nutrients for energy. Men and women are equally affected by this disease, and with age, the risk of getting sick increases. 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 and its excretion in the urine. A person begins to complain at first of constant intense thirst and copious urine output (up to 6 liters per day), itching of the skin, especially in the perineum, may also cause pustular diseases and sexual dysfunction. 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 passes into an unconscious state - the most severe complication of diabetes develops - diabetic coma. Prevention of diabetes is a balanced diet, maintaining normal body weight and timely treatment of inflammatory diseases of the biliary tract and pancreas. And with a hereditary predisposition, a periodic examination is necessary in order to recognize the disease in time and begin treatment.
| Adrenals - small flattened paired glands of yellowish color, 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 the endocrine glands, i.e. the substances (hormones) they secrete 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 the inner medulla. The cortical layer 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 (secrete) sex steroids - hormones that are similar in chemical structure and biological action to the hormones of the sex glands. In addition to sex cells, cortical cells produce two more very important groups of hormones: mineralocorticoids (aldosterone and deoxycorticosterone) and glucocorticoids (cortisol, corticosterone, etc.). Decreased secretion of adrenal hormones leads to a condition known as Addison's disease. These patients are treated with hormone replacement therapy. Excessive production of cortical hormones underlies the so-called. Cushing's syndrome. In this case, surgical removal of the adrenal tissue with excessive activity is sometimes performed, followed by the appointment of replacement doses of hormones. Increased secretion of male sex steroids (androgens) is the cause of virilism - the appearance of masculine features in women. Usually this is a consequence of a tumor in the adrenal cortex, so the best treatment is removal of the tumor. The medulla originates from the sympathetic ganglia of the nervous system of the embryo. 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 a 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 epinephrine and norepinephrine is to enhance the effects of the sympathetic nervous system; they increase heart rate and breathing, blood pressure, and also affect the complex functions of the nervous system itself. |
To date, doctors have studied the endocrine system well enough to prevent and cure hormonal disorders.
The main biological feature of a growing organism is a high metabolic rate. At the biological level, this manifests itself in high rates of metabolic reactions.
As you know, metabolism is a set of chemical reactions occurring in the internal environment of the body. Metabolism, in turn, is divided into catabolism and anabolism. Catabolism is a chemical process in which macromolecules are broken down into smaller molecules. The end products of catabolism are carbon dioxide (CO 2), water (H 2 O) and ammonia (NH 3).
Catabolism is characterized by the following patterns:
- In the process of catabolism, oxidation reactions predominate;
- The process proceeds with the consumption of oxygen;
- The process is accompanied by the release of energy, most of which is stored in the form of ATP (adenosine triphosphate). Part of the energy is released in the form of heat.
Anabolism includes various synthesis reactions and is characterized by the following features:
- Reactions are restorative in nature;
- the process proceeds with the consumption of hydrogen (in the form of NADP H 2);
- Anabolism proceeds with the consumption of energy, the source of which is ATP.
In an adult, both of these processes proceed at approximately the same rate, which ensures the renewal of the chemical composition of the body.
In children, adolescents and young men, catabolism and anabolism proceed at higher rates than in adults, and at the same time, anabolism in its speed significantly exceeds catabolism, which leads to the accumulation of chemicals in the body and, first of all, proteins. The accumulation of proteins in the body is a prerequisite for its growth and development.
Protein metabolism
The protein metabolism of a growing organism has a certain direction and its own characteristics. It must be taken into account that protein is the main building material for the cells and tissues of a growing organism. In the process of growth of muscle tissue in its cells, the content of proteins (sarcoplasm, enzymes, contractile, etc., which make up 80% of the dry residue) increases. The percentage of the ratio of muscle tissue weight to body weight increases. At 16 years old, it is about 44.2% of the total body weight, while at 8 years old it is only about 27.2%.
Proteins perform other important functions in the body (catalytic, contractile, regulatory, energy, protective, etc.).
The protein metabolism of a growing organism, as well as the metabolism as a whole, is characterized by high intensity and the predominance of anabolism reactions over catabolism reactions, as evidenced by a positive nitrogen balance.
Nitrogen balance is one of the most important indicators of protein metabolism.
In a positive balance, the amount of nitrogen input entering the body with dietary proteins is greater than the total amount of nitrogen excreted, excreted mainly in the urine (in the form of urea, ammonia, creatinine and other nitrogen-containing compounds). The percentage of use and retention of nitrogen entering the body is twice as high in an infant as in adults.
An indicator of the intensity of protein synthesis in a growing organism is also a high content of DNA and RNA in cells.
To maintain a positive nitrogen balance, necessary for normal growth and development, a sufficient amount of protein must be supplied to a growing organism with food.
The average daily protein requirement in our country for adults is about 100 g; for children, the absolute value is lower, but per kg of body weight higher: a 2-5-year-old child is recommended 3.5-4 g / kg body weight, a 12-13-year-old - 2.5 g / kg body weight, a 17-18-year-old - 1.5 g/kg.
The biological value of food proteins, motor activity and the nature of physical activity have a significant impact on the protein norm.
