Muscular system is an active part of the support locomotor system.

AFO of the musculoskeletal system

1. Muscle mass in relation to body weight in children is significantly less than in adults. So, in newborns it is 23.3% of the body weight, in a child of 8 years old - 27.7%, 15 years old - 32.6%, in an adult - 44.2%. The muscle mass in the postnatal period increases by 37 times, while the mass of the skeleton is only 27 times.
   Quantity and functionality muscle tissue characterize the quality and degree of optimality of the entire process of somato-physical development.
   The active processes of growth and differentiation of the muscular apparatus play a coordinating and determinative role in relation to the development of all life support systems - cardiovascular, respiratory, autonomic nervous systems, metabolic and energy supply systems.
2. The biochemical composition of muscles in children differs from that in adults. Thus, the content of myofibrillar proteins of muscle tissue in newborns is 2 times less than in older children and adults. As the child grows, the content of tropomyosin, sarcoplasmic proteins in muscle tissue increases and the amount of glycogen, lactic acid and nucleic acids decreases. The water content in the muscles is also significantly reduced.
3. Muscle development in children is uneven. First of all, the large muscles of the shoulder and forearm develop, and later the muscles of the hand. Children up to 6 years old do not succeed in fine work with their fingers. At the age of 6 - 7 years, the child can already be engaged in weaving, modeling. At this age, writing is possible. From 8 to 9 years of age, the ligaments are strengthened in children. Intensifies muscle development and there is significant muscle gain. At the end of puberty, muscle growth occurs not only in the arms, but also in the back, shoulder girdle and legs. At the age of 14-16, boys experience an almost two-fold increase in both total muscle mass and muscle strength. After 15 years, small muscles also develop intensively, the accuracy and coordination of small movements are improved. Therefore, physical activity should be strictly dosed, not carried out at a fast pace. The development of motor skills in children is not uniform. By the age of 10 - 12, the coordination of movements is quite perfect. However, children younger age are not yet capable of prolonged productive work and prolonged muscle tension.
4. During puberty, the harmony of movements is disturbed: awkwardness, angularity, sharpness of movements appear as a result of disharmony between the intensively increasing mass and the lag in their regulation.
5. For the normal development of children, it is necessary physical exercises and sports. Massage and gymnastics are widely used in children of all age groups. Excessive enthusiasm for sports by children, an attempt to achieve high results in a short time pose a threat to the health of children. Hence the importance of compliance and age restrictions for a particular type of specialization in sports.
6. During the period of growth processes, any weight loss is contraindicated. In adolescence, increased physical activity and restriction of nutrition lead to a block in the development of organs and functions associated with reproduction, form a risk for future motherhood or fatherhood, as well as for the consolidation of an adequate sexual orientation.
7. Bones form the basis of the human skeleton, being the skeleton and the place of attachment of muscles. Bone tissue develops in two alternative ways: directly from the mesenchyme (membranous osteogenesis, characteristic of the integumentary bones of the skull) and by cartilaginous osteogenesis.
8. The functions of bones are: protective - bones make up a rigid frame for internal organs; fixing - for internal organs; support - for the whole body; motor - to move it in space; exchange
   In the process of bone formation and remodeling, 3 stages are distinguished.
   The first stage of osteogenesis is an intensive anabolic process, during which the protein base of the bone tissue - the matrix - is created.
   In the second stage, the formation of centers of crystallization of hydroxyapatite occurs, followed by mineralization of the osteoid.
   The third stage of osteogenesis is the processes of remodeling and constant self-renewal of the bone, regulated by the parathyroid glands and depending on the provision of basic nutrients and vitamins with the leading value of vitamin D.
   Osteogenesis processes are provided normal level serum calcium (2.44 ± 0.37 mmol / l). Normally, the regulation of calcium metabolism and the maintenance of its constancy in the blood is carried out through a change in the rate of intestinal absorption and renal excretion. With a lack of calcium in food or poor absorption of it from the intestine, the level of calcium in the blood begins to be maintained due to the absorption of calcium from the bones.
9. Features of the structure of the skeleton in a child. The skull at the time of birth is represented by a large number of bones, the sutures (sagittal, coronal, occipital) are open and begin to close only from 3 to 4 months of life. In term infants, the lateral fontanelles are closed, the small fontanelle is open in 25% of newborns, mainly in premature infants, and closes no later than 4 to 8 weeks after birth. The large fontanelle, located at the intersection of the coronal and longitudinal sutures, is open in all newborns, its dimensions are from 3 × 3 to 1.5 × 2 cm.The closure time of the large fontanelle is individual, normally it occurs by 1 year, but possibly earlier ( 9 - 10 months), and later (1.5 years).
10. The spine of a newborn is devoid of physiological curves. Cervical lordosis develops after the baby starts to lift and hold his head (between 2 and 4 months). At 6 - 7 months, thoracic kyphosis is formed when the child sits down on his own. After the beginning of standing and walking (9 - 12 months), an anterior bend is formed in the lumbar spine. The final formation of physiological bends ends in the early school age... Due to the incompleteness of the formation of the spine, imperfect muscle fixation, uneven traction muscle groups under the influence of improper posture and uncomfortable furniture, curvature of the spine to the side (scoliosis) easily occurs and pathological posture develops.
11. The chest of a newborn is wide and short with horizontal ribs. The transverse diameter is 25% larger than the average longitudinal diameter. Further growth occurs chest in length, the front ends of the ribs descend. From the age of 3, rib breathing becomes effective. By the age of 12, the chest, as it were, moves in shape to the position of maximum exhalation. A sharp increase in the transverse diameter of the chest occurs by the age of 15.
12. The pelvic bones are relatively small in children early age, their growth is most intense in the first 6 years, and in girls these bones additionally grow in puberty.
13. Cartilage tissue is part of the skeleton in the form of cartilaginous coatings of the articular surfaces of bones, cartilage of intervertebral discs, costal cartilages, and also forms extra-skeletal supporting structures (cartilage of the trachea, bronchi, etc.). Early cartilage intrauterine development forms a skeleton, makes up 45% of body weight. In the process of development, cartilage tissue is replaced by bone. As a result, in an adult, the mass of all cartilage does not exceed 2% of the body weight. Cartilage consists of chondrocytes and a matrix, in which fibers and the main substance are distinguished. Distinguish between hyaline, fibrous, elastic cartilage.
14. Ligaments are connective tissue formations in the form of strands and plates, which are one of the types of continuous connection of bones (syndesmosis) and are part of the strengthening apparatus of the joints, with which their development is closely related. In newborns, connections are anatomically formed, but less strong and more extensible than in adults. The ligaments are characterized by high elasticity, high tensile strength and relatively low elongation. Together with the joint capsule and muscles, the ligaments provide the strengthening of the joints, the contact of the articular surfaces of the bones.
15. Joints begin to form early embryonic period from the mesenchyme. Joint gaps appear in the shoulder and hip joints at the 6th week of intrauterine development, in the elbow and knee joints at the 8th week, and in the wrist joints at the 8th - 9th week.
16. By the time of birth, the articular-ligamentous apparatus is anatomically formed. Subsequently, cartilage mineralization occurs (by the age of 14-16), the relief of the synovial membrane becomes more complicated, and the innervation of the joint is improved.
17. Milk teeth erupt after birth in a specific sequence. The teeth of the same name on each half of the jaw erupt simultaneously. The lower teeth tend to erupt earlier than the upper teeth. The exception is the lateral incisors - the upper teeth appear before the lower ones. The formula for determining the number of milk teeth: n - 4, where n is the child's age in months. By the age of 2, the child has all 20 milk teeth. In the first period (from eruption to 3 - 3.5 years), the teeth are closely spaced, the bite is orthognathic (the upper teeth cover the lower ones by one third) due to insufficient development of the lower jaw. The second period (from 2 to 6 years) is characterized by the transition of the bite into a straight line, the appearance of physiological gaps between the teeth, and tooth wear. The change of milk teeth to permanent ones begins at the age of 5. Around the age of 11, second painters appear. Third painters (wisdom teeth) erupt at the age of 17 - 25, and sometimes even later. For a rough estimate of the number of permanent teeth up to 12 years old, regardless of gender, use the formula: X (number of permanent teeth) = 4 n - 20, where n is the number of years the child has turned.

The skeleton of a growing child undergoes a lot of changes due to the influence of external and internal factors. During the prenatal period of a child's life, ossification begins quite late. There is a lot of cartilage in the baby's skeleton during birth.

When a child reaches 2 years of age, the structure of bones approaches that of an adult's skeleton, and at the age of 12 you will not find any difference.

After the baby is born, you may notice a discrepancy in body proportions. The head makes up 25% of the length of the whole body. By the age of two it is already 20%, and by the age of 12 the ratio is the same as that of an adult.

The sutures of the child's skull look like straight lines and grow together by 2-3 months, and upon reaching 3-4 years they grow together completely.

