Sheaths of the spinal cord. Dura mater, arachnoid mater, pia mater of the spinal cord. The spinal cord is covered with three connective tissue membranes, meninges, originating from the mesoderm. These shells are the following, if you go from the surface inwards: hard shell, duramater; arachnoid membrane, arachnoidea, and soft membrane, piamater. Cranially, all three membranes continue into the same membranes of the brain.
1. The hard shell of the spinal cord, duramaterspinalis, envelops the spinal cord in the form of a sac. It does not adhere closely to the walls of the spinal canal, which are covered with periosteum. The latter is also called the outer layer of the dura mater. Between the periosteum and the dura mater there is the epidural space, cavitas epiduralis. It contains fatty tissue and venous plexuses - plexusvenosivertebrales interni, into which venous blood flows from the spinal cord and vertebrae. The cranial dura fuses with the edges of the foramen magnum occipital bone, and caudally ends at the level of the II - III sacral vertebrae, tapering in the form of a thread, filumduraematrisspinalis, which is attached to the coccyx.
2. The arachnoid membrane of the spinal cord, arachnoideaspinalis, in the form of a thin transparent avascular sheet, is adjacent to the hard shell from the inside, separated from the latter by a slit-like subdural space, pierced by thin bars, spatium subdurale. Between the arachnoid membrane and the soft membrane directly covering the spinal cord there is a subarachnoid space, cavitassubarachnoidalis, in which the brain and nerve roots lie freely, surrounded by a large amount of cerebrospinal fluid, liquorcere-brospinalis. This space is especially wide in the lower part of the arachnoid sac, where it surrounds the caudaequina of the spinal cord (cisterna terminalis). The fluid filling the subarachnoid space is in continuous communication with the fluid of the subarachnoid spaces of the brain and cerebral ventricles. Between the arachnoid membrane and the soft membrane covering the spinal cord in the posterior cervical region, along the midline, a septum, septumcervicdleintermedium, is formed. In addition, on the sides of the spinal cord in the frontal plane there is a dentate ligament, lig. denticulatum, consisting of 19 - 23 teeth passing in the spaces between the anterior and posterior roots. The dentate ligaments serve to hold the brain in place, preventing it from stretching out in length. Through both ligg. denticulatae, the subarachnoid space is divided into anterior and posterior sections.
3. The soft membrane of the spinal cord, piamaterspinalis, covered on the surface with endothelium, directly envelops the spinal cord and contains vessels between its two layers, together with which it enters its grooves and the medulla, forming perivascular lymphatic spaces around the vessels.
8. Development of the brain (brain vesicles, parts of the brain).
The brain is located in the cranial cavity. Its upper surface is convex, and its lower surface - the base of the brain - is thickened and uneven. At the base of the brain, 12 pairs of cranial (or cranial) nerves arise from the brain. The brain is divided into the cerebral hemispheres (the most recent part in evolutionary development) and the brainstem with the cerebellum. The weight of the adult brain is on average 1375 g for men, 1245 g for women. The weight of the brain of a newborn is on average 330 - 340 g. In the embryonic period and in the first years of life, the brain grows rapidly, but only by the age of 20 it reaches its final size.
Scheme Brain Development
A. The neural tube in a longitudinal section, three brain vesicles are visible (1, 2 and 3); 4 - part of the neural tube from which the spinal cord develops.
B. Lateral view of the fetal brain (3rd month) - five brain vesicles; 1 - end brain (first vesicle); 2 - diencephalon (second bladder); 3 - midbrain (third bladder); 4 - hindbrain (fourth bladder); 5 - medulla oblongata (fifth cerebral vesicle).
The brain and spinal cord develop on the dorsal (dorsal) side of the embryo from the outer germ layer (ectoderm). At this point, the neural tube is formed with an expansion in the head section of the embryo. Initially, this expansion is represented by three brain vesicles: anterior, middle and posterior (diamond-shaped). Subsequently, the anterior and rhomboid vesicles divide and five brain vesicles are formed: terminal, intermediate, middle, posterior and oblong (accessory).
During development, the walls of the brain vesicles grow unevenly: either thickening, or remaining thin in some areas and pushing into the cavity of the vesicle, participating in the formation of the choroid plexuses of the ventricles.
The remnants of the cavities of the brain vesicles and the neural tube are the cerebral ventricles and the central canal of the spinal cord. From each brain vesicle certain parts of the brain develop. In this regard, out of the five cerebral vesicles in the brain, five main sections are distinguished: medulla oblongata, hindbrain, midbrain, diencephalon and telencephalon.