Violation of the growth and development of the child can be caused by both insufficient and excessive intake of dietary proteins.
An early manifestation of protein deficiency is a decrease in the amount of albumin in the blood and a decrease in the albumin-globulin ratio (A/G). A decrease in urea and total nitrogen in the daily urine of a growing organism is also a signal of insufficient intake of proteins from food.
Protein deficiency can lead to growth retardation, puberty, weight loss, weakening of the body's protective properties.
The intensity of metabolism in the body of an athlete increases the need for proteins, especially during loads of a speed-strength nature, during which the breakdown of proteins, mainly muscle proteins, increases.
With excessive intake of proteins in the body, digestive enzymes are not able to completely hydrolyze them. The activity of proteolytic enzymes that catalyze the digestion of proteins to amino acids (pepsin, trypsin, chymotrypsin, etc.) is low in children under 11-12 years old. With age, the secretory function of gastric juice increases, its acidity increases, reaching adult levels by the age of 13.
At an early age, the secretory function of the pancreas is also poorly developed. Due to the increased permeability of the intestinal wall in children, absorption into the blood along with amino acids is also partially cleaved proteins - peptides with toxic properties.
Violation of protein digestion can lead to disruption of the metabolic processes of a growing organism.
carbohydrate metabolism
Carbohydrate metabolism also has a number of age-specific features. Carbohydrates are the main source of energy. More than half of the daily energy value of the diet is provided by carbohydrates. Carbohydrates also perform a number of specialized functions in the body (structural, protective, and others).
The special role of carbohydrates as energy sources is due to the fact that they can be oxidized in the body both aerobically and anaerobically, while the oxidation of proteins and fats proceeds only aerobically. The need for carbohydrates for children of different ages is very individual, but carbohydrates should provide more than 50% of daily calories. With the growth of the child, as his energy expenditure increases, the absolute need for carbohydrates should increase.
With a reduced intake of carbohydrates from food, the body accelerates the use of fats and proteins as energy sources. Increased breakdown of proteins can lead to a decrease in their content in cells and the appearance of signs of "protein starvation".
Due to the imperfection of the neuroendocrine regulation of metabolism, children are more likely than adults to have a tendency to hypoglycemia, especially during physical exertion associated with the manifestation of endurance.
Unlike the body of an adult, the body of a child does not have the ability to quickly mobilize carbohydrate reserves and maintain a high intensity of carbohydrate metabolism.
Long-term increased consumption of carbohydrates can lead to metabolic disorders in children, since the digestion and absorption of carbohydrates have their own specific features. In the process of growth, a change in the carbohydrate composition of food occurs. So, in children under 1 year old, the main dietary carbohydrate is lactose, which is part of breast milk. Then this carbohydrate gives way to the leading role in the nutrition of sucrose and polysaccharides (starch, glycogen). In addition, in children, the saliva enzyme amylase, which catalyzes the breakdown of polysaccharides in the oral cavity, has a low activity and reaches its maximum activity only by 7 years of age. The amylolytic activity of pancreatic juice also slowly increases, which also makes it difficult to digest carbohydrates to monosaccharides (glucose and others).
The most important criterion for assessing the state of carbohydrate metabolism in children is the content of glucose in the blood on an empty stomach. In young children, it is 2.6 - 4.0 mmol / l and only by the age of 14-16 reaches the value of an adult: 3.9 - 6.1 mmol / l.
Fat metabolism
The fat metabolism of a growing organism also has specific features. Fats (lipids) play an important biological role. They are an energy material that can be deposited in fat depots and used further as fuel. In terms of energy value, fats are superior to carbohydrates and proteins. When 1 g of fat is oxidized, about 9 kcal of energy is released, and 1 g of carbohydrates or proteins - about 4 kcal. Lipids play a significant role in the processes of thermoregulation, have protective and mechanical significance, perform structural functions, etc.
The need for fats is determined by age, the external environment, the nature of physical activity, etc. For example, the need for fats per kg of body weight for a child of 7-10 years old is 2.6 g per day, and for children of 14-17 years old - 1.6-1.8 g per day. The absolute need for fats increases with age: for a 7-10-year-old child, it should be about 80 g per day, and for 14-17-year-olds - about 90-95 g. The need for fat in an adult is about 100 g.
An important role in the metabolic processes of the body is played by fat-like substances - lipoids. Among them, phospholipids and steroids are of particular importance. Phospholipids and cholesterol (representative of steroids) are essential components of cell membranes involved in the performance of barrier, transport, receptor and other functions. Steroids (cholesterol and its derivatives) perform a hormonal function (sex hormones and corticosteroids) and are involved in the formation of bile acids.
With age, the formation of bile acids increases, which allows you to increase the consumption of fats and their further inclusion in metabolic processes.
The intensity of lipid metabolism at different stages of ontogenesis is not the same. The breakdown of fats in infants occurs under the action of gastric lipase. In the process of child growth and with a change in the nature of nutrition, the main role in the digestion of fats is assigned to the enzyme - pancreatic juice lipase and bile acids.
