At what level does the spinal cord end. Anatomical and physiological features of the spinal cord

Date: 19.07.2019

The spinal cord is an essential part of the nervous system, located inside the spinal column. Anatomically upper end spinal cord connected to the brain, providing its peripheral sensitivity, and at the other end there is a spinal cone, which marks the end of this structure.

The spinal cord is located in the spinal canal, which reliably protects it from external damage, and in addition, allows for a normal stable blood supply to all spinal cord tissues along its entire length.

Anatomical structure

The spinal cord is perhaps the most ancient nervous system inherent in all vertebrates. The anatomy and physiology of the spinal cord make it possible not only to provide the innervation of the whole body, but also the stability and protection of this element of the nervous system. In humans, the spine has a lot of features that distinguish it from all other vertebrate creatures living on the planet, which is largely associated with the processes of evolution and the acquisition of the ability to walk upright.

In adult males, the spinal cord is about 45 cm long, while in females the spine is 41 cm on average.The average mass of the spinal cord in an adult varies from 34 to 38 g, which is about 2% of the total mass of the brain ...

The anatomy and physiology of the spinal cord are different complex structure therefore any damage has systemic consequences. The anatomy of the spinal cord includes a significant number of elements that ensure the function of this nerve formation. It should be noted that, despite the fact that the brain and spinal cord are conditionally different elements of the human nervous system, it should still be noted that the border between the spinal cord and the brain, passing at the level of the pyramidal fibers, is very conditional. In fact, the spinal cord and the brain are integral structures, so it is very difficult to consider them separately.

The spinal cord has a hollow canal inside, which is commonly called the central canal. The space that exists between the membranes of the spinal cord, between the white and gray matter filled with cerebrospinal fluid, which during medical practice known as cerebrospinal fluid. Structurally, a section of the central nervous system has the following parts and structure:

white matter;
Gray matter;
back spine;
nerve fibers;
anterior spine;
ganglion.

Considering the anatomical features of the spinal cord, it is necessary to note a rather powerful defense system, which does not end at the level of the spine. The spinal cord has its own defense, consisting of 3 membranes at once, which, although it looks vulnerable, still ensures the preservation of not only the entire structure from mechanical damage but also various pathogenic organisms. The central nervous system is covered with 3 membranes, which have the following names:

soft shell;
arachnoid;
hard shell.

The space between the uppermost hard shell and the hard bone-cartilaginous structures of the spine that surrounds the spinal canal is filled with blood vessels and adipose tissue, which helps to maintain the integrity of neurons during movement, falls and other potentially dangerous situations.

In cross-section, the sections taken in different parts column, allow you to identify the heterogeneity of the spinal cord in different parts of the spine. It is worth noting that, considering the anatomical features, one can immediately note the presence of a certain segmentation, comparable to the structure of the vertebrae. The anatomy of the human spinal cord has the same division into segments, like the entire spine. The following anatomical parts are distinguished:

cervical;
chest;
lumbar;
sacral;
coccygeal.

The correlation of one or another part of the spine with one or another segment of the spinal cord does not always depend on the location of the segment. The principle of determining a particular segment to a particular part is the presence of radicular branches in one or another part of the spine.

In the cervical part, the human spinal cord has 8 segments, in the thoracic part - 12, the lumbar and sacral parts have 5 segments each, while the coccygeal - 1 segment. Since the tailbone is a rudimentary tail, anatomical abnormalities in this area are not uncommon, in which the spinal cord in this part is not in one segment, but in three. In these cases, a person has a larger number of dorsal roots.

If there are no anatomical anomalies of development, in an adult, exactly 62 roots leave the spinal cord, with 31 on one side of the spinal column and 31 on the other. The spinal cord has a non-uniform thickness along its entire length.

In addition to the natural thickening in the area of the junction of the brain with the spinal cord, and in addition to the natural decrease in the thickness in the coccyx area, thickenings in the area cervical and the lumbosacral joint.

Basic physiological functions

Each of the elements of the spinal cord performs its own physiological functions and has its own anatomical features. Consideration of the physiological features of the interaction of different elements is best started with cerebrospinal fluid.

Cerebrospinal fluid, known as cerebrospinal fluid, has a number of critical functions that support the vital functions of all parts of the spinal cord. CSF performs the following physiological functions:

maintaining somatic pressure;
maintaining salt balance;
protection of spinal cord neurons from traumatic injury;
creation of a nutrient medium.

The spinal nerves are directly connected to the nerve endings that provide innervation to all tissues of the body. Reflex and conduction functions are monitored different kinds neurons that make up the spinal cord. Since the neuronal organization is extremely complex, a classification of the physiological functions of certain classes of nerve fibers was drawn up. The classification is carried out according to the following criteria:

In the department of the nervous system. This class includes the neurons of the autonomic and somatic nervous systems.
By appointment. All neurons located in the spinal cord are subdivided into intercalary, associative, afferent efferent.
By the way of influence. All neurons are subdivided into excitatory and inhibitory.

When considering the physiological characteristics of neurons, one has to admit that each class of neurons is in close interaction with the rest of the classes. So, as already noted, there are 4 main types of neurons according to their purpose, each of which performs its function in the general system and interacts with other types of neurons.

Inserted. Neurons belonging to this class are intermediate and serve to ensure interaction between afferent and efferent neurons, as well as with the brain stem, through which impulses are transmitted to the human brain.
Associative. Neurons belonging to this type are an independent operating apparatus that provides interaction between different segments within the existing ones. Thus, associative neurons control such parameters as muscle tone, coordination of body position, movements, etc.
Efferent. Neurons belonging to the efferent class perform somatic functions, since their main task is to innervate the main organs working group, that is, skeletal muscle.
Afferent. Neurons belonging to this group perform somatic functions, but at the same time provide innervation to tendons, skin receptors, and in addition, provide sympathetic interaction in efferent and intercalary neurons. Most of the afferent neurons are located in the ganglia of the spinal nerves.

Different types of neurons form whole pathways that serve to maintain the connection of the human spinal cord and brain with all tissues of the body.

In order to understand how exactly the transmission of impulses occurs, one should consider the anatomical and physiological features basic elements, that is, gray and white matter.

Gray matter

Gray matter is the most functional. When the column is cut, it can be seen that the gray matter is located inside the white and looks like a butterfly. In the very center of the gray matter, there is a central channel, through which the circulation of cerebrospinal fluid is observed, which ensures its nutrition and maintains balance. Upon detailed examination, 3 main sections can be distinguished, each of which has its own special neurons that provide certain functions:

Front area. This area contains motor neurons.
Back area. The posterior region of the gray matter is a horn-shaped branch that has sensory neurons.
Side area. This part of the gray matter is called the lateral horns, since it is this part that branches strongly and gives rise to the spinal roots. The neurons of the lateral horns give rise to the autonomic nervous system, and also provide the innervation of all internal organs and chest, abdominal cavity and pelvic organs.

