The structure of the human spinal cord. Where is the human spinal cord located and what is it responsible for? Functions of the brain and spinal cord in brief

The spinal cord is part of the central nervous system. It is located in the spinal canal. It is a thick-walled tube with a narrow channel inside, somewhat flattened in the anterior-posterior direction. It has a rather complex structure and ensures the transmission of nerve impulses from the brain to the peripheral structures of the nervous system, and also carries out its own reflex activity. Without the functioning of the spinal cord, normal breathing, heartbeat, digestion, urination, sexual activity, and any movements in the limbs are impossible. From this article you can learn about the structure of the spinal cord and the features of its functioning and physiology.

The spinal cord is laid on the 4th week of intrauterine development. Usually a woman does not even suspect that she will have a child. Throughout pregnancy, differentiation of various elements occurs, and some parts of the spinal cord completely complete their formation after birth during the first two years of life.

What does the spinal cord look like externally?

The beginning of the spinal cord is conditionally determined at the level of the upper edge of the 1st cervical vertebra and the large occipital foramen. In this area, the spinal cord is gently rebuilt into the brain, there is no clear separation between them. In this place, the intersection of the so-called pyramidal paths is carried out: the conductors responsible for the movements of the limbs. The lower edge of the spinal cord corresponds to the upper edge of the second lumbar vertebra. Thus, the length of the spinal cord is less than the length of the spinal canal. It is this feature of the location of the spinal cord that makes it possible to perform a spinal puncture at the level of the III-IV lumbar vertebrae (it is impossible to damage the spinal cord during a lumbar puncture between the spinous processes of the III-IV lumbar vertebrae, since it simply does not exist there).

The dimensions of the human spinal cord are as follows: length approximately 40-45 cm, thickness - 1-1.5 cm, weight - about 30-35 g.

There are several sections of the spinal cord along the length:

cervical;
chest;
lumbar;
sacral;
coccygeal.

The spinal cord is thicker in the region of the cervical and lumbosacral levels than in other parts, because in these places there are clusters of nerve cells that provide movement of the arms and legs.

The last sacral segments, together with the coccygeal, are called the conus of the spinal cord due to the corresponding geometric shape. The cone passes into the terminal (end) thread. The thread no longer has nerve elements in its composition, but only connective tissue, and is covered with the membranes of the spinal cord. The terminal thread is fixed to the II coccygeal vertebra.

The spinal cord is covered throughout its entire length by 3 meninges. The first (inner) shell of the spinal cord is called soft. It carries arterial and venous vessels that provide blood supply to the spinal cord. The next shell (middle) is arachnoid (arachnoid). Between the inner and middle shells is the subarachnoid (subarachnoid) space containing cerebrospinal fluid (CSF). When performing a lumbar puncture, the needle must fall into this space so that the cerebrospinal fluid can be taken for analysis. The outer shell of the spinal cord is hard. The dura mater continues to the intervertebral foramina, accompanying the nerve roots.

Inside the spinal canal, the spinal cord is fixed to the surface of the vertebrae with the help of ligaments.

In the middle of the spinal cord, along its entire length, there is a narrow tube, the central canal. It also contains cerebrospinal fluid.

From all sides deep into the spinal cord recesses protrude - cracks and furrows. The largest of them are the anterior and posterior median fissures, which delimit the two halves of the spinal cord (left and right). Each half has additional recesses (furrows). Furrows split the spinal cord into cords. The result is two anterior, two posterior and two lateral cords. Such an anatomical division has a functional basis - in different cords there are nerve fibers that carry various information (about pain, about touch, about temperature sensations, about movements, etc.). Blood vessels penetrate into the furrows and fissures.

Segmental structure of the spinal cord - what is it?

How is the spinal cord connected to the organs? In the transverse direction, the spinal cord is divided into special sections, or segments. Roots emerge from each segment, a pair of anterior and a pair of posterior ones, which communicate the nervous system with other organs. The roots exit the spinal canal, form nerves that go to various structures of the body. The anterior roots transmit information mainly about movements (stimulate muscle contraction), therefore they are called motor. The posterior roots carry information from receptors to the spinal cord, that is, they send information about sensations, therefore they are called sensitive.