The most characteristic feature, which everyone knows about, is the presence on the head of a child Rodnichkov... These are formations in the area of ​​the connection of several bones.

The fontanelle is a connecting membrane.

As a rule, you can find 4 such fontanelles:

• big,
• small,
• two side.

A very small number of babies are born with open lateral fontanelles. And only a quarter are born with an open small fontanelle, which is located between the crown and the occipital bone. It drags on to 3-4 months of life.

But the large fontanelle is located between the crown and the frontal bone and is well felt. Its size is about 2 by 2 cm. The fontanelle closes by 12-16 months.

During the first year of life, the baby's skull grows very intensively. Then a little slower up to 4 years. After 4 years, the growth of the skull slows down.

Features of the development of the skeletal system of children

Teenage girl with skeleton

Spine of a child

At birth, the baby's spine is straight and free of any bends. They appear already during the development of the child and the study of new support functions by him.

The cervical bend appears in the second month

A curvature in the chest area appears when the baby begins to sit.

By the age of 3-4 years, a child has a spine configuration characteristic of an adult.

When the spine is just forming its shape, it is quite flexible. It can rotate, tilt and bend. Therefore, this should be taken into account.

You can tolerate early curvature of the child's spine if you wear it constantly on one hand, ask the wrong position during sleep or feeding. To the deformity of the spine and chest the child can be caused by earlier sitting of the child and too tight swaddling.

In the first months of life, it is not worth swaddling a child tightly, so as not to squeeze his chest and not interfere with blood circulation.

Do not put the child until he does this himself, which will mean that his body is ready. Do not place your child in pillows, kangaroos, etc. This can lead to curvature of the vertebra.

Early curvature of the chest and vertebra

Can provide significant influence on the child's posture in the future. In the first months of a child's life, the growth of the lungs outstrips the growth of the chest itself. And she is, as it were, in a state of constant inhalation. The baby's ribs are almost horizontal.

Also, in the first months of a child's life, you may notice a curvature of the legs.

When do teeth appear?

A baby is born with tooth buds that appear in groups and at a certain time.

Teeth erupt at about the same time:

Baby teeth:

• Lower and upper incisors - 6 to 9 months.
• Lateral lower and upper - from 9 to 12 months.

When you celebrate your baby's first birthday, they usually have 8 teeth.

When the baby reaches 14-16 months, small molars begin to appear, at 16-20 months - canines, at 20-24 months, the rear small molars erupt.

Those. when your child is 2 full years old, he already has about 20 teeth.

The timing of the appearance of teeth is not always the same for all children.

We all know that when the teeth begin to cut, the child scratches the gums with his fists, pulls everything into his mouth. But the appearance of teeth is a physiological and painless process. Although many children are nervous, cry and sleep poorly. The temperature may rise, appetite is disturbed. It is also accompanied by profuse salivation.

The diet and day of the child during the teething period remains unchanged.

A good helper can be teether- a special toy that a child can gnaw and gently massages his gums, improves blood circulation.

Features of the development of muscle tissue

The baby's muscles are poorly developed and make up about 25% of body weight. In the process of gaining weight, muscle tissue grows due to an increase in the mass of fibers, and not their number, as in an adult.

When the central nervous system is just forming, and this happens in the first months of a child's life, children may experience increased muscle tone.

Flexor muscles predominate over extensor muscles, which explains the position of the child with bent arms and legs in the first periods of life.

Gradually, as the baby grows up, this phenomenon disappears.

The child's muscle strength is very small. The kid does not hold his head, cannot change his body position.

Motor ability appear gradually. First the neck, then the trunk, then the muscles of the limbs. The muscles of the legs, then the muscles of the arms.

Gradually the child becomes stronger, more active, etc.

Here are all the features of the musculoskeletal development of the child in the first periods of life.

Types and functional features of muscle tissue in children and adolescents

General information about muscles. There are about 600 skeletal muscles in the human body. The muscular system makes up a significant part of the total body weight of a person. So, at the age of 17-18 years, it is 43-44%, and in people with good physical fitness it can even reach 50%. In newborns, all muscle mass is only 23% of body weight.

The growth and development of individual muscle groups is uneven. First of all, babies develop abdominal muscles, a little later - chewing muscles. The muscles of a child, in contrast to the muscles of an adult, are paler, softer and more elastic. By the end of the first year of life, the muscles of the back and limbs noticeably increase, at which time the child begins to walk.

From birth to the end of the child's growth, the muscle mass increases 35 times. At 12–16 years of age (puberty), due to the lengthening of the tubular bones, the muscle tendons are also intensively lengthened. During this time, the muscles become long and thin, which makes teenagers look long-legged and long-armed. At the age of 15-18, transverse muscle growth occurs. Their development continues up to 25-30 years.

Muscle structure. In the muscle, the middle part is distinguished - the abdomen, consisting of muscle tissue, and the end sections - the tendons, formed by dense connective tissue. Tendons attach the muscles to the bones, but this is not necessary. Muscles can attach to various organs (the eyeball), to the skin (muscles of the face and neck), etc. The muscles of the newborn tendons are rather poorly developed, and only by the age of 12-14, muscle-tendon relations are established, which are characteristic of muscles an adult. The muscles of all higher animals are the most important working organs - effectors.

Muscles are smooth and striated. In the human body, smooth muscles are found in internal organs, blood vessels and skin. They are almost not controlled by the central nervous system, which is why they (and also the heart muscle) are sometimes called involuntary. These muscles have automatism and their own nervous network (intramural, or metasympathetic), which largely ensures their autonomy. Regulation of the tone and motor activity of smooth muscles is carried out by impulses coming through the autonomic nervous system and humoral (i.e., through the tissue fluid). Smooth muscles are capable of performing rather slow movements and prolonged tonic contractions. The motor activity of smooth muscles is often rhythmic, for example, pendulum and peristaltic bowel movements. Prolonged tonic contractions of smooth muscles are very clearly expressed in the sphincters of the hollow organs, which prevents the release of the contents. This allows urine to accumulate in bladder and bile in gallbladder, registration feces in the colon, etc.

The smooth muscles of the walls of blood vessels, especially arteries and arterioles, are in a state of constant tonic contraction. The tone of the muscle layer of the walls of the arteries regulates the size of their lumen and thereby the level blood pressure and blood supply to organs.

The striated muscles are composed of many individual muscle fibers that are located in a common connective tissue sheath and are attached to tendons, which, in turn, are connected to the skeleton. The striated muscles are divided into two types: a) parallel-fibrous (all fibers are parallel to the long axis of the muscle); b) pinnate (the fibers are located obliquely, attaching on one side to the central tendon cord, and on the other to the outer tendon sheath).

The strength of a muscle is proportional to the number of fibers, that is, the area of ​​the so-called physiological cross-section of the muscle, the surface area that crosses all active muscle fibers. Each skeletal muscle fiber is a thin (10 to 100 µm in diameter), long (up to 2–3 cm) multinucleated formation - symplast - arising in early ontogenesis from the fusion of myoblast cells.

Main feature a muscle fiber is the presence in its protoplasm (sarcoplasm) of a mass of thin (about 1 μm in diameter) filaments - myofibrils, which are located along the longitudinal axis of the fiber. Myofibrils are composed of alternating light and dark areas - discs. Moreover, in the mass of neighboring myofibrils in striated fibers, the disks of the same name are located at the same level, which gives a regular transverse striation (striation) to the entire muscle fiber.

A complex of one dark and two adjacent halves of light discs, limited by thin Z-lines, is called a sarcomere. Sarcomeres are a minimal element of the muscle fiber contractile apparatus.

The membrane of the muscle fiber - the plasmalemma - has a similar structure to the nerve membrane. Her distinctive feature is that it gives regular T-shaped invaginations (tubes with a diameter of 50 nm) approximately at the borders of the sarcomeres. The invaginations of the plasmalemma increase its area and, consequently, the total electrical capacity.

Inside the muscle fiber between the bundles of myofibrils, parallel to the longitudinal axis of the symplast, there are systems of tubules of the sarcoplasmic reticulum, which is a branched closed system closely adjacent to the myofibrils and its blind ends (end cisterns) to the T-shaped invaginations of the plasmalemma (T-system). The T-system and the sarcoplasmic reticulum are devices for transmitting excitation signals from the plasmalemma to the contractile apparatus of myofibrils.

Outside, the entire muscle is enclosed in a thin connective tissue sheath - the fascia.

Contractility as the main property of muscles. Excitability, conductivity and contractility are the main physiological properties of muscles. Muscle contractility is the shortening of the muscle or the development of tension. During the experiment, the muscle responds with a single contraction in response to a single stimulus. In humans and animals, muscles from the central nervous system receive not single impulses, but a series of impulses, to which they respond with a strong, prolonged contraction. This muscle contraction is called tetanic (or tetanus).

