The structure of the spinal canal. Spinal cord, structure and functions, anatomy of the human spinal canal. Reflex and motor functions

The spinal cord, the structure and functions of which are complex and multifaceted, is one of the main organs of the nervous system (central) of all vertebrates, including highly developed ones. The functioning of the spinal cord of animals (especially lower ones) is largely autonomous from other organs. In higher organisms (humans), the activity of the spinal cord is controlled and controlled by the centers of the brain and, to a certain extent, is dependent. The external structure of the spinal cord differs among individuals.

The study and detailed analysis of the structure of the spinal cord and its functional abilities have been carried out for many years, but even in our time they have not lost their relevance. Research in this area is the key to understanding the capabilities of any vertebrate.

The uniqueness of the structure lies in the set of elements, their diversity and originality. Each element of the system has its own purpose and clearly defined specified parameters. The materials with which nature has endowed the brain have so far not been amenable to artificial cultivation. The spine, in addition to its main functions, generally provides protection to the brain matter from external influences.

Spinal cord: structure and functions, location

The spinal cord is located in a special canal of the spine; in appearance it resembles a long (on average 40-45 cm), thin (10-15 mm in diameter) cylinder with a narrow canal in the center. Such a conventional cylinder is protected from above by shells.

In the spinal canal, the spinal cord extends from the highest vertebra of the neck above to the upper border of the second cingulate vertebra below. At the same time, it completely copies the shape and appearance of the spinal column. At the top, the cerebral body becomes a flattened brainstem that connects to the cerebrum. The point of transition to the oblong form is where the primary spinal nerve of the neck appears.

Below, the spinal cord trunk ends in a cone-shaped process, which decreases to the terminal spinal thinnest filament. This filament is called terminal; at first it contains nervous tissue, and at the end of its length it consists entirely of tissue formations characteristic of the composition of the membranes of the spinal cord. This thread enters the sacral canal and fuses with its periosteum. In addition, it contains coccygeal nerves (one or more root endings).

The spinal cord does not completely fill the entire volume of the canal formed in the spine. A space appears between the brain tissue and the walls of the canal. The resulting cavities are filled, in addition to the membranes of the spinal cord and its fluid, with a fatty environment and various blood-carrying vessels.

General plan of the building (external)

How is the spinal cord structured? Upon closer examination, a deviation from the cylindrical shape is noticeable. Its almost cylindrical middle part has slightly deformed front and back parts. Along its length, the entire spinal cord has a different diameter, which gradually increases towards the top. The maximum diameter is observed in 2 thickenings. At the top, a cervical thickening (diameter 13-15 mm) should be noted, which is characteristic of the exit of the spinal nerve canal for the upper extremities.

Below, the girdle-sacral specific thickening (about 12 mm) determines the location of the nerves leading to the human legs. In a cross section of the spinal cord trunk, the following types of sections can be obtained: the middle part is almost a circle, at the top is an oval, at the bottom the shape approaches a square.

The surface of the spinal cord cylinder does not have a smooth appearance. The outer surface along the entire length of the spinal cord contains the so-called anterior fissure. This gap is more pronounced and noticeable in the middle part and less noticeable at the ends. The far surface of the spinal cord has a narrow posterior shallow groove. In the groove, a septum located in the middle is visible in the form of a plate of glial tissue. These canals divide the entire spinal cord into two halves. Each half of the spinal cord, in turn, has shallow grooves on its surface - the anterolateral and posterolateral grooves. In the region of the upper thoracic region, at the section of the grooves, there is an inconspicuous posterior intermediate groove (Fig. 1). The figure shows a diagram of the spinal cord, where:

• radices – spinal roots;
• nn. spinales – spinal nerves;
• A – upper part;
• B – lower part.

Segmentation of structure

The structural features of the spinal cord are based on the segmentation and periodicity of the location of the nerve exits. The brain, located in the dorsal spine, includes 31 (extremely rarely - up to 33) segments. Any of these segments looks like a section in which the exit of two pairs of radicular processes is ensured.

The structure of the spinal cord can be characterized as 5 regions: coccygeal, sacral, cervical, thoracic and lumbar. It is in these parts (in their segments) that the nerves emerge. To the muscles of the head, upper extremities, organs of the chest cavity, heart and lungs, nerves extend from the upper thoracic and cervical parts. The muscle mass of the torso and all organs located in the peritoneum are connected to nerve canals formed in the thoracic and lumbar regions. Control of the limbs (legs) and part of the abdominal cavity from below is carried out by nerves for which the segments of the lower regions are responsible.

