Bundles of associative fibers of the posterior cord of the spinal cord and lateral cord of the spinal cord. Spinal cord

The spinal cord (medulla spinalis) is located in spinal canal. At level I cervical vertebra and the occipital bone, the spinal cord passes into the medulla oblongata, and extends downward to the level of the I–II lumbar vertebra, where it thins out and turns into a thin filament terminale. Length spinal cord 40–45 cm, thickness 1 cm. The spinal cord has cervical and lumbosacral thickenings, where they are localized nerve cells, providing innervation to the upper and lower extremities.

The spinal cord consists of 31–32 segments. A segment is a section of the spinal cord that contains one pair of spinal roots (anterior and posterior).

The anterior root of the spinal cord contains motor fibers, the posterior root contains sensory fibers. Connecting in the area of ​​the intervertebral node, they form a mixed spinal nerve.

The spinal cord is divided into five parts:

Cervical (8 segments);

Thoracic (12 segments);

Lumbar (5 segments);

Sacral (5 segments);

Coccygeal (1–2 rudimentary segments).

The spinal cord is slightly shorter than the spinal canal. In this regard, in the upper parts of the spinal cord, its roots run horizontally. Then, starting from the thoracic region, they descend somewhat downwards before emerging from the corresponding intervertebral foramina. In the lower sections, the roots go straight down, forming the so-called ponytail.

On the surface of the spinal cord, the anterior median fissure, posterior median sulcus, and symmetrically located anterior and posterior lateral sulci are visible. Between the anterior median fissure and the anterior lateral groove is the anterior cord (funiculus anterior), between the anterior and posterior lateral grooves - the lateral cord (funiculus lateralis), between the posterior lateral groove and the posterior median sulcus - the posterior cord (funiculus posterior), which is in the cervical part The spinal cord is divided by a shallow intermediate groove into a thin fasciculus gracilis. adjacent to the posterior median sulcus, and located outward from it, a wedge-shaped bundle (fasciculus cuneatus). The funiculi contain pathways.

The anterior roots emerge from the anterior lateral sulcus, and the dorsal roots enter the spinal cord in the region of the posterior lateral sulcus.

In a cross-section of the spinal cord, the gray matter located in the central parts of the spinal cord and the white matter lying on its periphery are clearly distinguished. Gray matter in a cross section resembles the shape of a butterfly with open wings or the letter “H”. In the gray matter of the spinal cord, more massive ones are distinguished. wide and short anterior horns and thinner, elongated posterior horns B thoracic regions the lateral horn is revealed, which is also less pronounced in the lumbar and cervical regions spinal cord. The right and left halves of the spinal cord are symmetrical and connected by commissures of gray and white matter. Anterior to the central canal is the anterior gray commissure (comissura grisea anterior), followed by the anterior white commissure (comissura alba anterior); posterior to the central canal, the posterior gray commissure and the posterior white commissure are located successively.

Large motor nerve cells are localized in the anterior horns of the spinal cord, the axons of which go to the anterior roots and innervate the striated muscles of the neck, trunk and limbs. The motor cells of the anterior horns are final authority in the implementation of any motor act, and also have trophic effects on the striated muscles.

Primary sensory cells are located in the spinal (intervertebral) nodes. Such a nerve cell has one process, which, moving away from it, is divided into two branches. One of them goes to the periphery, where it receives irritation from the skin, muscles, tendons or internal organs. and along another branch these impulses are transmitted to the spinal cord. Depending on the type of irritation and, therefore, the pathway along which it is transmitted, the fibers entering the spinal cord through the dorsal root may end on the cells of the dorsal or lateral horns or directly pass into the white matter of the spinal cord. Thus, the cells of the anterior horns carry out motor functions, cells posterior horns– a sensitivity function; spinal autonomic centers are localized in the lateral horns.

The white matter of the spinal cord consists of fibers of the pathways that interconnect both the different levels of the spinal cord with each other, and all overlying parts of the central nervous system with the spinal cord.

