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 ensure protection of the conductive tissue of both the brain and the spinal cord, as well as the formation of 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 temporal bone and the transverse occipital groove, 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 it top 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 parietal bone, close to 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. Branches run through its walls cranial nerves: in the upper – oculomotor and trochlear, in the lateral – optic nerve. The abducens nerve is located between the ophthalmic and trochlear nerves. Concerning blood vessels this area, then inside the sinus there is an internal carotid artery together with the carotid plexus, washed by venous blood. This cavity flows into upper branch ophthalmic vein. 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 completely covers the structures 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 circulates cerebrospinal fluid(cerebrospinal fluid, cerebrospinal fluid).
Schematic representation of the meninges of the spinal cord
On outer surface the arachnoid membrane in some places has outgrowths represented by rounded bodies Pink colour– granulations. They penetrate into the solid and promote the outflow of cerebrospinal fluid through filtration into venous system skulls 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, main feature This formation is that many arteries, veins and nerves pass through it. 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 throughout the brain are adjacent to the dentate ligament, which penetrates between the roots and separates subarachnoid space into two parts - front and rear space. The posterior section is divided into two halves by the intermediate cervical septum - into left and right parts.
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 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.
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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 vital 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 from 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 lining of the brain and spinal cord are susceptible to diseases that can occur as a result of injury spinal column, 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. Vaccinations help reduce the risk of disease Attentive attitude to the health of the spine.
The spinal cord (SC) is covered by three meninges, which have a connection with each other, with the spinal cord and bones, ligaments of the spine: internal (soft, vascular), middle (arachnoid, arachnoid), external (hard). All three SC sheaths pass from above into the same-named brain membranes, from below they fuse with each other and with the terminal filament of the SC, at the points where the spinal nerves exit the spinal canal, the SC membranes pass into the spinal nerve sheaths.
Soft shell tightly connected to the SC, penetrating into its cracks and grooves. It consists of connective tissue and blood vessels supplying the SC and nerves. That's why the soft shell is called choroid. Blood vessels penetrating into the brain tissue are surrounded in the form of a tunnel by the pia mater. The space between the pia mater and the blood vessels is called perivascular space. It communicates with the subarachnoid space and contains cerebrospinal fluid. At the transition to the blood capillaries, the perivascular space ends. Blood capillaries The CMs are surrounded in the form of a muff by astrocytes.
Outside the soft shell is a translucent arachnoid (arachnoid) membrane. The arachnoid membrane does not contain blood vessels; it consists of connective tissue covered on both sides with a layer of endothelial cells. The arachnoid membrane has numerous connections (arachnoid trabeculae) with the soft shell. The space between the arachnoid membrane and the pia mater is called subarachnoid space. The subarachnoid space usually ends at the level of the second sacral vertebra. Largest size this space is located in the area of the filum terminale of the SM. This part of the subarachnoid space is called the cistern terminalis. The main amount circulates in the subarachnoid space cerebrospinal fluid - cerebrospinal fluid, which protects the spinal cord from mechanical damage (performs a shock-absorbing function), ensures the maintenance of water-electrolyte homeostasis (constancy) of the spinal cord.
Dura mater formed by dense connective tissue. It is firmly fixed to the bones of the spine. The space between the dura mater and the arachnoid is called subdural space. It is also filled with cerebrospinal fluid. The space between the dura mater and the bones of the vertebrae is called epidural space. The epidural space is filled with adipose tissue and venous blood vessels that form the venous plexuses. From below, the dura spinal membrane passes into the terminal filum of the spinal cord and ends at the level of the body of the second sacral vertebra.
All three meninges as they exit the spinal cord spinal nerve pass into the sheaths of the spinal nerve: endoneurium, perineurium, epineurium. This feature makes it possible for infection to penetrate the spinal cord along the spinal nerves. Inside the spinal canal, each root (anterior, posterior) of the SC is covered with a soft and putinous membrane.
The spinal cord is surrounded by three membranes of mesenchymal origin. External - hard shell spinal cord. Behind it lies the middle arachnoid, which is separated from the previous one by the subdural space. Directly adjacent to the spinal cord is the inner soft membrane of the spinal cord. The inner shell is separated from the arachnoid by the subarachnoid space. In neurology, it is customary to call these last two the soft membrane, in contrast to the dura mater.