The anterior and posterior regions do not have clear edges and literally merge with each other, forming a complex spinal nerve.

Among other things, the roots extending from the gray matter are components of the anterior roots, the other component of which is the white matter and other nerve fibers.

White matter

The white matter literally envelops the gray matter. Weight white matter about 12 times the mass of gray matter. The grooves in the spinal cord serve to divide the white matter symmetrically into 3 cords. Each of the cords provides its own physiological functions in the structure of the spinal cord and has its own anatomical features. The white matter ropes are named as follows:

Posterior cord of white matter.
Anterior cord of white matter.
Lateral cord of white matter.

Each of these cords includes a combination of nerve fibers that form bundles and paths necessary for the regulation and transmission of certain nerve impulses.

The anterior cord of the white matter includes the following pathways:

anterior cortical-spinal (pyramidal) path;
reticular-spinal path;
anterior spinothalamic pathway;
tegmental-spinal path;
posterior longitudinal bundle;
the vestibular spinal path.

The posterior cord of the white matter includes the following pathways:

medial spinal path;
wedge-shaped bundle;
thin bunch.

The lateral cord of the white matter includes the following pathways:

red-nuclear-spinal path;
lateral cortical-spinal (pyramidal) path;
posterior spinal cord tract;
anterior spinal cord path;
lateral dorsal thalamic pathway.

There are other ways of conducting nerve impulses of different directions, but at present, not all atomic and physiological features of the spinal cord have been studied well enough, since this system is no less complex than the human brain.

Features of blood supply

The spinal cord is the most important part of the nervous system, therefore this organ has a very powerful and branched blood supply system, which provides it with all nutrients and oxygen. provided by the following large blood vessels:

vertebral artery, originating in the subclavian artery;
a branch of the deep cervical artery;
lateral sacral arteries;
intercostal lumbar artery;
anterior spinal artery;
posterior spinal arteries (2 pcs.).

In addition, the spinal cord literally envelops a network of small veins and capillaries that facilitate continuous feeding of neurons. When you cut any, you can immediately notice the presence of a branched network of small and large blood vessels. Nerve roots have accompanying blood arterial veins, and each root has its own blood branch.

The blood supply to the branches of the blood vessels originates from the large arteries that supply the column with nutrition. Among other things, the blood vessels that feed the neurons also feed the elements of the spinal column, thus, all these structures are connected by a single circulatory system.

The human nervous system is characterized by a complex organization - the structure and segments of the spinal cord clearly show coherence in the work of the organ and its management of vital processes.

Features of anatomy

The structure and anatomy of this unique object of the human body has its own characteristics. The external structure of the spinal cord looks like it resembles an elongated cord, and the cross section of the spinal cord reaches in various places from one to one and a half centimeters. It is carefully located in the cavity formed by the bodies and processes of the vertebrae. The spine protects him from damage, and the bone density provides him with a comfortable position. The ratio of the segments of the spinal cord and parts of the spinal column does not correspond to each other, since the length of the cord is shorter than the vertebral column. A perfect match at the level of the spinal column is observed only in children aged 5-6 years. Skeletopia of the segments and the spine column is shown on diagrams in medical publications.

Spinal cord

The strand takes its origin in the region of the occipital foramen of the cranium. In fact, the spinal cord is a part of the brain that goes into the spine and ends there, so the connection between the brain and the spinal cord is obvious. The spinal cord, like the brain, is an integral part of the unified human nervous system. The end of the strand can be noted at the level of the third section, namely, its first lumbar vertebrae. In this part, the protected cord becomes thinner, forming the cerebral cone of the spinal cord. The terminal thread, about 8 cm in size, can end below and grow together with the second vertebra in the coccygeal region.

The length of the spinal cord in newborns is relatively longer than in a person of mature age. A baby is born with a cord length that allows it to end at the level of the third vertebra in the lumbar spine. However, during growth, at some moments it is the nervous system that lags behind and the spinal cord is visually shortened in comparison with the growing vertebrae. The growth of the cord continues until about twenty years, after which its final size in length is 43-45 cm. The length of the spinal cord in women is a couple of centimeters shorter than in men. During this time, the weight increases eight times from the original indicators.

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Segmentation

The human spinal cord is divided into several sections with segments. The number of segments is 32. Each segment controls certain functions of innervation.

The structure of the spinal cord includes five sections. The topography of the spinal cord is presented as follows:

Spine structure

the cervical spine has 8 segments;
chest includes 12 segments;
the subsequent sections (lumbar and sacral) consist of 5 segments;
there are only 2 segments in the coccygeal region.

The diameter of the spinal cord varies from place to place. In two sections there is a thickening of the spinal cord that occurs in the first couple of years of a child's development due to an increased load on them. Cervical spinal cord thickening and lumbar quenching are responsible for locomotor activity and the work of the limbs.

Internal structure

The internal structure of the spinal cord is not the same. From beginning to end, the strand is covered with shells of their three layers. The inner shell is called the soft shell. In its thickness there is a complex of blood vessels with arteries and veins. They provide oxygen and nutrient supply.

Behind the soft membrane is the arachnoid or arachnoid layer, which contains fluid. It is called liquor. For the analysis of cerebrospinal fluid, biological material is taken from this shell.

The third shell, located along the outer edge, is called hard, and protects the inner shells. It reaches the intervertebral foramen. The strand itself is attached to the vertebrae with a series of ligaments. The central canal in the spinal cord, which runs through its entire length, is also filled with fluid.

Furrows and crevices

If you look at the structure of the human spinal cord from the outside, you will notice that it is riddled with cracks and grooves. They divide it into two halves. The largest slits are the anterior median and posterior slits. Each of the halves of the spinal cord has grooves dividing it into spinal cord cords, or spinal cord columns. There are three pairs of cords in total:

Spinal cord

posterior cord;
anterior cord;
lateral cord.

It is the fibers in the cords that are the conductors of nerve impulses. The spinal cord is also responsible for motor functions and sensory sensations. With the appearance of pathologies, certain functions of the body can fail, therefore, diagnostics and the condition of the spinal column are important for treatment.

Segmental principle

It has already been briefly mentioned that segments of the spinal cord are involved in the transmission of nerve impulses to tissues and organs. What does the spinal cord look like in segments and what is each of them responsible for?

Spinal cord segment structure

The structure of the spinal cord segment is such that it contains pairs of roots that are connected to other organs through nerves. The roots leave the spinal canal and form nerves that branch out to various tissues and organs. The anterior and posterior roots of the spinal cord are conductors of information. The anterior roots of the spinal cord are formed by axons in the front, they conduct motor information, and their main function is to stimulate muscle contraction.

Sensitivity is provided by the posterior roots, which transmit information from the stimulus through the activation of receptors and carry it to the posterior roots. At the junction of the anterior and posterior roots, the spinal ganglion is located - an accumulation of neurons located under the protective sheath.

