Age features of the musculoskeletal system. Features of the development of the muscular system of the child
In the development of a child, the state of the musculoskeletal system - the bone skeleton, joints, ligaments and muscles - is of greater importance.
The bone skeleton, along with the performance of the support function, performs the function of protection: internal organs from adverse effects - various kinds of injuries. Bone tissue in children contains little salt, it is soft and elastic. The process of bone ossification does not occur in the same period of a child's development. Particularly violent restructuring, bone tissue, changes in the skeleton are observed in the child when he begins to walk.
Spine small child consists almost entirely of cartilage and has no bends. When the child begins to hold his head, he has a cervical bend, facing the bulge forward. At 6-7 months, the child begins to sit, he has a bend in the thoracic part of the spine with a bulge back. When walking, the lumbar curvature is formed with a bulge forward. By the age of 3-4, the child's spine has all the bends characteristic of an adult, but the bones and ligaments are still elastic and the spine bends are aligned in the supine position. The constancy of the cervical and thoracic curvature of the spine is established by 7 years, and the lumbar - by 12 years. Ossification of the spine occurs gradually and is completed completely only after 20 years.
The chest of the newborn has a round-cylindrical shape, its anterior-posterior and transverse diameters are almost the same. When a child begins to walk, the shape of the chest approaches the norm of an adult. Ribs in children early age have horizontal direction which limits the excursion (movement) of the chest. By the age of 6-7, these features do not appear.
The bones of the arms and legs undergo changes as the child grows. Until the age of 7, their rapid ossification occurs. So, for example, the ossification nuclei in the femur of a child appear in various areas in different dates: in the epiphyses - still in prenatal period, in the epicondyles - at the 3-8th year of life; in the epiphyses of the lower leg - on. 3-6th years, and in the phalanges of the foot - in the 3rd year of life.
The pelvic bones of a newborn child consist of separate parts - the iliac, ischial, pubic, the fusion of which begins from 5-6 years.
Thus, the skeletal system of children under 7 years of age is characterized by the incompleteness of the bone-forming process, which makes it necessary to carefully protect it.
Muscle tissue in early and before school age undergoes morphological growth, functional improvement and differentiation. When standing upright and walking begins, the muscles of the pelvis and lower extremities develop intensively. The muscles of the hands begin to develop rapidly at the age of 6-7 after the structural formation of the bone base and under the influence of the exercise of the muscles of the hand as a result of the child's activity.
timely development bone- muscular system and motor functions in children of early and preschool age are largely facilitated by the correct organization of hygienic conditions, environment, nutrition and physical education.
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1. Development, age features of bones
Bone develops in two ways: from connective tissue; from cartilage.
The bones of the vault and lateral parts of the skull, the lower jaw and, according to some, the clavicle (and in lower vertebrates, some others) develop from the connective tissue - these are the so-called integumentary or tight-fitting bones. They develop directly from the connective tissue; its fibers thicken somewhat, bone cells appear between them, and in the intervals between the latter, lime salts are deposited. First islands of bone tissue are formed, which then merge with each other. Most of the bones of the skeleton develop from a cartilaginous base that has the same shape as the future bone. Cartilage tissue undergoes a process of destruction, absorption, and instead of it, bone tissue is formed, with the active participation of a special layer of educational cells (osteoblasts). This process can go both from the surface of the cartilage, from the sheath that dresses it, the perichondrium, which then turns into the periosteum, and inside it. Usually, the development of bone tissue begins at several points; in tubular bones, the epiphyses and diaphysis have separate ossification points.
Everyone, of course, knows that the age of a tree is easy to determine by the annual rings of its trunk. But not everyone knows that by the state of the bone in medical practice it is possible to determine the age of a person. Not so long ago, bone was generally considered an inert, frozen substance with purely mechanical functions. But electron microscopy, X-ray diffraction analysis, microroentgenography and others modern methods studies have shown that bone tissue is dynamic, it has the ability to constantly renew itself, and throughout a person's life, the quantitative and qualitative ratio between organic and inorganic substances changes in it. Moreover, each period of life is characterized by its own ratios (according to them, in particular, age is determined).
At one year old baby in bone tissue, organic substances predominate over inorganic, which in to a large extent determines the softness, elasticity of his bones. After all, it is organic substances and even water that provide bones with extensibility and elasticity. As a person ages, the percentage of non organic matter and growing bones become more and more hard. In length, the bones grow due to the epiphyseal cartilages located between the body of the bone and its head. When growth ends, and this happens by about 20-25 years, cartilage is completely replaced by bone tissue. Bone growth in thickness occurs by imposing new masses of bone substance from the side of the periosteum.
But the completion of the formation of the skeleton does not mean at all that the bone structures have acquired their final, frozen form. In the bone tissue continue to flow interrelated processes creation and destruction.
When a person crosses the forty-year milestone, the so-called involutive processes begin in the bone tissue, that is, the destruction of osteons is more intense than their creation. These processes can later lead to the development of osteoporosis, in which the bone crossbars of the spongy substance become thinner, some of them are completely absorbed, the spaces between the beams expand, and as a result, the amount of bone substance decreases, bone density decreases.
With age, there is not only less bone substance, but the percentage of organic substances in bone tissue decreases. And, in addition, the water content in the bone tissue decreases, it seems to dry out. Bones become brittle, brittle, and even with normal physical exertion, cracks may appear in them.
The bones of an elderly person are characterized by marginal bone growths. They are due to age-related changes that cartilage tissue undergoes, covering the articular surfaces of bones, and also forming the basis of intervertebral discs. With age, the interstitial layer of cartilage becomes thinner, which adversely affects the function of the joints. As if trying to compensate for these changes, to increase the area of support articular surfaces the bone grows.
Normally, age-related changes in the bones develop very slowly, gradually. Signs of osteoporosis usually appear after age 60. However, it is often necessary to observe people in whom at the age of 70-75 they are slightly expressed. But it also happens like this: skeletal system a man could be given all sixty, but he is only forty-five. Such premature aging skeletal system, as a rule, occurs in people leading sedentary image life, neglecting physical culture, sports.
But bones, no less than muscles, need physical training, under load. Movement - essential condition normal life organism in general and the musculoskeletal system in particular. Observations have shown that the resorption of bone beams occurs especially intensively in those parts of the bones that experience the least load. While the beams located along the most loaded lines of force, on the contrary, thicken. Therefore, perhaps the main factors in the prevention of pathological age-related changes bone tissue are physical education and physical labor.
In progress physical activity blood supply to bone tissue improves, metabolic processes are activated. Adapting to functional loads, bone tissue changes internal structure, the processes of creation are especially intensive in it; bones become more massive, stronger.
2. Age features of the skeleton
musculoskeletal system children
The skeleton of the body consists of the vertebral column and the chest. Together with the brain region of the skull, they form the axial skeleton of the body.