On the surface of any segment (on both sides) there are 2 anterior and 2 posterior filaments, which form the corresponding radicular endings. The anterior filaments usually contain the axons of nerve cells and form roots containing efferent (centrifugal) fibers for transmitting impulses to the periphery. In this case, the dorsal roots contain afferent fibers that ensure the reverse process of directing impulses from the periphery to the center.

Both roots of the same level are components of the spinal nerve, and all formed pairs belong to a specific segment.

Internal structure diagram

The internal general plan of the structure of the spinal cord is characterized by the presence, location and concentration of white and gray matter. The so-called gray matter is located in the center of the brain stem and is comparable in shape to a regular butterfly. Around the gray matter is concentrated the substance, which is usually called white. Along the length of the spinal cord cylinder, the volume and ratio of substance concentrations changes. In the central part, the volume of white matter of the spinal cord noticeably (many times) exceeds the content of gray matter.

At the top, the ratio changes and the amount of gray matter increases significantly. Similarly, the predominance of gray matter is observed in the lumbar region. Towards the bottom, the amount of both substances decreases, but the decrease in white matter occurs much faster. At the very bottom (in the conus region), almost the entire volume of the spinal cord trunk is filled with gray matter.

The central canal of the trunk is filled with liquor. In this case, the channel located in the center of the trunk and the cavities between the meninges are connected and allow spinal cord fluid to circulate through the formed channels.

Structure of white matter

An integral part of the white matter are the nerve fibers of the myelen group, forming a kind of bundle, and neuroglia. Various blood vessels run through the white matter. The grooves divide the white matter in each of the halves of the nucleus into several (usually three) funiculi. Particles concentrated in different halves of the substance located in the spinal canal are connected to each other by a thin white solder. There are three types of cords: anterior, lateral and posterior.

The white matter is traversed by fibers that create pathways for centrifugal and centripetal impulses. These fibers create their own bundles and provide connection between the spinal cord segments. The fascicles are adjacent to the adjacent gray matter.

Gray matter of the spinal cord

The gray matter located in the spinal canal includes characteristic nerve cells with their process endings, without a membrane. It is formed from gray columns located in different halves of the spinal cord, and they are connected by a cross-link (central substance). In the middle sections of the spinal cord, this substance has an inconspicuous central canal running through it from beginning to end. From below, the central channel widens. This dilated area is called the terminal ventricle.

The composition of gray matter is based on multipolar neurons, which distinguishes it from white matter. Groups of cells of the same type found in gray matter are called nuclei.

In the structure of the gray matter, protruding parts called horns are distinguishable. At the ends of these horns there are nuclei and processes of various nerve cells (Fig. 2). A diagram of 2 segments is presented, in which white matter is shown on the right and gray matter on the left.

Functional Features

The substance (located in the spinal canal), being an integral part of the central nervous system, performs complex and diverse functions. It is connected by centrifugal and centripetal nerve fibers with all the most important human organs. The spinal cord receives and transmits impulses from the motor system and all internal life-support systems and human organs.

The main task of the spinal cord is to provide reflex and conduction functions. In turn, the reflex function can be divided into afferent (sensitive) and efferent (motor).

Features of the reflex function

As the center that is responsible for the body's reflexes, the spinal cord has the ability to activate motor and autonomic (sensory) reflexes. With its nerve canals, it bilaterally connects peripheral organs with the brain.

The afferent function of the substance located in the spinal canal is achieved by delivering appropriate impulses to the necessary sections of the gray matter in the head. These impulses contain information about the impact of external and internal environmental factors. Through a parallel channel, the gray matter, in turn, transmits effector neurons and causes the corresponding organ to react. By transmitting autonomic reflexes, the central nervous system organ leads to changes in the activity of internal life support systems.

The motor function of the spinal cord is to implement and regulate the reflexes of the muscles of the movement system. Motor neurons belonging to the spinal cord carry impulses to the corresponding muscles located on the arms, legs, body, and neck.

The central nervous system organ, located in the spinal canal, becomes involved in the organization of all types of movement.

Conductor function

The conductive function of the spinal cord is determined by the uninterrupted transmission of impulses along its parallel communication paths between the periphery and the gray matter cortex in the head. Various impulses reaching the spinal cord from the radicular endings are transmitted from one segment to another along a short path, and to the cerebral cortex through a long path.

