What layers of membranes does the spinal cord consist of? Arachnoid

Cerebrospinal fluid fills the cavities between the brain and the bone structure, playing the role of a kind of shock absorber. Additional protection is provided by the membranes of the spinal cord.

In addition to creating a barrier that protects against mechanical damage, the membranes play an important role in metabolism and the production of hormones and mediators necessary for normal human life.

What membranes cover the human spinal cord?

The spinal cord has three membranes that perform protective and shock-absorbing functions. The membranes of the brain, which are a direct continuation of the spine, have a similar structure.

The membranes that protect the spinal cord are called: hard, middle (arachnoid) and soft.

The sequence of arrangement of the spinal cord membranes is as follows: the soft cord covers the spinal cord, then the arachnoid layer follows. There is a protective (hard) shell on top.

Functions and structural features of the spinal membranes

The membranes and intershell spaces of the spinal cord play an important role in human life.

The main task of shells is:

• The functions of the hard shell are as a natural shock absorber, reducing the mechanical impact on the brain during movement or injury. Directly involved in blood supply.
• Function of the arachnoid membrane - the layer plays an important role in the formation of hormones and metabolic processes in the body. Functions are associated with the structural features of the shell. Thus, between the soft and arachnoid layers, a subarachnoid space is formed - a cavity in which the cerebrospinal fluid is located.
  The significance of this is difficult to overestimate. Liquid not only creates conditions for maximum mechanical protection of the brain, but is also a catalyst for human metabolism.
  Another important task is the neurology of the shell. It is the cerebrospinal fluid that is responsible for creating nerve tissue. The middle shell of the spinal cord is a reticular connective tissue that has a small thickness and maximum strength.
  The appearance of the layer resembles endothelium or mesothelium. What makes the shell different is the absence of nerves (some medical professors question this claim).
• Soft shell function. The anatomy of the spinal canal shows the close interconnection of all the layers surrounding the brain. The soft and hard shell supplies the human brain with blood and essential nutrients. Helps normalize metabolism and maintain the body's performance.

The anatomy of the membranes shows a strong relationship between the functioning of the entire body and the structure of the spine. Any disturbances: changes in the volume of cerebrospinal fluid, inflammation of the layers lead to serious disruptions in the functioning of internal organs.

What diseases are the membranes susceptible to?

Damage to the membranes of the spinal cord and brain can be traumatic or infectious. Oncological problems often occur.

The most common diseases are:

The morphophysiological characteristics characteristic of inflammation of the membranes in their clinical picture resemble the signs characteristic of any infectious diseases and the development of oncological pathologies. To determine an accurate diagnosis, differential diagnostics, including MRI, are necessary.

How to treat inflammation of the membranes

Treatment methods are selected depending on the catalyst that caused the inflammatory process or metabolic disorders:

It is almost impossible to cure the disease at home. Seeing a doctor earlier increases the chances of a favorable treatment prognosis.

What is the danger of spinal lining disease?

The spinal membranes are connected to the cerebellum and hypothalamus of the brain. Inflammation leads to disturbances that affect the normal functioning of the body. Fever, vomiting, seizures are only a small part of the unpleasant consequences of the disease.

In the first half of the twentieth century, inflammation was fatal in 90% of cases. Modern medicine has reduced the probability of death to 10-15%.

For example, the outermost membrane covering the spinal cord is a real factory that provides nutrition to the spinal cord and brain. Violations lead to the development of vertebral hernias, cysts and over time can cause disability for the patient.

The outer covering of the spinal cord is formed by fibrous connective tissue. This makes it possible to reduce the load on the spinal column. The inner layers are associated with the formation of hormones and mediators necessary for normal human development and the functioning of internal organs.

As the membranes develop in childhood, a person gradually forms. Problems at work lead to mental and physical retardation of the child.

Measures to prevent inflammation of the membranes

Most types of inflammation can be prevented by timely vaccination of patients. Vaccinations are given to everyone who is at risk.

It is possible to reduce the percentage of diseases due to attentive attitude towards patients in the postoperative period. The use of preventive measures has reduced the likelihood of inflammatory processes.

The diseases are serious, so self-medication is unacceptable.

The spinal cord (medulla spinalis) is a section of the human central nervous system located in the spinal canal. The spinal canal is formed by a collection of vertebral foramina in the vertebrae. The spinal cord has the shape of a cylindrical cord with an internal cavity (spinal canal), and is held in a constant position by ligaments. The anterior (upper) end of the spinal cord passes into the medulla oblongata, and the posterior (lower) end into the so-called filum terminale.