The anterior cords of the spinal cord contain mainly pathways involved in motor functions:

1) anterior corticospinal (pyramidal) tract (uncrossed) coming mainly from the motor area of ​​the cerebral cortex and ending on the cells of the anterior horns;

2) vestibulospinal tract, coming from the lateral vestibular nucleus of the same side and ending on the cells of the anterior horns;

3) tegmental-spinal tract, starting in the upper colliculi of the quadrigeminal tract of the opposite side and ending on the cells of the anterior horns;

4) the anterior reticular-spinal tract, coming from the cells of the reticular formation of the brain stem of the same side and ending on the cells of the anterior horn.

In addition, near the gray matter there are fibers that connect different segments of the spinal cord with each other.

The lateral cords of the spinal cord contain both motor and sensory PATHWAYS. Motor pathways include:

Lateral corticospinal (pyramidal) tract (crossed) coming mainly from the motor area of ​​the cerebral cortex and ending on the cells of the anterior horns of the opposite side;

The spinal tract, coming from the red nucleus and ending on the cells of the anterior horns of the opposite side;

Reticular-spinal cord tracts, coming predominantly from the giant cell nucleus of the reticular formation of the opposite side and ending on the cells of the anterior horns;

The olivospinal tract connects the inferior olive to the motor neuron of the anterior horn.

The afferent, ascending conductors include the following paths of the lateral cord:

1) posterior (dorsal uncrossed) spinocerebellar tract, coming from the cells of the dorsal horn and ending in the cortex of the superior cerebellar vermis;

2) anterior (crossed) spinal-cerebellar tract, coming from the cells of the dorsal horns and ending in the cerebellar vermis;

3) the lateral spinothalamic tract, coming from the cells of the dorsal horns and ending in the thalamus.

In addition, the dorsal tegmental tract, spinal reticular tract, spino-olive tract and some other conduction systems pass through the lateral cord.

The afferent thin and cuneate fasciculi are located in the posterior cords of the spinal cord. The fibers included in them begin in the intervertebral nodes and end, respectively, in the nuclei of the thin and wedge-shaped fasciculi, located in the lower part of the medulla oblongata.

Thus, part of the reflex arcs is closed in the spinal cord and the excitation coming through the fibers of the dorsal roots is subjected to a certain analysis and then transmitted to the cells of the anterior horn; the spinal cord transmits impulses to all overlying parts of the central nervous system up to the cerebral cortex.

The reflex can be carried out in the presence of three successive links: 1) the afferent part, which includes receptors and pathways that transmit excitation to nerve centers; 2) the central part of the reflex arc, where the analysis and synthesis of incoming stimuli occurs and a response to them is developed; 3) the effector part of the reflex arc, where the response occurs through skeletal muscles, smooth muscles and glands. The spinal cord is thus one of the first stages at which the analysis and synthesis of stimuli both from internal organs and from receptors of the skin and muscles are carried out.

The spinal cord carries out trophic influences, i.e. damage to the nerve cells of the anterior horns leads to disruption of not only movements, but also the trophism of the corresponding muscles, which leads to their degeneration.

One of important functions The spinal cord regulates the activity of the pelvic organs. Damage to the spinal centers of these organs or the corresponding roots and nerves leads to persistent disturbances in urination and defecation.

These grooves divide each half of the white matter of the spinal cord into three longitudinal cords: anterior - funiculus anterior, lateral - funiculus lateralis And posterior - funiculus posterior. The posterior cord in the cervical and upper thoracic regions is further divided intermediate groove, sulcus intermedius posterior, on two bundles: fasciculus gracilis and fasciculus cuneatu s. Both of these bundles, under the same names, pass at the top to the posterior side of the medulla oblongata.

On both sides, the spinal nerve roots emerge from the spinal cord in two longitudinal rows. Anterior root, radix ventral is s. anterior, exiting through sulcus anterolateralis, consists of neurites of motor (centrifugal, or efferent) neurons, the cell bodies of which lie in the spinal cord, whereas posterior root, radix dorsalis s. posterior included in sulcus posterolateralis, contains processes of sensitive (centripetal, or afferent) neurons, the bodies of which lie in spinal nodes.

