home Audience 3 Spinal cord: structure and functions, basic physiology. Structure of the human spinal cord

Spinal cord: structure and functions, basic physiology. Structure of the human spinal cord

The human central nervous system performs many functions due to which our body is able to function normally. It consists of the head and spinal cord.

The spinal cord is the most important part nervous system person. The structure of the human spinal cord determines its functions and characteristics of work.

What it is?

The spinal cord and brain are two components of the central nervous system that form a single complex. The cephalic section passes into the dorsal section at the level brain stem in the greater occipital fossa.

The structure and function of the spinal cord are inextricably linked. This organ is a strand of nerve cells and processes that extend from the head to the sacrum.

Where is the spinal cord located? This organ is located in a special container inside the vertebrae, which is called the “spinal canal”. This arrangement of the most important component of our body is no coincidence.

The spinal canal performs following functions:

Protects nervous tissue from exposure to factors environment.
Contains membranes that protect and nourish nerve cells.
It has exit intervertebral openings for spinal roots and nerves.
Contains a small amount of circulating fluid that nourishes cells.

The human spinal cord is quite complex, but without understanding its anatomy it is impossible to fully imagine the features of its functioning.

Structure

How is the spinal cord structured? The structural features of this organ are very important to understand in order to understand the entire functioning of our body. Like other parts of the central nervous system, the tissue of this organ consists of gray and white matter.

What is it formed by? Gray matter? The gray matter of the spinal cord is represented by an accumulation of many cells - neurons. This section contains their nuclei and main organelles, which help them carry out their functions.

The gray matter of the spinal cord is grouped in the form of nuclei that extend throughout the organ. It is the kernels that carry out most of the functions.

The gray matter of the spinal cord contains the most important motor, sensory and autonomic centers, the function of which will be discussed below.

The white matter of the spinal cord is formed by other sections of nerve cells. This area of tissue is located around the nuclei and represents cell processes. The white matter consists of so-called axons - they transmit all impulses from the small nuclei of nerve cells to the place where the function is performed.

Anatomy is closely related to the tasks performed. Thus, when the motor nuclei are damaged, one of the functions of the organ is disrupted and the possibility of carrying out certain type movements.

The structure of this part of the nervous system is divided into:

Own apparatus of the spinal cord. It includes the gray matter described above, as well as the dorsal and anterior roots. This part of the brain is capable of independently performing an innate reflex.
Suprasegmental apparatus - represented by conductors or pathways that pass both in the overlying direction and in the underlying one.

Cross section

What does the spinal cord look like in cross section? The answer to this question allows us to understand a lot about the structure of this organ of the body.

The incision changes quite a lot visually depending on the level. However, the main components of the substance are largely similar:

At the center of the spinal cord is the spinal canal. This cavity is a continuation of the cerebral ventricles. The inside of the spinal canal is lined with special integumentary cells. The spinal canal contains a small amount of fluid that enters it from the cavity of the fourth ventricle. In the lower part of the organ, the cavity ends blindly.
The substance surrounding this hole is divided into gray and white. The bodies of nerve cells are located on the section in the form of a butterfly or the letter H. It is divided into anterior and posterior horns, and lateral horns are also formed in the area of the thoracic spine.
The anterior horns give rise to the anterior motor roots. The rear ones are sensitive, and the lateral ones are vegetative.
The white matter contains axons that are directed from top to bottom or bottom to top. In the upper parts of the white matter there is much more, since here the organ must be located much more big amount conducting paths.
The white matter is also divided into sections - anterior, posterior and lateral funiculi, each of which is formed by the axons of different neurons.

The spinal cord pathways within each cord are quite complex and are studied in detail by professional anatomists.

Segments

A segment of the spinal cord is a special functional unit of this most important element of the nervous system. This is the name of the area that is located on the same level with two anterior and posterior roots.

The sections of the spinal cord repeat the structure of the human spine. So the organ is divided into the following parts:

– in this rather important area there are 8 segments.
The thoracic region is the longest part of the organ, containing 12 segments.
The lumbar region - according to the number of lumbar vertebrae, has 5 segments.
Sacral section - this part of the organ is also represented by five segments.
Coccygeal - at different people this part can be shorter or longer and contains from one to three segments.

However, the adult spinal cord is somewhat shorter than the length spinal column, therefore, the segments of the spinal cord do not completely correspond to the location of the corresponding vertebrae, but are located slightly higher.

