Features of the structure of the spinal cord in a newborn. Features of the structure of the brain and spinal cord in a newborn
The spinal cord in newborns is morphologically more mature than the brain. This determines its more perfect functions and the presence of spinal automatisms at the time of birth. By the age of 2-3, myelination of the spinal cord and roots of the spinal cord, forming a ponytail, ends. The spinal cord grows in length more slowly than the spine. In a newborn, it ends at the level of Lm, while in an adult it ends at the upper edge of L. The final ratio of the spinal cord and spine is established by 5-6 years.
The nervous system in children. Myelination of nerve fibers in children
An important indicator of maturation nervous structures- myelination of nerve fibers. It develops in a centrifugal direction from the cell to the periphery. Phylo and ontogenetically older systems are myelinated earlier. Thus, myelination in the spinal cord begins at the 4th month. prenatal development, and in a newborn it is almost over. At the same time, they are myelinated first. motor fibers and then sensitive. AT different departments nervous system myelination occurs non-simultaneously. First, the fibers that carry out vital activity are myelinated. important features(sucking, swallowing, breathing, etc.). The cranial nerves myelinate more actively during the first 3–4 months of life. Their myelination is completed by about a year of age, with the exception of vagus nerve. The axons of the pyramidal pathway are covered with myelin mainly by 5-6 months of life, and finally by 4 years, which leads to a gradual increase in the range of motion and their accuracy.
The nervous system in children. The development of conditioned reflex activity in children.
One of the main criteria normal development the brain of a newborn is the state of the main unconditioned reflexes, since conditioned reflexes are formed on their basis. The cerebral cortex, even in a newborn, is prepared for the formation of conditioned reflexes. They form slowly at first. At the 23rd week of life, a conditional vestibular reflex to the breastfeeding position and rocking in the carrycot. Then there is a rapid accumulation of conditioned reflexes, formed from all analyzers and reinforced by the food dominant. A conditioned reflex to a sound stimulus in the form of a protective (blinking) movement of the eyelids is formed by the end of the 1st month of life, and a food reflex to a sound stimulus - by 2m. At the same time, the formation conditioned reflex into the world.
In general, already at the most early stages development, the maturation of the nervous system is carried out according to the principle of systemogenesis with the formation, first of all, of departments that provide vital reactions responsible for the primary adaptation of the child after birth (food, respiratory, excretory, protective).
The development of the central nervous system, and especially the brain, in the embryo is a long and intense process.
At the 4th week of the embryo's life, the formation of its nervous system begins. It first looks like a plate, the edges of which in the process of development are bent and form a tube (medullary tube). Three spherical bubbles appear at the end of the tube. In the future, two of them are divided in half. The resulting five bubbles represent the beginnings of the future main parts of the brain: medulla oblongata, pons and cerebellum; the midbrain, which plays a much smaller role in humans than in animals; visual tubercles and parts of the basal ganglia. Large hemispheres develop from the first bubble.
At the 8th week of the embryo's life, the formation of the cerebral cortex begins, which at first looks like a plate. Its development, which takes place over 8-12 weeks, goes through a series of stages, as a result of which the cortical plate is separated from the interstitial layer. The latter contains a large number of cells, which subsequently gradually migrate (move) into the cortex.
By the 13th week, the formation of the cortical plate ends and the period of its first differentiation begins. Two layers are formed: inner - loose, wide, and superficial, denser and thinner. The cortical plate matures unevenly. First of all, it develops central part, and after it maturation spreads radially in all directions to the periphery.
Distinctive and characteristic feature development human brain is the early isolation and especially intensive formation of its frontal and prefrontal parts, which play the most significant role in the entire mental activity person. In a peculiar sequence and unequal rate of maturation of various parts of the cortical plate, specific features namely the human brain.
After four months in the development of the brain tissue of the embryo, notable changes: the outer layer of the cortical plate begins to grow intensively; the growth of the inner layer is much slower, due to which, in top layer folds and furrows begin to form. They develop so rapidly that by the time of birth, the child's brain basically has all the furrows and convolutions that are characteristic of the adult brain. However, the change in the shape and size of the convolutions and furrows, as well as the formation of new small convolutions, continues after birth.
The changes taking place in the cerebral cortex of the embryo are not limited to its rapid growth. From the fifth month, the formation of different layers of cells begins, differentiation occurs and the cellular elements. The speed of these processes also turns out to be uneven in various places bark.