The roots go out into the holes between the vertebrae, so some of them pass exactly at the level, and the other part - at an angle. For example, in the cervical spine, such roots are located horizontally, and in the thoracic spine, along an oblique line. The rest of the sections force the roots to bend almost vertically downward. Some of the roots from these sections go so tightly to each other that in the photo the resulting bundle is called the cauda equina in the spinal cord.

Each segment is responsible for its own zone of innervation. The innervation zone includes internal organs, bones, muscles and skin. Knowing the zone of innervation, it is possible to clearly determine which segment of the nerve is responsible for it, to assume the pathology of this area. The segmental principle, showing where the cause of the pathology is located, helps both in the diagnosis and in the treatment of diseases. Physicians can take tests from the required segment in order to then assess the patient's health. Also, by treating one or another part of the pillar, you can cure a person from a number of pathologies.

Sectional structure

If you make a cross-section of the tie and look in the section, you can see the heterogeneity of its structure. The cross section of the spinal cord shows that the spinal cord is composed of substances of two colors - white and gray. The gray color is formed by a cluster of neurons, and the white color is a cluster of neuronal processes.

Externally, the groups of neurons are arranged in such a way that the shape of the slice image resembles the shape of a butterfly. The convex parts are clearly visible here - the anterior and posterior horns of the spinal cord. A photograph of some of the segments, taken by medical researchers, also reveals the lateral horns. The anterior horns contain the nuclei of the spinal cord as well as the largest neurons in the spinal cord. They are responsible for movement, and the hind horns perceive sensitive impulses. The lateral horns of the spinal cord are the conductors of the autonomic nervous system. Each segment is clearly responsible for one or another organ function.

For example, in the last cervical and first thoracic segments, there is a complex of neurons responsible for the innervation of the eye pupils. The third and subsequent cervical segments conduct impulses into the diaphragm, and the first five thoracic segments regulate the work of the heart. The neurons of the spinal cord from the second to the fifth segment in the sacral region regulate the work of the bladder, the same set of segments innervates the rectum. If people damage these segments in the event of injury, hemorrhage, inflammation, then problems with defecation and urination may begin. The diagram of innervation by segments shows how tightly it covers all systems of human organs and controls their activity. Having such information is very important for the doctor.

The spinal cord performs the most important functions for the body - reflex and conductive. The activities of all structures depend on the well-coordinated work of this body. The physiology of the spinal cord is designed in such a way that a person has a number of motor reflexes, for example, the elbow and knee reflexes. Also, the neurons of the brain and spinal cord coordinate the complex motor activity of the body. Like the spinal cord, the brain participates in the processing of signals from the outside through impulses. The importance of the spinal cord can hardly be overestimated, because it is also a conductor of information obtained by nerve impulses.

medulla spinalis) has, in comparison with the brain, a relatively simple structural principle and a pronounced segmental organization. It provides connections between the brain and the periphery and performs segmental reflex activity.

The spinal cord lies in the vertebral canal from the upper edge of the I cervical vertebra to the I or the upper edge of the II lumbar vertebra, repeating to a certain extent the direction of the curvature of the corresponding parts of the spinal column. In a 3-month-old fetus, it ends at level V of the lumbar vertebra, in a newborn, at level III of the lumbar vertebra.

The spinal cord, without a sharp border, passes into the medulla oblongata at the exit site of the first cervical spinal nerve. Skeletotopically, this border runs at the level between the lower edge of the foramen magnum and the upper edge of the 1st cervical vertebra.

At the bottom, the spinal cord passes into the cerebral cone (lat. conus medullaris), continuing into the terminal (spinal) thread (lat. filum terminale (spinale)), which has a diameter of up to 1 mm and is a reduced part of the lower spinal cord. The terminal thread, with the exception of its upper sections, where there are elements of nervous tissue, is a connective tissue formation. Together with the dura mater, it penetrates into the sacral canal and attaches at its end. That part of the terminal thread, which is located in the cavity of the dura mater and is not fused with it, is called the inner terminal thread (lat. filum terminale internum), the rest of it, fused with the dura mater, is the outer terminal thread (lat. filum terminale externum). The filum terminus is accompanied by the anterior spinal arteries and veins, as well as one or two coccygeal nerve roots.

The spinal cord does not occupy the entire cavity of the spinal canal: between the canal walls and the brain, there remains a space filled with adipose tissue, blood vessels, membranes of the brain and cerebrospinal fluid.

The length of the spinal cord in an adult ranges from 40 to 45 cm, width - from 1.0 to 1.5 cm, and the average weight is 35 g.

There are 4 surfaces of the spinal cord:

The spinal cord does not have the same diameter throughout. Its thickness increases slightly from bottom to top. Largest size in diameter, it is noted in two fusiform thickenings: in the upper section - this is a cervical thickening (lat. intumescentia cervicalis), corresponding to the exit of the spinal nerves going to the upper limbs, and in the lower section - this is a lumbosacral thickening (lat. intumescentia lumbosacralis), - the place where the nerves exit to the lower extremities. In the area of the cervical thickening, the transverse size of the spinal cord reaches 1.3-1.5 cm, in the middle of the thoracic part - 1 cm, in the region of the lumbosacral thickening - 1.2 cm; the anteroposterior size in the area of thickenings reaches 0.9 cm, in the chest part - 0.8 cm.

The cervical thickening begins at the level of the III-IV cervical vertebra, reaches the II thoracic vertebra, reaching the greatest width at the level of the V-VI cervical vertebra. The lumbosacral thickening extends from the level of the IX-X thoracic vertebra to the I lumbar, its greatest width corresponds to the level of the XII thoracic vertebra (at the height of the 3rd lumbar spinal nerve).

The shape of the transverse sections of the spinal cord at different levels is different: in the upper part, the cut has the shape of an oval, in the middle it is rounded, and in the lower part it approaches square.

On the anterior surface of the spinal cord, along its entire length, lies the anterior median fissure (lat. fissura mediana ventralis), into which the fold of the pia mater is embedded - the intermediate cervical septum (lat. septum cervicale intermedium). This gap is less deep at the upper and lower ends of the spinal cord and is most pronounced in its middle sections.

On the back of the brain there is a very narrow posterior median groove (lat. sulcus medianus dorsalis), into which the glial tissue plate penetrates - the posterior median septum (lat. septum medianum dorsale). The slit and groove divide the spinal cord into two halves - right and left. Both halves are connected by a narrow bridge of the brain tissue, in the middle of which is the central canal (lat. canalis centralis) of the spinal cord.

On the lateral surface of each half of the spinal cord, there are two shallow grooves. Anterolateral groove (lat. sulcus ventrolateralis), located outward from the anterior median fissure, more distant from it in the upper and middle parts of the spinal cord than in its lower part. The posterolateral groove (lat. sulcus dorsoolateralis), lies laterally from the posterior median sulcus. Both grooves run the entire length of the spinal cord.

In the cervical and partly in the upper thoracic regions, between the posterior median and posterolateral grooves, there is a mildly expressed posterior intermediate groove (lat. sulcus intermedius dorsalis) .

