The structure of the human spinal cord. The structure of the human spinal cord and its functions. The role of the reflex function

The functioning of all organs depends on how the central nervous system functions, as well as general health person. Plays a big role here spinal cord. It is located in such a way that it is in relationship with every cell of the body. All motor reflexes are determined by his actions. This organ transmits signals to the brain - to the “central headquarters”, which carries out opposite communication with the organs.

What does the spinal cord look like?

Brain structure

The human spinal cord, somewhat similar to an electrical cable, fills the spinal canal. Moreover, this organ consists of two halves inside, which distribute the responsibilities of the right and left sides of the body.

The formation of the brain occurs on the very early stage embryo development. It is this that is the basis on which all other elements of the embryo are built up. Having begun to develop at the end of the first month after conception, the spinal cord differentiates throughout pregnancy. At the same time, some departments undergo subsequent development in the first childhood years.

The entire spinal cord, placed in a canal, is wrapped in a triple membrane. At the same time, the inner one is soft enough, consisting of blood vessels, while the outer one is hard to provide protection to the tissues. Between them there is another “braid” - a cobweb. The space between this shell and the inner one contains liquid, which provides elasticity. The internal space is filled with a gray substance, shrouded in a white substance.

Cross section of the brain

If we consider the structure of the spinal cord in a cross section, then the structural shape of the gray substance, reminiscent of a small butterfly perched on a stump, is clearly visible in the cross-section. Each part of the structure has certain features, which are described below.

The nerve roots are “connected” to the gray matter, which, passing through the white matter, gather into nodes that determine the structure of the spinal nerve. Bundles of nerve fibers are the pathways that provide connections between the “central headquarters” and specific bodies. The spinal cord includes from 31 to 33 pairs of vertebrae, formed into segments.

Conus medullaris

The spinal canal is directly connected to the brain located in the head, and begins at the bottom of the back of the head. Unchanged, the canal passes all the way to the lumbar vertebrae and ends in a cone, which has a continuation in the form of a terminal filament, top part it contains nerve fibers.

The cone in its structure is represented by a three-layer connective tissue. On the vertebra in the area of the coccyx, where it is fused with the periosteum, the thread indicated above ends. The so-called “horse tail” is also located here - a bundle of lower nerves wrapping around the thread.

What is the nervous system represented by?

The main collection of nerve fibers is located in 2 places - sacral- lumbar region and in the neck area. This is expressed by peculiar seals responsible for the function of the limbs.

The spinal cord, filling the spinal canal, has a strictly fixed position and unchanged parameters. Its length in an adult is about 41-45 cm, while its weight is no more than 38 g.

The substance is gray

So, the medulla in a cross section looks like a moth, and is located inside the substance of a white tone. In the center, along the entire length of the spinal cord, there is a narrow canal, which is called the central canal. This channel is filled with cerebrospinal fluid, a type of cerebrospinal fluid responsible for the functioning of the nervous system.

Gray "moth"

The brain and the central spinal canal are interconnected. The spaces located between the membranes of the brain are also compatible - cerebrospinal fluid circulates in them. It is through puncture that it is taken for research when a number of problems affecting parts of the spinal cord are diagnosed.

Substance gray- This is a kind of pillars connected transversely by plates. There are only 2 adhesions: the posterior and anterior parts, which make up the central cerebral canal. They form a butterfly (letter H) from tissues.

Horns-protrusions extend from the substance to the sides. Paired wide ones fill the front part, narrow ones fill the back part:

The anterior ones contain movement neurons. Their processes (neurites) are formed into the roots of the spinal cord. The nuclei of the spinal cord, of which there are 5, are also created from neurons.
The posterior horn has its own nucleus of neurons in the middle. Each process (axon) is located towards the anterior horn, crossing the commissure. At the dorsal horn, an additional nucleus is formed from large neurons, which has dendrin branching in its structure.
Between the main horns there is also an intermediate medulla. Here you can observe a branch of the lateral horns. But it does not appear in all segments, but only from the 6th cervical to the 2nd lumbar. Nerve cells here create the lateral substance, responsible for the vegetative system.