The number of segments in all people is the same: 8 cervical segments, 12 thoracic, 5 lumbar, 5 sacral and 1-3 coccygeal (usually 1). Roots from each segment rush into the intervertebral foramen. Since the length of the spinal cord is shorter than the length of the spinal canal, the roots change their direction. In the cervical region they are directed horizontally, in the thoracic region - obliquely, in the lumbar and sacral regions - almost vertically down. Due to the difference in the length of the spinal cord and spine, the distance from the exit of the roots from the spinal cord to the intervertebral foramen also changes: in the cervical region, the roots are the shortest, and in the lumbosacral region, the longest. The roots of the four lower lumbar, five sacral and coccygeal segments form the so-called ponytail. It is he who is located in the spinal canal below the II lumbar vertebra, and not the spinal cord itself.

Each segment of the spinal cord is assigned a strictly defined zone of innervation on the periphery. This zone includes a patch of skin, certain muscles, bones, and part of the internal organs. These zones are almost the same in all people. This feature of the structure of the spinal cord allows you to diagnose the location of the pathological process in the disease. For example, knowing that the sensitivity of the skin in the umbilical region is regulated by the 10th thoracic segment, with the loss of sensations of touching the skin below this area, it can be assumed that the pathological process in the spinal cord is located below the 10th thoracic segment. A similar principle works only taking into account the comparison of the innervation zones of all structures (both skin, muscles, and internal organs).

If you cut the spinal cord in the transverse direction, it will look uneven in color. On the cut you can see two colors: gray and white. Gray color is the location of the bodies of neurons, and white color is the peripheral and central processes of neurons (nerve fibers). There are over 13 million nerve cells in the spinal cord.

The bodies of gray neurons are located in such a way that they have a bizarre butterfly shape. This butterfly has clearly visible bulges - the front horns (massive, thick) and the hind horns (much thinner and smaller). Some segments also have lateral horns. In the region of the anterior horns there are bodies of neurons responsible for movement, in the region of the posterior horns - neurons that perceive sensitive impulses, in the lateral horns - neurons of the autonomic nervous system. In some parts of the spinal cord, the bodies of nerve cells responsible for the functions of individual organs are concentrated. The localization sites of these neurons have been studied and clearly defined. So, in the 8th cervical and 1st thoracic segments there are neurons responsible for the innervation of the pupil of the eye, in the 3rd - 4th cervical segments - for the innervation of the main respiratory muscle (diaphragm), in the 1st - 5th thoracic segments - for regulation of cardiac activity. Why do you need to know? It is used in clinical diagnostics. For example, it is known that the lateral horns of the 2nd - 5th sacral segments of the spinal cord regulate the activity of the pelvic organs (bladder and rectum). In the presence of a pathological process in this area (hemorrhage, tumor, destruction during trauma, etc.), a person develops urinary and fecal incontinence.

The processes of the bodies of neurons form connections with each other, with different parts of the spinal cord and brain, respectively tend up and down. These nerve fibers, which are white in color, make up the white matter in the cross section. They also form cords. In the cords, the fibers are distributed in a special pattern. In the posterior cords there are conductors from the receptors of muscles and joints (joint-muscular feeling), from the skin (recognition of an object by touch with closed eyes, a sense of touch), that is, information goes in an upward direction. In the lateral cords, fibers pass that carry information about touch, pain, temperature sensitivity to the brain, to the cerebellum about the position of the body in space, muscle tone (ascending conductors). In addition, the lateral cords also contain descending fibers that provide body movements programmed in the brain. In the anterior cords, both descending (motor) and ascending (sensation of pressure on the skin, touch) paths pass.

The fibers can be short, in which case they connect the segments of the spinal cord to each other, and long, then they communicate with the brain. In some places, the fibers may cross over or simply cross over to the opposite side. The intersection of different conductors occurs at different levels (for example, the fibers responsible for the feeling of pain and temperature sensitivity intersect 2-3 segments above the level of entry into the spinal cord, and the fibers of the articular-muscular sense go uncrossed to the uppermost sections of the spinal cord). The result of this is the following fact: in the left half of the spinal cord there are conductors from the right parts of the body. This does not apply to all nerve fibers, but is especially characteristic of sensitive processes. The study of the course of nerve fibers is also necessary for the diagnosis of the lesion site in the disease.

Blood supply to the spinal cord

The spinal cord is nourished by blood vessels coming from the vertebral arteries and from the aorta. The uppermost cervical segments receive blood from the system of vertebral arteries (as well as part of the brain) through the so-called anterior and posterior spinal arteries.