In the fetus and newborn, a rather deep anterior intermediate sulcus is sometimes found, which, following the anterior surface of the upper cervical part of the spinal cord, is located between the anterior median fissure and the anterolateral sulcus.

A characteristic feature of the spinal cord is its segmentation and the correct periodicity of the output of the spinal nerves.

The spinal cord is divided into 5 parts: cervical (lat. pars cervicalis), chest (lat. pars thoracica), lumbar (lat. pars lumbalis), sacral (lat. pars sacralis) and the coccygeal part (lat. pars coccygea). In this case, the assignment of a segment of the spinal cord to one or another part does not depend on its real location, but on which part of the nerves leaving it leave the spinal canal. The cervical part consists of 8 segments, the thoracic - 12, lumbar - 5, sacral - 5, coccygeal - from 1 to 3. Total 31 - 33 segments.

Spinal cord roots

Anterior root filaments (lat. fila radicularia), which are the axons of nerve cells. The anterior root filaments form the anterior (motor) root (lat. radix ventralis). The anterior roots contain centrifugal efferent fibers that conduct motor impulses to the periphery of the body: to striated and smooth muscles, glands, etc.

The posterolateral groove includes the posterior radicular filaments, consisting of cell processes lying in the spinal node. The dorsal root filaments form the dorsal root (lat. radix dorsalis). The dorsal roots contain afferent (centripetal) nerve fibers that conduct sensory impulses from the periphery, i.e. from all tissues and organs of the body, to the central nervous system. On each dorsal root there is a spinal node (lat. ganglion spinale) .

The direction of the roots is not the same: in the cervical region they move off almost horizontally, in the thoracic region they go obliquely downward, in the lumbosacral region they follow straight down.

The anterior and posterior roots of the same level and one side immediately outward from the spinal node are connected, forming a spinal nerve (lat. n. spinalis), which is thus mixed. Each pair of spinal nerves (right and left) corresponds to a specific area - a segment - of the spinal cord.

Therefore, in the spinal cord there are as many segments as there are pairs of spinal nerves.

White and gray matter

On transverse sections of the spinal cord, the location of the white and gray matter is visible. The gray matter occupies the central part and has the shape of a butterfly with spread wings or letters N... The white matter is located around the gray, at the periphery of the spinal cord.

The ratio of gray to white matter in different parts of the spinal cord is different. In the cervical part, especially at the level of the cervical thickening, there is much more gray matter than in the middle areas of the chest, where the amount of white matter is much (about 10-12 times) greater than the mass of gray matter. In the lumbar region, especially at the level of the lumbar thickening, there is more gray matter than white. Towards the sacral part, the amount of gray matter decreases, but the amount of white decreases even more. In the area of the cerebral cone, almost the entire surface of the cross section is made of gray matter, and only along the periphery is a narrow layer of white.

White matter

The white matter of one half of the spinal cord is connected with the white matter of the other half by a very thin white commissure that runs transversely in front of the central canal (lat. commissura alba) .

The grooves of the spinal cord, with the exception of the posterior intermediate groove, delimit the white matter of each half into three cords of the spinal cord (lat. funiculi medullae spinalis). Distinguish:

In the upper half of the thoracic part and in the cervical part of the spinal cord, the posterior intermediate groove divides the posterior cord into two bundles: a thinner medial, so-called thin bundle, lying inside, and a more powerful lateral wedge-shaped bundle. Below, the wedge-shaped bundle is absent. The cords of the spinal cord continue into the initial section of the brain - the medulla oblongata.

As part of the white matter of the spinal cord, there are projection, constituting afferent and efferent pathways, as well as associative fibers. The latter carry out connections between the segments of the spinal cord and form anterior, lateral and posterior bundles of their own (lat. fasciculi proprii ventrales, laterales et dorsales ), which are adjacent to the gray matter of the spinal cord, surrounding it on all sides. These beams include:

Gray matter

The gray matter of the spinal cord (lat. substantia grisea) consists mainly of the bodies of nerve cells with their processes that do not have a myelin sheath. In it, two lateral parts are distinguished, located in both halves of the spinal cord, and the transverse part, connecting them in the form of a narrow bridge, is the central intermediate substance (lat. substantia intermedia centralis ). It continues into the lateral parts, occupying their middle, as a lateral intermediate substance (lat. substantia intermedia lateralis ) .

In the middle sections of the central intermediate substance, there is a very narrow cavity - the central canal (lat. canalis centralis). It stretches throughout the entire spinal cord, passing at the top into the cavity of the IV ventricle. Below, in the area of the cerebral cone, the central canal is widened and its diameter reaches 1 mm on average; this section of the central canal is called the terminal ventricle (lat. ventriculus terminalis) .

Histology

The spinal cord consists of two symmetrical halves, delimited from each other in front by a deep median fissure, and behind by a connective tissue septum. On fresh preparations of the spinal cord, the naked eye can see that its substance is heterogeneous. The inner part of the organ is darker - this is its gray matter (lat. substantia grisea). On the periphery of the spinal cord is a lighter white matter (lat. substantia alba). The gray matter in the cross section of the brain is represented in the form of the letter "H" or a butterfly. The protrusions of the gray matter are called horns. Distinguish between anterior, or ventral, posterior, or dorsal, and lateral, or lateral, horns.

Throughout the spinal cord, the ratio of gray and white matter changes. Gray matter is represented by the smallest number of cells in the thoracic region. The largest is in the lumbar.

Gray matter

The gray matter of the spinal cord consists of neuronal bodies, myelin-free and thin myelin fibers, and neuroglia. The main constituent of the gray matter, which distinguishes it from white, are multipolar neurons.

Cells, similar in size, fine structure and functional significance, lie in the gray matter in groups called nuclei. Among the neurons of the spinal cord, the following types of cells can be distinguished:

radicular cells (lat. neurocytus radiculatus), the axons of which leave the spinal cord as part of its anterior roots
internal cells (lat. neurocytus internus), the processes of which end in synapses within the gray matter of the spinal cord
bundle cells (lat. neurocytus funicularis), the axons of which pass in the white matter as separate bundles of fibers carrying nerve impulses from certain nuclei of the spinal cord to its other segments or to the corresponding parts of the brain, forming pathways.

Individual areas of the gray matter of the spinal cord differ significantly from each other in the composition of neurons, nerve fibers and neuroglia.

In the rear horns they distinguish spongy layer, gelatinous substance, and pectoral nucleus... Between the posterior and lateral horns, the gray matter protrudes into white in strands, as a result of which a net-like loosening is formed, which is called a net formation.

Spongy layer of the hind horns is characterized by a wide-looped glial skeleton, which contains a large number of small intercalary neurons.

V gelatinous substance glial elements predominate. Nerve cells here are small and their number is insignificant.