Along the first path of the central nervous system organ, located in the spinal canal, nerve impulses go to the desired part of the brain. Such ascending pathways are formed by the axons of receptor neurons, for example, the spinocerebellar tract, lateral spinothalamic tract, ventral spinothalamic tract.

The reverse (descending) path receives command impulses from the brain to the internal organs. These pathways are provided by the axons of nuclear neurons.

Summing up and conclusions

The spinal cord is a very complex and multifunctional system in the central nervous system circuit. The normal functioning of internal organs and the musculoskeletal system depends on the functioning of each part of the spinal cord.

A disruption or malfunction of a substance located in the spinal canal can cause immobility of a person, paralysis of any organ, disruption of the respiratory, digestive and other systems. Improving knowledge on such issues as the structure and functions of the spinal cord is the path to understanding human capabilities and the development of medicine.

The spinal cord lies in the spinal canal and in an adult is a cord 41-45 cm long, somewhat flattened from front to back. At the top it directly passes into the brain, and at the bottom it ends with a conical point, from which the terminal filament extends downwards. This thread descends into the sacral canal and is attached to its wall.

Structure

The spinal cord has two thickenings: cervical and lumbar, corresponding to the exit points of the nerves going to the upper and lower extremities. The anterior and posterior longitudinal grooves divide the organ into two symmetrical halves, each in turn has two weakly defined longitudinal grooves, from which the anterior and posterior roots emerge - the spinal nerves. The exit point of the roots does not correspond to the level of the intervertebral foramina and the roots, before leaving the canal, are directed to the sides and down. In the lumbar region they run parallel to the filum terminale and form a bundle called the cauda equina.

From the spinal cord, formed from the anterior (motor fibers) and posterior (sensory fibers) roots, 31 pairs of mixed spinal nerves depart. The area corresponding to the origin of a pair of spinal nerves is called a nerve segment, or a segment of the spinal cord. Each segment innervates specific skeletal muscles and skin areas.

The cervical and upper thoracic segments innervate the muscles of the head, girdles of the upper limbs, chest organs, heart and lungs. The lower thoracic segments and part of the lumbar segments are responsible for controlling the muscles of the trunk and intra-abdominal organs. From the lower lumbar segment and the sacral segment, nerves extend to the lower extremities and partially to the abdominal cavity.

Gray matter structure

A cross section of the spinal cord has the appearance of a butterfly, which is formed by gray matter surrounded by white matter. The wings of a butterfly are symmetrical sections in which the anterior, posterior and lateral columns (or horns) are distinguished. The front horns are wider than the rear ones. The posterior roots enter the posterior horns, and the anterior roots emerge from the anterior horns. In the center of the gray matter, along its entire length, there is a channel where cerebrospinal fluid circulates, which supplies nerve tissue with nutrients.

Gray matter is formed from more than 13 million nerve cells. Among them, three types are distinguished: radicular, bundle, and intercalary. The anterior roots contain the axons of the root cells. The processes of tuft cells connect the parts of the spinal cord with each other, and the intercalary ones end at synapses within the gray matter.

Neurons with a similar structure are united into the nuclei of the spinal cord. In the anterior horns, ventromedial, ventrolateral, dorsomedial and central pairs of nuclei are distinguished, in the posterior horns - proper and thoracic. In the lateral horns there is a lateral intermediate nucleus formed by association cells.

White matter structure

The white matter consists of processes and bundles of nerve cells that form the organ's conduction system. Constant and unhindered transmission of impulses is ensured by two groups of fibers:

1. Short bundles of nerve endings that occupy different levels of the spinal column are associative fibers.
2. Long fibers (projection) are divided into ascending, which go towards the cerebral hemispheres, and descending, which go from the hemispheres to the spinal cord.

Pathways

Long ascending and descending pathways connect the periphery to the brain using two-way communication. Afferent impulses along the spinal cord pathways are carried to the brain, transmitting to it information about all changes in the external and internal environment of the body. Along descending pathways, impulses from the brain are transmitted to effector neurons of the spinal cord and cause or regulate their activity.

Ascending paths:

1. Posterior funiculi (sensory tracts), which carry signals from skin receptors to the medulla oblongata.
2. Spinothalamic, send impulses to the thalamus.
3. Dorsal and ventral (spinocerebellar) are responsible for conducting excitation from proprioceptors to the cerebellum.

Descending Paths

1. Pyramidal - runs in the anterior and lateral columns of the spinal cord and is responsible for performing movements.
2. The extrapyramidal tract starts from the structures of the brain (red nucleus, basal ganglia, substantia nigra) and goes to the anterior horns and is responsible for involuntary (unconscious) movements.