Spinal nerves are nerves that run from the spinal cord to almost every area of ​​the body, from the back of the head to the lower extremities. The spinal nerves start from the junction of the anterior (motor) and posterior (sensitive) roots and represent a trunk (up to 1 cm in diameter) going to the periphery.

Thus, changes in the spine leading to pinching of the nerve spine, root, damage to blood vessels, etc., lead to a disruption in the functioning of the organ for which the damaged nerve spine is responsible.

Sheaths of the spinal cord.

There are three membranes of the spinal cord: hard, arachnoid and soft.

The hard shell is a cylindrical sac closed at the bottom, repeating the shape of the spinal canal.

This sac starts from the edge of the foramen magnum and continues to the level of the II-III sacral vertebra. It contains not only the spinal cord, but also the cauda equina. Below the II-III sacral vertebra, the hard shell continues for about 8 cm in the form of the so-called external filum terminale. It stretches to the second coccygeal vertebra, where it fuses with its periosteum. Between the periosteum of the spinal column and the hard shell is the epidural space, which is filled with a mass of loose fibrous connective tissue containing adipose tissue. The internal vertebral venous plexus is well developed in this space. The dura mater of the brain is built from dense fibrous connective tissue, is abundantly supplied with blood, and is well innervated by sensory branches from the spinal nerves.

The dura mater sac is strengthened in the spinal canal so that the dura mater extends onto the roots of the spinal nerves and the nerves themselves. The continuation of the hard shell grows to the edges of the intervertebral foramina. In addition, there are strands of connective tissue that attach the periosteum of the spinal canal and the dura mater to each other. These are the so-called anterior, dorsal and lateral ligaments of the dura mater.

The hard shell of the spinal cord is covered on the inside with a layer of flat connective tissue cells that resemble the mesothelium of the serous cavities, but do not correspond to it. Beneath the dura mater is the subdural space.

The arachnoid membrane is located inside the dura mater and forms a sac containing the spinal cord, the roots of the spinal nerves, including the roots of the cauda equina, and cerebrospinal fluid. The arachnoid membrane is separated from the spinal cord by the wide subarachnoid space, and from the dura mater by the subdural space. The arachnoid membrane is thin, translucent, but quite dense. It is based on reticular connective tissue with cells of various shapes. The arachnoid membrane is covered on the outer and inner sides with flat cells resembling mesothelium or endothelium. The existence of nerves in the arachnoid membrane is controversial.

Under the arachnoid membrane is the spinal cord, covered with a soft, or vascular, membrane fused to its surface. This connective tissue membrane consists of an outer longitudinal and inner circular layer of bundles of connective tissue collagen fibers; they are fused with each other and with the brain tissue. In the thickness of the soft shell there is a network of blood vessels intertwining the brain.

Their branches penetrate into the thickness of the brain, carrying with them the connective tissue of the soft shell.

Between the arachnoid and soft membranes there is a subarachnoid space. Cerebrospinal fluid fills beneath the arachnoid spaces of the spinal cord and brain, which communicate with each other through the foramen magnum.

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. Cranially, the hard shell fuses with the edges of the large foramen of the 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.

Arachnoidea, arachnoidea , thin, transparent, devoid of blood vessels and consists of connective tissue covered with endothelium. It encircles the spinal cord and brain on all sides and is connected to the soft shell lying inward from it with the help of numerous arachnoid trabeculae, and in a number of places fuses with it.

Arachnoid membrane of the spinal cord

Rice. 960. Arachnoid membrane of the spinal cord (photo. Specimen by V. Kharitonova). (Area of ​​a completely stained specimen. Trabeculae of the subarachnoid space.)

Arachnoidea mater spinalis (Fig.; see Fig.,), like the dura mater of the spinal cord, is a sac that relatively freely surrounds the spinal cord.

Between the arachnoid and pia mater of the spinal cord is subarachnoid space, cavitas subarachnoidea, - a more or less extensive cavity, especially in the anterior and posterior sections, reaching 1–2 mm in the transverse direction and made cerebrospinal fluid, liquor cerebrospinalis.

The arachnoid membrane of the spinal cord is connected to the dura mater of the spinal cord in the region of the spinal nerve roots, in those places where these roots penetrate the dura mater of the spinal cord (see earlier). It is connected to the soft membrane of the spinal cord through numerous, especially in the posterior sections, arachnoid trabeculae, which form the posterior subarachnoid septum.

In addition, the arachnoid membrane of the spinal cord is connected to both the hard and soft membranes of the spinal cord using special dentate ligaments, ligamenta denticulata. They are connective tissue plates (20–25 in total), located in the frontal plane on both lateral sides of the spinal cord and extending from the soft shell to the inner surface of the hard shell.