When the muscles contract, they do work that depends on their strength. The thicker the muscle, the more muscle fibers it contains, the stronger it is. Muscle per square meter cm of cross-section can lift loads up to 10 kg. The strength of the muscles also depends on the characteristics of their attachment to the bones. Bones and the muscles attached to them are a kind of levers. The strength of a muscle depends on how far from the fulcrum of the lever and closer to the point of application of gravity it attaches.

A person is able to maintain the same posture for a long time. This is called static muscle tension. For example, when a person just stands or holds his head in an upright position (i.e., makes so-called static efforts), his muscles are in a state of tension. Some exercises on rings, parallel bars, holding the barbell raised require such static work, which requires the simultaneous contraction of almost all muscle fibers. Of course, such a state cannot be prolonged due to the developing fatigue.

During dynamic work, various muscle groups contract. At the same time, the muscles performing dynamic work contract quickly, work with great tension, and therefore soon get tired. Usually at dynamic work different groups of muscle fibers contract alternately. This gives the muscle the ability to perform work for a long time.

By controlling the work of the muscles, the nervous system adapts their work to the current needs of the body, in this regard, the muscles work economically, with a high coefficient useful action... Work will become maximum, and fatigue will develop gradually, if you select the average (optimal) rhythm and amount of load for each type of muscle activity.

Muscle work is a prerequisite for their existence. If the muscles are inactive for a long time, muscle atrophy develops, they lose their working capacity. Training, that is, constant, fairly intense work of muscles, helps to increase their volume, increase strength and performance, and this is important for the physical development of the body as a whole.

Muscle tone. In humans, muscles are somewhat contracted even at rest. The condition in which tension is held for a long time is called muscle tone. Muscle tone may decrease slightly and the body may relax during sleep or anesthesia. Complete disappearance muscle tone occurs only after death. Tonic muscle contraction does not cause fatigue. Internal organs are kept in a normal position only due to muscle tone. The amount of muscle tone depends on the functional state of the central nervous system.

Skeletal muscle tone is directly determined by the supply of nerve impulses from the motor neurons of the spinal cord to the muscle with a large interval. The activity of neurons is supported by impulses coming from the overlying parts of the central nervous system, from receptors (proprioceptors), which are located in the muscles themselves. The role of muscle tone in ensuring coordination of movements is great. In newborns, the tone of the flexors of the arm predominates; in children 1–2 months - the tone of the extensor muscles, in children 3–5 months - the balance of the tone of the antagonist muscles. This circumstance is associated with increased excitability of the red nuclei of the midbrain. With the functional maturation of the pyramidal system, as well as the cerebral cortex, muscle tone decreases.

Elevated muscle tone the legs of the newborn gradually decrease (this occurs in the second half of the child's life), which is a necessary prerequisite for the development of walking.

Fatigue. During prolonged or strenuous work, muscle performance decreases, which is restored after rest. This phenomenon is called physical fatigue. With pronounced fatigue, prolonged muscle shortening and their inability to completely relax (contracture) develop. This is primarily due to changes that occur in the nervous system, a violation of the conduction of nerve impulses in synapses. Tired stocks chemical substances, which serve as sources of energy for contraction, are depleted, and metabolic products (lactic acid, etc.) accumulate.

The speed of onset of fatigue depends on the state of the nervous system, the frequency of the rhythm in which the work is performed, and on the magnitude of the load. Fatigue can be associated with an unfavorable environment. Uninteresting work quickly causes fatigue.

The younger the child, the faster he gets tired. In infancy, fatigue sets in after 1.5–2 hours of wakefulness. Immobility, prolonged inhibition of movements tire children.

Physical fatigue is a normal physiological phenomenon. After resting, working capacity is not only restored, but can also exceed the initial level. In 1903 I.M. Sechenov found that the performance of tired muscles right hand it recovers much faster if, during rest, work with the left hand. Such rest, in contrast to the simple rest of I.M. Sechenov called him active.

Thus, the alternation of mental and manual labor, outdoor games before classes, physical culture breaks during lessons and during breaks increase the efficiency of students.

Muscle growth and work

During intrauterine development, muscle fibers are formed heterochronously. Initially, the muscles of the tongue, lips, diaphragm, intercostal and dorsal muscles are differentiated, in the limbs - first the muscles of the arms, then the legs, in each limb, first, the proximal parts, and then the distal ones. Muscles of embryos contain less protein and more (up to 80%) water. The development and growth of different muscles after birth is also uneven. Muscles that provide motor functions that are extremely important to life begin to develop earlier and more. These are the muscles that are involved in breathing, sucking, grasping objects, that is, the diaphragm, muscles of the tongue, lips, hand, intercostal muscles. In addition, the muscles involved in the process of teaching and educating children of certain skills are trained and developed more.

A newborn has all the skeletal muscles, but they weigh 37 times less than an adult. Skeletal muscle grows and forms until about 20–25 years of age, influencing the growth and formation of the skeleton. The increase in muscle weight with age is uneven, this process is especially rapid during puberty.

Body weight increases with age, mainly due to an increase in skeletal muscle weight. The average weight of skeletal muscles as a percentage of body weight is distributed as follows: in newborns - 23.3; at 8 years old - 27.2; at 12 years old - 29.4; at 15 years old - 32.6; at the age of 18 - 44.2.

Age features of the growth and development of skeletal muscles. The following pattern of growth and development of skeletal muscles is observed at different age periods.

Period up to 1 year: the muscles of the shoulder girdle and arms are more developed than the muscles of the pelvis, thighs and legs.

Period from 2 to 4 years: in the arm and shoulder girdle, the proximal muscles are much thicker than the distal ones, the superficial muscles are thicker than the deep ones, the functionally active muscles are thicker than the less active ones. Fibers grow especially rapidly in the longissimus dorsi muscle and in the gluteus maximus muscle.

Period from 4 to 5 years: the muscles of the shoulder and forearm are developed, the muscles of the hands are underdeveloped. In early childhood, the muscles in the trunk develop much faster than the muscles in the arms and legs.

Period from 6 to 7 years: there is an acceleration in the development of the muscles of the hand, when the child begins to do light work and get used to writing. The development of the flexors outstrips the development of the extensors.

In addition, the flexors have more weight and physiological diameter than the extensors. The muscles of the fingers, especially the flexors, which are involved in gripping objects, have the greatest weight and physiological diameter. Compared to them, the flexors of the hand have a relatively lower weight and physiological diameter.

Period up to 9 years: the physiological diameter of the muscles that cause finger movements increases, while the muscles of the wrist and elbow joints grow less intensively.

Period up to 10 years: long flexor diameter thumb by the age of 10 it reaches almost 65% of the length of the diameter of an adult.

Age 12 to 16: Muscles grow that keep the body upright, especially the iliopsoas, which plays an important role in walking. By the age of 15–16, the thickness of the fibers of the iliopsoas muscle becomes greatest.

The anatomical diameter of the shoulder in the period from 3 to 16 years old increases by 2.5–3 times in boys, and less in girls.

The deep muscles of the back in the first years of life in children are still weak, and their tendon-ligamentous apparatus is underdeveloped, however, by the age of 12-14, these muscles are strengthened by the tendon-ligamentous apparatus, but less than in adults.

Muscle abdominal in newborns are not developed. From 1 year to 3 years, these muscles and their aponeuroses differ, and only by the age of 14-16 years, the anterior abdominal wall is strengthened almost in the same way as in an adult. Up to 9 years of age, the rectus abdominis muscle grows very intensively, its weight compared to the weight of a newborn increases almost 90 times, the internal oblique muscle - more than 70 times, the external oblique muscle - 67 times, the transverse - 60 times. These muscles resist the gradually increasing pressure of the internal organs.

In the biceps brachii and quadriceps femoris muscle fibers thicken: by 1 year - twice; by the age of 6 - five times; by the age of 17 - eight times; by the age of 20 - 17 times.

Muscle growth in length occurs at the junction of muscle fibers in the tendon. This process lasts up to 23-25 ​​years. From 13 to 15 years of age, the contractile section of the muscle grows especially rapidly. By the age of 14–15, muscle differentiation reaches a high level. The growth of fibers in thickness continues up to 30–35 years. The diameter of muscle fibers thickens: by 1 year, twice; by 5 years - five times; by the age of 17 - eight times; by the age of 20 - 17 times.

Muscle mass increases especially intensively in girls at the age of 11–12 years, in boys - at 13–14 years old. In adolescents, skeletal muscle mass increases by 12% in two to three years, while in the previous 7 years it has increased by only 5%. Skeletal muscle weight in adolescents is approximately 35% of body weight, and muscle strength is significantly increased. The muscles of the back, shoulder girdle, arms and legs develop significantly, which causes increased growth of tubular bones. The correct selection of physical exercises contributes to the harmonious development of skeletal muscles.

