What is the spinal cord? Brain and spinal cord

All vertebrates are 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 internal organs and the brain, and consists of several membranes, between which are various kinds liquids.

Anatomical information

First of all, let's determine where the spinal cord is located and what its structure is. This body located in the cavity spinal canal, between the processes and cartilages of the ridge. It originates from the brain, namely lower limit foramen magnum. The end point of this organ is 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 with 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 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 appears that the gray matter is the most central part brain, but in fact it performs the function of another, so to speak, shell. 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 much more complex structure, consists simultaneously of different types of cells and tissues, and is also characterized by unstable thickness. The substance is based on myelinated and non-myelinated nerve fibers and neuroglia - 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 white matter are efferent and afferent pathways to which associative fibers are attached. 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, arising 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. In addition, nerve cells are 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.

When examining neurological patients, attention should be paid to the condition of the carotid and vertebral arteries. In this case, the leading role belongs to ultrasound with Dopplerography (Fig. 4-14). If necessary, detected changes are confirmed by CT, MR or direct angiography.

Interventional radiology is the method of choice in the treatment of intracranial aneurysms and other vascular malformations. For this purpose, embolization of the aneurysm cavity is carried out using special embolization material (Fig. 4-15).

Rice. 4-13.CT angiography. Aneurysm of the right middle cerebral artery(arrow)

Rice. 4-14.Duplex study carotid artery. On the left is a longitudinal section of the vessel, on the right is a transverse section. In the initial section of the internal carotid artery, a plaque is visible, causing a pronounced narrowing of the lumen of the vessel

4.5. INTRACRANIAL HEMORRHAGES

(HEMATOMA)

Intracerebral and meningeal hemorrhages (hematomas) can be manifestations of complications hypertension, atherosclerosis or vascular malformation. Hemorrhages may be accompanied by

Rice. 4-15.Angiography of the vertebrobasilar vessels of a patient with an aneurysm of the terminal basilar artery (indicated by an arrow). On the left is an angiogram before surgery, on the right - after embolization of the aneurysm with microcoils. The aneurysm is no longer visualized

be driven by primary and secondary brain tumors. Hematomas are localized inside the brain (intracerebral) or between the membranes of the brain (subarachnoid, subdural, epidural).

Using CT, hemorrhage is easily diagnosed immediately after its development. This is explained by the high density gradient between the shed blood and the brain substance (Fig. 4-16). After some time, the intracerebral hematoma is surrounded by a zone of cerebral edema with reduced density. Extensive hemorrhages can lead to mass effect and break into the ventricles of the brain. Over time, the density of the hematoma decreases, and after 3-4 weeks it often becomes indistinguishable on CT. During the transition to a chronic state, atrophic and cystic changes develop at the site of the hematoma. The midline structures and/or sulci and ventricles of the brain are usually displaced towards the affected side. Brain hematomas at all stages of development (especially subacute and chronic) are clearly visible on MRI (Fig. 4-17).

Central nervous system- The brain and spinal cord are made up of gray and white matter.

Gray matter is a collection of bodies nerve cells, the white matter is formed by the axons of nerve cells. Gray coloration is also characteristic of those parts of the nervous system that contain clusters of neuron bodies that have migrated far beyond the neural tube (sympathetic and other nodes).

In that part of the neural tube that forms the spinal cord, neural cells are concentrated in the circumference of its cavity, forming Gray matter. The processes of these cells, located along the periphery of the tube wall, participate in the formation white matter. As the spinal cord develops, the cavity of the tube becomes narrow and turns into central canal of the spinal cord filled with cerebrospinal fluid.

In the anterior part of the neural tube, two interceptions are noticeable, which divide it into three primary vesicles: the anterior medullary vesicle, or forebrain. , prosencephalon, midbrain new bladder, or midbrain, mesencephalon, and the posterior medullary vesicle, or rhombencephalon, rhombencephalon.

