Anatomy of the human spinal cord membranes - information:

March 1, 2019

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The human spine is the basis of the musculoskeletal system. At the same time, it not only performs a supporting function and provides the ability to walk upright, but also represents a fairly flexible axis of the body, which is achieved due to the mobility of the vast majority of its individual parts. In this case, the anterior part of the spine participates in the formation of the walls of the thoracic and abdominal cavities. But one of its most important functions is to ensure the safety of the spinal cord that runs inside it.

Structural features

The spinal cord and brain are a single whole, an integral part of the nervous system. All mental functions, control of vital processes (activity, touch, sensitivity of the limbs) are carried out with their help. They are covered with protective structures that work harmoniously to provide nutrition and remove metabolic products.

The membranes of the spinal cord and brain are largely similar in structure. They continue the spine and envelop the spinal cord, preventing damage to it. This is a kind of “clothing” of the most important human organ, characterized by increased sensitivity. All layers are interconnected and they function as one, although their tasks are slightly different. There are three shells in total, and each has its own characteristics.

Dura shell

It is a fibrous formation with increased density, consisting of connective tissue. In the spine, it envelops the brain along with nerves and roots, spinal ganglia, as well as other membranes and fluid. The outer part is separated from the bone tissue by the epidural space, which consists of venous bundles and a fatty layer.

The hard shell of the spinal cord is inextricably linked with the same structure of the brain. In the head, the latter is fused with the periosteum, therefore it fits tightly to the inner surface of the skull, without forming an epidural space, which is its characteristic feature. The space between the dura mater and the arachnoid membrane is called the subdural; it is very narrow and filled with fluid similar to tissue.

The main functions of the hard shell are to create natural shock absorption, which reduces pressure and eliminates mechanical impact on the brain structure during movement or injury. In addition, there are a number of other tasks:

• synthesis of thrombin and fibrin - important hormones in the body;
• ensuring normal metabolic processes in tissues and lymph movement;
• normalization of blood pressure in the body;
• suppression of inflammatory processes;
• immunomodulation.

In addition, the shell has such an anatomy that it takes part in the blood supply. Tight closure with the vertebral bones allows it to reliably fix soft tissues in the ridge. This is important to ensure their safety during movement, physical exercise, falling, or injury.

Important! Connective tissue is attached to the periosteum by several types of ligaments: anterior, lateral, dorsal. If it is necessary to remove the dura mater, they present a serious obstacle for the surgeon due to the peculiarities of their structure.

Arachnoid

The arachnoid membrane of the human spinal cord is located on the outer part of the soft tissue, but deeper than the hard tissue. It covers the structure of the central nervous system and is devoid of color and blood vessels. In general, it is a connective tissue covered by endothelial cells. Connecting with the hard shell, it forms a space where the cerebrospinal fluid functions, but does not enter the grooves or depressions, passes by them, forming something like bridges. It is this cerebrospinal fluid that protects the nerve structures from various adverse effects and maintains water balance in the system.

Its main functions are:

What is spinal myelography

• formation of hormones in the body;
• maintaining natural metabolic processes;
• transportation of cerebrospinal fluid into the venous blood;
• mechanical protection of the brain;
• formation of nervous tissue (in particular, cerebrospinal fluid);
• generation of nerve impulses;
• participation in metabolic processes in neurons.

The middle shell has a complex structure and looks like a mesh fabric, with a small thickness but high strength. It was its resemblance to a spider's web that gave it its name. Some experts believe that it is devoid of nerve endings, but this is only a theory that has not been proven to date.

Visual structure and location of the spinal cord membranes

Soft shell

Closest to the brain is the soft shell, which has a loose structure and consists of connective tissue. It contains blood vessels and plexuses, nerve endings and small arteries, all of which are responsible for providing the brain with enough blood for normal functioning. Unlike the arachnoid, it goes into all the cracks and grooves.

But, despite their close location, the brain is not covered by it, since between them there is a small space called subpial. It is separated from the subarachnoid space by many blood vessels. Its main functions include supplying the brain with blood and nutrients, normalizing metabolism and metabolism, as well as maintaining the natural performance of the body.

The functioning of all membranes is interconnected and the structure of the spine as a whole. Various malfunctions, changes in the amount of cerebrospinal fluid or inflammatory processes at any level lead to serious consequences and disorders and diseases of internal organs.

hindbrain

This brain consists of the pons and the cerebellum. Let's look at the gray and white matter in them. The bridge is a large white ridge on the back side of the base. On the one hand, its border with the cerebral peduncles is pronounced, and on the other, with the medulla oblongata. If you make a cross section, the white matter of the brain and the gray nucleus will be visible very clearly. Transverse fibers divide the bridge into ventral and dorsal sections. In the ventral part, the white matter of the pathways is mainly present, and the gray matter forms its nuclei here.