The location of the segments relative to the vertebrae can be represented as follows:

In the cervical part, the corresponding sections are located approximately at the level of the vertebrae of the same name.
The upper thoracic and eighth cervical segments are one level higher than the vertebrae of the same name.
In the middle thoracic region, the segments are already 2 vertebrae higher than the same sections of the spinal column.
Lower thoracic region– the distance increases by one more vertebra.
The lumbar segments are located at the level of the thoracic vertebrae in the lower part of this part of the spine.
The sacral and coccygeal sections of the central nervous system correspond to the 12th thoracic and 1st lumbar vertebrae.

These relationships are very important for anatomists and neurosurgeons.

Spinal roots

The spinal cord and roots are inseparable structures, the functions of which are firmly connected.

The roots of the spinal cord are located in spinal canal and do not come out of it directly. Between them, at the level of the inner part of the intervertebral foramen, a single spinal nerve should form.

The functions of the spinal cord roots are different:

The anterior roots always extend from the organ. The anterior roots contain axons that travel from the central nervous system to the periphery. This is how, in particular, the motor function of the organ is carried out.
The dorsal roots contain sensory fibers. They are directed from the periphery to the center, that is, they enter the medullary cord. Thanks to them, sensory function can be carried out.

According to the segments, the roots form 31 pairs of spinal nerves, which already exit the canal through the intervertebral foramina. Next, the nerves carry out their direct function, are divided into individual fibers and innervate muscles, ligaments, internal organs and other elements of the body.

It is very important to distinguish between the anterior and posterior roots. Although they merge with each other to form a single nerve, their functions are completely different. The axons of the former are directed to the periphery, while the components of the dorsal roots, on the contrary, return to the center.

Spinal cord reflexes

Knowing the functions of this important element nervous system is impossible without understanding simple reflex arc. At the level of one segment it has quite shortcut:

People have spinal cord reflexes from birth and they can be used to determine the functional viability of a particular part of this organ.

The reflex arc can be represented as follows:

This path begins from a special nerve link called a receptor. This structure receives impulses from external environment.
Further, the path of the nerve impulse lies along centripetal sensory fibers, which are the axons of peripheral neurons. They carry information to the central nervous system.
The nerve impulse must enter the nerve cord, this occurs through the dorsal roots to the nuclei of the dorsal horns.
The next element is not always present. It is the central link that transmits impulse from the rear to the front horns.
The most important link in the reflex arc is the effector link. Located in the anterior horns. From here the impulse goes to the periphery.
Along the anterior horns, irritation from neurons is transmitted to the effector - the organ that carries out direct activities. Most often it is skeletal muscle.

The impulse from neurons travels through this complex path, for example, when tapping the tendons of the knee with a hammer.

Spinal cord: functions

What function does the spinal cord perform? The characteristics of the role of this organ are described in serious scientific volumes, but it can be reduced to two main tasks:

Reflex.
Conductor.

Completing these tasks is a very difficult process. The ability to implement them allows us to move, receive information from the environment and respond to irritation.

The reflex function of the spinal cord is largely described by the characteristics of the reflex arc presented above. This function of the spinal cord is to transmit and respond to impulses from the periphery to the center. The most important department The central nervous system receives information from receptors and transmits motor impulses to skeletal muscles.

The conduction function of the spinal cord is carried out by white matter, namely the conduction tracts. The characterization of individual pathways is quite complex. Some conducting fibers are directed upward to the head section, others come from there.

Now you have general idea about an organ such as the spinal cord, the structure and functions of which determine the characteristics of our interaction with the outside world.

Clinical role

What can the presented information be used for in practical medicine? Knowledge of the structural features and functions of the organ is necessary for diagnostic and therapeutic activities:

Understanding the anatomical features allows for timely diagnosis of certain pathological processes. An MRI image cannot be deciphered without a clear understanding normal structure nervous system.
Evaluation of clinical data is also based on the characteristics of the structure and functioning of the nervous system. Decreasing or increasing certain nerve reflexes helps determine the location of the lesion.
Understanding anatomical features allows surgeons to perform precise operations on the nervous system. The doctor will act on a specific area of tissue without affecting other parts of the organ.
Understanding brain function should help develop proper techniques conservative treatment. Restorative procedures for organic lesions nervous system are based on an understanding of the functioning of the spinal cord.
Finally, the cause of death of a person from diseases of the nervous system cannot be established without knowledge of the anatomy and functioning of its constituent organs.

The knowledge gained over centuries of research about the characteristics of the nervous system allows medical practice at a high modern level.