The vertebral column is part of the axial skeleton and represents the most important supporting structure of the body, it supports the head, and limbs are attached to it.
Vertebrae (excluding coccygeal vertebrae) at the end of the second month embryonic period have two nuclei in the arc, merged from several nuclei, and one main - in the body. During the first year of life, the nuclei of the arc, developing in the dorsal direction, grow together with each other. This process proceeds faster in the cervical vertebrae than in the coccygeal. Most often by the age of seven vertebral arches, with the exception of I sacral vertebra, fused (sometimes the sacral section remains open until the age of 15-18). Later comes bone connection nuclei of the arc with the nucleus of the vertebral body; this connection appears at the age of 3-6 years and first of all in the thoracic vertebrae. At the age of 8 years in girls, 10 years in boys, epiphyseal rings appear on the edges of the vertebral body, which form the marginal ridges of the vertebral body. During puberty or a little later, the ossification of the spinous and transverse processes ends, having additional secondary ossification nuclei on their tops. The atlas and axial vertebra develop somewhat differently. The vertebrae increase as rapidly as intervertebral discs and after 7 years relative value disk is greatly reduced. The nucleus pulposus contains a large amount of water and has a significant big sizes in a child than in an adult. In a newborn, the vertebral column is straight in the anteroposterior direction. In the future, as a result of a number of factors: the influence of the work of the muscles, independent sitting, the severity of the head, etc., bends of the spinal column appear. In the first 3 months life, the formation of a cervical bend occurs ( cervical lordosis). The thoracic flexure (thoracic kyphosis) is established by 6-7 months, the lumbar flexure (lumbar lordosis) is quite clearly formed by the end of the year of life.
The laying of the ribs initially consists of mesenchyme, which lies between the muscle segments and is replaced by cartilage. The process of ossification of the ribs proceeds, starting from the second month of the prenatal period, perichondral, and a little later - enchondral. The bone tissue in the body of the rib grows anteriorly, and the ossification nuclei in the area of the angle of the rib and in the area of the head appear at the age of 15-20 years. The front edges of the upper nine ribs are connected on each side by cartilaginous sternal strips, which, having approached each other, first in the upper sections, and then in the lower ones, are connected to each other, thus forming the sternum. This process takes place at 3-4 months of the intrauterine period. In the sternum, primary ossification nuclei for the handle and body and secondary ossification nuclei for the clavicular notches and for the xiphoid process are distinguished.
The process of ossification in the sternum proceeds unevenly in its different parts. So, in the handle, the primary ossification nucleus appears on the 6th month of the prenatal period, by the 10th year of life, the fusion of body parts occurs, the fusion of which ends by the age of 18. The xiphoid process, despite the fact that it has a secondary nucleus of ossification by the age of 6, often remains cartilaginous.
The sternum as a whole ossifies at the age of 30-35 years, sometimes even later and then not always. Formed by 12 pairs of ribs, 12 thoracic vertebrae and the sternum, together with the articular-ligamentous apparatus, the chest, under the influence of certain factors, goes through a number of stages of development. The development of the lungs, heart, liver, as well as the position of the body in space - lying, sitting, walking - all this, changing in age and functional terms, causes a change in the chest. The main formations of the chest - dorsal grooves, lateral walls, upper and lower chest apertures, costal arch, infrasternal angle - change their features in one or another period of their development, each time approaching the features of the chest of an adult.
It is believed that the development of the chest goes through four main periods: from birth to two years of age, there is a very intensive development; at the second stage, from 3 to 7 years, the development of the chest is quite fast, but slower than in the first period; the third stage, from 8 to 12 years, is characterized by somewhat slow development, the fourth stage is the period of puberty, when enhanced development is also noted. After that, slow growth continues until 20-25 years, when it ends.
3. Development, age-related features of the muscular system
The muscular system is a collection of muscle fibers capable of contracting, combined into bundles that form special organs - muscles, or are independently part of the internal organs. The mass of muscles is much greater than the mass of other organs: in an adult, up to 40%.
The muscles of the trunk develop from the lateral notochord and brain tube of the dorsal mesoderm, which divides into primary segments, or somites. After the isolation of the skelerotom, which goes to the formation of the spinal column, the remaining dorsomedial part of the somite forms the myotome, the cells of which (myoblasts) are elongated in the longitudinal direction, merge with each other and subsequently turn into symplasts of muscle fibers. Part of the myoblasts differentiates into special cells - myosatellites, lying next to the symplasts. Myotomes grow in the ventral direction and are divided into dorsal and ventral parts. From the dorsal part of the myotomes, the dorsal (dorsal) muscles of the body arise, and from the ventral part, the muscles located on the front and side sides of the body and called ventral.
In the embryo, muscles begin to form at the 6-7th week of pregnancy. Until the age of 5, the child's muscles are not sufficiently developed, the muscle fibers are short, thin, tender and almost not palpable in the subcutaneous fat layer.
The muscles of children grow by the period of sexual development. In the first year of life, they make up 20-25% of body weight, by 8 years - 27%, by 15 years - 15-44%. Increase muscle mass occurs due to a change in the size of each myofibril. In the development of muscles, an important role is played by the motor mode appropriate for the age, at an older age - playing sports.
In the development of children's muscular activity, training, repetition and improvement of fast skills play an important role. With the growth of the child and the development of the muscle fiber, the intensity of the increase in muscle strength increases. Indicators of muscle strength, determined using dynamometry. Greatest magnification muscle strength occurs at the age of 17-18 years.
Different muscles develop unevenly. In the first years of life, large muscles of the shoulders and forearms are formed. Motor skills develop up to 5-6 years, after 6-7 years abilities for writing, modeling, drawing develop. From 8-9 years old, the volume of muscles of the arms, legs, neck, shoulder girdle increases. During puberty, there is an increase in the volume of the muscles of the arms, back, legs. At 10-12 years of age, coordination of movements improves.
During puberty, due to an increase in muscle mass, angularity, awkwardness, and sharpness of movements appear. Physical exercises during this period should be of a strictly defined volume.
In the absence of motor load on the muscles (hypokinesia), there is a delay in muscle development, obesity may develop, vegetovascular dystonia, bone dysplasia.
4. Postural disorders in children
Poor posture is not easy aesthetic problem. If it is not corrected in time, it can become a source of diseases of the spine and not only.