In the process further development(from four to six months), the entire cortex acquires a six-layer structure, characteristic of the brain of an adult. However, even during this period, the speed of maturation, the thickness and shape of the cells in all six layers in different parts of the brain are not the same.
Development affects the change in the structure and size of the cells themselves, in their location. Particularly complex and intense is the process of cell development in frontal parts brain, constituting 1/3 of the entire cortex. The rate of development of the motor and sensory areas of the cortex is comparatively slower.
At the same time, by the time of birth, it is these zones, and especially the sensory one, that are most prepared for normal functioning. They reach maturity later frontal lobes guiding higher forms mental (adaptive) activity of a person.
Together with the formation of brain cells, the development of nerve fibers, i.e., pathways, also takes place. They form most early and intensively in the spinal cord and cerebellum. In the brain, nerve fibers begin to grow later, and by the time the child is born, a small amount of them penetrates into the gray matter - the cortex. However, neither in the gray nor in the white matter of the central gyri cerebral cortex fibers do not yet have a myelin sheath. The myelin (pulp) sheath of the nerve fiber provides the conduction of nerve excitation.
Despite the fact that in the entire process of development of the nervous system of the embryo, the process of brain formation turns out to be the most intensive, by the time the child is born, it is this organ that is the least prepared to perform its main function - the function of precise and subtle balancing of the body with the environment.
The spinal cord at the time of birth is the most developed part of the CNS. During the first three months of fetal life spinal cord occupies the entire length of the spinal canal. In the future, the spine grows faster than the spinal cord. Therefore, the lower end of the spinal cord rises in the spinal canal. In a newborn child, the lower end of the spinal cord is located on level III lumbar vertebra, in an adult - at the level of the II lumbar vertebra.
The spinal cord of a newborn is 14 cm long. By the age of 2, the length of the spinal cord reaches 20 cm, and by the age of 10, compared with the neonatal period, it doubles. In an adult, the length of the spinal cord is 43-45 cm. Various plots of the spinal cord in the process of growth develop differently: the thoracic region increases most of all, then the cervical and only then the lumbar. After 6 years, the spinal cord grows in transverse diameter. A number of furrows that appear on the spinal cord of a newborn, deepening, remain for life, some furrows disappear after birth.
The mass of the spinal cord at birth is 3-4 g, by 6 months it doubles, by 3 years the mass of the spinal cord exceeds 13 g, by 6 years it reaches 16 g. By the age of 20, the mass of the brain is equal to the mass of the adult spinal cord, while it 8 times more than a newborn.
In a newborn, the central canal is wider than in an adult. A decrease in its lumen occurs mainly within 1-2 years, as well as in later age periods when there is an increase in gray mass and white matter. The volume of the white matter of the spinal cord increases rapidly, especially due to the own bundles of the segmental apparatus, the formation of which occurs in more early dates compared with the timing of the formation of pathways connecting the spinal cord with the brain.
Spinal ganglions on early stages embryonic development located in the spinal canal quite deep, then they move into the intervertebral foramina. Due to the discrepancy between the length of the spinal cord and the spine, the direction of the anterior and posterior roots changes from horizontal to downward. Also in embryonic period the shape of the spinal cord changes: cervical and lumbar thickenings appear, which is associated with the development of the limbs. The cervical thickening develops faster than the lumbar, because upper limbs develop earlier. In a newborn, both thickenings are well expressed, but they reach their greatest development during the first years of life. The diameter of the remaining sections of the spinal cord increases slowly, by the age of 12 it doubles.
A 6-7 month old fetus has a lot of still undeveloped cells in the spinal cord, different in shape and location. By the time of birth, all nerve and glial cells of the spinal cord are well developed and only slightly differ in structure from cells in 6-year-old children. In older children, the cells become larger.
The nervous system of the fetus begins to develop in the early stages of embryonic life. From the outer germ layer - the ectoderm - a thickening is formed along the dorsal surface of the body of the embryo - the neural tube. Its head end develops into the brain, the rest - into the spinal cord.
A week-old embryo has a slight thickening in the oral (mouth) section of the neural tube. At the 3rd week of embryonic development, three primary cerebral vesicles (anterior, middle and posterior) are formed in the head section of the neural tube, from which the main sections of the brain develop - the final, middle, rhomboid brain.