The human spinal cord plays a huge role in maintaining the vital functions of the entire body. Thanks to it, we can move, have a sense of touch, and reflexes. This organ is reliably protected by nature, because its damage can lead to the loss of many functions, including motor functions. The membranes of the spinal cord protect the organ itself from damage and are involved in the production of certain hormones.
A fluid-filled cavity separates the bone structure and the spinal cord. The membranes that surround the spinal cord itself are:
The soft layer is formed by plexuses of elastic mesh and collagen bundles, covered with an epithelial layer. There are vessels, macrophages, fibroblasts here. The layer has a thickness of approximately 0.15 mm. According to its properties, the lower shell tightly grips the surface of the spinal cord and has high strength and elasticity. On the outside, it is combined with the arachnoid layer using peculiar crossbars.
Human spinal cord membranes
The middle shell of the spinal cord is also called the arachnoid, as it is formed from a large number of trabeculae, which are loosely located. At the same time, it is as durable as possible. It also has characteristic processes extending from its lateral surface and containing the roots of nerves and dentate ligaments. The dura mater of the spinal cord covers other layers. In its structure it is a tube made of connective tissue, its thickness is no more than 1 mm.
To prevent and treat JOINT DISEASES, our regular reader uses the increasingly popular NON-SURGERY treatment method recommended by leading German and Israeli orthopedists. After carefully reviewing it, we decided to offer it to your attention.
The soft and arachnoid membranes are separated by the subarachnoid space. It contains cerebrospinal fluid. It has another name - subarachnoid. The arachnoid and dura mater are separated by the subdural space. And finally, the space between the hard layer and the periosteum is called the epidural (epidural). It is filled with internal venous weaves in combination with adipose tissue.
Functional meaning
What's it like functional value have membranes of the spinal cord? Each of them plays a specific role.
The subarachnoid space of the spinal cord plays a critical role. It contains cerebrospinal fluid. It performs a shock-absorbing function and is responsible for the creation of nervous tissue and is a catalyst for metabolic processes.
The relationship between the membranes of the spinal cord and the brain
The brain is covered by the same layers as the spinal cord. In fact, some are continuations of others. The dura mater of the brain is formed from two layers of connective tissue that fit tightly to the bones of the skull with inside. In fact, they form its periosteum. While the hard layer surrounding the spinal cord is separated from the periosteum of the vertebrae by a layer of adipose tissue combined with venous networks in the epidural space.
The upper layer of the dura mater, which surrounds the brain and forms its periosteum, forms funnels in the recesses of the skull, which are the receptacle for the cranial nerves. The lower layer of the dura mater is interconnected with the arachnoid layer using threads of connective tissue. The trigeminal and vagus nerves are responsible for its innervation. In certain areas, the hard layer forms sinuses (splits), which are collectors for venous blood.
The middle layer of the brain is formed from connective tissue. It is attached to the pia mater with the help of threads and processes. In the subarachnoid space, they form cracks in which cavities arise, called subarachnoid cisterns.
The arachnoid layer is connected to the hard shell quite loosely and has granulation processes. They penetrate the hard layer and are embedded in the cranial bone or sinuses. Granulation pits appear at the entry points of the arachnoid granulations. They provide communication between the subarachnoid space and the venous sinuses.
The soft membrane tightly fits the brain. It contains many blood vessels and nerves. The peculiarities of its structure lie in the presence of vaginas that form around the vessels and pass into the brain itself. The space that forms between the blood vessel and the vagina is called perivascular. It is interconnected with the pericellular and subarachnoid space with different sides. Cerebrospinal fluid passes into the pericellular space. The soft membrane forms part of the vascular basis, as it penetrates deeply into the cavity of the ventricles.
Diseases of the membranes
The membranes of the brain and spinal cord are susceptible to diseases that can occur as a result of injury to the spinal column, an oncological process in the body or infectious infection:
To identify diseases of the membranes, differential diagnosis, which necessarily includes magnetic resonance imaging. Damaged membranes and intersheath spaces of the spinal cord often lead to disability and even death. Vaccination and careful attention to the health of the spine help reduce the risk of disease.
Spinal cord (medulla spinalis) enclosed inside the spinal canal (capalis vertebralis). The spinal cord at the top is connected directly with the medulla oblongata, at the bottom it ends with a short conus medullaris (conus medullaris), passing into the terminal thread (filum terminate).