Usually, a violation of posture occurs during periods of rapid growth: at 5-8, and especially at 11-12 years. This is the time when the bones and muscles increase in length, and the mechanisms for maintaining the posture have not yet adapted to the changes that have occurred. Deviations are observed in most children 7-8 years old (56-82% junior schoolchildren). There are many factors that cause curvature of the spine. For example, malnutrition and diseases often disrupt the proper growth and development of muscle, bone and cartilage tissues, which adversely affects the formation of posture. An important factor is congenital pathologies musculoskeletal system. For example, with bilateral congenital dislocation hip joints, there may be an increase in lumbar flexion. An important role in the formation of deviations is played by the uneven development of certain muscle groups, especially against the background of general muscle weakness. For example, shoulders pulled forward are the result of a preponderance of strength. pectoral muscles And insufficient strength muscles that bring the shoulder blades together, and “hanging shoulders” is the result of insufficient work of the trapezius muscle of the back. An important role is played by the overload of certain muscles with one-sided work, for example, the wrong position of the body during games or classes. All these reasons lead to an increase or decrease in existing physiological curves spine. As a result, the position of the shoulders and shoulder blades changes, resulting in an asymmetric position of the body. Incorrect posture gradually becomes habitual and can be fixed. Be sure to pay attention to how the child sits at the table during classes: does he put one leg under him. Perhaps he stoops or "skews" to one side, leaning on the elbow of a bent arm. TO wrong position body when sitting, should be attributed to the landing, in which the torso is turned, tilted to the side or strongly bent forward. The reason for this position may be that the chair is far away from the table or the table itself is too low. Or maybe the book the baby is looking at is too far away from him. An asymmetric position of the shoulder girdle can be formed as a result of the habit of sitting, raising right shoulder. The weakness of the muscular corset in children is primarily due to the lack of adequate physical activity, while with rapid growth, the strength of the abdominal and back muscles is simply necessary.
5. Flat feet in children
Flat feet is one of the most common diseases of the musculoskeletal system in children. This is a deformity of the foot with a flattening of its arch (in children, the longitudinal arch is usually deformed, due to which the sole becomes flat and touches the floor with its entire surface).
It is possible to determine exactly whether a child has flat feet or not only when the baby is five (or even six) years old. Why? First, children to certain age the bone apparatus of the foot is not yet strong, it is partly a cartilaginous structure, the ligaments and muscles are weak, subject to stretching. Secondly, the soles appear flat, as the arch of the foot is filled with a soft “cushion” of fat that masks bone base. At normal development of the musculoskeletal system, by the age of five or six, the arch of the foot acquires the shape necessary for proper functioning. However, in some cases, there is a deviation in development, due to which flat feet appear.
Factors affecting the development of flat feet:
heredity (if one of the relatives has / had this disease, you need to be especially careful: the child should be regularly shown to an orthopedic doctor),
wearing the “wrong” shoes (flat soles without heels, too narrow or wide),
excessive load on the legs (for example, when lifting weights or with increased body weight),
excessive flexibility (hypermobility) of the joints,
paralysis of the muscles of the foot and lower leg (due to polio or cerebral palsy),
foot injuries.
Flat feet is a disease that, in the absence of adequate therapy, leads to serious complications and severe deformation of the bones of the foot, as well as diseases of the musculoskeletal system. Timely treatment and prevention will return the child to health and confidence in their attractiveness!
6. Hygiene of the musculoskeletalapparatus of children in the preschool educational institution and in the family
Any children's furniture must comply with sanitary and hygienic requirements aimed at ensuring long-term performance, harmonious physical development, prevention of violations of posture and vision in children. When using properly selected, high-quality furniture in kindergartens and schools, children maintain visual acuity and hearing, a stable balance of the body is observed, cardiovascular, respiratory, digestive system, reduces muscle tension and the possibility of premature fatigue.
Hygienic requirements for children's furniture primarily relate to the size of tables and chairs, as well as the ratio of the main elements: table top, backrest and chair seat.
During the learning process, children experience stress due to the need to long time maintain working posture. This load increases sharply in case of improper arrangement of furniture, inconsistency of its size with the height and proportions of the body. Therefore, furniture must be selected in accordance with the distribution of children by height groups. As a result special studies for toddlers and preschool children up to 100 cm tall, a growth scale with an interval of 10 cm is adopted, for school-age children over 100 cm tall - 15 cm.
For children of the younger toddler group (from 7 months to 1 year 8 months), feeding tables with a ratio of elements corresponding to group A furniture can be used.
Three types of children's tables should be used in nursery gardens: four-seater for children 1.5 - 5 years old, double with a changing tilt of the lid and drawers for teaching aids for children 5 - 7 years old; double trapezoidal shape for children 1.5 - 4 years.
It is equally important to select children's tables and chairs not only for the height of the child on this moment but also taking into account the fact that children grow in different ways. Therefore, if you select, for example, school furniture for lower grades, you should pay attention to height-adjustable student tables and chairs, the size of which can vary from 2 to 4 or from 4 to 6 height groups. The price of such furniture is slightly higher than usual, but its purchase eliminates the need to purchase furniture for groups of different sizes, which means that it allows you to avoid additional costs in the future.
Hygienic requirements for children's shoes.
From a hygienic point of view, children's shoes must protect the body from hypothermia and overheating, protect the foot from physical damage, help muscles and tendons, and restrain the arch of the foot in correct position, to provide a suitable climate around the foot, to help maintain the desired temperature regime under all weather environmental conditions. Children's shoes must meet hygienic requirements - be comfortable, light, not restrict movement, fit the size and shape of the foot. Then the toes are placed freely and can be moved. But she can cause huge amount foot diseases. Narrow and small children's shoes complicate gait, pinch the leg, disrupt blood circulation, cause pain and eventually change the shape of the foot, disturb its normal growth, change the shape of the toes, promote the formation of hard-healing ulcers, and in winter period- frostbite. Very loose children's shoes are also harmful. Walking in it quickly tires, and there is every chance of scuffs, especially in the instep area. Children are not recommended to walk in tight shoes. Wearing it often leads to ingrown nails, curvature of the fingers, the formation of calluses and contributes to the development of flat feet. Flat feet are also observed with prolonged wearing of shoes without heels, for example, in slippers. Daily wearing of shoes with high (above 4 cm) heels is not recommended for teenage girls, because. complicates walking, shifting the center of gravity forward. The emphasis is transferred to the toes. Reduced footprint and stability. The man leans back. Such a deviation, at a young age, when the pelvic bones have not yet grown together, entails a change in its shape, and even changes the position of the pelvis. This may have a negative impact on reproductive function. At this time, a large lumbar curve is formed. The foot moves forward, the fingers are compressed in a narrow toe, the load on anterior section foot increases, as a result, flattening of the arch of the foot and deformity of the fingers develop. In shoes with high heels, it is easy to twist the leg at the joint, it is easy to lose balance.
Organization of physical activity (on a walk).
Planning work on the development of movements during a walk should contribute to the consolidation, improvement of games and physical exercises, and increase the motor activity of children. It is important to choose the right time for games and exercises. It is impossible to allow organized motor activity to be carried out at the expense of the time of independent activity of children.