Arachnoid membrane of the brain

Arachnoidea mater encephali (Fig. , ), covered, like the spinal cord shell of the same name, with endothelium, is connected to the soft shell of the brain by subarachnoid trabeculae, and to the hard shell by granulations of the arachnoid membrane. Between it and the dura mater of the brain there is a slit-like subdural space filled with a small amount of cerebrospinal fluid.

The outer surface of the arachnoid membrane of the brain is not fused with the adjacent dura mater. However, in places, mainly on the sides of the superior sagittal sinus and to a lesser extent on the sides of the transverse sinus, as well as near other sinuses, its processes of varying sizes - the so-called granulations of the arachnoid membrane, granulationes arachnoideales, enter the dura mater of the brain and, together with it, into the inner surface of the cranial bones or sinuses. In these places, small depressions are formed in the bones, the so-called granulation dimples; there are especially many of them near the sagittal suture of the cranial vault. Granulations of the arachnoid membrane are organs that filter the outflow of cerebrospinal fluid into the venous bed.

The inner surface of the arachnoid membrane faces the brain. On the prominent parts of the convolutions of the brain, it is closely adjacent to the pia mater of the brain, without, however, following the latter into the depths of the grooves and fissures. Thus, the arachnoid membrane of the brain spreads like bridges from gyrus to gyrus, and in places where there are no adhesions, spaces remain, called subarachnoid spaces, cavitates subarachnoideale.

The subarachnoid spaces of the entire surface of the brain, as well as the spinal cord, communicate with each other. In some places these spaces are quite significant and are called subarachnoid cisterns, cisternae subarachnoideae(rice. , ). The largest tanks stand out:

1. cerebellomedullary cistern, cisterna cerebellomedullaris, lies between the cerebellum and medulla oblongata;
2. cistern of the lateral fossa of the cerebrum, cisterna fossae lateralis cerebri, – in the lateral sulcus, corresponding to the lateral fossa of the cerebrum;
3. interpeduncular cistern, cisterna interpeduncularis, – between the cerebral peduncles;
4. cross tank, cisterna chiasmatis, – between the optic chiasm and the frontal lobes of the brain.

In addition, there are a number of large subarachnoid spaces that can be classified as cisterns: running along the upper surface and knee of the corpus callosum cistern of the corpus callosum; located at the bottom of the transverse fissure of the cerebrum, between the occipital lobes of the hemispheres and the superior surface of the cerebellum, bypass tank, which looks like a canal running along the sides of the cerebral peduncles and the roof of the midbrain; bridge side tank, lying under the middle cerebellar peduncles, and, finally, in the region of the basilar sulcus of the bridge - middle bridge tank.

The subarachnoid cavities of the brain communicate with each other, as well as through the median and lateral apertures with the cavity of the fourth ventricle, and through the latter with the cavity of the remaining ventricles of the brain.

Gathers in the subarachnoid space cerebrospinal fluid, liquor cerebrospinalis, from different parts of the brain.

The outflow of fluid from here goes through the perivascular, perineural fissures and through the granulations of the arachnoid membrane into the lymphatic and venous pathways.

The membranes of the brain and spinal cord are represented by hard, soft and arachnoid, having the Latin names dura mater, pia mater et arachnoidea encephali. The purpose of these anatomical structures is to provide protection for the conductive tissue of both the brain and the spinal column, as well as to form a volumetric space in which cerebrospinal fluid and cerebrospinal fluid circulate.

Dura mater

This part of the protective structures of the brain is represented by connective tissue, dense in consistency, fibrous structure. It has two surfaces – external and internal. The external one is well supplied with blood, includes a large number of vessels, and connects to the bones of the skull. This surface functions as periosteum on the inner surface of the cranial bones.

The dura mater (dura mater) has several parts that penetrate the cranial cavity. These processes are duplications (folds) of connective tissue.

The following formations are distinguished:

• falx cerebellum - located in the space limited by the halves of the cerebellum on the right and left, Latin name falx cerebelli:
• falx cerebri - like the first, located in the interhemispheric space of the brain, the Latin name is falx cerebri;
• the tentorium cerebellum is located above the posterior cranial fossa in the horizontal plane between the temporal bone and the transverse occipital sulcus; it delimits the upper surface of the cerebellar hemispheres and the occipital cerebral lobes;
• sella diaphragm – located above the sella turcica, forming its ceiling (operculum).

Layer structure of the meninges

The space between the processes and layers of the dura mater of the brain is called sinuses, the purpose of which is to create space for venous blood from the vessels of the brain, the Latin name is sinus dures matris.