The spinal cord, like the brain, is an integral part of the central nervous system of the human body. The functioning of an organ is disrupted if even the slightest defect occurs in this area, and this affects the functioning of other systems. The functions of the spinal cord are established during the prenatal period of a child’s development.

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Anatomical features

Such an organ extends along the spinal column, starting from the first vertebra of the neck (its upper edge, where it connects to the foramen magnum of the skull). As such, there is no clear transition from the spinal cord to the brain. “Pyramid paths” are concentrated in this area: conductors, functional organization which – ensuring the mobility of arms and legs.

In the lower back, the medulla ends at the level of the second lumbar vertebra. Based on this, it is worth noting that this organ is still shorter than the length of the spinal column. This makes it possible to carry out spinal tap a substance localized in the area of the 3-4 lumbar vertebrae. Total duration vital organ - no more than 45 cm, and thickness - no more than one and a half centimeters.

Since the spinal column has several sections, the spinal substance is also divided into sections: neck, chest, lower back, sacrum, coccyx. In those segments where the cervical and lumbosacral levels are localized, the thickness of the spinal cord is greater than in other areas of the spine. This can be explained by the location here of clusters of nerve cells that provide innervation to the limbs.

All sides of the organ are equipped with slits and grooves that go deep into the brain. Its two halves are separated by the anterior and posterior median fissures. Each half includes grooves that contribute to the division of the vertebral unit into several cords. Each of these cords contains separate nerves that carry various information(about pain, touch, temperature, movement, etc.).
Role and functions in the body
Functionally, the spinal cord performs the following tasks:
Regulating the functioning of organs and systems through the transmission of nerve impulses to them. In other words, it performs a reflex function.
Transmission of information to the brain, as well as from it to motor neurons.

The gray matter of this spinal segment contains many pathways that provide motor reactions of the body. The activity of each reflex occurs through a special department of the central nervous system - nerve center. In the latter, special cells are localized, which occupy a certain section of the organ and ensure the functionality of specific systems in the body. For example, they are provided with nerve cells localized in lumbar region spinal link. The urination process is in the sacrum, dilation of the pupils is in the thoracic.
The nervous center processes information sent by skin receptors, as well as other systems and organs in the body. As a response, the brain generates certain impulses, which are subsequently transmitted to the executive organs (for example, skeletal muscles, vascular apparatus, cardiac muscles, etc.). As a result, a change in the functional state of the latter occurs.
Motor neurons carry out the process of contraction of muscles in such parts of the body as limbs, intercostal spaces, etc. Regulation of such a reflex occurs with the help higher departments CNS. Nerve impulses that travel along the spinal cord to the brain transmit information about the dysfunction of any organ or system in the body. Impulses transmitted various organs into the spinal region and from there to the region of the dorsal roots of the brain, sensory neurons are processed. From them, information is distributed either to the posterior horns of the unit, or to cerebral hemispheres brain.
If at least one link that ensures the transmission of information is violated, the body loses the corresponding feeling. In most cases, the activity of such an important organ is disrupted if the back, in particular the spine, is injured.

What pathologies can develop?
As a rule, symptoms depend on which segment of the organ is affected by disease or injury, as well as on what type of pathology develops. Signs of brain dysfunction include:
impaired innervation of the legs and arms or other areas of the body;
severe pain syndrome in the spinal region;
unauthorized bowel movement;
psychosomatic disorders;
impaired mobility of the torso;
severe muscle or joint pain;
muscle atrophy.

The following diseases may be accompanied by similar symptoms:
Tumor. This includes both malignant and benign neoplasms, which can be located extradurally, intradurally, intramedullary. Extradural tumor is characterized by rapid progression and is localized in hard tissues. An intradural neoplasm develops under hard tissues. Intramedullary neoplasms are characterized by their development in a liquid substance.
Intervertebral hernia. initial stage development of a hernia - protrusion. When the fibrous ring of the disc is destroyed, the contents exit into the spinal canal. If the spinal cord was involved in the lesion, the development of myelopathy (not compression or chronic) is diagnosed.
Chronic myelopathy. Often (with untimely treatment) osteochondrosis becomes the cause of the development of spondylosis, which is the final dystrophic change tissue structures. In this case, the appearance of osteophytes is observed, which subsequently serve to compress the brain canal.
Heart attack. Caused by impaired circulation of the organ, the occurrence of necrotic processes and is characterized by the formation of blood clots and dissection of the aorta. It is recommended to immediately contact a specialist if pain occurs in this department. This is the only way to prevent irreversible consequences.