Spinal cord membranes

The organ is protected by three membranes: hard, arachnoid and soft.

1. The dura mater is located on the outside of the spinal cord and does not fit tightly to the walls of the spinal canal. The resulting space is called the epidural; connective tissue is located here. Below is the subdural space at the border with the arachnoid membrane.
2. The arachnoid membrane consists of loose connective tissue and is separated from the soft membrane by the subarachnoid space.
3. The pia mater directly covers the spinal cord, limited from it only by a thin glial membrane.

Blood supply

The anterior and posterior spinal arteries descend along the spinal cord and are connected to each other by multiple anastomoses. Thus, a vascular network is formed on its surface. Also, the central arteries depart from the anterior spinal artery, which penetrate into the substance of the spinal cord near the anterior commissure. 80% of the blood supply comes from the anterior spinal artery. Venous outflow occurs through the veins of the same name, which flow into the internal vertebral venous plexuses.

Functions

The spinal cord has two functions: reflex and conduction.

As a reflex center it carries out complex motor and autonomic reflexes, and is also the site of closure of reflex arcs, which consist of three links: afferent, intercalary and efferent.

It is connected by afferent (sensitive) pathways to receptors, and by efferent (motor) pathways to muscles and internal organs.

An example is the congenital and acquired reflexes of a person; they are closed at different levels of the spinal cord: the knee at the level of the 3-4 lumbar segment, the Achilles at the 1-2 sacral segment.

Conductor the function is based on the transmission of impulses from the periphery (from skin receptors, mucous membranes, internal organs) to the brain along the ascending pathways and back through the descending pathways.

Similarities and Differences in Brainstem and Spinal Cord Functions

The brainstem is the structure into which the spinal cord passes through the foramen magnum and has a structure similar to it. The similarity lies in their performance of reflex and conduction functions.

They differ in the location of the gray matter: the brain stem is characterized by accumulations of gray matter in the form of nuclei, which are responsible for vital functions: breathing, blood circulation, etc., and in the spinal cord it is in the form of columns. Also, the trunk is an autonomous substance in the regulation of sleep, vascular tone, consciousness, and the spinal cord carries out all actions under the control of the brain.

A person eats, breathes, moves and performs many other functions thanks to the central nervous system. It consists mainly of neurons (nerve cells) and their processes (axons), through which all signals pass. It is impossible not to mention glia, which is an auxiliary nerve fiber. Thanks to this tissue, neurons generate impulses that go to the brain and spinal cord. It is these 2 organs that are the basis of the central nervous system and control all processes in the body.

The human spinal cord plays a special role and you can understand where it is located by looking at the cross section of the spine, since that is where it is located. Focusing on the structure of this organ, you can understand what it is responsible for and how it interacts with most human systems.

The spinal cord consists mainly of the arachnoid membrane, as well as soft and hard components. The fat layer, localized directly under the bone tissue in the epidural space, protects the organ from damage.

Most people know where the spinal cord is located, but few understand its anatomical features. This organ can be imagined as a thick (1 cm) wire, almost half a meter long, which is localized in the spine. The seat of the spinal cord is the spinal canal, which consists of vertebrae, due to which it is protected from external influences.

The organ begins at the occipital foramen and ends at the lumbar level where it is presented in the form of a cone consisting of connective tissue. It is shaped like a thread and goes straight to the tailbone (2 vertebrae). You can see the segments of the spinal cord in this figure:

The roots of the spinal nerves emerge from the canal, which serve to carry out movements of the arms and legs. At the top and in the center they have 2 thickenings at the level of the neck and lower back. In the lower part, the roots of the spinal cord resemble a ball formed around the spinal filaments.

A cross section of the spinal cord looks like this:

The anatomy of the spinal cord is designed to answer many questions related to the work of this organ. Judging by the diagram, the groove of the spinal nerve is localized behind the organ, and a special hole is located in front. It is through it that the nerve roots emerge, innervating certain systems of the body.

The internal structure of a spinal cord segment reveals many details of its functioning. The organ consists primarily of white (a set of axons) and gray (a set of neuron bodies) substance. They are the beginning of many nerve pathways and such segments of the spinal cord are mainly responsible for reflexes and transmission of signals to the brain.