Both a sharp restriction of fat intake and their excessive intake with food can lead to metabolic disorders in children. During physical activity, especially long-term, aerobic activity, in children and adolescents, fats are used for energy supply to a greater extent than carbohydrate utilization, as evidenced by an increase in the concentration of free fatty acids (FFA) and glycerol already at the beginning of work.
The value of the respiratory coefficient in children and adolescents after prolonged exercise is less than 1, which indicates an increased utilization of fats. As you know, the respiratory coefficient is the ratio between the volumes of carbon dioxide excreted from the body and oxygen consumed (CO 2 /O 2) during the exercise. With loads provided by the anaerobic breakdown of carbohydrates to lactate, this coefficient is greater than 1. With loads performed due to the aerobic oxidation of carbohydrates, it is 1. With prolonged loads, when fats are the main source of energy, the respiratory coefficient becomes less than 1.
Water and mineral exchange
Water-mineral metabolism for a growing organism is essential and has its own characteristics.
Water is the vital medium of the body and is especially necessary during the period of growth, when it makes up the bulk of all organs and tissues. With the increase in the age of the child, its content gradually decreases, and the amount of minerals increases. The younger the organism, the more extracellular water it has, which is mainly involved in water metabolism. Most of the water in the adult human body is intracellular water. The need for water in a child of the first year of life per kilogram of body weight is three times higher than in adults. In the process of growth, this value remains quite high, decreasing only by the age of 14 to 50-70 ml / kg.
Water metabolism in a child is characterized by high intensity, greater mobility and is easily disturbed under the influence of various causes. This is due to the greater loss of water through the skin and lungs, the immaturity of the kidneys and the imperfection of hormonal regulation. The absolute need for water increases with age.
The exchange of water is closely connected with the exchange of carbohydrates, fats, proteins, but especially mineral salts. Minerals play an important role in many physicochemical processes of a growing organism (the formation of bone tissue, the synthesis of enzymes, hormones). They create the basis of the internal environment of the body, maintain osmotic pressure and acidity of the environment. The most necessary chemical elements for life include: sodium, potassium, chlorine, calcium, magnesium, phosphorus, iron, copper, iodine, fluorine, manganese, zinc, etc.
For the formation of the skeleton, growth and development of bone tissue, a growing organism needs a sufficient intake of calcium and phosphorus.
Calcium is also necessary for muscle contraction, nervous system tone, activation of certain enzymes, blood clotting, etc. The daily requirement for calcium in infants is 0.15-0.18 g and should gradually increase to 1 gram at school age. At the same time, the relative need for calcium (per kg of body weight) is especially high in the first years of a child's life.
The biological role of phosphorus is multifaceted. As mentioned above, it forms the basis of bone tissue, is part of nucleic acids, phospholipids, plays an important role in energy metabolism, which is due to its ability to form macroergic bonds, i.e. energy-rich bonds (ATP, ADP, CF).
Vitamin D plays an important role in the metabolism of calcium and phosphorus. Parathyroid hormone, together with vitamin D, stimulates the absorption of calcium and phosphorus from the intestines, and calcitonin with vitamin D is involved in the incorporation of calcium and phosphorus into bone tissue.
Physical education and sports significantly increase the need for minerals. Physical activity of moderate intensity has a positive effect on the metabolism of calcium and phosphorus, and intense, especially under anaerobic conditions, can lead to impaired posture, osteosynthesis and the development of osteoporosis.
In the processes of hematopoiesis, in addition to iron, copper, cobalt and nickel are involved. Lack of iodine leads to dysfunction of the thyroid gland, stunted growth and development, lack of fluorine leads to caries. Zinc deficiency is reflected in growth retardation and underdevelopment of the genital organs in young men.
Iron is an essential trace element used for the synthesis of hemoglobin, myoglobin, cytochromes - tissue respiration enzymes, etc.
Iron deficiency is often observed in adolescents, especially during puberty, which can lead to the development of nutritional anemia. Iron deficiency anemia occurs in about 20% of women, and among female athletes this figure is even higher.
Consequently, minerals, like water, are necessary for the normal course of all metabolic processes, especially for a growing organism. However, the growth and development of the child determines a certain pattern of mineral metabolism in children, which consists in the fact that their entry into the body and excretion from the body are not balanced with each other, as is the case in adults. Due to the imperfection of the processes of thermoregulation of a growing organism, children experience large losses of minerals with sweat.
In the regulation of the metabolic processes of a growing organism, vitamins are of great biological importance - biologically active substances that enter the body mainly with food.
The role of vitamins is multifaceted. Many of them provide a number of catalytic reactions, as they are involved in the construction of coenzymes (low molecular weight compounds involved together with the enzyme in catalysis). These vitamins include B 1 , B 2 , B 6 , PP, etc. Vitamins B 1 , C, PP, etc. stimulate oxidative processes, and vitamins A, E, C are the strongest antioxidants. Thus, vitamins can be considered as the most important factors in the growth, development and increase in the levels of energy supply and performance of the child.
Depending on the age of children and adolescents, the daily intake of vitamins varies.