The hind horns are rich in diffusely located intercalated cells... These are small multipolar associative and commissural cells, the axons of which end within the gray matter of the spinal cord of the same side (associative cells) or the opposite side (commissural cells).

Neurons of the spongy zone, gelatinous substance and intercalary cells provide communication between the sensitive cells of the spinal ganglia and the motor cells of the anterior horns, closing the local reflex arcs. In the middle of the rear horn is located own nucleus of the dorsal horn... It consists of intercalary neurons, the axons of which pass through the anterior white commissure to the opposite side of the spinal cord into the lateral cord of the white matter, where they are part of the ventral spinal cord and dorsal thalamic pathways and are sent to the cerebellum and thalamus.

Thoracic nucleus(Clarke's nucleus) consists of large interneurons with highly branched dendrites. Their axons go out into the lateral cord of the white matter of the same side and, as part of the posterior spinal-cerebellar tract (Fleksig's tract), rise to the cerebellum.

In the intermediate zone, there are medial intermediate nucleus, the axons of the cells of which join the anterior spinal-cerebellar tract (Govers tract) of the same side, and lateral intermediate nucleus located in the lateral horns and is a group of associative cells of the sympathetic reflex arc... The axons of these cells leave the brain along with the somatic motor fibers as part of the anterior roots and separate from them in the form of white connecting branches of the sympathetic trunk.

The anterior horns contain the largest neurons of the spinal cord, which have a body diameter of 100-150 microns and form nuclei of significant volume. This is the same as the neurons of the nuclei of the lateral horns, root cells, since their axons make up the bulk of the fibers of the anterior roots. As part of the mixed spinal nerves, they enter the periphery and form motor endings in the skeletal muscles. Thus, these nuclei represent the somatic motor centers. In the anterior horns, the medial and lateral groups of motor cells are most pronounced. The first innervates the muscles of the trunk and is well developed throughout the spinal cord. The second is located in the region of the cervical and lumbar thickenings and innervates the muscles of the limbs.

There are many scattered bundle neurons in the gray matter of the spinal cord. The axons of these cells emerge into the white matter and immediately divide into longer ascending and shorter descending branches. Together, these fibers form their own, or main, bundles of white matter, directly adjacent to the gray matter. In their course, they give many collaterals, which, like the branches themselves, end in synapses on the motor cells of the anterior horns of 4-5 adjacent segments of the spinal cord.

Rexed gray matter layers

The spinal cord is the part of the central nervous system located in the spinal canal. The conditional boundary between the medulla oblongata and the spinal cord is the place of intersection and discharge of the first cervical root.

The spinal cord, like the brain, is covered with meninges (see).

Anatomy (structure)... Along the length, the spinal cord is divided into 5 sections, or parts: cervical, thoracic, lumbar, sacral and coccygeal. The spinal cord has two thickenings: the cervical, associated with the innervation of the arms, and the lumbar, associated with the innervation of the legs.

Rice. 1. Cross section of the thoracic spinal cord: 1 - posterior median groove; 2 - posterior horn; 3 - lateral horn; 4 - front horn; 5-center channel; 6 - anterior median fissure; 7 - anterior cord; 8 - lateral cord; 9 - posterior cord.

Rice. 2. The location of the spinal cord in the spinal canal (cross section) and the exit of the roots of the spinal nerves: 1 - spinal cord; 2 - back spine; 3 - anterior spine; 4 - spinal cord; 5 - spinal nerve; 6 - vertebral body.

Rice. 3. The layout of the spinal cord in the spinal canal (longitudinal section) and the exit of the roots of the spinal nerves: A - cervical; B - chest; B - lumbar; G - sacral; D - coccygeal.

In the spinal cord, a distinction is made between gray and white matter. Gray matter is a collection of nerve cells to which nerve fibers approach and depart. In cross-section, the gray matter looks like a butterfly. In the center of the gray matter of the spinal cord is the central canal of the spinal cord, poorly visible to the naked eye. In the gray matter, anterior, posterior, and in the thoracic region and lateral horns are distinguished (Fig. 1). The processes of the cells of the spinal nodes, which make up the posterior roots, are suitable for the sensitive cells of the posterior horns; the anterior roots of the spinal cord depart from the motor cells of the anterior horns. The cells of the lateral horns belong to (see) and provide the sympathetic innervation of the internal organs, vessels, glands, and the cell groups of the gray matter of the sacral region - the parasympathetic innervation of the pelvic organs. The processes of the cells of the lateral horns are part of the anterior roots.

The roots of the spinal cord from the spinal canal exit through the intervertebral foramen of their vertebrae, heading downward to a more or less significant distance. They make a particularly long way in the lower part of the vertebral drip, forming a cauda equina (lumbar, sacral and coccygeal roots). The anterior and posterior roots come close to each other, forming the spinal nerve (Fig. 2). A segment of the spinal cord with two pairs of roots is called a spinal cord segment. In total, 31 pairs of anterior (motor, ending in the muscles) and 31 pairs of sensitive (coming from the spinal nodes) roots depart from the spinal cord. There are eight cervical, twelve thoracic, five lumbar, five sacral and one coccygeal segments. The spinal cord ends at level I - II of the lumbar vertebra; therefore, the level of the spinal cord segments does not correspond to the vertebrae of the same name (Fig. 3).

The white matter is located on the periphery of the spinal cord, consists of nerve fibers collected in bundles - these are the descending and ascending pathways; distinguish between anterior, posterior and lateral cords.

The spinal cord is relatively longer than that of an adult, and reaches the third lumbar vertebra. In the future, the spinal cord lags slightly behind growth, and therefore its lower end moves upward. The spinal canal of a newborn is large in relation to the spinal cord, but by the age of 5-6 years, the ratio of the spinal cord to the spinal canal becomes the same as in an adult. The growth of the spinal cord continues until about 20 years of age, and the weight of the spinal cord increases by about 8 times compared to the neonatal period.

The blood supply to the spinal cord is carried out by the anterior and posterior spinal arteries and spinal branches extending from the segmental branches of the descending aorta (intercostal and lumbar arteries).

Rice. 1-6. Cross sections of the spinal cord at various levels (semi-schematic). Rice. 1. Transition of the 1st cervical segment to the medulla oblongata. Rice. 2. I cervical segment. Rice. 3. VII cervical segment. Rice. 4. X thoracic segment. Rice. 5. III lumbar segment. Rice. 6. I sacral segment.