Subsequently, the anterior and posterior cerebral vesicles are each divided into two sections, as a result of which five cerebral vesicles form in a 4-5-week-old embryo: terminal (telencephalon), intermediate (diencephalon), middle (mesencephalon), posterior (methencephalon) and oblong ( myelencephalon) (Fig. 1). Subsequently from the final brain bladder development of the cerebral hemispheres and subcortical nuclei, from the intermediate - the diencephalon (visual tubercles, hypothalamus), from the middle one forms the midbrain - the quadrigemina, the legs of the brain, the Sylvian aqueduct, from the back - the bridge of the brain (pons varolii) and the cerebellum, from the medulla oblongata - the medulla oblongata. Rear end myelencephalon smoothly passes into the spinal cord.
A - neural plate: 1 - ectoderm; 2 - mesoderm; 3 - endoderm; 4 - neural plate; b - neural groove: 1 - chord; 2 - ectoderm; 3 - neural groove; c - neural tube: 1 - chord; 2 - central channel; 3 - neural tube; d - formation of brain bubbles: 1 - spinal cord; 2 - myelencephalon; 3 - metencephalon; 4 - telencephalon; 5 - diencephalon; 6 - mesencephalon; e - formation of the ventricles of the brain: 1 - IV ventricle; e - formation of the cerebral hemispheres; g - increase in the mass and volume of the brain: 1 - large hemispheres; 2 - cerebellum; 3 - bridge of the brain; 4 - medulla oblongata
From the cavities of the cerebral vesicles and the neural tube, the ventricles of the brain and the canal of the spinal cord are formed. The cavities of the posterior and oblong cerebral bladders turn into the IV ventricle, the cavity of the middle cerebral bladder - into a narrow canal called the aqueduct of the brain (Sylvian aqueduct), which communicates between the III and IV ventricles. The cavity of the intermediate bladder turns into the third ventricle, and the cavity of the terminal bladder - into two lateral ventricles. Through the paired interventricular foramen, the III ventricle communicates with each lateral ventricle; The IV ventricle communicates with the spinal canal. Cerebral fluid circulates in the ventricles and spinal canal.
The neurons of the developing nervous system, through their processes, establish connections between various departments brain and spinal cord, and also communicate with other organs. Sensitive neurons, entering into communication with other organs, end with receptors - peripheral devices that perceive irritation. Motor neurons end in a myoneural synapse - a contact formation of a nerve fiber with a muscle.
By the 3rd month of intrauterine development, the main parts of the central nervous system are distinguished: the cerebral hemispheres and the brain stem, the cerebral ventricles, and the spinal cord. By the 5th month, the main furrows of the cortex differentiate hemispheres, however, the cortex is still underdeveloped. At the 6th month, the functional prevalence of the higher parts of the fetal nervous system over the underlying parts is clearly revealed.
The brain of a newborn is relatively big size. Its average weight is 1/8 of the body weight, i.e., about 400 g, and in boys it is somewhat larger than in girls. The newborn has well-defined furrows, large convolutions, but their depth and height are small. There are relatively few small furrows, they appear gradually during the first years of life. By 9 months, the initial mass of the brain doubles and by the end of the first year it is 1/11 - 1/12 of the body weight. By the age of 3, the mass of the brain triples compared to its mass at birth, by the age of 5 it is 1/13 - 1/14 of body weight. By the age of 20, the initial mass of the brain increases by 4-5 times and in an adult is only 1/40 of the body mass. Brain growth occurs mainly due to the myelination of nerve conductors (i.e. covering them with a special, myelin, sheath) and an increase in the size of approximately 20 billion already present at birth. nerve cells. Along with the growth of the brain, the proportions of the skull change (Fig. 2).
A - ratio of the proportions of the skull of a 5-month-old embryo (1), a newborn (2), a 1-year-old child (3), and an adult (4); b - ratio facial skull adult and newborn
The brain tissue of a newborn is undifferentiated. Cortical cells, subcortical nodes, pyramidal pathways underdeveloped, poorly differentiated into gray and white matter. Nerve cells of fetuses and newborns are concentrated on the surface of the cerebral hemispheres and in the white matter of the brain. With an increase in the surface of the brain, nerve cells migrate into the gray matter; their concentration per 1 cm3 of the total brain volume decreases. At the same time, the density cerebral vessels increases.
In a newborn, the occipital lobe of the cerebral cortex is relatively larger than in an adult. The number of hemispheric convolutions, their shape, topographic position undergo certain changes as the child grows. Biggest changes occur in the first 5-6 years. Only by the age of 15-16 are the same relationships observed as in adults. Lateral ventricles the brain is relatively wide. Connecting both hemispheres, the corpus callosum is thin and short. During the first 5 years, it becomes thicker and longer, and by the age of 20, the corpus callosum reaches its final size.