The following sinuses exist:

• superior sagittal sinus - located in the area of ​​the large falciform process on the protruding side of its upper edge. Blood through this cavity enters the transverse sinus (transversus);
• the inferior sagittal sinus, which is located in the same area, but at the lower edge of the falciform process, flows into the straight sinus (rectus);
• transverse sinus - located in the transverse groove of the occipital bone, passes to the sinus sigmoideus, passing in the area of ​​the parietal bone, near the mastoid angle;
• the straight sinus is located at the junction of the tentorium cerebellum and the greater falciform fold, blood from it enters the sinus transversus in the same way as in the case of the greater transverse sinus;
• cavernous sinus - located on the right and left near the sella turcica, has the shape of a triangle in cross section. The branches of the cranial nerves pass through its walls: in the upper – the oculomotor and trochlear nerves, in the lateral – the ophthalmic nerve. The abducens nerve is located between the ophthalmic and trochlear nerves. As for the blood vessels of this area, inside the sinus there is the internal carotid artery along with the carotid plexus, washed by venous blood. The superior branch of the ophthalmic vein flows into this cavity. There are communications between the right and left cavernous sinuses, called the anterior and posterior intercavernous sinuses;
• the superior petrosal sinus is a continuation of the previously described sinus, located in the area of ​​the temporal bone (at the upper edge of its pyramid), being a connection between the transverse and cavernous sinuses;
• inferior petrosal sinus - located in the inferior petrosal groove, on the edges of which are the pyramid of the temporal bone and the occipital bone. Communicates with sinus cavernosus. In this area, by the fusion of the transverse connecting branches of the veins, the basilar plexus of veins is formed;
• occipital sinus - formed in the area of ​​the internal occipital crest (protrusion) from the sinus transversus. This sinus is divided into two parts, covering the edges of the occipital foramen on both sides and flowing into the sigmoid sinus. At the junction of these sinuses there is a venous plexus called confluens sinuum (confluence of sinuses).

Arachnoid

Deeper than the dura mater of the brain is the arachnoid, which covers the entire structure of the central nervous system. It is covered with endothelial tissue and connected to hard and soft supra- and subarachnoid septa formed by connective tissue. Together with the solid, it forms the subdural space in which a small volume of cerebrospinal fluid (CSF, cerebrospinal fluid) circulates.

Schematic representation of the meninges of the spinal cord

On the outer surface of the arachnoid membrane, in some places there are outgrowths, represented by rounded pink bodies - granulations. They penetrate the hard tissue and promote the outflow of cerebrospinal fluid through filtration into the venous system of the skull. The surface of the membrane adjacent to the brain tissue is connected by thin cords to the soft one, between them a space called subarachnoid or subarachnoid is formed.

Soft membrane of the brain

This is the membrane closest to the medulla, consisting of connective tissue structures, loose in consistency, containing plexuses of blood vessels and nerves. The small arteries passing through it connect with the bloodstream of the brain, separated only by a narrow space from the upper surface of the brain. This space is called supracerebral or subpial.

The pia mater is separated from the subarachnoid space by the perivascular space with many blood vessels. For transverse purposes of the encephalon and cerebellum, it is located between the areas limiting them, as a result of which the spaces of the third and fourth ventricles are closed and connected to the choroid plexuses.

Spinal cord membranes

The spinal cord is similarly surrounded by three layers of connective tissue membranes. The dura mater of the spinal cord differs from that adjacent to the encephalon in that it does not fit tightly to the edges of the spinal canal, which is covered with its own periosteum. The space that forms between these membranes is called the epidural; it contains the venous plexuses and fatty tissue. The hard shell penetrates with its processes into the intervertebral foramina, enveloping the roots of the spinal nerves.

Spine and adjacent structures

The soft membrane of the spinal cord is represented by two layers; the main feature of this formation is that it contains many arteries, veins and nerves. The medulla is adjacent to this membrane. Between the soft and hard is the arachnoid, represented by a thin sheet of connective tissue.

On the outside there is a subdural space, which in the lower part passes into the terminal ventricle. In the cavity formed by the layers of the dura and arachnoid membranes of the central nervous system, cerebrospinal fluid, or cerebrospinal fluid, circulates, which also enters the subarachnoid spaces of the encephalon ventricles.

The spinal structures along the entire length of the brain are adjacent to the dentate ligament, which penetrates between the roots and divides the subarachnoid space into two parts - the anterior and posterior space. The posterior section is divided into two halves by the intermediate cervical septum - into left and right parts.