Subsequently, five secondary bubbles are formed. Forebrain divided into two bladders: the telencephalon, telencephalon and diencephalon diencephalon.

The midbrain does not divide and becomes the third brain bladder. The rhombencephalon is divided into two vesicles: the hindbrain, metencephalon, and medulla oblongata, myelencephalon.

At the same time, as a result of uneven growth of the brain, a number of bends are formed: parietal - at the level of the middle brain bladder, pavement - in the region of the posterior brain bladder and occipital -on the border transition of the spinal cord into the medulla oblongata.

Due to the significant thickening of the walls and the complication of the surface topography of the brain, the cavities of the brain vesicles take the form of slits of different sizes and positions - ventricles of the brain.

The ventricles of the brain are filled with cerebrospinal fluid and communicate with each other and with the central canal of the spinal cord. The wall of each brain bladder develops into a specific part brain, and the cavity turns into the corresponding ventricle.

Ventral wall posterior section the rhombencephalon is converted into medulla oblongata, and back wall remains a thin plate and forms lower brain sail.

hindbrain make up the cerebellum and the pons. The cavity of the rhombencephalon turns into the fourth ventricle, which communicates through the holes with the subarachnoid space. The dorsal wall of the midbrain forms the roof of the midbrain, or quadrigemina, and the ventral wall forms the cerebral peduncles.

The cavity of the midbrain turns into a narrow canal - brain aqueduct, which connects the third and fourth ventricles.

The diencephalon also develops intensively. Its lateral walls are formed by the thalamus, and its ventral wall is formed by the hypothalamus.

The pineal body develops from the dorsal wall, but for most of its length this wall remains undifferentiated and forms an epithelial plate. Cavity diencephalon turns into a narrow sagittally located gap between the thalami -3 ventricle.

The telencephalon is represented by the right and left hemispheres big brain, covering all other brain vesicles. The hemispheres consist of the outermost cerebral cortex (cloak), which makes up almost the entire mass of the hemispheres basal ganglia and occupying the most ventral position of the olfactory brain. Pholiness telencephalon forms two lateral ventricles, of which the left one is conventionally considered the first lateral ventricle.

The spinal and cerebral sections of the brain, which developed from the neural tube, together with the nerves extending from them, both anatomically and functionally represent a single whole. Nerves are a collection of neuron processes. Dendrites of sensory cells located in the nodes of the spinal cord and cranial nerves, end in receptors at the periphery. Receptors perceive stimuli from the external and internal environment, transforming them into nerve impulse. The latter is transmitted along the dendrites through the body of the sensory neuron and then along its axon to the spinal cord or brain.

The axons of cells located in the gray matter of the brain and spinal cord, as part of the nerves, are called motor fibers. They end at the periphery with effectors, through which they transmit impulses from the brain and spinal cord to the executive organs.

The vast majority of nerves consist of afferent and efferent nerve fibers. Taking into account the predominant localization of neuron bodies in the brain and spinal cord and the special function of the brain and spinal cord, the entire unified nervous system is conventionally divided into central nervous system (CNS) - brain and spinal cord and peripheral nervous system, which includes the cranial and spinal nerves with a complex of nodes, as well as nerve plexuses.

According to functional -morphological features The nervous system is also divided into animal (somatic) and autonomic (autonomic) systems, and in the latter there are sympathetic and parasympathetic.

The spinal cord is formed from a cylindrical flattened tube with two thickenings. Its location is the canal of the spinal column.

Structure of the spinal cord

The length of the spinal cord with the central canal is 45 cm, and the diameter is 1 cm. It is located in cerebrospinal fluid, which ensures homeostasis and nutrition, and also absorbs shocks and shocks.

At the top it continues medulla oblongata, and the spinal cord ends with the first lumbar vertebrae.

The spinal cord is protected by three membranes. The arachnoid membrane is adjacent to the outer hard one, and the soft choroid directly adjacent to the brain. The cavity located between the soft and arachnoid membranes is filled with cerebrospinal fluid.