Video “Functions and structure of the spinal cord”
More interesting information about anatomical features We offer from the following video.

The spinal cord is the most important internal organ related to the structure of the central nervous system. The surface of the spinal cord has 3 membranes - arachnoid, hard and soft. The anatomy of the spinal cord is designed in such a way that the internal organ is the dominant system that supports the vital functions of the entire organism.

Structure of the spinal cord

The spinal cord is located in the cavity of the spinal canal, which is formed by the processes of the vertebrae and their bodies. The beginning of the structure of the spinal cord is the foramen magnum of the brain. Next, the spinal cord is located in the canal, representing a 40-centimeter “cord” surrounded by three membranes.

The internal organ ends with a cluster of nerve fibers at the level of the first vertebrae in lumbar region, called the horse's tail. This is where the narrowing begins, and then the internal organ is “stretched” into a terminal (terminal, terminal) filament, the diameter of which is 1 mm. The filum terminale extends to the coccygeal region, where it fuses with the periosteum.

The lower part of the trailing thread is tightly wrapped in ponytail fibers. When pain occurs in the coccyx area, doctors talk about a syndrome with the same name. The structure of the human spinal cord is such that the medulla itself is under constant protection - this is provided by the membranes and the spinal column itself.

External structure- these are shells and the space between them.

Meninges

Hard shell. It is located immediately behind the periosteum of the spine, but does not adhere closely to it. The epidural space is located between the periosteum and the dura mater. The tissue of the hard shell is connective; it contains vessels, lymphatic and circulatory. The epidural space is filled with fatty tissue. Venous plexuses are also located here.
Arachnoid- a network of thin plates of connective tissue, in structure reminiscent of a spider's web. The plates are composed of collagen and elastic fibers. Between the arachnoid and soft membrane there is a subarochnoid space with cerebrospinal fluid, which ensures the exchange and nutrition of neurons.
Soft shell. This is a vascular environment that has serrated ligaments for fixation and provides communication and nutrition between the cerebrospinal fluid and the brain.

Terminal thread

The terminal thread has 2 parts:

Internal, the length of which is approximately 15 cm. Interior The filum terminale consists of nervous tissue, is intertwined with the lumbar and sacral nerves and is located in a kind of hard shell sac.
External, length 8 cm. External part The terminal filament begins below the second sacral vertebra, it stretches to the second coccygeal vertebra, where it fuses with the periosteum.

Peculiarities

The internal structure of the spinal cord has thickenings in the lumbosacral and cervical regions. This structure is formed because in the corresponding parts of the spine there are a large number of exiting nerves that are directed to the lower or upper extremities.

The cervical thickening is located at the level of the third and fourth cervical vertebrae and lasts until the second thoracic vertebra.
The lumbosacral thickening is located from the level of the 9-10 thoracic vertebra and lasts until the 1st lumbar vertebra.

White and gray matter of the spinal cord

The cross-sectional diagram of the structure of the spinal cord is similar to the wings of a butterfly; this part of the internal organ is called gray matter. On the outside, gray matter is surrounded by white matter, but the cellular structure and functions of these substances differ significantly.

Gray matter consists of interneurons and motor neurons:

The white matter contains axons - these are nerve processes that create fibers of descending and ascending pathways.

Expert opinion

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Spinal nerves and segments

To the right and left of the central grooves of the spinal cord there are anterolateral and posterolateral grooves; anterior and posterior axons pass through them, which form nerve roots.

the anterior root contains motor neurons;
the dorsal root is sensory neurons.

Anterior and posterior roots at the exit from brain section unite into a single nerve ganglion. Since each segment has 2 anterior and 2 posterior nerve roots, together they form 2 spinal nerves - one on each side.

In total, the spinal cord has 64 nerves - that is, 31 nerves on each side.

Location nerve endings following:

in the cervical region - 8;
in the thoracic region - 12;
in the lumbar region - 5;
in the sacral region - 5;
V coccygeal region — 1.

The segments and sections of the spinal cord are not located at the same level in the spine due to different lengths (the spinal cord is much shorter than the spine).

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Functions of the organ

The structure and functions of the spinal cord are critical system, supporting normal functioning human body.

The functionality of the spinal cord is divided into 2 parts:

reflex - these are the simplest motor reflexes of the body, for example, when a hand is burned, a person begins to pull his hands away from the source of injury, or when he hits his knee with a hammer, a reflexive extension of the knee occurs;
The conduction function is the transmission of nerve impulses from the brain region to the inner part of the spinal cord, as well as the transmission of nerve impulses from the brain to the internal organs of the human body.