The dorsal part is represented by nuclei: switching, reticular formation, sensory systems and cranial nerves.

The cerebellum is located under the occipital lobes. It includes the hemispheres and the middle part called the “worm”. Gray matter makes up the cerebellar cortex and nuclei, which are tent-shaped, spherical, corky and dentate. The white matter of the brain in this part is located under the cerebellar cortex. It penetrates into all gyri as white plates and consists of different fibers that either connect the lobules and gyri, or are directed to the internal nuclei, or connect sections of the brain.

Spaces between shells

All the membranes of the spinal cord and brain, although they are close to each other, do not touch tightly. Spaces are formed between them, which have their own characteristics and functions.

• Epidural. It is located between the hard shell and the bone tissue of the spinal column. It is filled predominantly with fat cells to eliminate nutritional deficiencies. Cells become a strategic reserve for neurons in extreme situations, which ensures the control and functioning of processes in the body. This space reduces the load on the deep layers of the spinal cord, eliminating their deformation, due to its loose structure.
• Subdural. Located between the dura mater and the arachnoid membrane. It contains liquor, the amount of which always changes. On average, an adult has 150–250 ml. Cerebrospinal fluid provides the brain with nutrients (minerals, proteins), protects it from falls or impacts, maintaining pressure. Thanks to the movement of cerebrospinal fluid and its constituent lymphocytes and leukocytes, infectious processes are suppressed in the central nervous system and bacteria and microorganisms are absorbed.
• Subarachnoid. Located between the arachnoid and soft membrane. It constantly contains most of the cerebrospinal fluid. This allows you to most effectively protect the central nervous system, brainstem, cerebellum and medulla oblongata.

In case of tissue damage, the first step is to analyze the cerebrospinal fluid, as it allows you to determine the extent of the pathological process, predict the course, and choose effective control tactics. An infection or inflammation that appears in one area quickly spreads to neighboring ones. This is due to the constant movement of cerebrospinal fluid.

Gray and white matter of the spinal cord

The heterogeneous substance of this organ is gray and white. The first is formed by a huge number of neurons, which are concentrated in nuclei and come in three types:

• radicular cells;
• tufted neurons;
• internal cells.

The white matter of the spinal cord surrounds the gray matter. It includes nerve processes that make up three fiber systems:

• intercalary and afferent neurons connecting different parts of the spinal cord;
• sensory afferents, which are long centripetal;
• motor afferent or long centrifugal.

Diseases

The meninges can be injured or suffer from damage of an infectious nature. Increasingly, problems are associated with the development of oncology. They are recorded in patients of different ages and health conditions. In addition to infectious processes, there are other malfunctions:

• Fibrosis. It represents a negative consequence of the surgical intervention. It leads to an increase in the volume of the membrane, characteristic tissue scarring, and an inflammatory process that occurs immediately in all intershell spaces. The disease is also often provoked by cancer or spinal injuries.
• Meningitis. Severe pathology of the spinal cord, which occurs as a result of the penetration of a viral infection into the body (pneumococcus, meningococcus). It is accompanied by a number of characteristic symptoms and, if left untreated, can lead to serious complications and even death of the patient.
• Arachnoiditis. An inflammatory process develops in the lumbar region of the spinal cord, which also affects the membranes. All three levels suffer. Clinically, the disease manifests itself with focal symptoms and neurasthenic disorders.

The shells or the space between them can also be damaged as a result of injury. Usually these are bruises or fractures that cause compression of the spinal cord. Acute disruption of cerebrospinal fluid circulation causes paralysis or hydrocephalus. Many malfunctions of the membranes in the clinical picture can be confused with other infectious diseases, therefore an MRI is always prescribed to clarify the diagnosis.

Diencephalon

It is located between the corpus callosum and the fornix, and on the sides it fuses with the telencephalon. The dorsal section consists of the visual tuberosities, on the upper part of which there is the epitubercle, and in the ventral part there is the inferior tuberosity region.

The gray matter here consists of nuclei that are associated with centers of sensitivity. White matter is represented by conducting pathways in different directions, guaranteeing the connection of formations with the cerebral cortex and nuclei. The diencephalon also includes the pituitary gland and pineal gland.

Features of treatment

Inflammatory processes in the membranes of the spinal cord or brain require immediate treatment in a hospital setting. Self-medication of any disease at home often leads to death or serious complications. Therefore, when the first signs of illness appear, you should consult a doctor and follow all recommendations.