At some distance from the spinal cord, the motor root is adjacent to the sensory root and together they form trunk spinal nerve, truncus n. spinalis, which neurologists identify under the name funiculus. When the cord is inflamed (funiculitis), segmental disorders of both the motor and sensory spheres occur; in case of root disease (radiculitis), segmental disorders of one sphere are observed - either sensory or motor, and in case of inflammation of the branches of the nerve (neuritis), the disorders correspond to the zone of distribution of this nerve. The nerve trunk is usually very short, since upon exiting the intervertebral foramen the nerve splits into its main branches.

In the intervertebral foramina near the junction of both roots, the dorsal root has a thickening - spinal ganglion, containing false unipolar nerve cells (afferent neurons) with one process, which is then divided into two branches: one of them, the central one, goes as part of the dorsal root into the spinal cord, the other, peripheral, continues into the spinal nerve. Thus, there are no synapses in the spinal ganglia, since only the cell bodies of afferent neurons lie here. This distinguishes these nodes from the vegetative nodes of the peripheral nervous system, since in the latter intercalary and efferent neurons come into contact. Spinal nodes sacral roots lie inside the sacral canal, and coccygeal root node- inside the sac of the spinal cord.

Due to the fact that the spinal cord is shorter than the spinal canal, the exit site of the nerve roots does not correspond to the level of the intervertebral foramina. To get to the latter, the roots are directed not only to the sides of the brain, but also downwards, and the more vertically they extend from the spinal cord, the more vertical they are. In the lumbar part of the latter nerve roots descend to the corresponding intervertebral foramina in parallel filum terminate, clothing her and conus medullaris a thick bunch, which is called horse tail, cauda equina.

Fresh sections of the brain show that some structures are darker—the gray matter of the nervous system—and other structures are lighter—the white matter of the nervous system. The white matter of the nervous system is formed by myelinated nerve fibers, the gray matter by the unmyelinated parts of the neuron - somas and dendrites.

The white matter of the nervous system is represented by central tracts and peripheral nerves. The function of white matter is to transmit information from receptors to the central nervous system and from one part of the nervous system to another.

In the white matter immediately adjacent to the apex of the posterior horn, a border zone is distinguished.

White matter, substantia alba, as noted, is localized around the gray matter, along the periphery of the spinal cord. The white matter of one half of the spinal cord is connected to the white matter of the other half by a very thin white commissure, commissura alba, running transversely in front of the central canal.

The spinal cord grooves divide the white matter of each half into three cords. The anterior funiculus, funiculus ventralis, is located between the anterior median fissure and the anterior lateral groove. The posterior funiculus, funiculus dorsalis, is located between the posterior median and posterior lateral grooves. The lateral funiculus, funiculus lateralis, is located between the anterolateral and posterolateral grooves.

The white matter of the spinal cord is represented by processes of nerve cells that have myelin sheaths. The combination of these processes in the spinal cord cords form three systems of spinal cord pathways.

1. Own associative bundles (anterior, lateral and posterior), which provide connections between segments at different levels within the spinal cord (belong to the segmental apparatus). As a result, irritation coming from a certain area of ​​the body is transmitted not only to the corresponding segment of the spinal cord, but also affects other segments. As a result, a simple reflex can involve an entire group of muscles in the response, providing complex coordinated movement.

2. Ascending (afferent, sensory) bundles heading to the centers of the brain and cerebellum.

3. Descending (efferent, motor) pathways going from the brain to the cells of the anterior horns of the spinal cord.

The last two systems of bundles form a new young suprasegmental conduction apparatus of bilateral connections of the spinal cord and brain. It arose only when the brain appeared. And as the brain developed, the spinal cord pathways grew outward from the gray matter, forming its white matter. This explains the fact that the white matter surrounds the gray matter on all sides.

In the white matter of the anterior cords there are predominantly descending pathways, in the lateral cords there are both ascending and descending pathways, and in the posterior cords there are ascending pathways.

The anterior funiculus, funiculus ventralis, includes the following pathways:

1. Anterior corticospinal (pyramidal) tract, tractus corticospinalis anterior (pyramidalis) – motor, located near the anterior median fissure, occupies the medial sections of the anterior cord. Transmits impulses of motor reactions from the cerebral cortex to the anterior horns of the spinal cord.

2. The reticular-spinal tract, 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 pyramid path. Participates in the regulation of muscle tone.