The substance is white

The white substance enveloping the gray substance is a set of 3 pairs of cords. Between the grooves the anterior cord is located at the roots. There are also posterior and lateral, each located between specific grooves.

The fibers that form the light substance transmit signals emanating from the nerves. Some are directed through the canal into the brain, others - into the spinal cord and its underlying sections. Intersegmental connections are carried out by fibers of the gray substance.

The roots of the spinal cord, located posteriorly, are the fibers of the neurons of the spinal ganglia. Part is placed in the posterior horn, the rest diverge in different directions. A group of fibers entering the cords is directed to the brain - these are ascending pathways. Some of the fibers are located in the dorsal horns on intercalary neurons, the rest go to autonomous sections of the NS.

Types of pathways

It was already said above that the brain receives signals emanating from neurons. Signals move along these same paths in the opposite direction. The sphenoid bundle of neurons sends signals from endings located on the joints and muscles to the medulla oblongata.

The entire spinal cord, filling the spinal canal, functions as bundles that send signals to the upper and lower parts of the body. Each group starts with an impulse from “its” area and moves along the paths determined by it.

Thus, the medial intermediate nucleus gives rise to the anterior tract. On the opposite side of the horn is a pathway that is responsible for pain and heat sensations. Signals first enter the intermediate brain, and then the brain.

Functional features

Having studied the structure of the spinal cord, it is easy to come to the conclusion that this is sufficient a complex system, “built in” into the spinal canal, and technically resembling an intricate circuit electronic device. Ideally, it should work flawlessly and uninterruptedly, performing certain functions programmed by nature.

System structure

From the described structure of the brain it is clear that it has 2 main responsibilities: to be a conductor of impulses and to provide motor reflexes:

Reflexes mean the ability to involuntarily withdraw your hand at the risk of accidentally damaging it with a hammer while hammering nails, or sudden jump away from a mouse running past. Such actions are caused by a reflex arc that connects the skeletal muscles with the spinal cord. And the corresponding nerve impulses pass through it. At the same time, there are innate reflexes (established by nature at the genetic level) and acquired ones, which developed in the life process.
The functions of the conductor include impulse transmission along the ascending pathways from the spinal cord to the brain and into reverse order- descending. The spinal cord distributes these impulses to all human organs (according to installed program). For example, the sensitivity of the fingers is developed precisely due to the conductive function - a person touches a kitten, and an action signal is sent to the “headquarters”, forming certain associations there.

The channel through which motor functions are performed originates in the red nucleus, gradually moving to the anterior horns. A set of motor cells is located here. Reflex impulses are transmitted along the anterior pathways, voluntary impulses are transmitted along the lateral ones. The path to the forebrain from the vestibular nuclei ensures the balance function.

Vascular system

Brain function is not possible without normal blood supply, which is the same for the entire body. The spinal cord is constantly washed by blood passing through the arteries - spinal and radicular-spinal. The number of such vessels is individual, because Sometimes additional arteries are observed in some people.

How does blood supply to the brain occur?

There are always more dorsal roots (and therefore vessels), but their arteries are smaller in diameter. Each vessel washes its own blood supply zone. But the system also contains connections between vessels (anastomoses), which provides sufficient nutrition for the spinal cord.

An anastomosis is a backup channel used when the main vessel’s functions are impaired (for example, blockage by a blood clot). Then the spare element takes on the responsibility of transporting blood, immediately joining the process.

Plexus of blood vessels are formed in the membrane. So each root of the nerve system is accompanied by veins and arteries, forming a neurovascular bundle. It is its damage that leads to various pathologies manifested by painful symptoms.

To identify such a disorder, you will have to undergo a number of different diagnostic tests.