Along the entire spinal cord, additional vessels that carry blood from the aorta, the radicular-spinal arteries, flow into the anterior and posterior spinal arteries. The latter also come in front and rear. The number of such vessels is due to individual characteristics. Usually there are about 6-8 anterior radicular-spinal arteries, they are larger in diameter (the thickest ones approach the cervical and lumbar thickenings). The inferior radicular-spinal artery (the largest) is called the Adamkevich artery. Some people have an additional radicular-spinal artery coming from the sacral arteries, the Desproges-Gotteron artery. The zone of blood supply of the anterior radicular-spinal arteries occupies the following structures: the anterior and lateral horns, the base of the lateral horn, the central sections of the anterior and lateral cords.

There are an order of magnitude more posterior radicular-spinal arteries than the anterior ones - from 15 to 20. But they have a smaller diameter. The zone of their blood supply is the posterior third of the spinal cord in a transverse section (posterior cords, the main part of the posterior horn, part of the lateral cords).

In the system of radicular-spinal arteries, there are anastomoses, that is, the places where the vessels connect to each other. It plays an important role in the nutrition of the spinal cord. In the event that a vessel ceases to function (for example, a blood clot blocked the lumen), then blood flows through the anastomosis, and the neurons of the spinal cord continue to perform their functions.

The veins of the spinal cord accompany the arteries. The venous system of the spinal cord has extensive connections with the vertebral venous plexuses, the veins of the skull. Blood from the spinal cord through a whole system of vessels flows into the superior and inferior vena cava. In the place where the veins of the spinal cord pass through the dura mater, there are valves that do not allow blood to flow in the opposite direction.

Spinal Cord Functions

Basically, the spinal cord has only two functions:

reflex;
conductive.

Let's take a closer look at each of them.

Reflex function of the spinal cord

The reflex function of the spinal cord consists in the response of the nervous system to irritation. Did you touch something hot and involuntarily pull your hand away? This is a reflex. Did you get something down your throat and cough? This is also a reflex. Many of our daily activities are based precisely on the reflexes that are carried out thanks to the spinal cord.

So, a reflex is a response. How is it reproduced?

To make it clearer, let's take as an example the hand withdrawal response to touching a hot object (1). In the skin of the hand there are receptors (2) that perceive heat or cold. When a person touches hot, then from the receptor along the peripheral nerve fiber (3) an impulse (signaling about "hot") tends to the spinal cord. At the intervertebral foramen there is a spinal ganglion, in which the body of the neuron (4) is located, along the peripheral fiber of which the impulse came. Further along the central fiber from the body of the neuron (5), the impulse enters the posterior horns of the spinal cord, where it “switches” to another neuron (6). The processes of this neuron are sent to the anterior horns (7). In the anterior horns, the impulse switches to motor neurons (8) responsible for the work of the arm muscles. The processes of motor neurons (9) exit the spinal cord, pass through the intervertebral foramen, and, as part of the nerve, are sent to the muscles of the arm (10). The “hot” impulse causes the muscles to contract, and the hand pulls away from the hot object. Thus, a reflex ring (arc) was formed, which provided a response to the stimulus. At the same time, the brain did not participate in the process at all. The man withdrew his hand without thinking about it.

Each reflex arc has obligatory links: an afferent link (a receptor neuron with peripheral and central processes), an intercalary link (a neuron connecting an afferent link with an executor neuron) and an efferent link (a neuron that transmits an impulse to a direct executor - an organ, a muscle).

On the basis of such an arc, the reflex function of the spinal cord is built. Reflexes are congenital (which can be determined from birth) and acquired (formed in the process of life during learning), they are closed at various levels. For example, the knee jerk closes at the level of the 3rd-4th lumbar segments. Checking it, the doctor is convinced of the safety of all elements of the reflex arc, including segments of the spinal cord.

For a doctor, checking the reflex function of the spinal cord is important. This is done at every neurological examination. Most often, superficial reflexes are checked, which are caused by touch, stroke irritation, a prick of the skin or mucous membranes, and deep ones, which are caused by a blow of a neurological hammer. The surface reflexes carried out by the spinal cord include abdominal reflexes (dashed irritation of the skin of the abdomen normally causes contraction of the abdominal muscles on the same side), plantar reflex (dashed irritation of the skin of the outer edge of the sole in the direction from the heel to the fingers normally causes flexion of the toes) . Deep reflexes include flexion-elbow, carporadial, extensor-ulnar, knee, Achilles.