The choice of time for conducting and exercises on a walk depends on the previous work in the group. If a physical education or music lesson was held in the first half of the day, then it is advisable to organize games and exercises in the middle or end of the walk, and at the very beginning, give the children the opportunity to play on their own, exercise with a variety of benefits.
On other days, it is advisable to organize the motor activity of children at the beginning of the walk, which will enrich the content of their independent activity.
On the days of physical education classes with children, one outdoor game and some kind of physical exercise are organized ( sports exercise or exercise in the main form of movement). On other days, when the lesson is not held, an outdoor game, a sports exercise and an exercise in the main type of movement (jumping, climbing, throwing, throwing and catching a ball, etc.)
When conducting exercises, the main types of movements, you should use different methods of organization (frontal, subgroup, individual). The most appropriate is mixed use different ways organizations.
Due to the peculiarities of performing some movements (climbing the gymnastic ladder, balance exercises, long jumps and high jumps with a run), flow and individual methods are used.
The combination of different ways of organizing significantly increases the effectiveness of games and exercises during a walk. For example, a climbing exercise is performed by children in turn, and an exercise with balls is performed frontally, that is, by all children at the same time.
It is advisable to organize the exercises of children in the main types of movements into subgroups, depending on the degree of mobility of children. Each subgroup has its own task. For example, children of the first and second subgroups (with a high and medium level of mobility) perform exercises that require concentration, coordination and dexterity, while the teacher exercises control. Children of the third subgroup (with a low level of mobility) exercise in different types jumping rope.
The duration of organized motor activity is 30-35 minutes.
Formation correct posture - with siDenia, walking, standing, lying
Preschool age is the period of formation of posture, and it should be noted that the shortcomings of posture in preschoolers are still unstable. The child can take correct posture, if he is reminded of this, but his muscles, especially the back and abdomen, are not able to keep the spine upright for a long time, as they quickly get tired. Therefore, in the formation of correct posture, sufficient muscle strength, as well as their development and strengthening, plays an important role. Work on the formation of correct posture should be constantly carried out with all children, and not only with those who have any deviations.
Mandatory systematic physical exercise in the form of daily morning exercises, physical education, outdoor games in groups. Medical workers carry out special classes on exercise therapy, hardening, herbal medicine. It is very important to monitor the posture of preschoolers and to cultivate the ability to sit and stand correctly:
- posture at the table when drawing, looking at illustrations, when playing board games, it should be comfortable: the elbows of both hands are on the table, the forearms are symmetrical and free (according to upper third a little lower elbow joints) lie on the surface of the table. The shoulders are at the same level, the head is slightly tilted forward, the distance from the eyes to the table is 30-35 cm. The child should sit with the same load on both buttocks, without twisting to one side. Feet are on the floor. Ankle, knee and hip joints form a right angle;
- posture during sleep. It is best if the child sleeps on his back, on a small pillow. Sleeping on your side bends the spine, as does the habit of standing on one leg;
- standing posture. You have to stand with uniform distribution body weight on both legs;
- walking posture. Keep your shoulders at the same level, straighten your chest, pull your shoulder blades back without tension, tighten your stomach, look straight without lowering your head.
The main means of preventing postural disorders in preschoolers is physical exercise.
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The skeleton of a child in the process of growth and development undergoes complex transformations. Bone tissue in a child infancy It has fibrous structure, poor in mineral salts, rich in water and blood vessels. Each bone in a child is represented as several bones, which subsequently merge together. If an adult has 206 of them, then a newborn has 350 of them. Even after 14 years, bone fusion continues. For example, in a child in the first years, the pelvic bone consists of three individual bones, connected to each other by layers of cartilage, which are gradually replaced by bone tissue, and the bones grow together with each other
After birth, the bones continue to grow in thickness by layering the bone tissue from the outside and breaking down from the inside. This is a large part of the bones of the brain and facial skull. Otherwise, the long bones of the limbs grow, in which it is customary to distinguish middle part, or diaphysis, and the ends of the bone, or epiphyses. First, bone tissue is formed in the middle of the diaphysis. In long bones, cartilaginous layers remain between the diaphysis and epiphysis for a long time ( growth zones). Ossification begins from the middle part of the bone - from the diaphysis, where, due to the activity of bone cells, a bone cuff is formed. It increases towards the epiphyses, as a result of which the bone grows in length. At the same time, its thickness increases due to the formation of new layers of bone tissue. With ossification of the cartilaginous layer, the growth of the bone in length becomes impossible. Most long bones and vertebrae, the cartilaginous layer between the diaphyses and epiphyses persists up to 17-20 years, and in some cases even up to 22-25 years.
There are many cartilaginous parts in the skeleton of a newborn child. The epiphyses, that is, the ends of the long bones of the limbs, remain cartilaginous. In many bones, cartilaginous areas are preserved between individual ossification centers (Fig. 4.8).
The bones of the skull are not in contact with each other throughout. The gap between the frontal and two parietal bones is especially large - large fontanelle, which grows by the year. Small spring- the gap between the occipital and two parietal bones. It overgrows in the first month of life, and more often by birth (Fig. 4.9.). The skull grows unevenly. It grows rapidly in the first year: the head circumference increases by 30%, and the transverse diameter by more than 40%. Volume cerebral skull increases by 2.5 times. The size of the facial skull is increasing. The volume of the brain skull continues to increase and by the age of three reaches 80% of the volume of an adult. By this time, cranial sutures begin to form. The base of the brain skull continues to grow significantly, and by the age of 7-8 it becomes the same as in an adult. The facial skull also continues to grow. As dairy and permanent teeth the upper and lower jaws grow.
Development vertical position body leads to a number of significant changes in the motor apparatus: firstly, the tone and contractility extensor muscles; secondly, there are curves of the spine, which contribute to maintaining balance, have a springy effect when walking, running, jumping and facilitate the work of muscles while maintaining a vertical position of the body for a long time.
The spine in newborns is straightened, has no physiological bends. The first bend - cervical (lordosis) appears at the age of two months, when the child begins to hold his head. The forward-facing convexity of the cervical part of the spine becomes well pronounced much later, when the child independently and for a long time maintains a sitting position. The constancy of the cervical curvature is established by 7 years. At the same time, the convexity of the middle part of the spine facing backwards - the thoracic bend - is more clearly revealed. The thoracic curve (kyphosis) appears by 6 months, when the child can sit. Kyphosis- a bend directed by a bulge back. The sitting position, and especially standing, contributes to the formation of a lumbar bend, facing forward with a bulge. The bend directed forward by the convexity is called lordosis. It appears after a year, when the child begins to walk. With the formation of lumbar lordosis, the center of gravity moves backward, preventing the body from falling in a vertical position. Usually this bend becomes noticeable at the 2nd year of life.