The functions of the spinal cord are varied and depend on the level at which part the nerves are located. For example, the nerve tracts of the anterior roots of the central nervous system come from the white matter. The back of the fibers are sensitivity indicators. From them a segment of the spinal cord is formed, in which the spinal roots on both sides are collected. The main task of white matter is to transmit received impulses to the brain for further processing.

The structure of the human spinal cord is not as complex as it seems. The main thing to remember is that the spine includes 31 segments. They all differ in size and are divided into 5 sections. Each of them performs specific functions of the spinal cord.

White matter

The spinal canal is where white matter accumulates. It consists of 3 cords surrounding the gray matter and consists mainly of axons covered with a myelin sheath. Thanks to myelin, the signal moves through them faster, and the substance gets its own shade.

White matter is responsible for innervation of the lower extremities and sending impulses to the brain. You can see its cords, as well as the horns of the gray matter in this picture:

Gray matter

Most people don't understand what gray matter looks like or why it is shaped the way it is, but it's actually quite simple. Due to the accumulation of nerve cells (motor and interneurons) and the virtual complete absence of axons, it has a gray color. The gray matter is localized in the spinal canal and many people think it is a butterfly because of the pillars and plate in the center.

The gray matter is primarily responsible for motor reflexes.

In its center there is a canal, which is a container for the cerebrospinal fluid, which is the cerebrospinal fluid. Its functions include protection from damage and maintaining acceptable pressure inside the skull.

The main amount of gray matter is in the anterior horns. They consist mainly of motor nerve cells, which perform the function of innervation of muscle tissue at the level of this segment. A smaller amount of substance goes to the posterior horns. They consist mainly of interneurons, which serve to communicate with other nerve cells.

If you look at the spinal canal in section, you will notice the intermediate zone, localized in the space between the anterior and posterior horns. This area is located only at the level of the 8th vertebra of the cervical region and extends up to the 2nd segment of the lumbar region. The lateral horns, which are a collection of nerve cells, begin in this area.

The role of pathways

The pathways serve to connect the spinal cord and brain and originate in the posterior cord of the white matter. They are divided into 2 types:

• Ascending pathways (signal transmission);
• Descending pathways (receiving the signal).

To have complete information about their anatomical features, you need to look at this figure:

The signal is transmitted through certain bundles, for example, the upper part of the body in the spinal cord is the sphenoid plexus, and the lower part is thin. You can see where these fibers are located next to in this figure:

The spinocerebellar tract plays a special role in the conduction system. It starts from the skeletal muscles and ends directly in the cerebellum itself. Special attention should be paid to the thalamic pathway. It is responsible for the perception of pain and human temperature. The thalamus receives input from the anterior cerebellar tract, which consists primarily of interneurons.

Functions

A person has always had many questions regarding his body, because it is difficult to understand how all systems are connected. The structure and functions of the spinal cord are interconnected, so any pathological changes have dire consequences. It is virtually impossible to eliminate them, so you need to take care of your spine.

The spinal cord is responsible for the following functions:

• Conductor. Its essence lies in transmitting a signal to certain parts of the body, depending on the location of the nerve bundle. If it comes to the upper half of the body, then the cervical region is responsible for it, the lumbar region is responsible for the organs, and the sacral region innervates the pelvis and lower limbs.
• Reflex. This function is performed without the participation of the brain, for example, if you touch a hot iron, the limb moves involuntarily.

Fixed spinal cord

There are many different pathologies associated with the spinal cord, the treatment of which is carried out mainly in a hospital setting. Such diseases include tethered spinal cord syndrome. This pathological process is diagnosed extremely rarely and the disease is typical for both children and adults. The pathology is characterized by fixation of the spinal cord to the spinal column. Most often the problem occurs in the lumbar region.

A fixed spinal cord is usually detected in a diagnostic center using instrumental examination methods (MRI), and it occurs due to the following reasons:

• Neoplasms compressing the spinal cord;
• Scar tissue that appears after surgery;
• Severe injury in the lumbar region;
• Chiari defect.

Typically, tethered spinal cord syndrome in patients manifests itself in the form of neurological symptoms and the main manifestations concern the legs and the area of ​​​​damage. A person’s lower limbs become deformed, it becomes difficult to walk, and malfunctions in the functioning of the pelvic organs appear.

The disease occurs at any age and the course of treatment usually consists of surgery and a long recovery period. Basically, after surgery, it is possible to eliminate the defect and partially relieve the patient from the consequences of the pathology. Because of this, people begin to actually walk freely and stop experiencing pain.