The conduction function of the spinal cord

The conductive function of the spinal cord is to transmit impulses from the periphery (from the skin, mucous membranes, internal organs) to the center (the brain) and vice versa. The conductors of the spinal cord, which make up its white matter, carry out the transmission of information in the ascending and descending direction. An impulse about external influences is sent to the brain, and a certain sensation is formed in a person (for example, you stroke a cat, and you get a feeling of something soft and smooth in your hand). Without the spinal cord, this is impossible. This is evidenced by cases of spinal cord injuries, when the connections between the brain and spinal cord are broken (for example, rupture of the spinal cord). Such people lose sensitivity, touch does not form sensations in them.

The brain receives impulses not only about touches, but also about the position of the body in space, the state of muscle tension, pain, and so on.

Downward impulses allow the brain to “rule” the body. Thus, what a person has conceived is carried out with the help of the spinal cord. Do you want to catch up with the departing bus? The idea is immediately realized - the necessary muscles are set in motion (and you don’t think about which muscles you need to contract and which to relax). This is done by the spinal cord.

Of course, the realization of motor acts or the formation of sensations require a complex and well-coordinated activity of all structures of the spinal cord. In fact, you need to use thousands of neurons to get the result.

The spinal cord is a very important anatomical structure. Its normal functioning ensures the entire life of a person. It serves as an intermediate link between the brain and various parts of the body, transmitting information in the form of impulses in both directions. Knowledge of the features of the structure and functioning of the spinal cord is necessary for the diagnosis of diseases of the nervous system.

Video on the topic "The structure and functions of the spinal cord"

Scientific and educational film of the times of the USSR on the topic "Spinal Cord"

The spinal cord performs conduction and reflex functions.

Conductor function carried out by ascending and descending pathways passing through the white matter of the spinal cord. They connect individual segments of the spinal cord with each other, as well as with the brain.

reflex function It is carried out by means of unconditioned reflexes, which close at the level of certain segments of the spinal cord and are responsible for the simplest adaptive reactions. The cervical segments of the spinal cord (C3 - C5) innervate the movements of the diaphragm, the thoracic (T1 - T12) - the external and internal intercostal muscles; cervical (C5 - C8) and thoracic (T1 - T2) are the centers of movement of the upper limbs, lumbar (L2 - L4) and sacral (S1 - S2) are the centers of movement of the lower extremities.

In addition, the spinal cord is involved in implementation of autonomic reflexes - response of internal organs to irritation of visceral and somatic receptors. The vegetative centers of the spinal cord, located in the lateral horns, are involved in the regulation of blood pressure, cardiac activity, secretion and motility of the digestive tract, and the function of the genitourinary system.

In the lumbosacral region of the spinal cord there is a defecation center, from which impulses arrive through the parasympathetic fibers in the pelvic nerve, which increase the motility of the rectum and provide a controlled defecation act. An arbitrary act of defecation is performed due to the descending influences of the brain on the spinal center. In the II-IV sacral segments of the spinal cord there is a reflex center of urination, which provides a controlled separation of urine. The brain controls urination and provides one hundred arbitrariness. In a newborn child, urination and defecation are involuntary acts, and only as the regulatory function of the cerebral cortex matures do they become voluntarily controlled (usually this occurs in the first 2-3 years of a child's life).

Brain- the most important department of the central nervous system - surrounded by the meninges and located in the cranial cavity. It consists of brain stem : medulla oblongata, pons, cerebellum, midbrain, diencephalon, and the so-called telencephalon, consisting of subcortical, or basal, ganglia and cerebral hemispheres (Fig. 11.4). The upper surface of the brain in shape corresponds to the inner concave surface of the cranial vault, the lower surface (the base of the brain) has a complex relief corresponding to the cranial fossae of the inner base of the skull.

Rice. 11.4.