With the help of conductive communication, almost every mental action is carried out - get up, walk, lie down, sit down, draw, pass, cut, etc. A person does not even think about most of the actions, performing them at a reflex level in everyday life.

It is important to note that reflex features can be performed without the participation of brain functions. This feature of a living organism has been proven by scientific experiments conducted on frogs. For example, researchers determined how frogs reacted to pain of various types without the participation of the brain - reflexes manifested themselves in both mild pain and severe pain.

If we briefly describe the structure and functions, the human body is a unique system where all internal organs and systems interact harmoniously.

It is also important to note that each segment of the spine is directly connected to specific internal organs, providing them with the necessary functionality:

The cervical and thoracic regions are connected to the head, chest muscles, and organs chest;
the lumbar region is connected with the internal organs of the gastrointestinal tract, kidneys and muscular system of the human body;
the sacral region is “responsible” for functionality lower limbs and pelvic organs.

The spinal cord is a complex and vulnerable system, the condition of which affects not only general health, but also many reflexes. Diseases or injuries affecting the spinal cord are extremely dangerous, because they end in failure, and in best case scenario lead to disability.

How to forget about back and joint pain?

We all know what pain and discomfort are. Arthrosis, arthritis, osteochondrosis and back pain seriously spoil life, limiting normal activities - it is impossible to raise an arm, step on a leg, or get out of bed.

The structure of the spinal cord is an elongated, flattened cylindrical cord located in the spinal canal from the level of the base of the skull (level of the first cervical vertebra) to the first and second lumbar vertebrae. The upper parts of the spinal cord pass into the brain, the lower parts end with the conus medullaris, the apex of which continues into a thin filum terminale. The length of the spinal cord structure in an adult is on average 43 cm, weight is about 38 g.

A segment is a section of the spinal cord with the right and left anterior (motor) roots emerging from it and the right and left dorsal (sensitive) roots penetrating into it.

The structure of the spinal cord has 31–32 segments. The segmental apparatus of the spinal cord is its gray matter, as well as the corresponding anterior and posterior roots. Along the entire length of the spinal cord, the anterior and posterior roots depart from it, which, merging, form a pair of right and left spinal nerves. Each segment corresponds to a specific part of the body innervated by this segment.

How does the spinal cord work?

The structure of the spinal cord is divided into 5 sections: cervical, thoracic, lumbar, sacral, and at the very bottom there are one or two rudimentary coccygeal segments. The spinal cord has two thickenings. Cervical - provides innervation upper limbs, and lumbosacral - provides innervation to the lower extremities.

The spinal cord grows slower than the spinal column, resulting in a change in the direction of the roots. The segments and vertebrae are not in the same horizontal plane; in the thoracic region the roots go obliquely downward, and in the lower lumbar and sacrococcygeal regions the roots go vertically down, forming a powerful bundle called the cauda equina.

The median fissure runs along the entire anterior surface of the spinal cord, and the posterior median sulcus runs along the posterior surface. They serve as so-called boundaries, dividing the spinal cord into two symmetrical halves.

The spinal cord consists of gray and white matter. Gray matter occupies a central position. Symmetrically located areas of gray matter resemble the wings of a butterfly.

It has a wider anterior horn and a narrow posterior horn. On the outside of the anterior horns there is a protrusion called the lateral horn.

Types of nerve cells

The gray matter of the spinal cord consists of nerve cells, nerve fibers and glial elements. There are several types of nerve cells:

1) motor – located in the anterior horns;

2) sensitive – located in hind horns;

3) cerebellar receptor cells - located at the base of the dorsal horn, they give rise to the spinocerebellar tract;

4) vegetative – located in the lateral horns;

5) associative - located throughout the gray matter. Motor and sensory nerve cells are

neurons of pain and temperature sensitivity.

The gray matter of the spinal cord belongs to the segmental apparatus and performs motor, sensory, reflex and vegetative-trophic functions.

The white matter of the spinal cord consists of myelinated fibers of the descending and ascending systems. Descending systems consist of axons of nerve cells located in various departments brain. The ascending systems consist of the axons of the nerve cells of the dorsal horns. The white matter also includes the anterior, lateral and posterior funiculi. The anterior cords are located between the anterior horns and anterior roots; lateral - occupy part of the white matter between the anterior and posterior horns. The dorsal funiculi are located between the dorsal horns and dorsal roots.