3. The tegnospinal tract, tractus tectospinalis, located anterior to the pyramidal tract, connects the subcortical centers of vision (superior colliculi) and hearing (inferior colliculi) with the motor nuclei of the anterior horns of the spinal cord. The presence of this tract allows for reflexive defensive reactions to sudden visual and auditory stimuli.

4. The anterior spinothalamic tract, tractus spinothalamicus anterior, is located slightly anterior to the reticulospinal tract. Conducts impulses of tactile sensitivity (touch and pressure).

5. The vestibulospinal tract, tractus vestibulospinalis, is located in the anterior sections of the anterior cord and extends to the border of the anterior cord with the lateral cord, i.e. to the anterolateral groove. The fibers of this pathway come from the vestibular nuclei of the VIII pair cranial nerves located in the medulla oblongata, to the motor neurons of the anterior horns of the spinal cord. Participates in maintaining body balance.

6. The posterior longitudinal fasciculus, fasciculus longitudinalis dorsalis, stretches from the brain stem to the upper segments of the spinal cord. Conducts nerve impulses that coordinate muscle function eyeball and neck muscles, due to which a friendly rotation of the head and eyes is carried out in the desired direction.

The lateral cord, funiculus lateralis, contains the following pathways:

1. The posterior spinocerebellar tract, tractus spinocerebellaris posterior, (Flexig's bundle), conducts impulses of proprioceptive sensitivity.

2. The anterior spinocerebellar tract, tractus spinocerebellaris anterior, (Gowers bundle), also carrying unconscious proprioceptive impulses to the cerebellum (unconscious coordination of movements).

3. The lateral spinothalamic tract, tractus spinothalamicus lateralis, conducts impulses of pain and temperature sensitivity.

The descending tracts of the lateral funiculus include:

4. The lateral corticospinal tract, tractus corticospinalis lateralis (pyramidalis), conducts motor impulses from the cerebral cortex to the anterior horns of the spinal cord.

5. The red nuclear spinal tract, tractus rubrospinalis, is a conductor of impulses for automatic (subconscious) control of movements and tone of skeletal muscles.

6. Olivospinal tract, tr. olivospinalis,

The posterior cord, funiculus dorsalis, at the level of the cervical and upper thoracic segments of the spinal cord by the posterior intermediate groove, sulcus intermedius dorsalis, is divided into two bundles. The medial one is directly adjacent to the posterior median sulcus - this is a thin fascicle (Gaull's fascicle), fasciculus gracilis. Slightly more lateral is the wedge-shaped bundle, fasciculus cuneatus (Burdach's bundle).

Thin Bun consists of longer conductors coming from lower sections torso and lower extremities of the corresponding side to the medulla oblongata. Moreover, these conductors enter the spinal cord as part of the dorsal roots 19 lower segments spinal cord and occupy a medial position in the posterior cord.

Wedge-shaped bundle includes shorter conductors running from the upper limbs and upper torso also to the medulla oblongata. These conductors enter the spinal cord as part of the dorsal roots of the 12 upper segments of the spinal cord and occupy a lateral position in the dorsal funiculus.

Gaulle and Burdach bundles– these are conductors of conscious proprioceptive sensitivity (articular-muscular feeling) of the cortical direction. In addition, they are conductors of the cutaneous stereognostic sense. Thus, they carry information to the cerebral cortex about the position of the body and its parts in space and relative to each other.

All systems and organs in the human body are interconnected. And all functions are controlled by two centers: . Today we will talk about and the white formation it contains. The white matter of the spinal cord (substantia alba) is a complex system of unmyelinated nerve fibers of varying thickness and length. This system also includes support nerve tissue, and blood vessels surrounded by connective tissue.

What does white matter consist of? The substance contains many processes of nerve cells; they make up the conductive tracts of the spinal cord:

• descending bundles (efferent, motor), they go to the cells of the anterior horns of the human spinal cord from the brain.
• ascending (afferent, sensory) bundles that go to the cerebellum and cerebral centers.
• short bundles of fibers that connect segments of the spinal cord, they are present at various levels of the spinal cord.