Gray matter, located on its cross section, occupies central part. It is surrounded by white matter that forms nerve fibers. These neuron processes are located along the spinal cord.

The gray matter has the shape of the letter H. The projections that face forward are the anterior horns, and those that face back are usually called the posterior horns. The lateral horns are located in the thoracic region.

The spinal cord has 31 segments, each with a pair of anterior and posterior roots. Coming out of the spinal canal, they merge and form a mixed spinal nerve.

To the left and right sides 31 pairs of spinal nerves branch off the body: 12 thoracic, 8 cervical, 5 sacral, 5 lumbar and 1 coccygeal. Also in the spinal cord there are lumbar and cervical thickenings, which are formed by clusters of neurons.

Functions of the spinal cord

The spinal cord performs a reflex function - it provides the body with simple motor reactions. Also, its gray matter closes reflex arcs movement reflexes.

The functions of the spinal cord include the regulation of the skeletal muscles of the limbs and trunk. Functions sacral region associated with defecation, urination and sexual reflexes, and thoracic region regulates the functioning of the respiratory system and the activity of the heart.

The spinal cord carries out and conductive function . This is due to the fact that receptor impulses enter it through the fibers of the dorsal roots, and follow ascending pathways to the brain and the sections that are located above.

And vice versa - from the departments of the central nervous system, which lie above, the spinal cord receives command signals.

Connection between the spinal cord and the brain

Impulses emanating from the brain and following descending paths, regulate the activity of the motor centers of the spinal cord. The brain controls the functioning of the spinal cord.

Pulses support muscle tone and form volitional and voluntary movements.

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 note glia, which is an auxiliary. 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 primarily of arachnoid, as well as from soft and hard components. The fat layer located directly under the organ protects the organ from damage. bone tissue in the epidural space.

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 functioning of this organ. Judging by the diagram behind the organ, a groove is localized spinal nerve, and there is a special hole in the front. It is through him that they exit nerve roots that innervate 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, from the white matter come nerve pathways anterior roots of the central nervous system. Rear end fibers are indicators of sensitivity. Of these, a segment of the spinal cord is formed, in which the spinal roots at both sides. 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 it, 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. See his cords as well as his horns gray matter can be seen 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 actually complete absence it has axons grey colour. 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 cerebrospinal fluid, which is. Its functions include damage protection and support permissible 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 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 cervical region and extends up to the 2nd segment of the lumbar region. This is the area where they begin side horns, which are a collection of nerve cells.

The role of pathways

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

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

To position complete information about them anatomical features you need to look at this picture:

The signal is transmitted through certain beams, for example, top part The body in the spinal cord is represented by the sphenoid plexus, and the lower one 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, therefore, for any pathological changes arise horrible 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 is to transmit a signal certain parts the body depending on the location of the nerve bundle. If it concerns upper half body, then he is responsible for it cervical region, for the lumbar organs, and the sacral 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

The spinal cord is associated with many various pathologies, whose treatment is carried out primarily 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 spinal column. Most often the problem occurs in the lumbar region.

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

Neoplasms compressing the spinal cord;
Emerging scar tissue after surgery;
Severe injury in the lumbar region;
Chiari defect.

Typically, tethered spinal cord syndrome in patients manifests itself as 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 long period recovery. 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 represents a violation facial nerve As a result, contractions of the muscle tissue located on the face occur. The disease occurs without pain and such spasms are called clonic. They arise due to compression nerve tissue in the area of its exit from the brain. Diagnostics pathological process 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. To treat the facial nerve, Baclofen, Levatracem, Gabapentin, Carbamazepine, etc. are used. You will have to take enough of them for 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 have been recorded complete cure facial nerve and relief of hemispasm. Worked especially well drug therapy on early stages development of pathology.

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

The most effective and quick treatment hemispasm is surgery. It is carried out to eliminate compression and if the operation is successful, the patient is discharged within a week. Achieved full effect recovery is quite fast, 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.