Age features of the structure of skeletal muscles. Skeletal muscle chemistry and structure also change with age. Children's muscles contain more water and less dense substances than adults. The biochemical activity of red muscle fibers is greater than that of white ones. This is due to differences in the number of mitochondria or in the activity of their enzymes. The amount of myoglobin (an indicator of the intensity of oxidative processes) increases with age. In a newborn, skeletal muscles have 0.6% myoglobin, in adults - 2.7%. In addition, children have relatively fewer contractile proteins - myosin and actin. This difference decreases with age.

Muscle fibers in children contain relatively more cores, they are shorter and thinner, however, both their length and thickness increase with age. Muscle fibers in newborns are thin, tender, their transverse striation is relatively weak and surrounded by large layers of loose connective tissue... Tendons take up relatively more space. Many of the nuclei inside muscle fibers do not lie at the cell membrane. Myofibrils are surrounded by clear layers of sarcoplasm.

The following dynamics of changes in the structure of skeletal muscles depending on age is observed.

1. At 2–3 years, muscle fibers are twice as thick as in newborns, they are located more densely, the number of myofibrils increases, and sarcoplasma decreases, the nuclei adjoin the membrane.

2. At 7 years of age, the thickness of muscle fibers is three times thicker than in newborns, and their transverse striation is clearly expressed.

3. By the age of 15-16, the structure of muscle tissue becomes the same as in adults. By this time, the formation of the sarcolemma is completed.

The maturation of muscle fibers is traced by the change in the frequency and amplitude of biocurrents recorded from the biceps brachii muscle when holding the load:

in children 7–8 years old, as the time of holding the load increases, the frequency and amplitude of biocurrents decrease more and more. This proves the immaturity of some of their muscle fibers;

in children 12–14 years old, the frequency and amplitude of biocurrents do not change within 6–9 s of holding the load at maximum height or decrease at a later date. This indicates the maturity of the muscle fibers.

In children, unlike adults, muscles attach to bones farther from the axes of rotation of the joints, therefore, their contraction is accompanied by less loss of strength than in adults. With age, the ratio between the muscle and its tendon, which grows more intensively, changes significantly. As a result, the nature of the attachment of the muscle to the bone changes, therefore the efficiency increases. By about 12-14 years of age, the muscle-tendon relationship, which is typical for an adult, stabilizes. In the girdle of the upper extremities until the age of 15, the development of the muscular abdomen and tendons occurs equally intensively, after 15 and up to 23–25 years, the tendon grows more intensively.

The elasticity of children's muscles is about twice that of adults. When contracted, they shorten more, and when stretched, they lengthen more.

Muscle spindles appear at 10-14 weeks of uterine life. An increase in their length and diameter occurs in the first years of a child's life. In the period from 6 to 10 years, the transverse size of the spindles changes slightly. In the period of 12–15 years, muscle spindles complete their development and have the same structure as in adults at 20–30 years old.

The beginning of the formation of sensitive innervation occurs at 3.5-4 months of uterine life, and by 7-8 months, the nerve fibers reach significant development. By the time of birth, centripetal nerve fibers are actively myelinated.

Muscle spindles of a single muscle have the same structure, but their number and level of development of individual structures in different muscles are not the same. The complexity of their structure depends on the amplitude of movement and the strength of muscle contraction. This is due to the coordination work of a muscle: the higher it is, the more muscle spindles it contains and the more complex they are. Some muscles have no non-stretching muscle spindles. Such muscles, for example, are short muscles palms and feet.

Motor nerve endings (myoneural apparatus) appear in a child even in the uterine period of life (at the age of 3.5–5 months). They develop in the same way in different muscles. By the time of birth, the number of nerve endings in the muscles of the arm is greater than in the intercostal muscles and muscles of the lower leg. In a newborn, motor nerve fibers are covered with a myelin sheath, which thickens strongly by the age of 7. By the age of 3-5, the nerve endings become much more complex, by the age of 7-14 they are even more differentiated, and by the age of 19-20 they reach full maturity.

Age-related changes in muscle excitability and lability. For the work of the muscular apparatus, not only the properties of the muscles themselves are important, but also age-related changes. physiological properties motor nerves that innervate them. To assess the excitability of nerve fibers, a relative indicator is used, expressed in units of time, - chronaxia. In newborns, more prolonged chronaxia is noted. During the first year of life, there is a decrease in the level of chronaxia by about 3-4 times. In subsequent years, the value of chronaxia gradually decreases, but in school-age children it still exceeds the indices of chronaxia in an adult. Thus, the decrease in chronaxia from birth to school period indicates that the excitability of nerves and muscles increases with age.

For children 8-11 years old, as well as for adults, an excess of flexor chronaxia over extensor chronaxia is characteristic. The difference in chronaxia of antagonist muscles is most pronounced in the arms than in the legs. Chronaxia of the distal muscles exceeds that of the proximal muscles. For example, the chronaxia of the shoulder muscles is approximately half as long as the chronaxia of the forearm muscles. Less toned muscles have longer chronaxia than more toned ones. For example, in the biceps femoris and tibialis anterior muscle, chronaxia is longer than in their antagonists, the quadriceps femoris and gastrocnemius muscle. The transition from light to dark lengthens chronaxia, and vice versa.

Chronaxia changes during the day in children of primary school age. After 1–2 general education lessons, a decrease in motor chronaxia is observed, and by the end school day it often recovers to its previous level or even increases. After light general education lessons, motor chronaxia most often decreases, and after difficult lessons it increases.

As we grow older, fluctuations in the motor chronaxia gradually decrease, while the chronaxia of the vestibular apparatus increases.

Functional mobility, or lability, in contrast to chronaxia, determines not only least time required for the onset of excitation, but also the time required to complete the excitation and restore the ability of the tissue to give new subsequent impulses of excitation. The faster the skeletal muscle reacts, the more excitation impulses pass through it per unit of time, the greater its lability. Consequently, muscle lability increases with an increase in the mobility of the nervous process in motor neurons (acceleration of the transition of excitation into inhibition), and vice versa - with an increase in the rate of muscle contraction. The slower the muscles react, the less their lability. In children, lability increases with age, and by the age of 14–15 it reaches the level of lability of adults.

Change in muscle tone. In early childhood, there is severe tension in certain muscles, such as the muscles of the hands and hip flexors, due to the involvement of skeletal muscles in the generation of heat at rest. This muscle tone is of reflex origin and decreases with age.

The tone of skeletal muscles is manifested in their resistance to active deformation when squeezed and stretched. At ages 8–9, boys have a higher muscle tone, such as the hamstrings, than girls. By the age of 10–11, muscle tone decreases and then increases significantly again. The greatest increase in skeletal muscle tone is observed in adolescents 12-15 years old, especially boys, in whom it reaches youthful meanings... With the transition from preschool to preschool age, there is a gradual cessation of the participation of skeletal muscles in heat production at rest. At rest, the muscles relax more and more.

In contrast to the voluntary tension of skeletal muscles, the process of their voluntary relaxation is more difficult to achieve. This ability increases with age, so the stiffness of movements decreases in boys up to 12-13 years old, in girls - up to 14-15 years. Then the opposite process takes place: the stiffness of movements again increases from 14-15 years old, while in boys aged 16-18 years it is much more than in girls.

The structure of the sarcomere and the mechanism of muscle fiber contraction. Sarcomere is a repeating segment of the myofibril, consisting of two halves of a light (optically isotropic) disk (I-disk) and one dark (anisotropic) disk (A-disk). Electron microscopic and biochemical analysis showed that the dark disc is formed by a parallel bundle of thick (about 10 nm in diameter) myosin filaments, the length of which is about 1.6 μm. The molecular weight of the myosin protein is 500,000 D. The heads of myosin molecules (20 nm long) are located on myosin filaments. The light-colored discs contain thin filaments (5 nm in diameter and 1 μm long), which are built of protein and actin ( molecular mass- 42 000 D), as well as tropomyosin and troponin. In the area of ​​the Z-line, delimiting adjacent sarcomeres, a bundle of fine filaments is held together by a Z-membrane.

The ratio of thin and thick filaments in the sarcomere is 2: 1. The myosin and actin filaments of the sarcomere are arranged so that thin filaments can freely enter between thick filaments, that is, "move" into the A-disk, this happens during muscle contraction. Therefore, the length of the light part of the sarcomere (I-disk) can be different: with passive stretching of the muscle, it increases to a maximum, with contraction it can decrease to zero.

The contraction mechanism is the movement (pulling) of thin filaments along the thick ones to the center of the sarcomere due to the "rowing" movements of the myosin heads, which periodically attach to the thin filaments, forming transverse actomyosin bridges. Investigating the movements of the bridges using the X-ray diffraction method, it was determined that the amplitude of these movements is 20 nm, and the frequency is 5-50 vibrations per second. In this case, each bridge is then attached and pulls the thread, then detached in anticipation of a new attachment. A huge number of bridges work out of sync, so their total thrust is uniform over time. Numerous studies have established the following mechanism for the cyclic work of the myosin bridge.