There is another pathology that some experts associate with the spinal cord, namely hemispasm (hemifacial spasm). It is a disorder of the facial nerve resulting in contractions of the muscle tissue located on the face. The disease occurs without pain and such spasms are called clonic. They arise due to compression of the nervous tissue in the area where it exits the brain. Diagnosis of the pathological process is carried out using MRI and electromyography. According to statistics compiled every year, hemifacial spasm can be diagnosed in 1 in 120,000 people and women suffer from it 2 times more often.

Mostly, compression of the facial nerve occurs due to blood vessels or a neoplasm, but sometimes hemispasm occurs due to the following reasons:

• Demyelination process;
• Spikes;
• Bone abnormalities;
• Tumors located in the brain.

Hemifacial spasm can be eliminated with drug therapy. Baclofen, Levatrace, Gabapentin, Carbamazepine, etc. are used to treat the facial nerve. They will have to be taken for quite a long time, so this course has its disadvantages:

• Over time, the effect of the medications begins to wear off more and more quickly, and to treat the facial nerve you will have to change the medications or increase the dosage;
• Many of the drugs listed have a sedative effect, so people diagnosed with hemispasm are often in a sleepy state.

Despite the disadvantages, many cases of complete healing of the facial nerve and relief of hemispasm have been recorded. Drug therapy had a particularly good effect on the early stages of pathology development.

Hemifacial spasm can also be eliminated by injecting botulinum toxin. It quite effectively eliminates the problem at any stage. The disadvantages of the procedure include high cost and contraindications, which include allergic reactions to the composition of the drug and eye diseases.

The most effective and fastest treatment for hemispasm is surgery. It is carried out to eliminate compression and if the operation is successful, the patient is discharged within a week. The full recovery effect is achieved quite quickly, but in some cases it lasts up to six months.

The spinal cord is an important center of the nervous system and any deviations in its structure can affect the entire body. That is why, if neurological symptoms appear, you should contact a neurologist for examination and diagnosis.

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 the lumbar region, called the cauda equina. 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.

The external structure is the shells and the space between them.

Meninges

1. 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.
2. Arachnoid- a network of thin plates of connective tissue, the structure of which resembles 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.
3. 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

• Internal, the length of which is approximately 15 cm. The internal part of 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.
• The outer one, the length of which is 8 cm. The outer part of the terminal filament begins below the second vertebra of the sacral region, 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.

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 are the anterolateral and posterolateral grooves, through which the anterior and posterior axons pass, which form the nerve roots.

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

The anterior and posterior roots at the exit from the medulla are connected into a single nerve node (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.

• in the cervical region - 8;
• in the thoracic region - 12;
• in the lumbar region - 5;
• in the sacral region - 5;
• in the 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).

A little about secrets

Have you ever experienced constant back and joint pain? Judging by the fact that you are reading this article, you are already personally familiar with osteochondrosis, arthrosis and arthritis. Surely you have tried a bunch of medications, creams, ointments, injections, doctors and, apparently, none of the above has helped you... And there is an explanation for this: it is simply not profitable for pharmacists to sell a working product, since they will lose customers! Nevertheless, Chinese medicine has known the recipe for getting rid of these diseases for thousands of years, and it is simple and clear. Read more"

Functions of the organ

The structure and functions of the spinal cord are the most important system that supports the normal functioning of the human body.

• 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.

• the cervical and thoracic regions are connected to the head, chest muscles, and chest organs;
• 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 the functionality of the lower extremities and pelvic organs.

The spinal cord is a complex and vulnerable system, the condition of which determines not only general well-being, but also many reflexes. Diseases or injuries affecting the spinal cord are extremely dangerous, because they end in failure and, at best, 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.

- a rather complex system that is responsible for many processes in the body and which is quite difficult to understand on your own. Basic knowledge can be obtained by studying anatomy at school, but when it comes to a more in-depth analysis, many incomprehensible issues arise.

Let's try to figure out what the spinal cord is, how it is structured, what functions it performs, and just understand why it is needed at all.

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Spinal cord as part of the nervous system

- one of the components of the human nervous system. In Latin its name looks like medulla spinalis.

It is a thick cylindrical tube with a narrow channel located inside it. It is located in the spinal canal, or, more simply, inside the spine.

This organ has a rather complex structure and segmental structure. The main function of this organ is the transmission of various impulses and signals from the human brain to specific organs. In addition, it performs reflex activity, that is, it is responsible for human reflexes, both simple and more complex reflexes.