Throughout preschool age, bends in strong degree depend on the position of the body. After a long lying down, for example, after a night's sleep, the cervical curve and especially the lumbar curve may completely disappear, reappearing and intensifying towards the end of the day under the influence of sitting and walking. Even at primary school age, the curves flatten significantly during the night. By the age of 7, there are already clearly defined cervical and thoracic curves. Fixation of the lumbar flexion occurs at 12-14 years of age. The curves of the spine are specific feature human and arose in connection with the vertical position of the body. Thanks to the bends, the spinal column is springy. Shocks and shocks during walking, running, jumping are weakened and faded, which protects the brain from concussions (Fig. 4.10.).
The growth of the spine in length occurs especially intensively in the first two years and during puberty. Between the vertebrae are discs made of cartilage, which contribute to the mobility of the spinal column. Disc height changes with age. Ossification of the vertebrae continues throughout childhood.
In newborns and infants up to 6 months, the chest has the shape of a cylinder or a truncated cone. The diameter of its lower section exceeds the diameter upper division. The ribs are horizontal. The chest of the first months appears to be shortened. Then it changes, and physiological omission of the ribs appears. The ribs take on a more oblique direction, the intercostal spaces become narrower. Features of the child's chest are smoothed out by 6-7 years, its final formation occurs by 12-13 years.
The thorax forms the backbone chest cavity. It protects the heart, lungs, liver and serves as an attachment site respiratory muscles and muscles upper limbs. According to the change in the chest, the volume of the lungs increases. Changing the position of the ribs contributes to an increase in the movements of the chest, which is why respiratory movements are carried out more efficiently.
The lumbar girdle forms the sacrum and 2 pelvic bones. Each pelvic bone in newborns consists of three bones, their fusion begins at 5-6 years of age, and ends at 17-18 years of age.
In newborns, the bones of the wrist are just emerging, becoming clearly visible by the age of 7, their ossification is completed by the age of 12. Ossification of the phalanges of the fingers is completed by the age of 11. An unformed hand gets tired quickly
By the age of two years, the bones of a child are close in structure to the bones of an adult and by the age of 12 they no longer differ from them.
With the help of the musculoskeletal system, essential function organism - movement. Movement plays an important role in metabolic processes, has a positive effect on the work of all internal organs.
The muscles of the newborn and infant are poorly developed. They make up 25% of body weight, while in an adult 40-43%. The size of the muscles depends on the work they perform. During the development of the child, muscle groups grow unevenly. In infants, first of all, the abdominal muscles develop. By the year, in connection with crawling and the beginning of walking, the muscles of the back and limbs noticeably grow. For the entire period of growth of the child, the mass of muscles increases by 35 times. An increase in muscle mass is achieved by their lengthening and thickening, due to an increase in 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 individual features organism, and mainly from physical activity.
Already in the first days of life, the child shows great physical activity. Basically, these are erratic movements of the limbs.
Children in the first months of life have increased tone muscles. The flexor tone predominates over the extensor tone. With the normal development of the child, motor skills are formed sequentially.
At 1-2 months, the baby keeps his head upright. In the position on his stomach, 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.
three month old baby begins to roll over from back to stomach. At 3-3.5 months, with the support of the armpits, it rests with its feet. At the age of 4-5 months, movements begin to be well controlled by vision: seeing new item, the child stretches out his hands to him, grabs and, as a rule, drags him into his mouth.
At 6 months, he sits on his own. She crawls at 7-8 months. By 7 months, the child maintains 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. At 10 months - stands without support. At 12 months, the child takes the first independent steps.
Maintaining an upright posture requires the well-coordinated activity of nearly 300 large and small muscles. Each muscle must contract with a strictly defined force in order, together with other muscles, to fix the bones of the skeleton that are movably connected to each other in a certain position. Muscle work is especially difficult when walking and running. During walking, about 50 muscles are involved in moving the leg forward. While one leg takes a step forward, the muscles of the other, along with the muscles of the body, provide balance, which is complicated by the continuous movement of the center of gravity.
In a child, coordination of the work of muscles when standing and walking is not established immediately: At first, the child walks with his legs wide apart and balancing with his arms spread apart. Only gradually, by the age of 3-4, the coordination of movements becomes so precise that the child easily walks and runs, maintaining balance.
At the age of 4-5 years, a child can jump, jump on one leg, slide along ice paths, skate, do various gymnastic and acrobatic exercises.
The movements of the small muscles of the hand begin to be mastered by the end of the first and the beginning of the 2nd year of life. The child can grasp and hold small items not only with the whole brush, but with the thumb and forefinger. By the age of 3-5, the most diverse, well-coordinated and precise finger movements are available to him: a child can learn to draw, play the piano, cut with scissors. It can be considered that the coordination of movements of various muscle groups characteristic of an adult is established by the age of 6. Intensive muscle growth and an increase in their strength are observed after 6 years. By the age of 8, muscles already account for about 27% of body weight, which is explained by their natural training.
Another property of muscles develops very slowly - their endurance. Endurance of the motor apparatus is determined by the working capacity of the muscles, their ability to perform dynamic and static work for a long time. Children are more adapted to perform dynamic work than static work, since the latter causes rapid muscle fatigue. Preschool children are very mobile. An approximate calculation shows that in a day, especially in summer, a child, moving, covers up to 15-20 km. In other words, there is a significant natural training of the motor apparatus. A child of 3-4 years old is usually not able to walk for a long time with a calm, even step. His movements are constantly changing. The static tension of his muscles can only be unchanged for a short time.
At senior preschool age physical activity more varied. Muscles become much stronger, and movements are well coordinated. Endurance increases somewhat, but still the child very quickly moves from one activity to another. When walking, his movements acquire the correct rhythm, but only for a while, for example, for 5, 10 or 15 minutes. The ability to maintain a fixed posture is increased, especially when sitting, but not for long. Endurance remains especially low in relation to the maximum power voltage. Muscle endurance increases from 8-10 years. Endurance to dynamic work depends not only on the degree of muscle development, but also on the performance of internal organs, especially the circulatory and respiratory systems, so any physical activity(mobile and sports games, gymnastics, walks) must be strictly dosed. The greatest endurance to dynamic work is achieved by the age of 25-30.
Thus, in preschool and primary school age, the growth and development of the musculoskeletal system is far from over. Teachers should remember this and try to fulfill the hygienic requirements for organizing the living conditions of the child.
Consists of the skeleton (bones), muscles, ligaments and joints. These structures form cavities for internal organs, protect internal organs, and also provide motor acts.