Basic parameters of white matter

The spinal cord is a special substance located inside bone tissue. This important system is located in the human spine. In cross-section, the structural unit resembles a butterfly; the white and gray matter in it are evenly distributed. Inside the spinal cord, a white substance is covered with sulfur and forms the center of the structure.

The white matter is divided into segments, the lateral, anterior and posterior sulcus. They form the spinal cords:

• The lateral cord is located between the anterior and posterior horn of the spinal cord. It contains descending and ascending paths.
• The posterior funiculus is located between the anterior and posterior horn of the gray matter. Contains wedge-shaped, delicate, ascending tufts. They are separated from each other, the posterior intermediate grooves serve as separators. The wedge-shaped fasciculus is responsible for conducting impulses from the upper limbs. A gentle bundle transmits impulses from the lower extremities to the brain.
• The anterior cord of white matter is located between the anterior fissure and the anterior horn of gray matter. It contains descending pathways, through which the signal goes from the cortex, as well as from the midbrain to important human systems.

The structure of the white matter is a complex system of pulpy fibers of different thicknesses; together with the supporting tissue, it is called neuroglia. It contains small blood vessels that have almost no connective tissue. The two halves of the white matter are connected by a commissure. The white commissure also extends in the region of the transversely extending spinal canal, located in front of the central canal. The fibers are connected into bundles that conduct nerve impulses.

Main ascending paths

The task of the ascending pathways is to transmit impulses from peripheral nerves to the brain, most often to the cortical and cerebellar regions of the central nervous system. There are ascending paths that are too welded together; they cannot be assessed separately from each other. Let us identify six fused and independent ascending bundles of white matter.

• Wedge-shaped bundle of Burdach and thin bundle of Gaulle (in Figure 1,2). The bundles consist of dorsal ganglion cells. The wedge-shaped bundle has 12 upper segments, the thin bundle has 19 lower segments. The fibers of these bundles go into the spinal cord, pass through the dorsal roots, providing access to special neurons. They, in turn, go to the cores of the same name.
• Lateral and ventral pathways. They consist of sensory cells of the spinal ganglia extending to the dorsal horns.
• Govers' spinocerebellar tract. It contains special neurons, they go to the Clarke nucleus area. They rise up upper sections trunk of the nervous system, where they enter the ipsilateral half of the cerebellum through the superior peduncles.
• Flexing's spinocerebellar tract. At the very beginning of the path, the neurons of the spinal ganglia are contained, then the path goes to the nuclear cells in the intermediate zone of the gray matter. Neurons pass through the inferior cerebellar peduncle and reach the longitudinal medulla.

Main descending paths

Descending pathways are associated with ganglia and the gray matter region. Nerve impulses are transmitted through bundles, they come from the human nervous system and are sent to the periphery. These pathways have not yet been sufficiently studied. They often intertwine with each other, forming monolithic structures. Some paths cannot be considered without separation:

• Lateral and ventral corticospinal tracts. They begin from the pyramidal neurons of the motor cortex in their lower part. The fibers then pass through the base of the midbrain, cerebral hemispheres brain, pass through the ventral sections of the Varoliev, medulla oblongata, reaching the spinal cord.
• Vestibulospinal tracts. This is a general concept; it includes several types of bundles formed from the vestibular nuclei, which are located in the medulla oblongata. They end in the anterior cells of the anterior horns.
• Tectospinal tract. It ascends from cells in the quadrigeminal region of the midbrain and ends in the region of the mononeurons of the anterior horns.
• Rubrospinal tract. It originates from cells that are located in the region of the red nuclei of the nervous system, intersects in the region of the midbrain, and ends in the region of the neurons of the intermediate zone.
• Reticulospinal tract. This is the connecting link between the reticular formation and the spinal cord.
• Olive spinal tract. Formed by neurons of olivary cells located in the longitudinal brain, it ends in the region of mononeurons.

We looked at the main ways that have been more or less studied by scientists in currently. It is worth noting that there are also local bundles that perform a conductive function, which also connect different segments of different levels of the spinal cord.