Spinal cord cords

The anterior funiculi contain the following pathways:

1) anterior, motor, corticospinal (pyramidal) pathway. This pathway transmits impulses of motor reactions from the cerebral cortex to the anterior horns of the spinal cord;

2) the anterior spinothalamic pathway ensures the conduction of impulses of tactile sensitivity (touch and pressure);

3) vestibulospinal tract, allows you to maintain balance and coordinate movements. The lateral funiculi contain the following pathways:

1) the posterior spinocerebellar tract is a conductor of reflex proprioceptive impulses sent to the cerebellum;

2) anterior spinocerebellar tract, it transmits impulses to the cerebellar cortex;

3) lateral spinothalamic tract - the path for conducting impulses of pain and temperature sensitivity;

4) the lateral corticospinal tract is the main motor pathway providing conscious movements;

The posterior funiculi contain two pairs of ascending bundles: a thin bundle (Gaull's bundle) and a wedge-shaped bundle (Burdach's bundle). These bundles are conductors of the joint-muscular, vibration and tactile senses.

The spinal cord is externally enveloped in three membranes: hard, arachnoid and soft. There are spaces between these membranes: epidural - between the sheets of the dura mater of the spinal cord; subdural - between the dura and arachnoid membranes; subarachnoid – located between the hard and soft membranes. Circulation occurs in the subarachnoid space cerebrospinal fluid.

The dura mater of the spinal cord is an oblong sac with strong and thick walls, located in the spinal canal and containing the spinal cord with roots and membranes.

Inner surface The hard shell of the spinal cord is separated from the arachnoid membrane by a narrow slit-like subdural space. It is penetrated by a large number of thin connective tissue crossbars. At the top, the subdural space of the spinal cord communicates freely with a similar space in the cranial cavity.

The arachnoid membrane of the spinal cord is tightly adjacent to the spinal cord. There are two layers in it - inner and outer, between these layers there are blood vessels.

The human spinal cord is the most important organ of the central nervous system, connecting all organs with the central nervous system and conducting reflexes. It is covered on top with three shells:

hard, cobwebby and soft

Between the arachnoid and soft (vascular) membrane and in its central canal there is cerebrospinal fluid (liquor)

IN epidural space (the space between solid meninges and the surface of the spine) - vessels and adipose tissue

What is the external structure of the spinal cord?

This is a long cord in the spinal canal, in the form of a cylindrical cord, approximately 45 mm long, about 1 cm wide, flatter in front and behind than on the sides. It has a conditional upper and lower bound. The upper one begins between the line of the foramen magnum and the first cervical vertebra: in this place the spinal cord connects to the brain through the intermediate medulla. The lower one is at the level of 1-2 lumbar vertebrae, after which the cord takes on a conical shape and then “degenerates” into a thin spinal cord ( terminal) with a diameter of about 1 mm, which stretches to the second vertebra of the coccygeal region. The terminal filament consists of two parts - internal and external:

internal - approximately 15 cm long, consists of nervous tissue, intertwined by the lumbar and sacral nerves and is located in a sac of dura mater
outer - about 8 cm, begins below the 2nd vertebra of the sacral region and stretches in the form of a connection of the hard, arachnoid and soft membranes to the 2nd coccygeal vertebra and fuses with the periosteum

The outer terminal filament, hanging down to the coccyx, with the nerve fibers intertwining it, is very similar in appearance to a horse’s tail. Therefore, pain and phenomena that occur when nerves are pinched below the 2nd sacral vertebra are often called cauda equina syndrome.

The spinal cord has thickenings in the cervical and lumbosacral regions. This is explained by the presence of a large number of exiting nerves in these places, going to the upper as well as to the lower extremities:

Cervical thickening extends from the 3rd - 4th cervical vertebrae to the 2nd thoracic vertebrae, reaching a maximum in the 5th - 6th
Lumbosacral - from the level of the 9th - 10th thoracic vertebrae to the 1st lumbar with a maximum in the 12th thoracic

Gray and white matter of the spinal cord

If you look at the structure of the spinal cord in cross section, then in the center you can see a gray area in the form of a butterfly spreading its wings. This is the gray matter of the spinal cord. It is surrounded on the outside by a white substance. The cellular structure of gray and white matter differs from each other, as do their functions.

The gray matter of the spinal cord consists of motor and interneurons:

motor neurons transmit motor reflexes
intercalary - provide communication between the neurons themselves

White matter consists of so-called axons— nerve processes from which the fibers of the descending and ascending pathways are created.