The spinal cord is divided into four parts: the cervical (pars cervicalis), chest (pars thoracica), lumbar (pars lumbalis), sacral (parssacralis). The segments of the spinal cord correspond to the vertebrae. In the upper and middle cervical regions (C I - IV) the segment number corresponds to the number of the vertebra, in the lower cervical and upper thoracic regions (C VI - Th III) - a difference of 1 in favor of the segment, in the middle thoracic (Th VI - VII,) - a difference of 2 in favor of the segment, in the lower thoracic (Th VIII - X) - a difference of 3 in favor of the segment, vertebra L, correspond to segments L IV -S V. The spinal cord forms two thickenings: the cervical (intumescentia cervicalis), lying from the V cervical to the I thoracic vertebra, and the lumbosacral (intumescentia lumbosacralis), enclosed between the I lumbar and II sacral vertebrae.
The anterior median fissure is located on the anterior surface of the spinal cord (fissura mediana anterior), behind is the posterior median sulcus (sulcus medianus posterior). The anterior cord lies in front (funiculus anterior), on the side of it there is a lateral cord (funiculus lateralis), behind - posterior cord (funiculus posterior). These cords are separated from each other by grooves: anterolateral (sulcus anterolateralis), posterolateral (sulcus posterolateralis), as well as the described anterior and posterior median fissures.
In cross section, the spinal cord consists of gray matter (substantia grisea), centrally located, and white matter (substantia alba), lying on the periphery. The gray matter is arranged in the shape of the letter H. It forms an anterior horn on each side (cornu anterius), posterior horn (cornu posterius) and central gray matter (substantia grisea centralis). In the center of the latter there is a central channel (canalis centralis), communicating at the top with the IV ventricle, and at the bottom passing into the terminal ventricle (ventriculus terminalis).
Shells and intershell spaces of the spinal cord
The spinal cord is divided into pia mater, arachnoid and dura mater:
Soft membrane of the spinal cord (pia mater spinalis) tightly covers the substance of the brain, contains many vessels.
Arachnoid membrane of the spinal cord (Arachnoidea spinalis) thin, with fewer vessels.
Dura mater of the spinal cord (dura mater spinalis) - a dense connective tissue plate covering the arachnoid membrane. Unlike the dura mater, the brain is divided into two layers: outer and inner. the outer leaf lies tightly against the walls of the spinal canal and is closely connected with the periosteum and ligamentous apparatus his. The inner layer, or the dura mater itself, extends from the foramen magnum to the II-III sacral vertebrae, forming the dural sac, which encloses the spinal cord. On the sides of the spinal canal, the dura mater gives off processes that make up the sheath for the spinal nerves emerging from the canal through the intervertebral foramina.
There are spaces in the spinal cord:
Between the outer and inner layers of the dura mater there is the epidural space (cavum epidurale).
Subdural space (cavum subdurale) - a slit-like space between the dura mater and the arachnoid membrane of the spinal cord.
Subarachnoid space (cavum subarachnoidealis) located between the arachnoid and pia mater of the spinal cord, filled with cerebrospinal fluid. The bundles of connective tissue between the arachnoid and pia mater are especially strongly developed on the sides, between the anterior and posterior roots of the spinal cord, where they form dental ligaments (ligg.denticulata) associated with the dura mater. these ligaments pass in the frontal plane throughout the dural sac up to lumbar region and divide the subarachnoid space into two chambers: anterior and posterior.
The subarachnoid space of the spinal cord directly passes into the same space of the brain with its cisterns. The largest of them, cisterna cerebellomedullaris, communicates with the cavity of the fourth ventricle of the brain and the central canal of the spinal cord. The part of the dural sac located between the II lumbar and II sacral vertebrae is filled with the cauda equina with the filum terminale of the spinal cord and cerebrospinal fluid. Spinal puncture (puncture of the subarachnoid space), performed below the II lumbar vertebra, is the safest, because the spinal cord stem does not reach here.
The membranes of the brain and spinal cord come in only a few types. Modern medicine distinguish hard, cobweb and soft structures. Their main task is to protect the brain from stress, concussions, injuries, microtraumas and other factors that can negatively affect work nervous system, nourish the brain with useful elements. Without them, the cerebrospinal fluid alone would not be able to fully cope with the shock-absorbing function.
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 important body a person who is different hypersensitivity. 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 the 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 blood pressure in organism;
- 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, execution physical exercise, falling, getting injured.
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 soft fabric, but deeper than solid. 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:
- formation of hormones in the body;
- maintaining natural metabolic processes;
- transportation of cerebrospinal fluid to 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 are all responsible for providing the brain with enough blood to function properly. 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.
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. Located between the hard shell and bone tissue 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 supplies the brain nutrients(minerals, proteins), protects it during 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 is constantly located most of 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 degree pathological process, predict the course, choose effective combat 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.