The cerebellum in a newborn is poorly developed, located relatively high, has an oblong shape, small thickness and shallow furrows. The bridge of the brain moves towards the slope as the child grows. occipital bone. The medulla oblongata of the newborn is located more horizontally. The cranial nerves are located symmetrically at the base of the brain.
AT postpartum period undergoes changes and the spinal cord. Compared to the brain, the spinal cord of a newborn has a more complete morphological structure. In this regard, it turns out to be more perfect in terms of functionality.
The spinal cord in a newborn is relatively longer than in an adult. In the future, the growth of the spinal cord lags behind the growth of the spine, and therefore its lower end “moves” upward. Spinal cord growth continues until about 20 years of age. During this time, its mass increases by about 8 times.
The final ratio of the spinal cord and spinal canal established by 5 - 6 years. The growth of the spinal cord is most pronounced in the thoracic region. Cervical and lumbar thickening of the spinal cord begin to form in the first years of a child's life. The cells innervating the upper and lower limbs are concentrated in these thickenings. With age, there is an increase in the number of cells in the gray matter of the spinal cord, and a change in their microstructure is also observed. The spinal cord has a dense network venous plexuses, which is explained in relation to rapid growth spinal cord veins compared with the rate of its growth.
The peripheral nervous system of the newborn is insufficiently myelinated, the bundles of nerve fibers are rare and unevenly distributed. Myelination processes occur unevenly in different departments. myelination cranial nerves most actively occurs in the first 3 - 4 months and ends by 1 year. myelination spinal nerves lasts up to 2-3 years. The autonomic nervous system has been functioning since birth. In the future, the fusion of individual nodes and the formation of powerful plexuses of the sympathetic nervous system are noted.
At the early stages of embryogenesis, clearly differentiated “hard” connections are formed between different parts of the nervous system, which form the basis for vital innate reactions. A set of these reactions provides primary adaptation after birth (for example, food, respiratory, defensive reactions). The interaction of neuronal groups that provide a particular reaction or a set of reactions constitutes a functional system.
Depending on where the damage was, the symptoms may vary. If you were injured cervical region spine, then when you change the position of the baby or if you take him in your arms, the child has a sharp cry. You can also observe torticollis, the neck can be elongated or shortened, hemorrhages on the skin of the neck, dry skin near the injury site.
With a severe injury of the upper cervical segments, there are such symptoms: lethargy, muscle hypotension, arterial hypotension, hypothermia (body temperature drops below normal), absence of pain reflexes. After birth is broken normal breathing. There is shortness of breath, irregular breathing. When examining the baby, it will be seen that rib cage not symmetrical.
Depending on where the injury was inflicted, there are:
- Duchenne-Erb palsy - damage to the spinal cord at the level brachial plexus.
- paralysis of Dejerine-Klumpke - damage at the level of the middle and lower bundles of the brachial plexus. With it, the hands and fingers do not bend.
- Kerer's palsy - complete paralysis of the upper limb.
If the lumbosacral region is affected, then the movements of the lower extremities are impaired or absent.
How are these injuries treated?
The sooner treatment is started, the greater the chance of a successful recovery.The first thing doctors do is fix the baby's head and neck. Duration is 10-14 days. At this time, it is important to carefully dress and swaddle the baby, be sure to support the head and neck. You can only feed with a bottle or through a tube until the pain goes away and the condition of the crumbs returns to normal.
Also, from the eighth day, physiotherapy is prescribed: electrophoresis, thermal procedures (paraffin), electrical stimulation, later acupuncture.
If the child feels better, then massage is indicated for general strengthening. Hydrokinesitherapy is also used, these are baths with the addition of sea salt, coniferous extracts. The water temperature should be 36.5-37 degrees. Take a bath for no more than ten minutes.
In order not to arise birth trauma spinal cord of newborns, sparing management of childbirth is necessary.
The spinal cord is the oldest part of the central nervous system. spinal cord by appearance is a long, cylindrical, flattened from front to back strand with a narrow central channel inside.
The length of the spinal cord of an adult is on average 43 cm, weight - about 34-38 g, which is approximately 2% of the mass of the brain.