The brain is intensively formed during embryogenesis, its main parts are already separated by the 3rd month of intrauterine development, and by the 5th month the main sulci of the cerebral hemispheres are clearly visible. In a newborn, the mass of the brain is about 400 g, its ratio with body weight is significantly different from that of an adult - it is 1/8 of the body weight, while in an adult it is 1/40. The most intensive period of growth and development of the human brain falls on the period of early childhood, then its growth rate decreases somewhat, but continues to remain high until the age of 6-7, by which time the brain mass already reaches 4/5 of the adult brain mass. The final maturation of the brain ends only by the age of 17–20, its mass increases by 4–5 times compared to newborns and averages 1400 g for men and 1260 g for women (the mass of an adult brain ranges from 1100 to 2000 g). ). The length of the brain in an adult is 160–180 mm, and the diameter is up to 140 mm. In the future, the mass and volume of the brain remain maximum and constant for each person. It is interesting that the mass of the brain does not directly correlate with the mental abilities of a person, however, with a decrease in brain mass below 1000 g, a decrease in intelligence is natural.

Changes in the size, shape, and mass of the brain during development are accompanied by changes in its internal structure. The structure of neurons, the form of interneuronal connections become more complicated, white and gray matter become clearly demarcated, various pathways of the brain are formed.

The development of the brain, like other systems, is heterochronous (uneven). Before others, those structures on which the normal vital activity of the organism depends at this age stage mature. Functional usefulness is first achieved by stem, subcortical and cortical structures that regulate the vegetative functions of the body. These departments in their development approach the brain of an adult by the age of 2-4 years.

The spinal cord is an important organ of animals and humans. Damage leads to paralysis of the limbs and disruption of the organs. The activity of the whole organism depends on the correct structure and functions of the spinal cord.

Morphology and location in the body

The spinal cord departs from the brain and is located in the spinal canal, which is formed by the arches of the vertebrae connected into a ring. The upper part is connected to the medulla oblongata, the lower part fuses with the vertebrae of the coccyx.

There are five divisions of the spinal cord:

cervical (8 vertebrae);
chest (12 vertebrae);
lumbar (5 vertebrae);
sacral (5 vertebrae);
coccygeal (1 vertebra).

The spinal cord ends at the level of the first lumbar vertebra. From here a bundle of nerve fibers leaves, which is called the cauda equina. The narrowing spinal cord becomes the terminal or spinal cord, the thickness of which does not exceed 1 mm. The end of the thread fuses with the periosteum of the coccygeal region.

Rice. 1. External structure and parts of the spinal cord.

The length of the spinal cord of an adult varies from 40 to 45 cm, and the width is from 1 to 1.5 cm. The diameter is not the same in different parts of the spine. The mass of the brain is on average 35 g.

Shells

The spinal cord is like a cord. Between the spinal canal and the brain is a space filled with adipose tissue, blood vessels, and cerebrospinal fluid.

Internal structure

In cross section, the spinal cord is shaped like a butterfly. In the center is a hollow central canal that surrounds two types of nerve matter:

gray - accumulation of nerve cells (neurons);
white - accumulation of processes (axons) of nerve cells.

The gray matter branches. Thickened anterior and elongated posterior horns extend in different directions. The thoracic region also has lateral horns. From the anterior horns, bundles of nerve fibers extend in different directions - the anterior roots. The posterior roots approach the posterior horns. 31 pairs are formed, i.e. in total, 64 ganglions approach and depart.

Outside, gray matter is surrounded by dense white matter. Between the posterior horns, the white matter forms a narrow fold - the median fissure. On the other hand, between the anterior horns there is a wider fold with a small notch - the median sulcus.

Rice. 3. Cross section of the spinal cord with outgoing bundles.

White and gray matter are composed of different types of tissue and play a specific role. Briefly about the structure and function of the spinal cord is presented in the table.

The spinal cord has two thickenings - in the cervical (13-15 mm) and lumbar (12 mm) sections. From here comes the largest number of nerves, heading to the upper and lower extremities. The cervical thickening begins at the level of 3-4 cervical vertebra and ends at the second thoracic vertebra. Lumbar thickening begins at the level of 9-10 thoracic vertebra and ends at 1 lumbar vertebra.

Functions

The spinal cord plays an important role in the functioning of the central nervous system and performs two functions:

conductive - some neurons are responsible for transmitting signals to the brain (ascending pathways), some receive signals from the brain and give “orders” to organs (descending pathways);
reflex - signals come from receptors to the spinal cord and directly through the reflex arc receive a feedback.

Due to the reflex function, the hand withdraws “by itself” when burned or sneezing occurs when an irritant enters the nose.

What have we learned?

From the topic of the article on anatomy for grade 8, we learned about the external and internal structure of the spinal cord, as well as its functions. The spinal cord carries out reflexes and motor activity of the body, controls the work of internal organs, transmitting signals to the brain and receiving a “response”.