1. At rest, the bridge is charged with energy (myosin is phosphorylated), but it cannot combine with the actin filament, since a system of tropomyosin filament and troponin globule is wedged between them.

2. When the muscle fiber is activated and Ca + 2 ions appear in the myoplasm (in the presence of ATP), troponin changes its conformation and pushes back the tropomyosin filament, opening up the possibility of connection with actin for the myosin head.

3. The connection of the phosphorylated myosin head with actin abruptly changes the conformation of the bridge (it “bends”) and moves the actin filaments one step (20 nm), and then the bridge breaks. The energy required for this appears as a result of the breakdown of the high-energy phosphate bond included in phosphorylactomyosin.

4. Then, due to a drop in the local concentration of Ca + 2 and its detachment from troponin, tropomyosin again blocks actin, and myosin is again phosphorylated due to ATP. ATP not only energizes systems for further work, but also contributes to the temporary separation of the threads, that is, it plasticizes the muscle, makes it capable of stretching under the influence external forces... It is believed that one labor movement one bridge consumes one ATP molecule, and the role of ATPase is played by actomyosin (in the presence of Mg + 2 and Ca + 2). With a single contraction, a total of 0.3 μM ATP is spent per 1 g of muscle.

Thus, ATP plays a double role in muscle work: on the one hand, by phosphorylating myosin, it provides energy for contraction, on the other hand, being in a free state, it provides muscle relaxation (its plasticization). If ATP disappears from the myoplasm, a continuous contraction develops - contracture.

All these phenomena can be shown on isolated actomyosin complex-filaments: such filaments harden without ATP (rigor is observed), in the presence of ATP they relax, and when Ca + 2 is added, they produce a reversible contraction similar to normal.

Muscles are laced blood vessels, through which nutrients and oxygen are supplied to them with blood, and metabolic products are carried out. In addition, the muscles are rich in lymphatic vessels.

Muscles have nerve endings - receptors that sense the degree of muscle contraction and stretching.

The main muscle groups of the human body. The shape and size of the muscles depend on the work they do. Muscles are long, wide, short and circular. Long muscles are located on the limbs, short ones - where the range of motion is small (for example, between the vertebrae). Broad muscles are located mainly on the trunk, in the walls of body cavities (for example, muscles of the abdomen, back, chest). The circular muscles - the sphincters - lie around the openings of the body, narrowing as they contract.

By function, muscles are divided into flexors, extensors, adductor and abductor muscles, and muscles that rotate inward and outward.

I. The muscles of the trunk include: 1) muscles of the chest; 2) abdominal muscles; 3) back muscles.

II. The muscles located between the ribs (intercostal), as well as other muscles of the chest, are involved in the function of breathing. They are called the respiratory muscles. These include the diaphragm, which separates the chest cavity from the abdominal cavity.

III. Well-developed chest muscles set in motion and strengthen the upper limbs on the trunk. These include: 1) pectoralis major muscle; 2) the pectoralis minor muscle; 3) serratus anterior muscle.

IV. The abdominal muscles have different functions. They form the wall of the abdominal cavity and, due to their tone, keep the internal organs from displacement, lowering and loss. By contracting, the abdominal muscles act on the internal organs like the abdominal press, promoting the flow of urine, feces and labor. Contraction of the abdominal muscles also helps the blood flow in the venous system, the implementation of respiratory movements. The abdominal muscles are involved in the forward flexion of the spinal column.

Due to the possible weakness of the abdominal muscles, not only the prolapse of the abdominal organs occurs, but also the formation of hernias. A hernia is the exit of internal organs (intestines, stomach, greater omentum) from the abdominal cavity under the skin of the abdomen.

V. The muscles of the abdominal wall include: 1) rectus abdominis muscle; 2) pyramidal muscle; 3) the square muscle of the lower back; 4) broad abdominal muscles (external and internal, oblique and transverse).

Vi. A dense tendon cord runs along the midline of the abdomen - the so-called white line. On the sides of it is the rectus abdominis muscle, which has a longitudinal direction of the fibers.

Vii. On the back are numerous muscles along the spinal column. These are the deep muscles of the back. They are attached mainly to the processes of the vertebrae and participate in the movements of the spinal column back and to the side.

VIII. TO superficial muscles back include: 1) the trapezius muscle of the back; 2) the broadest muscle of the back. They provide movement of the upper limbs and chest.

IX. Among the muscles of the head are distinguished:

1) chewing muscles. These include: the temporalis muscle; chewing muscle; pterygoid muscles. Contractions of these muscles cause complex chewing movements of the lower jaw;

2) facial muscles. These muscles are attached to the skin of the face with one and sometimes two of their ends. When contracted, they displace the skin, creating a certain facial expression, that is, one or another facial expression. The facial muscles also include the circular muscles of the eye and mouth.

X. Neck muscles tilt the head back, tilt and turn it.

XI. The muscles of stairs raise the ribs, thus participating in inhalation.

XII. The muscles attached to the hyoid bone, when contracted, change the position of the tongue and larynx when swallowing and pronouncing various sounds.

XIII. The upper limb belt is connected to the trunk only in the area of ​​the sternoclavicular joint. It is strengthened by the muscles of the trunk: 1) trapezius muscle; 2) pectoralis minor; 3) rhomboid muscle; 4) the serratus anterior muscle; 5) the muscle that lifts the scapula.

XIV. The muscles of the girdle of the limbs are set in motion upper limb in the shoulder joint. The most important of these is the deltoid muscle. When contracted, this muscle flexes the arm at the shoulder joint and draws the arms to a horizontal position.

XV. In the shoulder area, there is a group of flexor muscles in the front, and extensor muscles in the back. Among the muscles of the anterior group, the biceps brachii is distinguished, the posterior one is the triceps brachii.

Xvi. The muscles of the forearm on the front surface are represented by the flexors, on the back - by the extensors.

XVII. Among the muscles of the hand, there are: 1) the long palmar muscle; 2) flexors of the fingers.

Xviii. The muscles in the girdle area of ​​the lower extremities move the leg in hip joint as well as the spinal column. The anterior muscle group is represented by one large muscle - the iliopsoas. To the posterior external muscle group pelvic girdle include: 1) large muscle; 2) the gluteus medius muscle; 3) the gluteus maximus muscle.

XIX. The legs have a more massive skeleton than the arms. Their musculature has more strength, but less variety and limited range of motion.

On the front thigh is the longest sartorius muscle in the human body (up to 50 cm). She flexes her leg at the hip and knee joints.

The quadriceps muscle of the thigh lies deeper than the sartorius muscle, while it fits the thigh bone from almost all sides. The main function of this muscle is to extend the knee joint. When standing, the quadriceps muscle does not give knee joint bend.

On the back surface of the lower leg is the gastrocnemius muscle, which flexes the lower leg, flexes and slightly rotates the foot outward.

.J Muscle growth after birth. Even in the first half of the prenatal period of development, muscles acquire a characteristic their shape and structure ^ Subsequently, their length and thickness increase rapidly. They grow in length according to the growth of the bones of the skeleton by lengthening the muscle fibers and especially ~ sukhjilia, with the help of which the "muscles attach to the bones." in the muscles of the remnants of "primary muscle tissue. However, in general (by about 90%) growth in thickness occurs by increasing the diameter of the fibers ^ In newborns, it does not exceed 10-15 thousandths of a millimeter, and by 3-4 years it increases by 2-2 , 5 times. In subsequent years, the diameter of muscle fibers largely depends on the individual characteristics of the organism, and mainly on motor activity.

In a newborn, muscles account for 20-22% of the total body weight, that is, approximately half as much as in an adult, whose muscle is most often 35-45% of body weight. Therefore, over the entire period from birth to adulthood, the increase in muscle weight should be twice as "intense as the increase total weight body. However, at first, until the child began to walk, muscles grow even more slowly than

^^ im ^ prgyanichm r. prdpm ^ So, in the first 4 months of life, the total body weight doubles, and the muscle weight increases only by 60% and is 16% of the body weight. From the end of the first year of life ", under the influence of training, muscle growth gradually becomes more intense ^ and by the age of 6 to the share of muscles again accounts for about 22% of the total body weight, and by the age of 8 -27 ° / o. Muscles grow especially intensively in the period from 14-15 to 17-18 years. Thus, the share of muscles at the age of 14, on average, 30 ^ _, body weight, and at 18-20 years-40%.

"development of movements. By the time the child is born, the child's motor apparatus is sufficiently developed to perform a number of simple movements.

The ability of muscles to contract appears even earlier - by the end of the second month of intrauterine life. Muscle tone gradually develops, and during intrauterine development and in infancy, the tone of the flexor muscles prevails over the tone of the extensor muscles, which is important for maintaining the natural position of the body in the uterus (Fig. 17).