Each artery is accompanied by vena cava, into which blood flows from the spinal cord. To prevent the fluid from returning back, a set of special enclosing valves are located on the dura mater, which determine the correct direction of movement of the blood “river”.

Video. Spinal cord

Without normal reliable operation of such important body, like the spinal cord, it is impossible not only to move, but also to breathe. Any activity (digestion, bowel movements and urination, heartbeat, libido, etc.) is unthinkable without his participation, because brain functions completely control all these actions.

They are the ones who warn a person against various bruises and injuries, because... impulses carry information not only about touches, smells, movements, but also orient the body in space, and also help to respond to dangers. Therefore, it is so important to maintain the functionality of the important component squeezed into the spinal canal.

The spinal cord is part of the central nervous system. It is difficult to overestimate the work of this organ in the human body. After all, with any defects, it becomes impossible for the body to fully communicate with the outside world. No wonder it birth defects, which can be detected using ultrasound diagnostics already in the first trimester of pregnancy, 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 border of the spinal cord is considered to be the line connecting the upper edge of the first cervical vertebra with the lower edge of the occipital foramen.

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

It is interesting that 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 spinal column.

This fact is important in clinical practice, since when performing the well-known procedure at the lumbar level, the spinal cord is absolutely out of danger from 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 - with outside includes the tissues of the periosteum of the spinal canal, followed by the epidural space and inner layer hard shell.
Arachnoid - a thin, colorless plate fused with the hard shell in the area of the intervertebral foramina. Where there are no fusions, there is a subdural space.
Soft or vascular - separated from the previous membrane by the subarachnoid space with cerebrospinal fluid. Herself soft shell adjacent to the spinal cord, consists mostly of vessels.

The entire organ is completely immersed in the cerebrospinal fluid of the subarachnoid space and “floats” in it. Its fixed position is given 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 average length is about 42-44 cm, depending
from a person's height.
Weight is approximately 48-50 times less than the weight of the brain,
is 34-38 g.

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

There are 2 grooves running along the back and front of the spinal cord, which divide it into two absolutely symmetrical halves. Along the entire length of the organ there is a hole in the middle - the central canal, which connects at the top with one of the ventricles of the brain. Below, towards the area of the conus medullaris, the central canal expands, forming the so-called terminal ventricle.

Consists of neurons (nerve tissue cells), the bodies of which, concentrated in the center, form the spinal cord 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 inside the white matter is somewhat different in shape, which in cross section vaguely resembles a butterfly.

A specific type of cross section allows us to identify the following anatomical structures in the spinal gray matter:

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

The gray matter is surrounded on the outer side by white matter - these are essentially processes of neurons from the gray matter or nerve fibers. The diameter of the nerve fibers is no 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 sections 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 arranged in the form of conductive spinal tract 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.

Modern effective method treatment of back pain - pharmacopuncture. Minimum doses of drugs administered in active points, work better than tablets and regular injections: .

Which is better for diagnosing spinal pathologies: MRI or CT scan? Let's 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 (sensitive) roots.

The area of the spinal cord that is the “launching pad” for one pair of nerves is called a segment or neuromere. 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 part of the spine with the same name due to the difference in the length of the spine and the spinal cord. But the spinal roots still emerge from the corresponding intervertebral foramina.

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

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

Functions of the spinal cord

Now let’s talk about the physiology of the spinal cord, about what “responsibilities” are assigned to it.

The spinal cord contains segmental or working nerve centers that are directly connected to and control the human body. It is through these spinal working centers that the human body is subject to control by the brain.

In this case, certain spinal segments control clearly 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
	Breasts: 1,2, 5-8	Muscles and skin of the hands
	Breasts: 2-12	Muscles and skin of the body
	Chest: 1-11	Intercostal muscles
	Chest: 1-5	Muscles and skin of the head and neck, heart and lungs
	Chest: 5-6	Lower esophagus
	Chest: 6-10	Digestive organs
	Lumbar: 1-2	Inguinal ligament, adrenal glands, 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 genitalia, perineum (reflex centers of urination, erection and defecation)

The spinal cord carries out some autonomic or complex motor reflexes without brain intervention at all, thanks to the two-way connection it has with all parts of the human body - this is how the spinal cord performs its reflex functions. For example, the reflex centers for urination or erection are located in 3-5 sacral segments, and with spinal damage in this place, these reflexes may be lost.