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 registered in patients of different ages and health status. In addition to infectious processes, there are other malfunctions:
- Fibrosis. Represents negative consequence performed 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). Accompanied nearby 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 violation cerebrospinal fluid circulation causes paralysis or hydrocephalus. Many shell failures clinical picture may be confused with others infectious diseases Therefore, an MRI is always prescribed to clarify the diagnosis.
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 fatal outcome or serious complications. Therefore, when the first signs of illness appear, you should consult a doctor and follow all recommendations.
Features of therapy 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 medication is 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, it is prescribed surgical intervention.
- Infectious processes. The entry of pathogenic bacteria into the organ requires the prescription of antibiotics. In most cases this is a drug broad action. An important point is also control 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 unified system and are directly connected to the hypothalamus and cerebellum. Violation of their integrity or inflammatory processes lead to deterioration 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.
Arachnoid membrane of the spinal cord
Section of the skull showing the membranes of the brain
Arachnoid medulla- one of three membranes covering the brain and spinal cord. It is located between the other two membranes - the most superficial dura mater and the deepest pia mater, separated from the latter by a subarachnoid (subarachnoid) space filled with 120-140 ml of cerebrospinal fluid. The subarachnoid space contains blood vessels. In the lower part of the spinal canal, the roots of the spinal nerves (“cauda equina”) float freely in the cerebrospinal fluid of the subarachnoid space.
Cerebrospinal fluid enters the subarachnoid space from the openings in the fourth ventricle of the brain; the largest amount is contained in the cisterns of the subarachnoid space - extensions located above the large fissures and grooves of the brain.
The arachnoid membrane, as the name suggests, has the appearance of a thin web formed by connective tissue, contains a large number of fibroblasts. Multiple filamentous branching cords (trabeculae) extend from the arachnoid membrane, which are woven into the pia mater. On both sides the arachnoid membrane is covered with glial cells.
The arachnoid membrane forms villous outgrowths - pachyon granulations (lat. granulationes arachnoidales), protruding into the lumen of the venous sinuses formed by the dura mater, as well as into the blood and lymphatic capillaries at the site of exit of the roots of the cranial and spinal nerves from the cranial cavity and spinal canal. Through granulation, reabsorption of cerebrospinal fluid occurs through the layer of glial cells and the sinus endothelium into the venous blood. With age, the number and size of villi increase.
The arachnoid and pia mater are sometimes considered as a common structure, leptomeninges (Greek. leptomeninx), while the dura mater is called pachymeninx (Greek. pachymeninx).
Illustrations
Links
Wikimedia Foundation. 2010.
See what “Arachnoid membrane of the spinal cord” is in other dictionaries:
Spinal cord membranes (meninges medullae spinalis) in the spinal canal- Transverse section at the level of the intervertebral disc. dura mater of the spinal cord; epidural space; arachnoid; dorsal root brain nerve a: anterior root; spinal node; spinal nerve; subarachnoid... ... Atlas of Human Anatomy
arachnoid membrane- (arachnoidea) a thin connective tissue membrane located between the hard and soft membranes. It covers the brain without going into the grooves and crevices of the brain, unlike the deeper soft shell. Therefore, between these shells... ... Glossary of terms and concepts on human anatomy
Central nervous system (CNS) I. Cervical nerves. II. Thoracic nerves. III. Lumbar nerves. IV. Sacral nerves. V. Coccygeal nerves. / 1. Brain. 2. Diencephalon. 3. Midbrain. 4. Bridge. 5. Cerebellum. 6. Medulla oblongata. 7.… …Wikipedia
- (meninges) connective tissue structures covering the brain and spinal cord. There is a hard shell (dura mater, pachymeninx), arachnoid (arachnoidea) and vascular, or soft (vasculosa, pia mater). The arachnoid and soft membranes are combined... ... Medical encyclopedia
Spinal cord- (medulla spinalis) (Fig. 254, 258, 260, 275) is a cord of brain tissue located in the spinal canal. Its length in an adult reaches 41-45 cm, and its width is 1-1.5 cm. Upper section the spinal cord smoothly passes into... ... Atlas of Human Anatomy- (Encephalon). A. Anatomy of the human brain: 1) the structure of the brain, 2) the membranes of the brain, 3) blood circulation in the brain, 4) brain tissue, 5) the course of fibers in the brain, 6) the weight of the brain. B. Embryonic development of the brain in vertebrates. WITH.… … encyclopedic Dictionary F. Brockhaus and I.A. Ephron
BRAIN- BRAIN. Contents: Methods for studying the brain..... . . 485 Phylogenetic and ontogenetic development of the brain.............. 489 Bee of the brain.............. 502 Anatomy of the brain Macroscopic and ... ... Great Medical Encyclopedia