The role of white matter of the spinal cord

The white matter connective system acts as a conductor in the spinal cord. There is no contact between the gray matter of the spinal cord and the main brain, they do not contact each other, do not transmit impulses to each other and affect the functioning of the body. These are all functions of the white matter of the spinal cord. The body, due to the connecting capabilities of the spinal cord, works as an integral mechanism. The transmission of nerve impulses and information flows occurs according to a certain pattern:

1. Impulses sent by gray matter travel along thin threads of white matter that connect to different parts of the main human nervous system.
2. The signals activate the right parts of the brain, moving at lightning speed.
3. Information is quickly processed in our own centers.
4. The information response is immediately sent back to the center of the spinal cord. For this purpose, strings of white substance are used. From the center of the spinal cord, signals diverge to different parts human body.

This is all a rather complex structure, but the processes are actually instantaneous, a person can lower or raise his hand, feel pain, sit down or stand up.

Connection between white matter and brain regions

The brain includes several zones. The human skull contains the medulla oblongata, telencephalon, midbrain, diencephalon and cerebellum. The white matter of the spinal cord is in good contact with these structures; it can establish contact with a specific part of the spine. When there are signals associated with speech development, motor and reflex activity, gustatory, auditory, visual sensations, speech development, white matter telencephalon is activated. The white substance of the medulla oblongata is responsible for conduction and reflex function, activating complex and simple functions of the whole organism.

The gray and white matter of the midbrain, which interacts with the spinal connections, are responsible for various processes in the human body. The white matter of the midbrain has the ability to enter into active phase processes:

• Activation of reflexes due to sound exposure.
• Regulation of muscle tone.
• Regulation of auditory activity centers.
• Performing righting and righting reflexes.

In order for information to quickly travel through the spinal cord to the central nervous system, its path lies through the diencephalon, so the body’s work is more coordinated and accurate.

More than 13 million neurons are contained in the gray matter of the spinal cord; they make up entire centers. From these centers, signals are sent to the white matter every fraction of a second, and from it to the main brain. It is thanks to this that a person can live full life: smell, distinguish sounds, rest and move.

Information moves along the descending and ascending tracts of white matter. Ascending Paths move information that is encrypted in nerve impulses to the cerebellum and large centers of the main brain. The processed data is returned in downstream directions.

Risk of damage to the spinal cord tracts

The white matter is located under three membranes, they protect the entire spinal cord from damage. It is also protected by a solid spine frame. But there is still a risk of injury. The possibility cannot be ignored infectious lesion, although this is not a common occurrence in medical practice. More often, spinal injuries are observed, in which the white matter is primarily affected.

Functional impairment may be reversible, partially reversible, or have irreversible consequences. It all depends on the nature of the damage or injury.

Any injury can lead to the loss of the most important functions of the human body. When an extensive rupture or damage to the spinal cord occurs, irreversible consequences appear and the conduction function is disrupted. When a spinal bruise occurs, when the spinal cord is compressed, damage occurs to the connections between the nerve cells of the white matter. The consequences may vary depending on the nature of the injury.

Sometimes certain fibers are torn, but the possibility of restoration and healing of nerve impulses remains. This may take considerable time, because nerve fibers grow together very poorly, and the possibility of conducting nerve impulses depends on their integrity. The conductivity of electrical impulses can be partially restored with some damage, then sensitivity will be restored, but not completely.

The likelihood of recovery is affected not only by the degree of injury, but also by how professionally first aid was provided, how resuscitation and rehabilitation were carried out. After all, after damage, it is necessary to teach the nerve endings to conduct electrical impulses again. The recovery process is also affected by age, the presence of chronic diseases, and metabolic rate.

Interesting facts about white matter

The spinal cord is fraught with many mysteries, so scientists around the world are constantly conducting research to study it.

• The spinal cord actively develops and grows from birth until the age of five to reach a size of 45 cm.
• The older a person is, the more white matter there is in his spinal cord. It replaces dead nerve cells.
• Evolutionary changes in the spinal cord occurred earlier than in the brain.
• Only in the spinal cord are the nerve centers responsible for sexual arousal.
• It is believed that music helps proper development spinal cord.
• Interesting, but in fact the white substance is beige in color.