The wings of the “butterfly” are narrower and form front horns gray matter, wider - rear. The anterior horns contain motor neurons, in the rear - insertion. Between the symmetrical lateral parts there is a transverse bridge of brain tissue, in the center of which there is a channel communicating top part with a cerebral ventricle and filled with cerebrospinal fluid. In some sections or even along its entire length in adults, the central canal may become overgrown.

Relative to this canal, to the left and right of it, the gray matter of the spinal cord looks like symmetrically shaped columns connected to each other by anterior and posterior commissures:

the anterior and posterior columns correspond to the anterior and posterior horns in cross section
lateral projections form a side pillar

The lateral projections are not present along their entire length, but only between the 8th cervical and 2nd lumbar segments. Therefore, the cross section in segments where there are no lateral protrusions has an oval or round shape.

The connection of symmetrical columns in the anterior and posterior parts forms two grooves on the surface of the brain: the anterior, deeper one, and the posterior. The anterior fissure ends in a septum adjacent to the posterior border of the gray matter.

Spinal nerves and segments

To the left and right of these central grooves are located respectively anterolateral And posterolateral grooves through which the anterior and posterior filaments emerge ( axons), forming nerve roots. The anterior root in its structure is motor neurons anterior horn. The posterior one, responsible for sensitivity, consists of interneurons posterior horn. Immediately at the exit from the medullary segment, both the anterior and posterior roots unite into one nerve or nerve ganglion ( ganglion). Since in total there are two anterior and two posterior roots in each segment, in total they form two spinal nerve(one on each side). Now it is not difficult to calculate how many nerves the human spinal cord has.

To do this, let us consider its segmental structure. There are 31 segments in total:

8 - in the cervical region
12 - in the chest
5 - lumbar
5 - in the sacrum
1 - in the coccygeal

This means that the spinal cord has only 62 nerves - 31 on each side.

The sections and segments of the spinal cord and spine are not at the same level due to the difference in length (the spinal cord is shorter than the spine). This must be taken into account when comparing the brain segment and vertebral number during radiology and tomography: if at the beginning cervical region this level corresponds to the number of the vertebra, and in its lower part lies one vertebra above, then in the sacral and coccygeal regions this difference is already several vertebrae.

Two important functions of the spinal cord

The spinal cord performs two important functions — reflex And conductor. Each of its segments is associated with specific organs, ensuring their functionality. For example:

Cervical and thoracic region - connects with the head, arms, chest organs, chest muscles
Lumbar region - gastrointestinal tract, kidneys, muscular system torso
Sacral region - pelvic organs, legs

Reflex functions are simple reflexes inherent in nature. For example:

pain reaction - pull your hand away if it hurts.
knee reflex

Reflexes can be carried out without the participation of the brain

This is proven simple experiments on animals. Biologists conducted experiments with frogs, checking how they react to pain in the absence of a head: a reaction was noted to both weak and strong painful stimuli.

The conductor functions of the spinal cord consist of conducting an impulse along the ascending path to the brain, and from there along the descending path in the form of a return command to some organ

Thanks to this conductive connection, any mental action is carried out:
get up, go, take, throw, lift, run, cut, draw- and many others that a person, without noticing, does in his daily life at home and at work.

Such a unique connection between the central brain, spinal cord, the entire central nervous system and all organs of the body and its limbs remains, as before, the dream of robotics. Not one, not even the most modern robot is not yet able to carry out even a thousandth of those various movements and actions that are subject to the bioorganism. As a rule, such robots are programmed for highly specialized activities and are mainly used in automatic conveyor production.

Functions of gray and white matter. To understand how these magnificent functions of the spinal cord are carried out, consider the structure of the gray and white matter of the brain at the cellular level.

The gray matter of the spinal cord in the anterior horns contains nerve cells large sizes which are called efferent(motor) and are combined into five nuclei:

central
anterolateral
posterolateral
anteromedial and posteromedial

The sensory roots of small cells of the dorsal horns are specific cell processes from the sensory ganglia of the spinal cord. In the dorsal horns, the structure of the gray matter is heterogeneous. Most of the cells form their own nuclei (central and thoracic). The border zone of the white matter, located near the posterior horns, is adjacent to the spongy and gelatinous zones of the gray matter, the cell processes of which, together with the processes of small diffusely scattered cells of the posterior horns, form synapses (contacts) with the neurons of the anterior horns and between adjacent segments. These neurites are called anterior, lateral and posterior bundles of their own. Their connection with the brain is carried out using white matter pathways. Along the edge of the horns, these tufts form a white border.