Human nervous system

The meaning of the spinal cord

There are only two main and most important functions:

• Reflex. To put it simply, a whole series of reflex arcs are closed on this organ. It is thanks to this that reflexes are carried out (the so-called spinal reflexes).
• Conductor. The organ in this case acts as a conductor. It conducts signals that come from various organs to the brain. It is through this organ that the brain receives all information and processes it. Everything works the same way in the opposite direction.

Spinal cord location

The organ is located in the spinal canal (located). This canal is quite long and practically reaches the lower vertebrae. In fact, this is a special canal, which is an oblong hole in which the spinal cord lies. From the sides it is protected by vertebrae, as well as intervertebral discs.

The organ is also located at the lower edge of the foramen magnum, where connections with the brain occur. It is in this place that there is a huge number of roots that directly connect to the human brain. This connection is called the left and right spinal nerves.

Spinal cord location

The bottom ends at the level of 1-11 vertebrae. Afterwards the organ turns into a thin terminal filament. In fact, it is still the spinal cord, because it contains nervous tissue.

Topography and shape of the spinal cord

Let's look at the features of location (topography) and shape.

To do this, consider a number of features:

• The average length is 42-43 centimeters. In men, the length is often several centimeters longer, while in women, on the contrary, it is shorter.
• Weight 33-39 grams.
• There is a middle gap on the front part, it is clearly visible. You can notice that it seems to be growing into the organ. In essence, it creates a kind of partition that divides the brain into two sections.
• In the cervical and lumbosacral regions it is possible to
• mark two fairly serious thickenings. This is due to the fact that innervation of the upper and. In simple terms, this is where the nerve endings from the limbs “attach” to the spinal cord, which
• Allows them to transmit the necessary signals.
• The spinal cord is topographically practically not connected with the vertebrae. The various sections are not located depending on a specific vertebra or several vertebrae.

The increase in volume in these areas is due to the fact that this is where the largest number of nerve cells are located, as well as fibers through which signals are transmitted from the limbs and back.

Despite the fact that the spine is a kind of “storage place” for the organ, the location of the nerve endings, especially in the lower part of the spine, does not correspond to specific vertebrae. This is due to the fact that the length of the spinal cord is less than the length of the human spine.

That is why it is necessary for doctors to know the exact location of each of the segments, because they will not be able to navigate along the spine.

Location in the spine

Characteristics of the spinal cord depending on age

Let's consider the features, depending on the age of the person:

• In a newly born child, the length of the organ is 13.5-14.5 centimeters.
• At 2 years, the length increases to 20 centimeters.
• At about 10 years old, the length can reach 29 centimeters.
• Growth ends in different ways, depending on the characteristics of a particular person’s body.

Let's look at the external features and changes depending on age:

• In infants, cervical and lumbar thickening is more noticeable than in adults. The same applies to the width of the central channel.
• The above features become almost invisible by the age of two.
• The volume of white matter grows many times faster than the volume of gray matter. This is due to the fact that the segmental apparatus is formed earlier than the pathways that connect the brain and spinal cord.

Otherwise, there are practically no age-related characteristics, because from birth the spinal cord performs almost all functions, as in an adult.

Features of the structure of the spinal cord

Now let's look at the structural features, one by one examining each segment separately that makes up the organ.

Spinal cord membranes

The spinal cord is located in a kind of canal, but at the same time it has protection, which also performs a huge number of functions.

The spinal membranes of the spinal cord, of which there are three in total:

• hard shell;
• arachnoid;
• soft shell.

All shells are interconnected, and below they fuse with the terminal filament.

Spinal cord membranes

The spinal cord contains white and gray matter.

Let's try to figure out what it is:

• White matter - a complex system of pulpal and non-pulmonary nerve fibers, as well as supporting nervous tissue.
• Gray matter - these are nerve cells and their processes.

White and gray matter of the spinal cord

Spinal cord sections

There are five main sections of the spine, let’s look at them starting from the top:

• cervical;
• chest;
• lumbar;
• sacral;
• coccygeal

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Spinal nerves

They are paired nerve trunks, of which there are 31 pairs in total:

• 8 cervical;
• 12 breast;
• 5 lumbar;
• 5 sacral;
• pair of coccygeal

Each nerve is responsible for a specific area of ​​the body. This area contains bones, muscles, internal organs or skin. The task of a specific pair of nerves is to transmit impulses from the area to the spinal cord and back. It is thanks to this that a person can feel pain, discomfort, temperature, etc.