Structure of the spinal cord

Spinal cord, medulla spinalis (Greek myelos), lies in the spinal canal and in adults is a long (45 cm in men and 41-42 cm in women), somewhat flattened from front to back cylindrical cord, which at the top (cranially) directly passes into the medulla oblongata , and below (caudally) ends in a conical point, conus medullaris, at the level of the II lumbar vertebra. Knowledge of this fact is of practical importance (in order not to damage the spinal cord during a lumbar puncture for the purpose of taking cerebrospinal fluid or for the purpose of spinal anesthesia, you need to insert the syringe needle between the spinous processes of the III and IV lumbar vertebrae).

From the conus medullaris the so-called terminal filament , filum terminale, representing the atrophied lower part of the spinal cord, which below consists of a continuation of the membranes of the spinal cord and is attached to the II coccygeal vertebra.

The spinal cord along its length has two thickenings corresponding to the roots of the nerves of the upper and lower limbs: the top one is called cervical thickening , intumescentia cervicalis, and the lower - lumbosacral , intumescentia lumbosacralis. Of these thickenings, the lumbosacral one is more extensive, but the cervical one is more differentiated, which is associated with a more complex innervation of the hand as an organ of labor. Formed due to thickening of the lateral walls of the spinal tube and passing along the midline anterior and posterior longitudinal grooves : deep fissura mediana anterior, and superficial, sulcus medianus posterior, the spinal cord is divided into two symmetrical halves - right and left; each of them, in turn, has a weakly defined longitudinal groove running along the line of entry of the posterior roots (sulcus posterolateralis) and along the line of exit of the anterior roots (sulcus anterolateralis).

These grooves divide each half of the white matter of the spinal cord into three longitudinal cords: front - funiculus anterior, side - funiculus lateralis and rear - funiculus posterior. The posterior cord in the cervical and upper thoracic regions is further divided by the intermediate groove, sulcus intermedius posterior, into two bundles: fasciculus gracilis and fasciculus cuneatus . Both of these bundles, under the same names, pass at the top to the posterior side of the medulla oblongata.

On both sides, the spinal nerve roots emerge from the spinal cord in two longitudinal rows. Anterior root , radix ventral is s. anterior, exiting through the sulcus anterolateralis, consists of neurites motor (centrifugal, or efferent) neurons, whose cell bodies lie in the spinal cord, while dorsal root , radix dorsalis s. posterior, part of the sulcus posterolateralis, contains processes sensitive (centripetal, or afferent) neurons, whose bodies lie in the spinal ganglia.

At some distance from the spinal cord, the motor root is adjacent to the sensory and they together form the trunk of the spinal nerve, truncus n. spinalis, which neurologists distinguish under the name cord, funiculus. When the cord is inflamed (funiculitis), segmental disorders of both motor and sensory function occur.

spheres; in case of root disease (radiculitis), segmental disorders of one sphere are observed - either sensory or motor, and in case of inflammation of the branches of the nerve (neuritis), the disorders correspond to the zone of distribution of this nerve. The nerve trunk is usually very short, since upon exiting the intervertebral foramen the nerve splits into its main branches.

In the intervertebral foramina near the junction of both roots, the dorsal root has a thickening - spinal ganglion , ganglion spinale, containing false unipolar nerve cells (afferent neurons) with one process, which is then divided into two branches: one of them, the central one, goes as part of the dorsal root into the spinal cord, the other, peripheral, continues into the spinal nerve. Thus, there are no synapses in the spinal ganglia, since only the cell bodies of afferent neurons lie here. This distinguishes the named nodes from the autonomic nodes of the peripheral nervous system, since in the latter intercalary and efferent neurons come into contact. The spinal nodes of the sacral roots lie inside the sacral canal, and the node of the coccygeal root lies inside the sac of the dura mater of the spinal cord.

Due to the fact that the spinal cord is shorter than the spinal canal, the exit site of the nerve roots does not correspond to the level of the intervertebral foramina. To get to the latter, the roots are directed not only to the sides of the brain, but also downward, and the more vertically they extend from the spinal cord, the more vertical they are. In the lumbar part of the latter, the nerve roots descend to the corresponding intervertebral foramina parallel to the filum terminate, covering it and the conus medullaris with a thick bundle, which is called ponytail , cauda equina.