The skeleton forms the structural basis of the body, determines its shape and size. In the skeleton of an adult, there are more than 200 bones, which primarily perform a supporting function and are a kind of leverage in the implementation of motor acts. At the same time, bones are actively involved in metabolic processes: they accumulate mineral salts and, if necessary, supply their body (mainly calcium and phosphorus salts). Bones also contain hematopoietic tissue - red bone marrow.
Bones contain approximately 60% minerals, 30% organic components (mainly ossein protein and bone cell bodies-osteoblasts) and 10% water. Such a combination of substances in the structure of bones provides them with significant strength (30 times stronger than brick and 2.5 times stronger than granite) and greater elasticity, elasticity and viscosity (9 times higher than the viscosity of lead). The bones are characterized by a significant margin of safety (for example, the femur can withstand a load of 1.5 tons). In children tubular bones grow in length due to cartilage between the ends of the bones (epiphysis) and their body (diaphysis), and in thickness - due to the surface tissue - the periosteum. Flat bones grow in all directions only due to the periosteum. At the end of the growth of the human body, cartilage in many bones is replaced by bone tissue. The development of the skeleton in men ends at 20-24 years, and in women - at 17-21 years.
Individual bones and even parts of the skeleton mature at different periods. So, until the age of 14, only the middle parts of the vertebrae are ossified, while their other parts remain cartilaginous, and only at 21-23 years old do they become completely bony. By the same period, the ossification of most other bones of the skeleton is also completed.
An important stage in the development of the human skeleton is the formation and fixation of the folds of the spine, which are divided into those that are directed with the convex side forward and are called lordosis (occur in the neck and lumbar spine) and those that are directed backward and are called kyphosis (thoracic and sacral sections of the spine). The presence of lordosis and kyphosis is a necessary phenomenon, due to the upright posture of a person when standing and walking; it is also necessary to maintain the balance of the body and ensure the function of shock absorption when moving, jumping, etc. . Until the age of 5-6, the folds of the spine are little fixed, and if the child lies down, then most often these folds disappear (level out). Fixation of the folds of the spine occurs gradually: up to 7-8 years, only the cervical and thoracic flexures are formed, and at 12-14 years - lordosis of the lumbar spine and kyphosis of the sacral spine. The final fixation of lordosis and kyphosis is completed with the ossification of the vertebrae of the spine (17-20 years). In the frontal projection (when viewed from the front or from the back), a normally developed spine should be even.
Growth and development of bones. IN In the embryonic period of development, the skeleton is laid as a connective tissue formation. In some bones, foci of ossification appear directly in the connective tissue skeleton, i.e., the bone in its development bypasses the cartilaginous stage. Such bones are called primary(bones.skulls). Most bones are characterized by the replacement of connective tissue with cartilage, after which the cartilage is destroyed and bone tissue is formed instead. This is how they are formed secondary bones.
Ossification occurs in two ways: endochondral ossification, when foci of ossification appear within the cartilage, and peri-chondral, starting from its surface.-
The collagen fibers of the forming bone tissue (in certain areas) contain active crystallization centers with reactive groups. It is believed that the process of calcification begins with the interaction of the amino acid lysine, which is part of the reactive group of collagen, with phosphate ions. At the first stages of mineralization, the crystals of inorganic salts are not oriented relative to the axes of collagen fibrils. But as the mineralization proceeds, the resulting crystals are oriented with their long axes parallel to the axes of those collagen fibrils with which they are associated. In the epiphyses, in short bones, in the processes of bones, ossification is carried out according to the endochondral type, and in the diaphysis, along the perichondral type. Ossification begins in the middle part of the diaphysis, where a bone cuff is formed due to the activity of osteoblasts. The bone cuff grows towards the epiphyses. At the same time, its thickness increases due to the formation of more and more new layers of bone tissue. At the same time, resorption of cartilage and bone tissue occurs inside, and a bone marrow cavity is formed. Thus, from the outside there is a new layering of layers of bone tissue, and from the inside, the destruction of the remnants of cartilage and bone tissue. Due to this, the bone grows in thickness. At a certain stage of embryonic development, foci of ossification appear in the epiphyses. However, for a long time, a cartilaginous zone remains on the border of the diaphysis and epiphysis - growth plate, determining the ability of bones to grow in length.
To carry out the complex process of bone formation
It is necessary to have a complete diet, both qualitatively and quantitatively. The child's food should contain a sufficient amount of salt P and Ca, without which the process of calcification is impossible, as well as the necessary amount of vitamins. Thus, a lack of vitamin A causes vasoconstriction of the periosteum and the associated malnutrition of the developing bone tissue, as a result of which the bone stops growing. With a lack of vitamin C, bone plates do not form. With a lack of vitamin IN the exchange of phosphorus and calcium is disturbed. The disease occurs rahit, manifested in violation of the process of formation of bone tissue. This
the disease is characterized by softening of bone tissue, and consequent deformation of the bones, as well as increased growth of tissue, which differs from bone in its structure and chemical composition (Fig. 91).
Age features of the structure of bones. Ossification begins in the prenatal period of development, when primary ossification nuclei. A significantly larger number of ossification nuclei occurs after the birth of a child. These nuclei are called secondary. In total, 806 ossification nuclei are formed in the human skeleton during development.
Only in the skull, almost all ossification nuclei appear in the prenatal period of development. In all other parts of the skeleton, the number of secondary nuclei is greater than the number of primary ones. In an adult, the number of bones is significantly less than in a teenager of 14 years old: in an adult - 206, at 14 years old - 356. It follows that even after 14 years of age, the fusion of bones continues.
The bone of a newborn is characterized by a large amount of cartilaginous tissue, a large thickness of the periosteum, a rich vascular network, and an irregular arrangement of the Haversian canals. Apatite crystals are very small, the diameter of collagen fibers is small. Newly formed bone tissue is rich in water. The inorganic substance of a bone makes up only half of its mass. All this makes the bone less dense, porous, more resilient, elastic and flexible.
Rice. 91. Skeletal changes in rickets:
A- curvature of the legs; IN- deformity of the skull, spine, chest.
Age features of the skull skeleton. The skull begins to differentiate in the 2nd month of intrauterine life. The bones of the skull develop both primary and secondary. By the time of birth, ossification nuclei are present in all bones of the skull, but their growth and fusion occurs in the postnatal period. In a newborn, the volume of the brain skull is 8 times larger than the facial one, and in an adult it is only 2-2.5 times. At 2 years old, the face/skull ratio is 1:6, at 5 years old - 1:4, at 10 years old - 1:3 (Fig. 92, B). The smaller size of the facial skull in newborns depends on the underdevelopment of the facial, mainly jaw, bones. With the growth of teeth, these ratios approach their ratio in an adult.
In a newborn, between the bones of the skull there are spaces about 3 mm in size, filled with connective tissue. They are called seams. In the process of postnatal development, the width of the sutures decreases, so that the connective tissue layer becomes barely visible. After 30 years, ossification of the sutures occurs.