The spinal cord has a segmental structure. At the level of the foramen magnum, it passes into the brain, and at the level of 1-2 lumbar vertebrae, it ends with a cerebral cone, from which the terminal / terminal / thread leaves, surrounded by the roots of the lumbar and sacral spinal nerves. At the points of origin of the nerves to the upper and lower limbs there are thickenings. These thickenings are called cervical and lumbar / lumbosacral /. In uterine development, these thickenings are not expressed, the cervical thickening is at the level of the V-VI cervical segments and the lumbosacral thickening in the region of the III-IV lumbar segments. Morphological boundaries between segments of the spinal cord do not exist, so the division into segments is functional.
31 pairs of spinal nerves depart from the spinal cord: 8 pairs of cervical, 12 pairs of thoracic, 5 pairs of lumbar, 5 pairs of sacral and a pair of coccygeal.
The spinal cord is made up of nerve cells and fibers gray matter, which has the shape of the letter H or a butterfly on a cross section. On the periphery of the gray matter is white matter, formed nerve fibers. At the center of the gray matter is the central canal, which contains cerebrospinal fluid. The upper end of the canal communicates with the IV ventricle, and the lower end forms the terminal ventricle. In the gray matter, the anterior, lateral and posterior columns are distinguished, and in the transverse section they are, respectively, the anterior, lateral and posterior horns. Motor neurons are located in the anterior horns, sensory neurons and in the lateral - neurons that form the centers of the sympathetic nervous system.
The human spinal cord contains about 13 neurons, of which 3% are motor neurons, and 97% are intercalary. The function of the spinal cord is that it serves as a coordinating center for simple spinal reflexes /knee reflex/ and autonomic reflexes /contraction Bladder/, and also provides a connection between spinal nerves and the brain.
The spinal cord has two functions: reflex and conduction.
In a newborn, the spinal cord is 14 cm long, by two years - 20 cm, by 10 years - 29 cm. The mass of the spinal cord in a newborn is 5.5 grams, by two years - 13 grams, by 7 years - 19 gr. In a newborn, two thickenings are well expressed, and the central canal is wider than in an adult. In the first two years, there is a change in the lumen of the central canal. The volume of white matter increases faster than the volume of gray matter.
Brain.
The brain consists of: oblong, posterior, middle, intermediate and telencephalon. The hindbrain is divided into the pons and the cerebellum.
The brain is in the cavity cerebral skull. It has a convex upper lateral surface and bottom surface- flattened - the base of the brain
The mass of the brain of an adult is from 1100 to 2000 grams, from 20 to 60 years, the mass and volume remain maximum and constant, after 60 years it slightly decreases.
The brain consists of bodies of neurons, nerve tracts and blood vessels. The brain is made up of 3 parts: hemispheres big brain, cerebellum and brain stem.
The large brain consists of two hemispheres - the right and left, which are connected to each other by a thick commissure / commissure / - the corpus callosum. Right and left hemisphere divided by a longitudinal fissure
The hemispheres have superior lateral, medial, and inferior surfaces.
The dorsal and lateral surface of the cerebral cortex is usually divided into four lobes, which are named after the corresponding bones of the skull: frontal, parietal, occipital, temporal
Each hemisphere is divided into lobes - frontal, parietal, occipital, temporal, insular.
The hemispheres are made up of gray and white matter. The layer of gray matter is called the cerebral cortex.
The brain develops from an enlarged part of the brain tube back department turns into dorsal from the forebrain.
In a newborn, the mass of the brain weighs 370 - 400 grams. During the first year of life, it doubles, and by the age of 6 it increases 3 times. Then there is a slow weight gain, ending at 20-29 years of age.
The brain is surrounded by three membranes:
1. External - solid.
2. Medium - cobweb.
3. Internal - soft / vascular /.
The medulla oblongata is located between the hindbrain and the spinal cord. The length of the medulla oblongata in an adult is 25 mm. It has the shape of a truncated cone or bulb.
Functions of the medulla oblongata:
Reflex functions
Cerebellum - located under the occipital lobes of the cerebral hemisphere and lies in cranial fossa. The maximum width is 11.5 cm, length is 3-4 cm. The cerebellum accounts for about 11% of the weight of the brain. In the cerebellum, there are: hemispheres, and between them - the cerebellar vermis.
midbrain unlike other parts of the brain, it is less complex. It has a roof and legs. The cavity of the midbrain is the aqueduct of the brain.
diencephalon in the process of embryogenesis develops from the anterior cerebral bladder. Forms the walls of the third cerebral ventricle. The diencephalon is located under the corpus callosum and consists of the thalamus, epithalamus, metathalamus, and hypothalamus.
The cerebral cortex is phylogenetically the youngest and at the same time complex department brain intended
for processing sensory information, forming behavioral
body reactions.