Conductive spinal function is ensured by the fact that all the pathways connecting parts of the nervous system with each other are localized in the white matter. Along the ascending pathways, information from tactile, temperature, pain receptors and movement receptors from the muscles (proprioceptors) is transmitted 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 to the cervical spinal segments - in the vast majority of cases this leads to immediate respiratory arrest and death.

Serious damage to other spinal segments located below may not cause death, but partial or complete loss disability will result in almost 100% of cases. Therefore, nature intended that the spinal cord be under reliable protection spine.

The expression “healthy spine” in most cases is equivalent to the expression “healthy spinal cord” which is one of necessary conditions quality full life person.

We offer interesting video, which will help to understand the anatomy of the spinal structures and their functioning.

The spinal cord is the part of the central nervous system located in the spinal canal. The conventional boundary between the medulla oblongata and the spinal cord is considered to be the place of decussion and origin of the first cervical root.

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

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

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

Rice. 2. Location of the spinal cord in the spinal canal (cross-section) and exit of the spinal nerve roots: 1 - spinal cord; 2 - posterior root; 3 - anterior root; 4 - spinal node; 5 - spinal nerve; 6 - vertebral body.

Rice. 3. Diagram of the location of the spinal cord in the spinal canal (longitudinal section) and the exit of the spinal nerve roots: A - cervical; B - breast; B - lumbar; G - sacral; D - coccygeal.

The spinal cord is divided into gray and white matter. Gray matter is a collection of nerve cells to which nerve fibers approach and depart. In a cross section, the gray matter has the appearance of a butterfly. In the center of the gray matter of the spinal cord is the central canal of the spinal cord, barely visible to the naked eye. In the gray matter, there are anterior, posterior, and in the thoracic region, lateral horns (Fig. 1). To sensitive cells posterior horns the processes of the cells of the spinal ganglia, which make up the dorsal roots, are suitable; The anterior roots of the spinal cord extend from the motor cells of the anterior horns. The cells of the lateral horns belong to (see) and provide sympathetic innervation of the internal organs, vessels, glands, and the cell groups of the gray matter of the sacral region - parasympathetic innervation pelvic organs. The processes of the cells of the lateral horns are part of the anterior roots.

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

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

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

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

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

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

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

The spinal cord is the most important part of the human nervous system. 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 the 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 gray matter made of? 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 in close connection with the tasks being carried out. 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 spinal canal is lined from the inside with special cover 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 rear horns, and in the area of the thoracic spine, lateral horns are also formed.
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 upper sections there is much more white matter, since here the organ must have a much larger number of pathways.
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 spinal cord of an adult is somewhat shorter than the length of the spinal column, so 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 spinal cord roots are located in the spinal canal and do not exit directly from it. 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. Thus, in particular, it is carried out motor function organ.
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 single segment level, it has a fairly short path:

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 the 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 activity. 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 part of 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 anatomical features allows for timely diagnosis of certain pathological processes. An MRI image cannot be deciphered without a clear understanding of the normal structure of the nervous system.
Evaluation of clinical data is also based on the characteristics of the structure and functioning of the nervous system. Decrease or increase in certain nerve reflexes helps to establish the localization 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.

All vertebrates have a spinal cord. It is a narrow elongated cord, the length of which is on average 50 cm. It plays the role of a channel connecting the internal organs and the brain, and consists of several membranes, between which there are various kinds of liquids.