The lateral horns of gray matter perform the following important functions:

In the intermediate zone of gray matter (lateral horns) there are sympathetic cells vegetative nervous system, it is through them that communication with internal organs is carried out. The processes of these cells connect to the anterior roots
Here it is formed spinocerebellar path:
At the level of the cervical and upper thoracic segments there is reticular zone - a bundle of a large number of nerves associated with zones of activation of the cerebral cortex and reflex activity.

The segmental activity of the gray matter of the brain, the posterior and anterior roots of the nerves, and the own bundles of white matter bordering the gray is called the reflex function of the spinal cord. The reflexes themselves are called unconditional, according to Academician Pavlov’s definition.

The conductive functions of white matter are carried out through three cords - its outer sections, limited by grooves:

Anterior funiculus - the area between the anterior median and lateral grooves
Posterior funiculus - between the posterior median and lateral grooves
Lateral funiculus - between the anterolateral and posterolateral grooves

White matter axons form three conduction systems:

short bundles called associative fibers that connect different segments of the spinal cord
ascending sensitive (afferent) beams directed to parts of the brain
descending motor (efferent) bundles directed from the brain to the neurons of the gray matter of the anterior horns

Ascending and descending conduction pathways. Let's look at some of the functions of the white matter cord pathways as an example:

Front ropes:

Anterior pyramidal (corticospinal) tract- transmission of motor impulses from the cerebral cortex to the spinal cord (anterior horns)
Spinothalamic anterior tract- transmission of tactile impulses affecting the surface of the skin (tactile sensitivity)
Tectospinal tract- connecting the visual centers under the cerebral cortex with the nuclei of the anterior horns, creates a protective reflex caused by sound or visual stimuli
Bundle of Held and Leventhal (vestibular tract)- white matter fibers connect the vestibular nuclei of eight pairs of cranial nerves with motor neurons of the anterior horns
Longitudinal posterior beam— connecting the upper segments of the spinal cord with the brain stem, coordinates the work eye muscles with cervical, etc.

The ascending pathways of the lateral cords carry impulses of deep sensitivity (feelings of one’s body) along the corticospinal, spinothalamic and tegmental spinal tracts.

Descending tracts of the lateral funiculi:

Lateral corticospinal (pyramidal)- transmits the impulse of movement from the cerebral cortex to the gray matter of the anterior horns
Red nuclear spinal tract(located in front of the lateral pyramidal), the spinocerebellar posterior and spinothalamic lateral tracts are adjacent to it.
The red nucleus spinal tract carries out automatic control of movements and muscle tone on a subconscious level.

Different parts of the spinal cord have different proportions of gray and white brain matter. This is explained by the different number of ascending and descending paths. The lower spinal segments have more gray matter. As you move up, it becomes less, and white matter, on the contrary, increases, as new ones are added ascending paths, and at the level of the upper cervical segments and the middle part of the chest white - most of all. But in the area of both the cervical and lumbar thickenings, gray matter predominates.

As you can see, the spinal cord has a very complex structure. The connection between nerve bundles and fibers is vulnerable, and serious injury or disease can disrupt this structure and lead to disruption of the conduction pathways, which is why below the conduction “break” point there can be complete paralysis and loss of sensitivity. Therefore, at the slightest dangerous sign, the spinal cord must be examined and treated promptly.

Spinal cord puncture

To diagnose infectious diseases (encephalitis, meningitis and other diseases), a spinal cord puncture (lumbar puncture) is used - inserting a needle into the spinal canal. It is carried out this way:
IN subarachnoid the space of the spinal cord at a level below the second lumbar vertebra is inserted with a needle and taken cerebrospinal fluid (cerebrospinal fluid).
This procedure is safe, since below the second vertebra in an adult there is no spinal cord, and therefore there is no threat of damage to it.

However, it requires special care so as not to introduce infection or epithelial cells under the membrane of the spinal cord.

Spinal cord puncture is performed not only for diagnosis, but also for treatment, in such cases:

injection of chemotherapy drugs or antibiotics under the lining of the brain
for epidural anesthesia during operations
for the treatment of hydrocephalus and reduction intracranial pressure(removal of excess cerebrospinal fluid)

Spinal cord puncture has the following contraindications:

spinal canal stenosis
displacement (dislocation) of the brain
dehydration (dehydration)

Take care of it important body, engage in basic prevention:

Take antiviral medications during a viral meningitis epidemic
Try not to have picnics in the forested area in May-early June (the period when the encephalitis tick is active)