By the end of the third month, the human fetus can clench its fingers into a fist in response to touching the hand. A month later, barely noticeable and very slow contractions of the muscles of the trunk and limbs, mainly the extensors, begin to appear occasionally. These are the so-called stirring. Gradually, they become more frequent and so pronounced that the pregnant woman clearly feels them. Long before birth, respiratory movements appear, which are expressed in a slight alternating increase and decrease in the volume of the chest, as well as swallowing and sucking movements. The elementary coordination of movements necessary for flexion and extension of the limbs, for sucking, swallowing and breathing movements, for head movements, undoubtedly appears even before birth. However, movements are extremely slow.

Already in the first days of life, the child shows great physical activity. Basically, these are irregular movements of the limbs. In the prone position, the child turns the head to the side, then the body and, as if rolling, lies on its back. If you hold it in an upright position, the head tilts forward, since its center of gravity is in front of the fulcrum, that is, the point of articulation of the skull with the spine, and the tone of the posterior cervical muscles is insufficient to maintain the correct position of the head.

In the second month of life, the child turns his head towards the light and somewhat later towards the sound. In the prone position, he raises his head, and by the end of the second month, leaning on his hands, he raises not only his head, but also his chest.

A three-month-old baby begins to roll over from his back to his stomach. The movements of his hands are gradually becoming more and more varied.

Rice. 19. The appearance of curvatures of the spine in connection with sitting and standing.

figurative. At the age of 4-5 months, they begin to be well controlled by vision: upon seeing a new object, the child stretches out his hands to it, grabs it and, as a rule, drags it into his mouth.

By the age of 7 months, the child retains a good sitting position, and after another month he sits down on his own and, holding on to various objects, rises to his feet. Gradually, he begins to crawl on all fours, and by the end of the year or in the first months of the second of the year life, at first every now and then falling, and then more and more confidently walks around the room without assistance.

Mastering vertical position the trunk or the whole body leads to a number of significant changes in the locomotor system: first, the tone and contractility of the extensor muscles sharply increase; Secondly, bends appear soil-_IPchnikP | i ^ vT- ^ r "t-" Q rn ^ rn ^ r

springy ow and me nir pra_ hplbe, run.-jumping and ease the work of muscles with long-term preservation of the vertical position of the body. the spine of the newborn along the entire length has a weak pronounced posterior bulge; in its lower part, the bulge is more pronounced - this is cross.pvp-to.opchikpy.y bend. The cervical bend begins to form by the end of the second month, when the tone of the posterior cervical muscles increases and the child begins to first raise the head in the prone position, and then hold it in an upright position of the body. The forward-facing bulge of the cervical spine becomes well pronounced much later, when the child independently and for a long time maintains a sitting position. At the same time bpgtrr pt-_, the backward-facing bulge of the middle part is clearly visible dialer - rough bend. Stagnant sitting position and ~ oSo "oen- but standing promotes education lumbar bend, reversed

convex forward. Usually this bend becomes noticeable only in the 2nd year of life (Fig. 19).

In children preschool age bends are still in the making and are highly dependent on body position. After prolonged lying, for example after a night's sleep, the cervical bend and especially the lumbar bend may completely disappear, reappearing and intensifying towards the end of the day under the influence of sitting and walking. Even at younger school age, the curves flatten considerably during the night. The variability of the bends gradually disappears.

Children of preschool age are characterized by extreme flexibility of the trunk, which is explained by the great thickness and pliability of the intervertebral cartilage and late ossification of the vertebral epiphyses. The bends of the spine are formed, and subsequently fixed under the influence of pressure from the side upper parts body. The direction of the pressure depends on posture, that is, sitting, standing and walking postures.

End of work -

This topic belongs to the section:

Cellular structure and development of the body

On the site read: "cell structure and development of the body"

If you need additional material on this topic, or you did not find what you were looking for, we recommend using the search in our database of works:

What will we do with the received material:

If this material turned out to be useful for you, you can save it to your page on social networks:

Tweet

All topics in this section:

Kabanov A.N. and Chabovskaya A.P
К-12 Anatomy, physiology and hygiene of preschool children. Textbook for preschool pedagogical schools. M., "Education", 1969. 288 with illustrations. The textbook is written according to the program

The structure, composition and properties of body cells. Also in
the first half of the 19th century the cellular structure of organisms was established. The bulk of each cell is a viscous, mucus-like semi-liquid substance - cytoplasm. It contains about

Growth and development
Regularities of growth and development. Body proportions change greatly with age (Fig. 2). In a newborn, the height of the head is approximately "L, and in an adult -" / 8 of the length of all

General overview of the human skeleton
The value of the locomotor system. The motor apparatus, or musculoskeletal system, includes the skeleton and skeletal muscles. Skedet is a solid skeleton on which you depend

L- & gt
The corresponding parts are also in lower limbs(leg) thigh; two bones of the lower leg - tibia and tibia; foot, consisting of the bones of the tarsus, metatarsus and

Properties and development of bone tissue
Cartilage and bone tissue. During the development of vertebrates, the bone skeleton did not appear immediately. The ancestors of modern vertebrates had a cartilaginous skeleton. In a human embryo

Development of the human skeleton
The skeleton of a newborn. The first islets, or centers, of ossification appear already at the beginning of the second month of intrauterine development, and by the time of birth they are absent only in the bone

Muscle work
Leverage principle. By contracting, the muscles perform work, either fixing the position of the bones in the joint and making movement impossible, or, conversely, changing their relative position, i.e.

Development of the basic properties of the locomotor apparatus
Coordination of movements. Maintaining an upright body position requires a well-coordinated activity of nearly three hundred large and small muscles. Each muscle must contract with st

Developing correct posture
Normal posture. Posture, that is, the habitual posture when sitting, "standing, walking, begins to form from early childhood. Normal, or correct, is considered such a posture, which

General overview of the structure and functions of the nervous system
Central and peripheral departments. In the nervous system, the central and peripheral divisions are distinguished (col. Table V). The central section includes the spinal cord,

Conducting excitation in the nervous system
Excitement as a response to irritation. The phenomena associated with excitement have long been studied on an isolated neuromuscular preparation of a frog, for which most often and

Coordination of body functions
Reflex as a reaction of the whole organism. The flow of impulses arising from irritation of visual, pain or other receptors enters the brain and becomes a source of coordinated

Development of the nervous system
The neonatal period. Even 3 months before the normal date of birth, the nervous system of the fetus is sufficiently developed to ensure the functioning of the body in conditions outside

Conditioned reflexes and their formation
Pavlovsky method of studying higher nervous activity. For a long time, the idea arose that feelings, thoughts and desires are associated with the existence of an unknowable dope. It was believed

Inhibition of conditioned reflexes
B ^ Unconditional inhibition. In the cerebral cortex, "as in other parts of the brain, excitation of any one area causes negative induction, that is, a decrease in excitability in

Analytical and synthetic activity of the cerebral cortex
Analyze and synthesize irritation. Countless, continuously occurring changes in the environment and in the body itself, acting as stimuli on the corresponding receptors. stans

Study of conditioned reflexes in humans
Conditioned reflex character of human higher nervous activity. Since 1906, N.I.Pavlov's student and follower N.I. Krasnogorsk

Features of the higher nervous activity of children
Formation of the first conditioned reflexes. Higher nervous activity is manifested in education conditioned reflexes... In a premature baby, conditioned

Development of speech
The value of speech components of complex stimuli. From the first months of a child's life, people are surrounded. He sees them, hears human speech, which very early becomes conditional

Isolation of individual signs of irritants. At
the formation of positive and negative conditioned reflexes to several similar complex stimuli, the process of isolating individual components or signs occurs, which allows both

Types of higher nervous activity
Classification of types. Greek physician Hippocrates, who lived in the IV century. BC, wrote that each person, based on the characteristics of his behavior, can be attributed to one of four

Sleep and its physiological significance
p> Sleep and wakefulness. Regular change of sleep and wakefulness is a necessary condition for normal life human body... During wakefulness, increased

Hygienic organization of sleep
Duration of sleep in children. Early children infancy sleep almost continuously, waking up only for the feeding period. A newborn baby sleeps 20-21 hours a day. Subsequently

Fatigue and fight against it
Fatigue and tiredness. Any physical or mental work causes a number of changes in the state and reactions of the body. For example, attention, memory, vision and

Preschool regime
The main components of the regime. The correct mode is rational and clear alternation different types activities and rest during the day, their course in a certain, daily

Hygienic requirements for classes and games
Furniture. For preschool institutions furniture (tables and chairs) of various sizes has been developed according to the height of the children. Furniture of the same size can be used by children

Children's nervousness
Disorders of higher nervous activity. I.P. Pavlov, in experiments on dogs, stopped that it is possible to cause serious disturbances in higher nervous activity if

General patterns of analyzer functions
,. Analysis of irritation. The activity of the brain, aimed at organizing and coordinating the work of all organs, as well as orientation in the environment, requires accurate and continuous

Skin Analyzer
The value of the skin analyzer. Receptors located in the skin make it possible to touch, that is, to feel the effect on the skin of irritants external environment... Through human skin receptors

Internal analyzers
Information on own body... In all organs, there are various receptors that are sensitive to certain chemical changes, to pressure, stretching, temperature changes

Olfactory and taste analyzers
The value of olfactory and gustatory analyzers. The olfactory analyzer receptors are located in the upper part of the right and left half of the nasal cavity, occupying a total area of ​​approx.