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The spinal cord is part of the central nervous system. It is difficult to overestimate the work of this organ in the human body. Indeed, with any of its defects, it becomes impossible to carry out a full-fledged connection of the body with the outside world. It is not for nothing that his congenital malformations, which can be detected using ultrasound diagnostics already in the first trimester of bearing a child, are most often an indication for termination of pregnancy. The importance of the functions of the spinal cord in the human body determines the complexity and uniqueness of its structure.

It is located in the spinal canal, being a direct continuation of the medulla oblongata. Conventionally, the upper anatomical boundary of the spinal cord is considered to be the line of connection of the upper edge of the first cervical vertebra with the lower edge of the foramen magnum.

The spinal cord ends approximately at the level of the first two lumbar vertebrae, where it gradually narrows: first to the cerebral cone, then to the medullary or terminal filament, which, passing through the canal of the sacral spine, is attached to its end.

Interestingly, in an embryo, the spinal cord is equal in length to the spine, but then they grow unevenly - the growth of the spine is much more intense. As a result, already in an adult, the spinal cord is several tens of centimeters shorter than the spinal column.

This fact is important in clinical practice, since during the well-known spinal cord at the lumbar level, there is absolutely no danger of mechanical damage.

Spinal membranes

The spinal cord is reliably protected not only by the bone tissue of the spine, but also by its own three membranes:

Solid - from the outside it includes the tissues of the periosteum of the spinal canal, then follows the epidural space and the inner layer of the hard shell.
Cobweb - a thin, colorless plate, fused with a hard shell in the region of the intervertebral foramina. Where there are no adhesions, there is a subdural space.
Soft or vascular - separated from the previous shell by the subarachnoid space with cerebrospinal fluid. The soft shell itself adjoins the spinal cord, consists mostly of blood vessels.

The entire organ is completely immersed in the cerebrospinal fluid of the subarachnoid space and “floats” in it. A fixed position is given to it by special ligaments (dentate and intermediate cervical septum), with the help of which the inner part is attached to the shells.

External characteristics

The shape of the spinal cord is a long cylinder, slightly flattened from front to back.
The length is on average about 42-44 cm, depending
from human growth.
Weight about 48-50 times less than the weight of the brain,
is 34-38 g.

Repeating the outlines of the spine, the spinal structures have the same physiological curves. At the level of the neck and the lower part of the thoracic, beginning of the lumbar, two thickenings are distinguished - these are the exit points of the roots of the spinal nerves, which are responsible for the innervation of the arms and legs, respectively.

Behind and in front, 2 grooves pass along the spinal cord, which divide it into two absolutely symmetrical halves. Throughout the body in the middle there is a hole - the central channel, which at the top connects to one of the ventricles of the brain. Below, towards the region of the cerebral cone, the central canal expands, forming the so-called terminal ventricle.

Consists of neurons (cells of the nervous tissue), the bodies of which are concentrated in the center, form the spinal gray matter. According to scientists, there are only about 13 million neurons in the spinal cord - thousands of times less than in the brain. The location of the gray matter within the white is by no means somewhat different in shape, which in the cross section vaguely resembles a butterfly.

The specific view of the transverse section allows you to highlight the following anatomical structures in the spinal gray matter:

The front horns are rounded and wide. Consist of motor neurons that transmit impulses to the muscles. From here begin the anterior roots of the spinal nerves - the motor roots.
The posterior horns are long, narrow, and consist of intermediate neurons. They receive signals from the sensory roots of the spinal nerves - the posterior roots. There are also neurons that, through nerve fibers, carry out the interconnection of different parts of the spinal cord.
Lateral horns - found only in the lower segments of the spinal cord. They contain the so-called vegetative nuclei (for example, centers of pupil dilation, innervation of the sweat glands).

Gray matter is surrounded by white matter on the outside - these are essentially processes of neurons from gray matter or nerve fibers. The diameter of the nerve fibers is not more than 0.1 mm, but their length sometimes reaches one and a half meters.

The functional purpose of nerve fibers can be different:

ensuring the interconnection of different levels of the spinal cord;
transmission of data from the brain to the spinal cord;
ensuring the delivery of information from the spinal to the head.

Nerve fibers, integrating into bundles, are located in the form of conducting spinal tracts along the entire length of the spinal cord.