Spinal nerves

Spinal cord segments

There are as many segments as there are pairs of roots - 31. A segment represents a specific area of ​​the human body for which a specific pair of roots is responsible.

All of them are divided into:

• cervical;
• chest;
• lumbar;
• sacral;
• coccygeal

Due to the fact that the length of the spine is greater than the length of the spinal cord, it turns out that the nerve roots only in the upper part correspond to the level of the intervertebral foramina.

Below, in order to enter a special hole, the nerves of the lower sections descend lower parallel to the spine. Thus, they emerge at the level of the filum terminale.

Spinal cord segments

Veins and arteries of the spinal cord

The organ receives blood through the anterior and a pair of posterior spiral arteries. But these arteries are capable of supplying only 2-3 upper cervical segments. The rest of the part is fed by the radicular-spiral arteries, which receive blood from the branches of the vertebral and ascending cervical arteries.

Below, the spine receives blood from the intercostal and lumbar arteries. Both of these arteries are peculiar branches of the well-known artery called the aorta.

Functions of the spinal cord

Let's move on to looking at functions. For convenience, we will consider each separately.

Reflex and motor functions

This function is responsible for human reflexes. For example, if a person touches something very hot, he will reflexively withdraw his hand. This is a reflex or motor function. But let’s take a step-by-step look at how it’s all tripled and how it’s connected to the spinal cord.

It’s best to look at everything using an example, so let’s imagine a situation where a person touched a very hot object with his hand:

1. When touched, the signal is primarily received by receptors that are located throughout the human body.
2. The receptor transmits a signal to the nerve fiber.
3. The signal is sent along the nerve fiber to the spinal cord.
4. On the approach to the organ there is a spinal ganglion, where the body of the neuron is located. It was along its peripheral fiber that the impulse transmitted from the receptors was received.
5. Now the impulse is transmitted along the central fiber to the posterior horns of the spinal cord. At this moment, a kind of switching of the impulse to another neuron occurs.
6. The processes of the new neuron transmit the impulse to the anterior horns.
7. Now the return journey begins, because the anterior horns transmit the impulse to the motor neurons. They are responsible for the movement of the upper limbs.
8. Through these neurons, the impulse is transmitted directly to the hand, after which the person removes it (motor function).

Reflex arc in the circuit

As a result of this whole process, a person withdraws his hand from the hot object and a reflex arc closes. The whole process takes a split second, so when touching any object, a person immediately feels its temperature, consistency and other features.

Conductor function

In this situation, the organ acts as a conductor. The conductor in this case is between the receptors and the brain. The receptors receive an impulse that is transmitted to the spinal cord and then to the brain. The information is analyzed there and transmitted back.

Thanks to this function, a person receives sensitivity, as well as a sense of himself in space. This has been proven many times, and this becomes especially evident in cases of serious spinal injuries.

Integrative function

This function is often forgotten, but it is no less important for a person than others. The integrative function manifests itself in reactions that cannot be classified as simple reflexes. In order for the body to respond, it is necessary to involve other parts of the human nervous system. This is how the spinal cord can form a connection between organs.

These include reflexes of chewing, swallowing, regulation of digestion, breathing and much more. In fact, this is an invisible function that ensures normal functioning.

Spinal cord dysfunction

Impaired function can lead to serious consequences and often even death. Disorders often occur either due to injury or due to various diseases.

For example, due to dysfunction of the spinal cord, a person may lose sensitivity, in which case he may, for example, stop feeling temperature. In the worst case, the disorder can lead to uncontrollable actions of the limbs (or paralysis), disruption of the functioning of internal organs and the nervous system as a whole.

Spinal cord diseases

A list of the most common diseases that interfere with the full functioning of the organ in question:

• Heart attack.
• Polio.
• Transverse myelitis.
• Tumors.
• Decompression sickness.
• Nerve root lesions.
• Arteriovenous malformations.

Spinal cord puncture

Puncture of cerebrospinal fluid (CSF)- a procedure that pursues diagnostic, anesthetic and therapeutic purposes. The procedure itself consists of an injection of an angle under the arachnoid membrane between the 3rd and 4th vertebrae, and then a certain amount of cerebrospinal fluid is extracted for research.

During the procedure, the brain itself is not affected, so there is no need to worry about violations. However, this procedure is quite serious and painful.

Spinal cord puncture

Conclusion

To summarize, it should be said that the spinal cord is one of the most important organs in the human body. In many ways, it is thanks to it that a person can lead normal life activities, and also thanks to this organ, almost the entire nervous system functions.