Ascending (blue) and descending (red) paths and their further connections: 1 - tractus corticospinalis ant .; 2 and 3 - tractus corticospinalis lat. (fibers after decussatio pyramidum); 4 - nucleus fasciculi gracilis (Gaul); 5, 6 and 8 - motor nuclei of the cranial nerves; 7 - lemniscus medlalis; 9 - tractus corticospinalis; 10 - tractus corticonuclearis; 11 - capsula interna; 12 and 19 - pyramidal cells of the lower sections of the precentral gyrus; 13 - nucleus lentiformis; 14 - fasciculus thalamocorticalis; 15 - corpus callosum; 16 - nucleus caudatus; 17 - ventrlculus tertius; 18 - nucleus ventralls thalami; 20 - nucleus lat. thalami; 21 - crossed fibers of tractus corticonuclearis; 22 - tractus nucleothalamlcus; 23 - tractus bulbothalamicus; 24 - nodes of the brain stem; 25 - sensitive peripheral fibers of the trunk nodes; 26 - sensitive cores of the trunk; 27 - tractus bulbocerebellaris; 28 - nucleus fasciculi cuneati; 29 - fasciculus cuneatus; 30 - ganglion splnale; 31 - peripheral sensory fibers of the spinal cord; 32 - fasciculus gracilis; 33 - tractus spinothalamicus lat .; 34 - cells of the posterior horn of the spinal cord; 35 - tractus spinothalamicus lat., Its cross in the white commissure of the spinal cord.

Spinal cord (medulla spinalis) by outward appearance is a long, cylindrical, flattened from front to back strand. In this regard, the transverse diameter of the spinal cord is larger than the anteroposterior one.

The spinal cord is located in the vertebral canal and passes into the brain at the level of the lower edge of the foramen magnum. In this place, the roots emerge from the spinal cord (its upper border), forming the right and left spinal nerves. The lower border of the spinal cord corresponds to the level I-II of the lumbar vertebrae. Below this level, the apex of the cerebral cone of the spinal cord continues into a thin terminal (terminal) thread. Filum terminale in their upper divisions still contains nervous tissue and is a rudiment of the caudal end of the spinal cord. This part of the filum terminale, called the internal one, is surrounded by the roots of the lumbar and sacral spinal nerves and together with them is located in a blindly ending sac formed by the hard membrane of the spinal cord. In an adult, the inner part of the filum terminale is about 15 cm long. Below level II of the sacral vertebra, the filum terminale is a connective tissue formation, which is a continuation of all three membranes of the spinal cord and is called the outer part of the filum terminale. The length of this part is about 8 cm. It ends at the level of the body of the II coccygeal vertebra, growing together with its periosteum.

The length of the spinal cord in an adult is on average 43 cm (in men - 45 cm, in women - 41-42 cm), weight - about 34-38 g, which is about 2% of the mass of the brain.

In the cervical and lumbosacral spinal cord, two noticeable thickenings are found - the cervical thickening (intumescentia cervicalis) and the lumbosacral thickening (intumescentia lumbosacralis). The formation of thickenings is explained by the fact that from the cervical and lumbosacral spinal cord, the upper and lower limbs... In these sections, the spinal cord contains more than other sections, the number of nerve cells and fibers. In the lower parts of the spinal cord gradually narrows and forms a cerebral cone (conus medullaris).

On the anterior surface of the spinal cord, the anterior median fissure (fissura medidna anterior) is visible, which protrudes into the tissue of the spinal cord deeper than the posterior median sulcus (sulcus medianus posterior). They are the boundaries dividing the spinal cord into two symmetrical halves. In the depths of the posterior median sulcus there is a glial penetrating almost into the entire thickness of the white matter. posterior median septum(septum medianum posterius). This septum reaches the posterior surface of the gray matter of the spinal cord.

On the anterior surface of the spinal cord, on each side of the anterior slit, there is an anterior lateral sulcus (sulcus anterolateralis). It is the exit point from the spinal cord of the anterior (motor) roots of the spinal nerves and the border on the surface of the spinal cord between the anterior and lateral cords. On the posterior surface on each half of the spinal cord there is a posterior lateral groove (sulcus posterolateralis) - the place where the posterior sensory roots of the spinal nerves enter the spinal cord. This groove serves as the border between the lateral and posterior cords.

The anterior root (radix anterior) consists of the processes of motor (motor) nerve cells located in the anterior horn of the gray matter of the spinal cord. The posterior root (radix posterior) is sensitive, represented by a set of central processes of pseudo-unipolar cells penetrating into the spinal cord, whose bodies form a spinal ganglion (ganglion spinale), which lies in the spinal canal at the junction of the posterior root with the anterior one. Throughout the spinal cord, 31 - 33 pairs of roots depart from each side of it. The anterior and posterior roots at the inner edge of the intervertebral foramen approach, merge with each other and form the spinal nerve (nervus spinalis).

Thus, 31-33 pairs of spinal nerves are formed from the roots. The part of the spinal cord corresponding to two pairs of roots (two anterior and two posterior) is called a segment. Accordingly, 31-33 pairs of spinal nerves in the spinal cord are divided into 31-33 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1-3 coccygeal segments. Each segment of the spinal cord corresponds to a specific part of the body that receives innervation from this segment. Segments are designated with initial letters indicating the area (part) of the spinal cord, and numbers corresponding to the ordinal number of the segment:

cervical segments (segmenta cervicalia) - СI-CVIII;
thoracic segments (segmenta thoracica) - ThI-ThXII;
lumbar segments (segmenta lumbalia) - LI-LV;
sacral segments (segmenta sacralia) - SI-SV;
coccygeal segments (segmenta coccygea) - CoI-CoIII.

It is very important for the doctor to know the topographic relationship of the spinal cord segments with the spinal column (skeletotopy of the segments). The length of the spinal cord is significantly less than the length of the spinal column. Therefore, the serial number of any segment of the spinal cord and the level of its position, starting from the lower cervical spine, do not correspond to the serial number of the vertebra. The positions of the segments in relation to the vertebrae can be determined as follows. The upper cervical segments are located at the level corresponding to their ordinal number of the vertebral bodies. The upper thoracic segments lie one vertebra higher than the bodies of the corresponding vertebrae. In the middle thoracic region, this difference between the corresponding segment of the spinal cord increases by 2 vertebrae, in the lower thoracic region - by 3. The lumbar segments of the spinal cord lie in the vertebral canal at the level of bodies X and XI of the thoracic vertebrae, the sacral and coccygeal segments - at the level of the XII thoracic and I lumbar vertebrae.

The spinal cord consists of nerve cells and fibers of gray matter, which in cross section has the form of the letter H or a butterfly with spread wings. At the periphery of the gray matter is a white matter formed only by nerve fibers.

In the gray matter of the spinal cord there is a central canal (canalis centralis). It is a remnant of the neural tube cavity and contains spinal fluid, or cerebrospinal fluid. The upper end of the canal communicates with the IV ventricle of the brain, and the lower, slightly expanding, forms a blindly ending small end ventricle (ventriculus terminalis). The walls of the central canal of the spinal cord are lined with ependyma, around which there is a central gelatinous (gray) substance (substantia gelatinosa centralis). Ependyma is a dense layer of epepdymocytes (neuroglial cells) that perform demarcation and support functions. On the surface facing the cavity of the central canal, there are numerous cilia that can facilitate the flow of cerebrospinal fluid in the canal. Inside the brain tissue from ependymocytes, thin long branching processes that perform a supporting function extend. In an adult, the central canal grows in various parts of the spinal cord, and sometimes throughout the entire length.