Narrowing (stenosis) of the spinal canal in most cases requires surgical treatment. The causes and symptoms of stenosis are described in.

A modern effective method of treating back pain is pharmacopuncture. The minimum doses of drugs injected into active points work better than tablets and conventional injections:.

What is better for diagnosing spinal pathologies: MRI or computed tomography? We tell.

Spinal nerve roots

The spinal nerve, by its nature, is neither sensory nor motor - it contains nerve fibers of both types, since it combines the anterior (motor) and posterior (sensory) roots.

The area of the spinal cord, which is the "launching pad" for one pair of nerves, is called a segment or neuromer. Accordingly, the spinal cord consists of only
from 31-33 segments.

It is interesting and important to know that the spinal segment is not always located in the region of the spine with the same name due to the difference in the length of the spine and spinal cord. But on the other hand, the spinal roots still come out of the corresponding intervertebral foramina.

For example, the lumbar spinal segment is located in the thoracic spine, and the corresponding spinal nerves exit from the intervertebral foramina in the lumbar spine.

The spinal nerve roots travel some distance to reach "their" intervertebral foramen - this fact underlies the appearance in the spinal canal of a structure called the "cauda equina" and which is a bundle of spinal roots.

Spinal Cord Functions

And now let's talk about the physiology of the spinal cord, about what "duties" are assigned to it.

Segmental or working nerve centers are localized in the spinal cord, which are directly connected with the human body and control it. It is through these spinal working centers that the human body is subject to control by the brain.

At the same time, certain spinal segments control well-defined parts of the body by receiving nerve impulses from them along sensory fibers and transmitting response impulses to them along motor fibers:

	Spinal segments (location, serial number)	Innervated areas
	Neck: 3-5	Diaphragm
	Neck: 6-8	Hand joints
	Breast: 1.2, 5-8	Muscles and skin of the hands
	Chest: 2-12	Muscles and skin of the body
	Chest: 1-11	intercostal muscles
	Breast: 1-5	Muscles and skin of the head and neck, heart and lungs
	Breast: 5-6	lower esophagus
	Breast: 6-10	Digestive organs
	Lumbar: 1-2	Inguinal ligament, adrenals, kidneys and ureters, bladder, prostate, uterus
	Lumbar: 3-5	Muscles and skin of the legs
	sacral: 1-2	Muscles and skin of the legs
	sacral: 3-5	External genital organs, perineum (reflex centers for urination, erection and defecation)

Some vegetative or complex motor reflexes are performed by the spinal cord without the intervention of the brain at all, thanks to its two-way connection with all parts of the human body - this is how the spinal cord performs its reflex functions. For example, the reflex centers of urination or erection are located in 3-5 sacral segments, and with spinal injury in this place, these reflexes may be lost.

Conduction spinal function It is ensured by the fact that in the white matter all the pathways connecting parts of the nervous system are localized to each other. Information from tactile, temperature, pain receptors and movement receptors from muscles (proprioreceptors) is transmitted along ascending pathways first to the spinal cord and then to the corresponding parts of the brain. Descending pathways connect the brain and spinal cord in reverse order: with their help, the brain controls the activity of human muscles.

Risk of damage and injury

Any spinal cord injury threatens a person's life.

The most dangerous are injuries of the cervical spinal segments - in the vast majority of cases, this leads to immediate respiratory arrest and death.

Serious injuries to other spinal segments located below may not cause death, but they will lead to partial or complete disability in almost 100% of cases. Therefore, nature has designed it so that the spinal cord is under reliable protection of the spine.

The expression "healthy spine" in most cases is equivalent to the expression "healthy spinal cord", which is one of the necessary conditions for a high-quality full-fledged human life.

We offer an interesting video that will help you understand the anatomy of the spinal structures and their functioning.

The spinal cord is a section of the central nervous system of the spine, which is a cord 45 cm long and 1 cm wide.

The structure of the spinal cord

The spinal cord is located in the spinal canal. Behind and in front are two furrows, thanks to which the brain is divided into the right and left halves. It is covered with three membranes: vascular, arachnoid and solid. The space between the choroid and arachnoid is filled with cerebrospinal fluid.

In the center of the spinal cord, you can see the gray matter, in the cut, it resembles a butterfly in shape. The gray matter consists of motor and interneurons. The outer layer of the brain is the white matter of axons, collected in descending and ascending pathways.