Anatomical information

First of all, let's determine where the spinal cord is located and what its structure is. This organ is located in the cavity of the spinal canal, between the processes and cartilages of the ridge. It originates from the brain, namely at the lower border of the foramen magnum. End point This organ is located between the 1st and 2nd lumbar vertebrae. At this point, the transformation into the conus medullaris occurs, which, in turn, transforms into the filum terminale. It reaches the tailbone and forms a bundle of nerve connections there, which is called the “cauda equina.” The length of the spinal cord depends on the height of the person and can be either 40 or 50 centimeters. Its weight also varies - from 34 to 39 grams.

Components

Since the spinal cord is the second most important center of the nervous system, it consists primarily of neurons. The organ has three membranes: soft, arachnoid and hard. In the center there is a main channel that transports all impulses to the brain, and the space between it and the tissues is filled cerebrospinal fluid. The hard outer shell is located in the epidural space, which is filled with fat and a venous network. It is worth adding that the organ has a structure that imitates the spine, that is, it looks like a long thin cord. For this reason, it was not difficult for our ancestors, who worked in the field of anatomy, to determine exactly where the spinal cord is located and to which other organs it is directly “connected.”

Basic “working” elements

The functions possessed by the spinal cord center would be impossible without two substrates - white and gray. They are located directly in the channel of the brain itself, while the amount of one or another substance predominates on various areas. The bulk of the gray substrate is concentrated in the upper part of the tube and in the lumbar region. White matter predominates in the chest area, and the lower it is, the more its amount decreases and gradually comes to zero. When we take a cross section of the spinal cord, we also see that the gray matter is the middle, which looks like the letter H, and it is surrounded on all sides by a white membrane.

Features of gray matter

This substrate consists mainly of nerve fibers, cells and processes. Initially, it seems that the gray matter is the most central part of the brain, but in fact it functions as just another shell, so to speak. In the very center there is a very narrow cavity, which widens slightly only in the area of the cervical vertebrae (at this stage the diameter is less than 1 mm). This cavity is the very channel through which the spinal cord transmits all the necessary information to the brain.

Characteristics of white matter

This substrate has a much more complex structure, consisting simultaneously of different types of cells and tissues, and is also characterized by an unstable thickness. The substance is based on myelinated and unmyelinated nerve fibers and neuroglia, the supporting nervous tissue. It's all shrouded in cobwebs blood vessels, between which connective tissue lies. Most neurons are collected in bundles, which makes the substrate viscous and dense. Important components of the white matter are the efferent and afferent pathways, to which association fibers join. These elements ensure the connection of all parts of the spinal cord with each other.

How reflexes are formed

The main function of the spinal cord is reflex. Numerous nerve plexuses and channels are adjacent to the organ on all sides, which carry impulses from all components of our body. This system coordinates and directs involuntary movements that occur during sleep, sensations of pain, etc. The reflexes of all vertebrates are relatively identical and are divided into several types:

Flexion reflex - the name speaks for itself. To be more precise, this is protective function the body, allowing us to remove a damaging stimulus, for example, quickly pull our hand away from something hot.
Proprioceptive is a reflex that prevents excessive stretching of muscle tissue.
Rhythmic and tonic functions are also the task of the spinal cord.
Animals and newborn children have a primitive reflex - an extensor impulse. The bottom line is that when the heel is compressed, involuntary straightening occurs knee joint. This function is considered primitive, and if a person, having matured, continues to react to such a stimulus, it means that his spinal cord is damaged.

Connection function

The tube running along the spine is called the brain for a reason. The structure of this organ is similar to the head center, in addition, they are directly connected to each other. The spinal cord contains a whole web of neurons, these fibers stretch to the most remote corners of our body and carry all the information about what is happening inside and outside us. Besides, nerve cells enveloped in vessels and capillaries, which form into special channels and go directly to the brain. As a result, it turns out that our spine, or rather what is in it, literally collects all the information about the functioning of the organs and transmits it to the main center.

It is worth remembering that any damage to the spinal cord is extremely dangerous. By losing at least one segment of it, you cut the “thread” through which your entire body functions.