C 36. The structure and development of the eye
Eye structure. The peripheral part of the visual analyzer, in other words, the receptors that are sensitive to light, are located inside the organ of vision, or the eye (col. Table XI), which p

Farsightedness and myopia
v0 Natural hyperopia in children. In a newborn, the cornea and lens are more convex, and their size is almost the same as in adults. In vivo, i.e. in stretched

Perception of light and color
Photosensitive apparatus of the eye. A ray of light, having passed through the optical media of the eye, penetrates the retina and falls on its outer layer (Fig. 51). Here are the spectator's receptors

Spatial vision
,; Binocular Vision / In most animals, each eye has its own separate field of view. A person sees a significant part of the fields of view of both eyes simultaneously with the right and left

Organization of activities requiring eye strain
Excessive eye strain, if it is often repeated, contributes to the development of myopia, and often strabismus. Therefore it is necessary great attention to give the organization of such an environment, the cat

The importance of the circulatory system
Circular motion of blood. The blood filling the cardiovascular system is in a continuous circular motion - ^ color. tab. XII) .. The role of the pump transferring

A. blood 43. composition of blood
^ Blood plasma. "Blood is an opaque, red liquid," in which there are many smallest blood corpuscles,

Age features of blood
Blood formation in children. In newborns, the red bone marrow fills not only the gaps between the spongy material of the bones, but also the cavities inside the diaphysis of the long

Inflammation as a general defense reaction of the body
Penetration of foreign substances into the skin or any organ of the body, especially microbes, as well as damage from a bruise, burn or injury, almost always cause an inflammatory reaction:

Immunity
« Natural immunity... Immunity is the body's immunity to infection. Susceptibility to a particular disease is not the same, not only among different

The heart and its work
/) in the structure of the heart. The heart is located in the chest cavity almost along the midline of the body, behind the sternum and somewhat to the left of it. The upper part of the heart, from which they depart

Age features of the structure and work of the heart
Fetal circulation. The fetus, like an adult, has two circles of blood circulation - large and small.However, during intrauterine development, the supply of oxygen to the body

The movement of blood through the vessels
Argeria, capillaries, veins. By their structure, arteries, capilters and veins are very different from each other (Fig. 63). The thick wall of the arteries is mainly composed of smooth muscle and exercise

Regulation of blood circulation
Providing the body's need for oxygen. In the body, in every organ of the body, there are reserves of nutrients, but there are no reserves of oxygen. Therefore, oxygen delivery is carried out

Exercise your heart
Reserve powers of the heart. The minute volume of blood ejected by the heart into the aorta changes dramatically depending on the body's need for oxygen. So, with a fast run, with a heavy f

Respiratory structure
The meaning of breathing. Breathing is the exchange of gases Mf ^ .ny "" p ^ hchampm and the environment. ^ man, like all mammals, this exchange is carried out in a special

Respiratory movements
Jl & C ^ OUJULfLmfi1 &<£^ ^ G^^^Q Вдыхательные и выдыхательны? мышцы. Кровь, прите­кающая к легким, богата углекислотой, но бедна кис

Formation of pulmonary respiration in a newborn. Already
by the end of the 5th month of intrauterine development, weak respiratory movements of the chest become noticeable, at first rare, and later more frequent - up to 30-40 per minute. As you know, the fetus is surrounded

The meaning of proper breathing
Breathing rhythm. In preschool children, breathing is usually uneven. The breathing rhythm changes, that is, the alternation of inhalation and exhalation does not remain constant: then the inhalation is short.

Preschool air mode
Microclimate. When building a dwelling, a person creates a microclimate in it, that is, a local climate, which is characterized by the physical properties of air (temperature, humidity, ionization

The entry of food into the digestive tract
The importance of digestion. Food contains such things. which without prrgtnyarntrgtt.ng ^ nggeTTaDuikH do not mshut iittnttttShut from the digestive system r krgä ^

Timing of eruption of milk and permanent teeth
Name of teeth Terms of teething of milk constants 6 - 8 months. 7-10 "14

Digestion of food
Pavlovsky method of studying the work of the digestive glands. Digestion consists in the breakdown of complex particles of proteins, fats and carbohydrates into such that could, firstly,

The work of the digestive system in general
Consistency of work. Throughout the long path of the digestive tract, the digestive organs work with amazing precision and consistency. The sight, smell or conversation is enough

Age features of the structure and work of the digestive system
The digestive organs of the newborn. The digestive organs begin to function long before the birth date. However, until the end of the intrauterine period, the secretory f

Metabolism and energy in the body
Assimilation and dissimilation. Substances entering the baby's body undergo complex processes and turn into the substance of the cell itself. This is the assimilation of substances, their assimilation to substances of class

Energy side of metabolism and nutritional norms
Daily energy expenditure. The expenditure of energy by the human body to a large extent depends on the living conditions, the nature and amount of work performed, body weight, state of health

Physiological and hygienic foundations of catering
Appetite. The work of the digestive system largely depends on the desire to eat, in other words, on the appetite. Feeling of appetite is associated with increased excitability of so-called foods.

Feeding infants
Diet in infancy. During the first months of life, the child's nutrition is entirely provided by the mother's body. The transition to the consumption of regular food occurs gradually for a long time.

Organization of meals for children from 1 to 7 years old
Compilation of the menu. By the end of the 1st year of life, the child gets used to a variety of foods and, as a rule, can be transferred to a common table. At first, they give pureed food in the form of cereals and

Gastrointestinal diseases in children
Dyspepsia. Dyspepsia (indigestion) occurs in infants with restlessness, rapid stools, regurgitation, or mild vomiting. Indigestion can be the cause of dyspepsia.

Food hygiene
Requirements for food products. Food products supplied to children's institutions must be fresh and sound, free from foreign impurities, and must not contain disease-causing

Urine formation
Ways of isolating metabolic products. Each cell secretes decay products that are formed during the process of metabolism. They enter the tissue fluid, and from there into the blood. Timely

Removal of urine from the body
Urinary tract. From the renal pelvis, urine enters the ureter - a hollow tube about 30 cm long. There are smooth muscles in the wall of the ureter. They are peristaltic abbreviated

Hormonal regulation of body functions
The value of the endocrine glands. Ede1ami__ vlu-trenny secretions nyachyryatptrn ftprnniii) trn ^ and ^ t tissue which produces and secretes into the blood or.

Internal secretion of a growing organism
The period of intrauterine development. Initially, intrauterine development is influenced by the hormones of the mother's body. Most endocrine glands are formed in the fetus

Male and female genital organs
The structure of the male genital organs. The function of the male reproductive organs is the formation and excretion of spermatozoa. The organ in which they are formed is called the seed.

Structure and function of the skin
The value of the skin. The outer cover of the body, or skin, protects the body from the harmful effects of the environment, prevents liquid or gaseous substances from entering it. Basically

Heat transfer from the skin under different meteorological conditions
When the air temperature rises, the numerous vessels of the skin expand, and a large amount of blood flows through them. As a result, the skin heats up and the transfer of heat to the surrounding air occurs

Skin lesions in various diseases
Causes of damage to the child's skin. In children, skin lesions can occur with various infectious and non-infectious diseases. The younger the child, the easier it is to develop and the harder it is.

Hygiene of skin and clothes
Skin care. Skin hygiene is of great importance for the prevention of not only skin, but also a number of other, especially gastrointestinal, diseases. For skin care, you must have

Hardening basics
Hardening value. The hardening of an organism is called an increase in its resistance in relation to sharp fluctuations in temperature and other meteorological conditions. Dos hardening

Hardening agents
Indoor air. Air is the most accessible means of hardening throughout the year, even for those children who, for health reasons, can be opposed by other types of hardening.

Acute infectious diseases
Measles. Measles is a highly contagious disease. Its causative agent is a filterable virus, very volatile and not viable outside the human body. A patient with measles spreads it during

Chronic infectious diseases
Tuberculosis. Tuberculosis is a chronic infectious disease, the course and outcome of which largely depends on the body's resistance. The main source of infection is sick

Burns and frostbite
Thermal and chemical burns. Burns can be caused by flames, boiling water, steam, acids, alkalis, certain medications (lapis, iodine, ammonia, etc.), electric

Bites and ingestion of foreign bodies
First aid for bites. In summer, especially outside the city, children are often bitten by mosquitoes. Swelling, redness appears at the site of the bite,

Loss of consciousness
Fainting. Loss of consciousness caused by the onset of anemia of the brain is called fainting. The cause of fainting can be fatigue, intense excitement or nervous shock, hunger, si

Hygienic education of children
Instilling hygiene skills in children. Hygienic education of children is aimed at instilling in them hygienic skills and the communication of basic knowledge that substantiates these skills. One

Sanitary and educational work with parents
Work with parents aimed at improving hygienic knowledge of the care and upbringing of children should be carried out in preschool institutions according to a specially developed plan, if necessary.