In the gray matter, two types of horns are distinguished: the anterior, in which motor neurons are located, and the posterior, the location of the intercalary neurons.

In the structure of the spinal cord, there are 31 segments. From each stretch the anterior and posterior roots, which, merging, form the spinal nerve. When leaving the brain, the nerves immediately break up into roots - back and front. The posterior roots are formed with the help of axons of afferent neurons and they are directed to the posterior horns of the gray matter. At this point, they form synapses with efferent neurons, whose axons form the anterior roots of the spinal nerves.

In the posterior roots are the spinal ganglions, in which sensitive nerve cells are located.

The spinal canal runs through the center of the spinal cord. To the muscles of the head, lungs, heart, organs of the chest cavity and upper limbs, the nerves depart from the segments of the upper thoracic and cervical parts of the brain. The organs of the abdominal cavity and the muscles of the trunk are controlled by segments of the lumbar and thoracic parts. The muscles of the lower abdomen and the muscles of the lower extremities are controlled by the sacral and lower lumbar segments of the brain.

Spinal Cord Functions

There are two main functions of the spinal cord:

Conductor;
Reflex.

The conductor function consists in the fact that nerve impulses move along the ascending paths of the brain to the brain, and commands are received along the descending paths from the brain to the working organs.

The reflex function of the spinal cord is that it allows you to perform the simplest reflexes (knee reflex, hand withdrawal, flexion and extension of the upper and lower extremities, etc.).

Under the control of the spinal cord, only simple motor reflexes are carried out. All other movements, such as walking, running, etc., require the mandatory participation of the brain.

Pathologies of the spinal cord

Based on the causes of pathologies of the spinal cord, three groups of its diseases can be distinguished:

Malformations - postpartum or congenital abnormalities in the structure of the brain;
Diseases caused by tumors, neuroinfections, impaired spinal circulation, hereditary diseases of the nervous system;
Spinal cord injuries, which include bruises and fractures, compression, concussions, dislocations and hemorrhages. They can appear both independently and in combination with other factors.

Any disease of the spinal cord has very serious consequences. A special type of disease can be attributed to spinal cord injuries, which, according to statistics, can be divided into three groups:

Car accidents are the most common cause of spinal cord injury. Driving motorcycles is especially traumatic, since there is no rear seat back that protects the spine.
Falling from a height can be either accidental or intentional. In any case, the risk of spinal cord injury is quite high. Often athletes, fans of extreme sports and jumping from a height are injured in this way.
Domestic and extraordinary injuries. Often they occur as a result of a descent and fall in an unfortunate place, falling down stairs or on ice. Knife and bullet wounds and many other cases can also be attributed to this group.

With spinal cord injuries, the conduction function is primarily disrupted, which leads to very deplorable consequences. So, for example, damage to the brain in the cervical region leads to the fact that the functions of the brain are preserved, but lose connection with most organs and muscles of the body, which leads to paralysis of the body. The same disorders occur when the peripheral nerves are damaged. If sensory nerves are damaged, then sensation is impaired in certain areas of the body, and damage to the motor nerves impairs the movement of certain muscles.

Most of the nerves are mixed, and their damage causes both the impossibility of movement and loss of sensation.

Puncture of the spinal cord

Spinal puncture is the introduction of a special needle into the subarachnoid space. A puncture of the spinal cord is performed in special laboratories, where the patency of this organ is determined and the pressure of the cerebrospinal fluid is measured. The puncture is carried out both for therapeutic and diagnostic purposes. It allows you to timely diagnose the presence of a hemorrhage and its intensity, find inflammatory processes in the meninges, determine the nature of a stroke, determine changes in the nature of the cerebrospinal fluid, signaling diseases of the central nervous system.

Often, a puncture is done to introduce radiopaque and medicinal fluids.

For therapeutic purposes, a puncture is performed to extract blood or purulent fluid, as well as to administer antibiotics and antiseptics.

Indications for puncture of the spinal cord:

Meningoencephalitis;
Unexpected hemorrhages in the subarachnoid space due to rupture of the aneurysm;
cysticercosis;
myelitis;
meningitis;
Neurosyphilis;
Traumatic brain injury;
Liquorrhea;
Echinococcosis.

Sometimes during operations on the brain, a spinal cord puncture is used to reduce intracranial pressure parameters, as well as to facilitate access to malignant neoplasms.