The gray matter (substantia gnsea) along the spinal cord to the right and left of the central canal forms symmetrical gray columns (columnae griseae). Anterior and posterior to the central canal of the spinal cord, these pillars are connected to each other by thin plates of gray matter, called anterior and posterior gray adhesions.

In each column of gray matter, its front part is distinguished - the front post (columna ventralis, s. Anterior), and the back part - the back post (columna dorsalis, s. Posterior). At the level of the lower cervical, all thoracic and two upper lumbar segments (from CVII to LI-LII) of the spinal cord, the gray matter on each side forms a lateral protrusion - the lateral column (columna lateralis). In other parts of the spinal cord (above the VIII cervical and below the II lumbar segments), the lateral columns are absent.

On a cross section of the spinal cord, the columns of gray matter on each side look like horns. A wider anterior horn (cornu ventrale, s.anterius) and a narrow posterior horn (cornu dorsale, s. Posterius) are distinguished, corresponding to the anterior and posterior pillars. The lateral horn (cornu laterale) corresponds to the lateral intermediate (autonomous) column of the gray matter of the spinal cord.

In the anterior horns there are large nerve root cells - motor (efferent) neurons. These neurons form 5 nuclei: two lateral (anterior and posterolateral), two medial (anterior and posterior medial) and a central nucleus. The posterior horns of the spinal cord are mainly represented by smaller cells. As part of the posterior, or sensitive, roots are the central processes of pseudo-unipolar cells located in the spinal (sensitive) nodes.

The gray matter of the posterior horns of the spinal cord is heterogeneous. The bulk of the nerve cells of the posterior horn forms its own nucleus. In the white matter, immediately adjacent to the apex of the posterior horn of the gray matter, a border zone is distinguished. Anterior to the latter, there is a spongy zone, which was named in connection with the presence in this section of a large-loop glial network containing nerve cells. A gelatinous substance (substantia galatinosa), consisting of small nerve cells, stands out even more anteriorly. The processes of the nerve cells of the gelatinous substance, the spongy zone and the bundle cells diffusely scattered throughout the gray matter communicate with the neighboring segments. As a rule, these processes end in synapses with neurons located in the anterior horns of their segment, as well as above and below the segments. Heading from the posterior horns of the gray matter to the anterior horns, the processes of these cells are located along the periphery of the gray matter, forming a narrow border of white matter near it. These bundles of nerve fibers are called anterior, lateral and posterior intrinsic bundles(fasciculi proprii ventrales, s. anteriores, laterales et dorsales, s. posteriores). The cells of all nuclei of the dorsal horns of the gray matter are, as a rule, intercalary (intermediate, or conductor) neurons. Neurites emanating from nerve cells, the totality of which makes up the central and thoracic nuclei of the posterior horns, are sent in the white matter of the spinal cord to the brain.

In the medial part of the base of the lateral horn, a well-defined layer of white matter pectoral nucleus(nucleus thoracicus), consisting of large nerve cells. This nucleus stretches along the entire posterior column of gray matter in the form of a cellular cord (Clarke nucleus). The largest diameter of this nucleus is at the level from the XI thoracic segment to the I lumbar segment.

The intermediate zone of the gray matter of the spinal cord is located between the anterior and posterior horns. Here, from the VIII cervical to the II lumbar segment, there is a protrusion of the gray matter - the lateral horn. In the lateral horns, there are the centers of the sympathetic part of the autonomic nervous system in the form of several groups of small nerve cells combined into a lateral intermediate (gray) substance. The axons of these cells pass through the anterior horn and exit the spinal cord as part of the anterior roots.

In the intermediate zone, the central intermediate (gray) substance is located, the processes of cells of which are involved in the formation of the spinal cord. At the level of the cervical segments of the spinal cord between the anterior and posterior horns, and at the level of the upper thoracic segments - between the lateral and posterior horns in the white matter adjacent to the gray, the reticular formation (formatio reticularis) is located. Here it looks like thin bars of gray matter, intersecting in different directions, and consists of nerve cells with big amount processes.

The gray matter of the spinal cord with the posterior and anterior roots of the spinal nerves and their own bundles of white matter bordering the gray matter form own, or segmental, spinal cord apparatus. The main purpose of the segmental apparatus as the phylogenetically oldest part of the spinal cord is to carry out innate reactions (reflexes) in response to stimulation (internal or external). IP Palov defined this type of activity of the segmental apparatus of the spinal cord by the term "unconditioned reflexes".

White matter(substantia alba), as noted, is located outside of the gray matter. The grooves of the spinal cord divide the white matter into three cords symmetrically located on the right and left. The anterior cord (funiculus ventralis anterior) is located between the anterior median fissure and the anterior lateral groove. In the white matter, posterior to the anterior median fissure is distinguished anterior white commissure(commissura alba), which connects the anterior cords of the right and left sides. The posterior cord (funiculus dorsalis, s. Posterior) is located between the posterior median and lateral grooves. The lateral cord (funiculus lateralis) is the area of white matter between the anterior and posterior lateral grooves.

The white matter of the spinal cord is represented by the processes of nerve cells. The totality of these processes in the cords of the spinal cord make up three bundle systems (tracts, or pathways) of the spinal cord:

short bundles of associative fibers, connecting segments of the spinal cord located at different levels;
vdescending(afferent, sensitive) bundles, heading to the centers large brain and the cerebellum;
downstream(efferent, motor) bundles, going from the brain to the cells of the anterior horns of the spinal cord.

The last two bundle systems form a new (in contrast to the phylogenetically older segmental apparatus) supra-segmental conduction apparatus bilateral connections of the spinal cord and brain. In the white matter of the anterior cords, there are mainly descending pathways, in the lateral cords - both ascending and descending pathways, in the posterior cords there are ascending pathways.

The anterior cord includes the following pathways:

1. Anterior cortical-cerebrospinal (pyramidal) motor path, contains processes of giant pyramidal cells (giant pyramidal neurocytes). The bundles of nerve fibers that form this path lie near the anterior median fissure, occupying the anteromedial sections of the anterior cord. The pathway transmits impulses of motor reactions from the cerebral cortex to the anterior horns of the spinal cord.

The reticular-spinal path (tractus reticulospinalis) conducts impulses from the reticular formation of the brain to the motor nuclei of the anterior horns of the spinal cord. It is located in the central part of the anterior cord, lateral to the cortical-spinal path.

The anterior spinal-thalamic path (tractus spinothalamicus ventralis, s. Anterior) is located somewhat anterior to the reticular-spinal path. Conducts impulses of tactile sensitivity (touch and pressure).

The lining-spinal path (tractus tectospinalis) connects the subcortical centers of vision (upper mounds of the roof of the midbrain) and hearing (lower mounds) with the motor nuclei of the anterior horns of the spinal cord. It is located medial to the anterior cortical-spinal (pyramidal) pathway. The bundle of these fibers is directly adjacent to the anterior median fissure. The presence of such a tract makes it possible to carry out reflex protective movements during visual and auditory stimuli.