The corners of the bones of the skull do not ossify at the time of birth, and connective tissue also fills the places of their connection. These areas are called fontanelles(Fig. 92, A). There are anterior, posterior and lateral fontanelles. Anterior, frontal fontanel located between the frontal and parietal bones, its size is 2.5-5 cm. It progressively decreases by 6 months of postnatal development and completely closes by 1.5-2 years. Posterior, occipital fontanel located between the occipital and parietal bones, it has a size of up to 1 cm. Usually it is already closed by the time of birth, but sometimes it lasts up to 4-8 weeks. Side frontfontanelle is placed at the junction of the frontal, parietal, main and temporal bones, A side rear- between the occipital and temporal bones. Their closure occurs either in the prenatal period of development, or in the first weeks after birth. With rickets, the closure of the fontanelles occurs at a later date.
Rice. 92. Features of the skull of newborns:
L - location of fontanelles: / -- frontal; 2 - occipital; 3 - rear side;
4 - front side; B- the relationship between the front and brain parts of the skull
in newborns and adults / - in a newborn; 2 - in an adult
Rice. 93. Development of the frontal sinus(A) and maxillary sinuses(B).
Long-term preservation of fontanelles is considered one of the symptoms of this disease. The presence of fontanelles and sutures at the time of birth is of great importance, because it allows the bones of the child's skull to move at birth, thereby facilitating the passage through the mother's birth canal.
The occipital bone in newborns consists of four non-fused bones, the temporal - of three, the lower jaw - of two halves, the frontal - of two, in sphenoid bone the anterior and posterior parts of its body, as well as the wings with the body, are not fused. In the first year of life, large wings fuse with the body of the sphenoid bone, the fusion of the anterior and posterior parts of its body occurs only at the age of 13. The halves of the lower jaw fuse by 2 years. Fusion of individual parts of the temporal bone occurs at 2-3 years, the occipital - at 4-5 years. Fusion of two halves frontal bone ends by the end of the 3rd year of life, the seam between them disappears at 7-8 years.
Sinuses in the bones of the skull are formed mainly after the birth of a child. The newborn has only the rudiment topmaxillary, or maxillary, cavity. The formation of the sinuses ends only in adulthood. Figure 93 clearly shows changes in the size of the sinuses in different periods of postnatal development.
In a newborn, the bones of the skull are very thin, their thickness is 8 times less than in an adult. However, due to the intensive process of bone formation, already in the first year of life, the wall thickness increases by 3 times.
The volume of the skull changes quite quickly: in a newborn it is 1 / 3> at 6 months - "/g, and by 2 years - 2/3 of the volume of the adult's skull. From 10-12 years old, its size changes little.
Age features of the body skeleton. The vertebrae that form the vertebral column develop as secondary bones, that is, they pass through the cartilaginous stage. The ossification nuclei in them appear on the 2nd month of intrauterine development. The process of ossification of the spinal column occurs in a strictly defined order. Foci of ossification first appear in the thoracic vertebrae, and then ossification spreads towards the cervical and coccygeal regions.
On the 40-50th day of intrauterine development, the ossification nucleus appears in the body of the 12th thoracic vertebra, by the end of the 4th month, the bodies of all thoracic vertebrae, cervical, lumbar and the first two sacral vertebrae have ossification nuclei. In the same period, ossification nuclei appear in the arches of the vertebrae. The fusion of the ossification nuclei of the right and left halves of the vertebral arches occurs only after birth. The spine of a newborn is open at the back along the line of all arches of the vertebrae. Only by the age of 7 all the arcs are closed. The only exception may be the arch of the first sacral vertebra. Sometimes it closes later. The anterior arch of the atlas can remain open until 9 years of age.
At 8-11 years old, ossification nuclei appear in the epiphyseal cartilaginous discs that limit the vertebrae from above and below. From 15 to 24 years old, the bone epiphyseal discs fuse with the vertebral body. First of all, this occurs in the thoracic spine, then in the cervical and lumbar. Complete fusion of the processes with the vertebral body is carried out at the age of 18-24 years.
The vertebral bodies in newborns are flattened so that their transverse diameter is larger than the longitudinal one and the ratio between the diameters is 5:3. During puberty, this ratio becomes 4:3, and in an adult - 3:3. In general, for the entire period of development, the length of the spine increases by 3.5 times. The first 2 years the growth of the spine is very intense, then it slows down and again becomes more intense during puberty, it increases by 3.5 times.
Rice. 94. Curves of the spine:
A- the shape of the spine of an adult; B- the appearance of bends in children: / - in connection with holding the head; 2 - when sitting; 3 - while standing.
The first 2 years the growth of the spine is very intense, then it slows down and again becomes more intense during puberty.
The spinal column of a newborn has only a slight sacral bend (Fig. 94). The cervical bend appears first at the age of 2.5-3 months, when the child begins to hold his head. The bend directed by the convexity forward is called lordosis. Therefore, the first to appear cervical lordosis. Around the age of 6 months, when the baby begins to sit, there is a bend in thoracic region, directed backwards. Such bends, directed by a convexity backwards, are called kyphosis. By the time you start walking, it is formed lumbar curve. This is accompanied by a change in the position of the center of gravity, which prevents the body from falling when moving to a vertical position. Thus, by the year there are already all the curves of the spine. At first, the resulting bends are not fixed and disappear when the muscles relax. Fixation of bends in the cervical and thoracic spine occurs at 6-7 years, and in the lumbar - by 12 years.
Ossification of the sternum occurs in a secondary way, and the first nuclei of ossification appear in the handle and its body even in the prenatal period of development. In the xiphoid process, the nucleus of ossification occurs only at 6-12 years.
Complete fusion of all bone sections of the sternum is carried out after 25 years.
Ossification of the cartilaginous ribs begins at 6-8 weeks of fetal development. First of all, nuclei appear in the middle ribs. Secondary nuclei appear at 8-11 years of age. The fusion of the bone parts of the rib occurs at the age of 18-19 years, and the head and body of the rib - at 20-25 years.
In newborns, the chest is shaped like a bell or pear. The upper part of the chest is narrow, the lower part is expanded due to the high location of the internal organs, its anterior-posterior diameter is larger than the transverse one (Fig. 95). With the development of the lungs, which begin to occupy a large space, the upper ribs, which were located obliquely, begin to occupy a horizontal position.
Rice. 95. Various formschest:
A- in newborns; B- in adults.