Anatomy, physiology and hygiene of preschool children
textbook for preschool pedagogical schools. Editor A. M. Pridantseva. Layout and design by artist V. I. Preobrazhenskaya. Cover by artist D. K. Ivanov. Colour

The muscular system is organically linked with the bone, since they jointly provide human movement.

The muscular system in children is poorly developed. Muscle weight in relation to total body weight in children is less than in adults, as can be seen from the following data:
- for a newborn - 23.3%;
- for a child of 8 years old - 27.2%;
- for a 15-year-old teenager - 32.6%;
- for a boy of 17-18 years old - 44.2%.

Muscles in children differ in their structure, composition and function from the muscles of an adult. Muscles in children are paler and softer in appearance, richer in water, but poorer in protein and fat, as well as extractive and inorganic substances. Only by the age of 15-18 the amount of water in the muscles decreases, they become denser, the content of protein, fat and inorganic substances in them increases. At this age, the mass of the tendons also increases in comparison with the muscles, and therefore their firmness and elasticity increase.

Muscle development in children is uneven. They develop larger muscles first, such as the shoulder and forearm muscles, while smaller muscles develop later. So, in a 4-5 year old child, the muscles of the shoulder and forearm are relatively developed, but the muscles of the hand are still far from developed, and therefore, fine work with fingers at this age is not yet available to children. The qualitative function of the muscles of the hand develops sufficiently in a child at the age of 6-7 years, when children can already engage in such work as weaving, modeling and other exercises with low-resistance material. The development of the muscles of the hand at this age makes it possible to gradually teach the child to write. But the exercises in writing at this age should be short-term, so as not to tire the muscles of the hand that are still far from strong.

An increase in the rate of development of all muscles and an increase in muscle strength in children is observed after 8-9 years, when the ligaments are also strengthened and a significant increase in muscle volume is noted. In the following years, the strength of the muscles increases steadily. The increase in muscle strength in adolescents at the end of puberty is especially intense. During these years, there is an intensive increase in muscle mass.

At the end of puberty, there is not only an increase in the strength of the muscles of the arm, but also the muscles of the back, shoulder girdle and legs develop powerfully. According to Dementyev's research, the greatest gain in strength occurs between the ages of 15 and 18. After 15 years, small muscles also develop intensively, in connection with which the accuracy and coordination of small movements are improved and an economy of movements is achieved, which makes it possible to achieve the greatest results with the least effort during physical (manual) labor. At the same time, the technique of movements is also being improved.

In children and adolescents, fatigue of working muscles occurs more quickly than in adults. But at the same time, muscle fatigue in children passes faster, since this is favored by a faster exchange and more abundant delivery of oxygen to them, which restores the excitability of a tired muscle and increases its temporarily weakened elasticity. All this suggests that when organizing and conducting physical exercises, sports activities and physical labor of children and adolescents, it is necessary not to overburden their muscles, dose the load and conduct these exercises at a slow pace with appropriate rest pauses.

The development of motor skills in children and adolescents does not occur evenly, but in leaps and bounds. By the age of 6-7, the child is already free to use his muscles, but precise movements are still difficult for him and are accompanied by great efforts. When forcing a child to make precise movements, he quickly gets tired. Imperfection of movements in children at this age depends on insufficient development of coordination mechanisms in the central nervous system.

Coordination of movements, expressed in their accuracy and dexterity, becomes more perfect in children aged 8-12 years. At the same time, the mobility of children increases and their movements become varied. However, children of primary and partly middle school age are still not capable of prolonged productive physical work and prolonged muscle tension. This circumstance must be taken into account when organizing physical culture and labor activities for children.

By the age of 10-13, the child already has some harmony of movements. But during puberty, this harmony is violated, since at this time the adolescent's motor apparatus is being rebuilt. In this regard, primitive mechanisms (movements) are released from regulation by the higher parts of the central nervous system. Outwardly, in adolescents, this manifests itself in an abundance of movements, awkwardness, some of their angularity, lack of coordination and in violation of inhibition. By the end of puberty, these adolescent motor deficits level off, and the development of the motor apparatus is largely completed.

The above features of the development of the muscles and motor skills of children and adolescents put forward a number of hygienic requirements aimed, on the one hand, at protecting their muscular system, and on the other, at its development and strengthening. Given the relatively rapid fatigue of the muscles in children and adolescents and its insufficient training, it is necessary to avoid prolonged and even more excessive physical stress, bearing in mind the possible sad consequences that could lead to the crippling of a growing organism and a delay in its development. This applies not only to children of preschool and primary school age, but also to adolescents in high school and vocational schools.

To ensure the normal development of muscles in children and adolescents, moderate physical exercise is necessary, be it sports, agricultural or other physical labor. When working, the muscles receive a more abundant flow of blood, which contains nutrients and oxygen. The blood flowing in during the work of the muscle nourishes not only it, but also the bones to which it is attached, as well as the ligaments. Muscle work also has a positive effect on the formation of red blood cells in the bone marrow, thereby improving blood composition. Muscle work has a beneficial effect on the entire body, in particular on organs such as the heart and lungs, and activates metabolic processes.

Muscle activity is organically linked with the work of the brain and nerves, which have a mutual influence on each other. As noted above, muscle exercise promotes the development of the cerebral cortex. The upbringing of mental qualities, such as perception, memory, will, is associated with rational physical education. The work of the brain proceeds more productively when its nutrition is enhanced by the blood delivered to it. Thus, moderate physical exercise stimulates mental activity. However, with excessive muscle contractions, not only muscle fatigue occurs, but also the nervous system.

Excessive muscle tensions, especially when they occur for a long time, adversely affect the vital activity of the whole organism and can lead to severe diseases of the heart, lungs and other organs. With such excessive prolonged muscle tension, the heart works much more intensively, the heart muscle gets tired, as a result of which its contractions become slower. With prolonged tension in the muscles of the hands while playing the piano, sewing and writing, a condition known as writing cramps sometimes occurs, which is expressed by severe pain in the muscles of the arm and the inability to continue working. All this must be borne in mind when conducting educational work with children and adolescents.

However, not only excessive prolonged muscle tension, but also insufficient work of individual muscle groups, has an adverse effect on the body. The consequences of this are disorders in certain parts of the body, affecting the entire body. So, with a prolonged motionless sitting position without interruptions for active rest in the form of movements of the whole body, the blood circulation of the abdominal organs (stomach, intestines and liver) is disturbed, as a result of which constipation may appear. Therefore, it is so important to arrange breaks for rest during sedentary work, which should be accompanied by free movements, if possible, of the entire musculature of the body. Such rest after prolonged motionless sedentary work will be much more effective if it is carried out in the fresh air.

The most important thing in the hygiene of the muscular system of children and adolescents is its exercise, training, which gradually involves individual muscle groups (in their mutual connection) in movements and thereby ensures the development of muscles and improves motor skills. The study of new movements, for example, during the initial training in writing, gymnastics, playing musical instruments, certain types of physical labor, requires from children not only significant muscular expenditures, but also considerable neuropsychic stress, entailing physical and mental fatigue. Systematic, gradually increasing, but at the same time strictly dosed training of individual muscle movements in the process of teaching the above exercises makes these movements habitual, easy and enjoyable. If these activities are not excessive in time and stress, then they usually do not cause fatigue in a trained child and adolescent. In connection with the above, the enormous hygienic and pedagogical significance of training the muscular system becomes obvious.

From a hygienic point of view, it is extremely important to ensure the comprehensive development of the muscles of children and adolescents and to avoid unilateral stress on one or another muscle group. With a one-sided load on any one muscle group, its overdevelopment occurs due to some underdevelopment of the remaining muscle groups, and this circumstance negatively affects the activity of the whole organism. Only a comprehensive exercise of the muscles ensures the normal physical development of the growing organism as a whole and contributes to the improvement of the morphological and functional properties of individual organs and systems.

At primary school age, the main type of physical exercise is outdoor games. At this age, some strength exercises are already available, but only those that do not require strong tension. Gymnastic exercises in primary school age are becoming more important than in preschool age, but they are not yet the main type of physical culture for children in this period. Only in middle and senior school age, gymnastics and sports become the main types of physical culture among adolescents, since at this age the muscular system has developed enough for this kind of exercise.

When solving problems of physical culture among children and adolescents, it is not enough to take into account only the peculiarities of the skeletal and muscular systems. In this regard, the features of the cardiovascular system of children and adolescents are of great importance. Only taking into account all the factors of the development of the body can ensure the correct organization of educational work among children and adolescents and the conduct of measures among them in the field of individual hygiene.