Between the anterior cortical-spinal (pyramidal) pathway in front and the anterior gray commissure, the posterior longitudinal bundle (fasciculus longitudinalis dorsalis, s. Posterior) is located behind. This bundle extends from the brainstem to the upper segments of the spinal cord. The fibers of the bundle conduct nerve impulses, coordinating, in particular, the work of the muscles of the eyeball and the muscles of the neck.

The vestibular spinal tract (tractus vestibulospinalis) is located on the border of the anterior cord with the lateral one. This pathway is localized in the superficial layers of the white matter of the anterior cord of the spinal cord, directly near its anterior lateral groove. The fibers of this path come from the vestibular nuclei of the VIII pair cranial nerves located in the medulla oblongata to the motor cells of the anterior horns of the spinal cord.

The lateral cord (funiculus lateralis) of the spinal cord contains the following pathways:

1. Posterior spinal cord (tractus spinocerebellaris dorsalis, s. Posterior, Flexig beam) conducts impulses of proprioceptive sensitivity, occupies the posterolateral sections of the lateral cord near the posterior lateral groove. Medially, the bundle of fibers of this pathway is adjacent to the lateral cortical-spinal and lateral spinal-thalamic pathways. In front of the bundles of the posterior spinal cord tract are in contact with the bundles of the same anterior tract.

Anterior spinal cord (tractus spinocerebellaris ventralis, s. Anterior, Govers beam), also carrying proprioceptive impulses to the cerebellum, located in the anterolateral parts of the lateral cord. In front, it is adjacent to the anterior lateral groove of the spinal cord, bordered by the olive-spinal pathway. Medially, the anterior cerebellar tract is adjacent to the lateral spinal thalamic and dorsal tegmental tracts.

The lateral spinal-thalamic tract (tractus spinothalamicus lateralis) is located in the anterior sections of the lateral cord, between the anterior and posterior spinal-cerebellar tracts - from the lateral side, the red-spinal and vestibular spinal tract - from the medial side. Conducts impulses of pain and temperature sensitivity.

The descending systems of the fibers of the lateral cord include the lateral cortical-spinal (pyramidal) and red-nuclear-spinal (extrapyramidal) pathways.

The lateral cortical-spinal (pyramidal) pathway (tractus corticospinalis (pyramidalis) lateralis] conducts motor impulses from the cerebral cortex to the anterior horns of the spinal cord. part of the area of the lateral cord, especially in the upper segments of the spinal cord. In the lower segments, it occupies a smaller and smaller area in sections. In front of this path is the red-nuclear-spinal pathway.
The red-spinal path (tractus rubrospinalis) is located anterior to the lateral cortical-spinal (pyramidal) path. Laterally, in a narrow area, the posterior spinal-cerebellar pathway (its anterior sections) and the lateral spinal-thalamic pathway are adjacent to it. The red-spinal tract is a conductor of impulses for automatic (subconscious) control of movements and tone of skeletal muscles to the anterior horns of the spinal cord.

In the lateral cords of the spinal cord, there are also bundles of nerve fibers that form other pathways (for example, the spinal cord, the olive-spinal cord, etc.).

The posterior cord (funiculus dorsalis, s. Posterior) at the level of the cervical and upper thoracic segments of the spinal cord is divided by the posterior intermediate groove into two bundles. The medial is directly adjacent to the posterior longitudinal groove - this is a thin bundle (fasciculus gracilis, Gaulle beam). Lateral to it is a wedge-shaped bundle (fasciculus cuneatus, Burdakh bundle), medially adjacent to the posterior horn. The thin bundle consists of longer conductors running from the lower torso and lower limbs of the corresponding side to the medulla oblongata. It includes fibers that make up the posterior roots of the 19 lower segments of the spinal cord and occupy its more medial part in the posterior cord. Due to the entry into the 12 upper segments of the spinal cord fibers belonging to the neurons innervating the upper limbs and upper part trunk, a wedge-shaped bundle is formed, which occupies a lateral position in the posterior cord of the spinal cord. Thin and wedge-shaped beams are beams of proprioceptive sensitivity (joint-muscular feeling), which carry information to the cerebral cortex about the position of the body and its parts in space.

In different parts of the spinal cord, the ratio of the areas (on horizontal sections) occupied by gray and white matter is not the same. So, in the lower segments, in particular, in the area of the lumbar thickening, the gray matter on the cut takes up most of it. Changes in the quantitative ratios of gray and white matter are explained by the fact that in the lower parts of the spinal cord the number of fibers of the descending pathways following from the brain is significantly reduced, and the ascending pathways are just beginning to form. The number of fibers forming the ascending pathways gradually increases from the lower segments to the upper ones. On transverse sections of the middle thoracic and upper cervical segments of the spinal cord, the area of the white matter is larger. In the region of the cervical and lumbar enlargements, the area occupied by the gray matter is larger than in other parts of the spinal cord.

The newborn has a length of 14 cm (13.6-14.8 cm). The lower border of the brain is at the level of the lower edge of the II lumbar vertebra. By the age of two, the length of the spinal cord reaches 20 cm, and by the age of 10 it doubles compared to the neonatal period. The thoracic segments of the spinal cord grow most rapidly. The mass of the spinal cord of a newborn is about 5.5 g, in children 1 year old - 10 g. By the age of 3 years, the mass of the spinal cord exceeds 13 g, and at 7 years old it is about 19 g.

The cross-sectional view of the spinal cord is the same as that of an adult. In a newborn, the cervical and lumbar thickening is well pronounced, the central canal is wider than in an adult. The decrease in the lumen of the central canal occurs mainly within 1-2 years, as well as in later age periods when the mass of gray and white matter increases. The volume of white matter increases faster, especially due to its own bundles of the segmental apparatus, which is formed earlier than the pathways connecting the spinal cord with the brain.

Spinal cord blood vessels. Branches from the vertebral artery (from the subclavian artery), the deep cervical artery (from the costal-cervical trunk), as well as from the posterior intercostal lumbar and lateral sacral arteries approach the spinal cord. Adjacent to it are three long longitudinal arterial vessels: the anterior and two posterior spinal arteries.

Anterior spinal artery(unpaired) adjoins the anterior longitudinal slit of the spinal cord. It is formed from two similarly named arteries (branches of the right and left vertebral arteries) in the upper parts of the spinal cord. Posterior spinal artery steam room. Each of the arteries is adjacent to the posterior surface of the spinal cord near the entry into the brain of the posterior roots of the spinal nerves. These 3 arteries continue to the lower end of the spinal cord. The anterior and two posterior spinal arteries are connected to each other on the surface of the spinal cord by numerous anastomoses and with the branches of the intercostal, lumbar and lateral sacral arteries, which penetrate into the spinal canal through the intervertebral foramen and send thin branches into the brain substance.