In this regard, the chest takes a barrel-shaped shape. The upper edge of the sternum in an infant is at the level of the first thoracic vertebra. The curvature of the ribs is small. The angle between the ribs and the spine, as well as between the ribs and the sternum, is large. So, the costovertebral angle in a newborn is 82 °, and at 3 years old - 62 °. The shape of the chest during this period corresponds to the phase of maximum inspiration. From this it is clear that breathing at this age is carried out mainly due to the diaphragm. By the age of 3-4, the upper edge of the sternum descends to the level of the 3rd-4th thoracic vertebra (as in adults). Along with the sternum, the ribs descend, their curvature increases, the costovertebral angle and the angle between the ribs and the sternum decrease. This leads to an increasing dependence of the act of breathing on changes in the volume of the chest. This dependence is already clearly manifested in a 3-year-old child.
The shape of an adult chest acquires by 12-13 years.
Age features of the skeleton of the limbs. All bones of the belt upper limbs, with the exception of the clavicle, they go through a lean stage. IN collarbone precartilaginous tissue is immediately replaced by bone. The process of ossification, which began in it at the 6th week of intrauterine development, almost completely ends by the time of birth. Only the sternal end of the clavicle does not have a nucleus of ossification. It appears only by the age of 16-22, and its fusion with the body occurs by the age of 25.
In most bones of the free upper limbs, primary ossification nuclei occur within 2-3 months of embryonic development. In the bones of the wrist, they appear after birth: in the capitate and hooked - at the 4-5th month, and in the rest - in the period from 2 to 11 years. Fusion of primary and secondary ossification nuclei in the bones of the girdle ends by the age of 16–25.
Almost all bones lower limb belts primary ossification nuclei also appear in the embryonic period of development. Only in the bones of the tarsus (scaphoid, cuboid and sphenoid) they are formed in the period from 3 months after birth to 5 years.
Taz the newborn has the shape of a funnel. Its anteroposterior dimension is larger than the transverse one. The lower opening of the pelvis is very small. The entry plane is much more vertical than in the adult. The pelvis of a newborn is made up of separate, unfused bones. The ossification nuclei in the ilium, ischium and pubic bones appear in the period from 3.5 to 4.5 months of intrauterine development. From 12 to 19 years old, secondary ossification nuclei appear. The fusion of all three pelvic bones occurs at the age of 14-16, and the secondary nuclei are connected to the previously formed and fused pelvic bones only by the age of 25.
In the postnatal period, there is a change in the shape and size of the pelvis under the influence of a variety of factors: under the influence of pressure exerted by body weight and abdominal organs,
under the influence of muscles, as a result of pressure from the head of the femur, under the influence of sex hormones, etc. As a result of these various influences, the anteroposterior diameter of the pelvis increases (from 2.7 cm in a newborn to 8.5 cm at 6 years and 9.5 cm at 12 years old), its transverse size increases, which at 13-14 years old becomes the same as in adults. The plane of the pelvis in the transverse diameter becomes oval at this age.
After 9 years, there is a difference in the shape of the pelvis in boys and girls: in boys, the pelvis is higher and narrower than in girls.
Thus, not only at preschool age, but also at school, the growth and development of the skeleton is far from complete. This should be remembered by teachers, educators, parents and try to fulfill all the hygiene requirements that apply to the organization of the living conditions of the child. Furniture that does not correspond to the growth of the child, poor lighting of the room during his classes, uncomfortable shoes, high-heeled shoes, limitation of physical activity, insufficient exposure to fresh air, improper nutrition in quantitative and qualitative terms can cause certain violations of the formation of the skeleton , which in turn can be the cause of the pathology of internal organs. So, a pronounced kyphosis (stooped back) often leads to a disorder in the activity of the respiratory system. Deformation of the sternum can adversely affect the functioning of the heart, etc. Sometimes there are lateral curvature of the spine - scoliosis. They can also cause disruption of the organs of the chest cavity.
AGE FEATURES OF SKELETAL MUSCLES
Changes in the macro- and microstructure of skeletal muscles withgrowth. The formation of skeletal muscles occurs at very early stages of development. At the 8th week of intrauterine development, all muscles are already distinguishable, and by the 10th week their tendons develop. The connection of the primary laying of the muscles with the corresponding nerves is found already in the 2nd month of development. However, motor nerve endings first appear only on the 4th month of intrauterine development.
The maturation of muscle fibers is associated with an increase in the number of myofibrils, the appearance of transverse striation, and an increase in the number of nuclei. It is carried out in different muscle fibers at different speeds. First of all, the fibers of the muscles of the tongue, lips, intercostal muscles, muscles of the back and diaphragm are differentiated. Then - the muscles of the upper limb and lastly - the muscles of the lower limb.
In newborns, muscle mass is 23.3% (in adults - 44.2%) of the total body weight. The tendon part of the muscle is poorly developed and is less than in adults, part of the entire length of the muscle; fascia and tendons broad muscles very thin, fragile, easily separated from them. The connective tissue that forms the intramuscular septa differs from the connective tissue of the adult muscles by a larger number of cells and a smaller number of fibers. Striated muscle fibers are characterized by very a large number nuclei that are oval in shape. Longitudinal diameter refers to the transverse as 2:1. Different muscle fibers in newborns differ little in their diameter. Sarcolemma begins to emerge by the 6th month of fetal development. In a newborn, it is clearly expressed and is characterized by the presence of a large number of thin fibers, in the arrangement of which there are no signs of orderliness.
In the process of postnatal development, further changes occur in both the macro- and microstructure of skeletal muscles. The maturation of different muscles and even different bundles of fibers of the same muscle occurs at different rates. This speed is determined by the function that this anatomical formation performs at a particular age stage. As a rule, functionally active muscles mature first. In general, muscle mass over the entire period of development increases by about 21%. By the age of 8, the mass of muscles in relation to the mass of the whole body becomes equal to 27.2%, by the period of puberty - 32.6%, and at 17-18 years - 44.2%. It follows that the most intense weight gain occurs during puberty. By the time of the birth of a child, the muscles of the trunk, head, and upper limbs reach the greatest development. Their mass is about 40% of the mass of all muscles (in adults - up to 30%).
The mass of the muscles of the upper limbs in relation to the mass of the muscles of the whole body increases from birth to 23-25 years, when the ontogenetic maturation of the muscles ends, by only 2%. Consequently, by the time of birth, they already have a fairly large mass, and its further increase was in full accordance with the increase in the mass of the whole body. At the same time, the mass of the muscles of the lower extremities in relation to the body mass increases over the entire period of development by more than 16%. In the muscles of the upper extremities, the mass of those that cause finger movements increases especially sharply at preschool and primary school age. The mass of the extensor muscles increases more intensively than that of the flexors, since by the time of birth the flexors, which determine the characteristic posture of the fetus during fetal development, are already significantly developed. The extensors, which ensure the vertical position of the body, mature intensively after the birth of a child.
Muscles that cause a large range of motion grow intensively in length, and muscles whose function requires contractions of great strength increase in diameter. Their development is characterized by an increase in the degree of pinnation.