Features of treatment of possible pathologies:

• Viral infection. Monitor body temperature and take enough fluids. If a person cannot drink a lot of water, droppers with saline solution are prescribed. If cysts form or the volume of cerebrospinal fluid increases, then medications are required to normalize the pressure. The chosen tactics to combat inflammation are adjusted as the patient’s condition improves.
• Injury. The membranes of the spinal cord provide its normal nutrition and blood circulation, therefore, when scars, adhesions and other damage form, this function is disrupted, the movement of cerebrospinal fluid is hampered, which leads to the appearance of cysts and intervertebral hernia. Treatment in this case includes taking a set of medications to improve metabolic processes. If traditional therapy is ineffective, surgical intervention is prescribed.
• Infectious processes. The entry of pathogenic bacteria into the organ requires the prescription of antibiotics. In most cases, this is a broad-spectrum drug. An important point is also monitoring water balance and body temperature.

The consequences of diseases of the membranes can be unpredictable. Inflammatory processes cause disturbances in the functioning of the body, fever, vomiting, seizures, and convulsions. Often hemorrhages lead to paralysis, which makes a person disabled for life.

The spinal membranes form a single system and are directly connected to the hypothalamus and cerebellum. Violation of their integrity or inflammatory processes lead to a deterioration in the general condition. Usually accompanied by seizures, vomiting, and fever. Modern medicine has reduced the mortality rate due to such diseases to 10–15%. But the risk still exists. Therefore, when you notice the first signs, you should immediately consult a doctor.

Midbrain

It starts from the mesencephalon. On the one hand, it corresponds to the surface of the brain stem between the pineal gland and the superior medullary velum, and on the other, to the area between the mammillary bodies and the anterior part of the pons.

It includes the cerebral aqueduct, on one side of which the boundary is provided by the roof, and on the other by the covering of the cerebral peduncles. In the ventral region, the posterior perforated substance and the peduncles of the cerebrum are distinguished, and in the dorsal region, the roof plate and the handles of the inferior and superior colliculi are distinguished.

If we look at the white and gray matter of the brain in the cerebral aqueduct, we will see that the white surrounds the central gray matter, which consists of small cells and has a thickness of 2 to 5 millimeters. It consists of the trochlear, trigeminal and oculomotor nerves, together with the accessory nucleus of the latter and the intermediate nucleus.

Nerve fibers

Mostly commissural fibers are found in the corpus callosum. They are located in the cerebral commissures, which connect the cortex on different hemispheres and symmetrical points.

Association fibers group areas on one hemisphere. In this case, short ones connect neighboring convolutions, and long ones connect those located at a far distance from each other.

Projection fibers connect the cortex with those formations located below, and then with the periphery.

If the internal capsule is viewed in section from the front, the lenticular nucleus and the posterior limb will be visible. Projection fibers are divided into:

• fibers located from the thalamus to the cortex and in the opposite direction, they excite the cortex and are centrifugal;
• fibers directed to the motor nuclei of the nerves;
• fibers that conduct impulses to the muscles of the whole body;
• fibers directed from the cortex to the pontine nuclei, providing a regulatory and inhibitory effect on the work of the cerebellum.

Those projection fibers that are located closest to the cortex create the corona radiata. Then their main part passes into the internal capsule, where the white matter is located between the caudate and lenticular nuclei, as well as the thalamus.

There is an extremely complex pattern on the surface, with alternating grooves and ridges between them. They are called convolutions. Deep grooves divide the hemispheres into large areas called lobes. In general, the grooves of the brain are deeply individual; they can vary greatly from person to person.

The hemispheres have five lobes:

• frontal;
• parietal;
• temporal;
• occipital;
• island.

The central sulcus originates at the top of the hemisphere and moves down and forward to the frontal lobe. The area posterior to the central sulcus is the parietal lobe, which ends in the parieto-occipital sulcus.

The frontal lobe is divided into four convolutions, vertical and horizontal. In the temporal lobe, the lateral surface is represented by three gyri, which are delimited from each other.

The furrows of the occipital lobe are variable. But everyone, as a rule, has a transverse one, which is connected to the end of the interparietal groove.

On the parietal lobe there is a groove that runs horizontally parallel to the central one and merges with another groove. Depending on their location, this lobe is divided into three convolutions.

The island has a triangular shape. It is covered with short convolutions.

Finite brain

It is represented by two hemispheres, which are separated by a gap running along them. It is connected in depth by the corpus callosum and commissures.

The cavity is represented by the lateral ventricles located in one and the second hemisphere. These hemispheres consist of:

• a cloak of neocortex or six-layer cortex, distinguished by nerve cells;
• striatum from the basal ganglia - ancient, old and new;
• partitions.

But sometimes there is another classification:

• olfactory brain;
• subcortex;
• gray matter of the cortex.

Without touching on the gray matter, let's focus immediately on the white matter.