The hard shell of the spinal cord (dura mater spinalis) is an oblong sac with fairly strong and thick (compared to other membranes) walls, located in the spinal canal and containing the spinal cord with the anterior and posterior roots of the spinal nerves and other membranes. Outside surface The dura mater is separated from the periosteum lining the inside of the spinal canal by the suprathecal epidural space (cavitas epiduralis). The latter is filled with fatty tissue and contains the internal vertebral venous plexus. Above, in the region of the foramen magnum, the dura mater of the spinal cord firmly fuses with the edges of the foramen magnum and continues into the dura mater of the brain. In the spinal canal, the hard shell is strengthened with the help of processes that continue into the perineural membranes of the spinal nerves, fused with the periosteum at each intervertebral foramen. In addition, the hard shell of the spinal cord is strengthened by numerous fibrous bundles running from the shell to the back longitudinal ligament spinal column
The inner surface of the dura mater of the spinal cord is separated from the arachnoid by a narrow slit-like subdural space. which is penetrated by a large number of thin bundles of connective tissue fibers. In the upper parts of the spinal canal, the subdural space of the spinal cord communicates freely with a similar space in the cranial cavity. Below, its space ends blindly at the level of the 11th sacral vertebra. Below, the bundles of fibers belonging to the dura mater of the spinal cord continue into the terminal (external) filum.
Arachnoid membrane of the spinal cord (arachnoidea mater spinalis) is a thin plate located inward from the hard shell. The arachnoid membrane fuses with the latter near the intervertebral foramina.
Soft (choroidal) membrane of the spinal cord (pia mater spinalis) is tightly adjacent to the spinal cord and fuses with it. Connective tissue fibers branching from this membrane accompany the blood vessels and, together with them, penetrate into the substance of the spinal cord. From the soft shell, the arachnoid is separated by the arachnoid space (cavitas subarachnoidalis), filled with cerebrospinal fluid (liquor cerebrospinalis), total which is about 120-140 ml. In the lower sections, the subarachnoid space contains the roots of the spinal nerves surrounded by cerebral fluid. In this place (below the second lumbar vertebra) it is most convenient to obtain cerebrospinal fluid for examination by puncture with a needle (without the risk of damaging the spinal cord).
In the upper parts, the subarachnoid space of the spinal cord continues into the subarachnoid space of the brain. The subarachnoid space contains numerous connective tissue bundles and plates connecting the arachnoid membrane with the soft tissue and the spinal cord. From the lateral surfaces of the spinal cord (from the soft shell covering it), between the anterior and posterior roots, to the right and left, a thin durable plate extends to the arachnoid membrane - the denticulate ligament (ligamentum denticulatum). The ligament has a continuous origin from the soft shell, and in the lateral direction it is divided into teeth (20-30), which grow together not only with the arachnoid, but also with the hard shell of the spinal cord. The upper tooth of the ligament is located at the level of the foramen magnum, the lower one is between the roots of the 12th thoracic and 1st lumbar spinal nerves. Thus, the spinal cord appears to be suspended in the subarachnoid space with the help of the frontally located dentate ligament. On the posterior surface of the spinal cord, along the posterior median sulcus, a sagittally located septum runs from the pia mater to the arachnoid. In addition to the dentate ligament and the posterior septum, in the subarachnoid space there are unstable thin bundles of connective tissue fibers (septa, filaments) connecting the pia and arachnoid membranes of the spinal cord.
In the lumbar and sacral regions The spinal canal, where the bundle of spinal nerve roots (cauda equina) is located, the dentate ligament and the posterior subarachnoid septum are absent. fat cell and the venous plexuses of the epidural space, the membranes of the spinal cord, cerebrospinal fluid and ligamentous apparatus do not constrain the spinal cord during spinal movements. They also protect the spinal cord from shocks and shocks that occur during human body movements.
The spinal cord is located in the spinal canal. However, between the walls of the canal and the surface of the spinal cord there remains a space 3–6 mm wide, in which the meninges and the contents of the intermeningeal spaces are located.
The spinal cord is covered by three membranes - soft, arachnoid and hard.
1. The soft shell of the spinal cord is strong and quite elastic, directly adjacent to the surface of the spinal cord. At the top it passes into the pia mater of the brain. The thickness of the soft shell is about 0.15 mm. It is rich in blood vessels that provide blood supply to the spinal cord, which is why it has a pinkish-white color.
The dentate ligaments extend from the lateral surface of the soft shell, closer to the anterior roots of the spinal nerves. They are located in the frontal plane and have the appearance of triangular teeth. The apexes of the teeth of these ligaments are covered by the processes of the arachnoid membrane and end on the inner surface of the dura mater in the middle between two adjacent spinal nerves. The duplication of the soft shell is immersed in the anterior median fissure during the development of the spinal cord and in an adult it takes the form of a septum.
- 2. The arachnoid membrane of the spinal cord is located outside the soft membrane. It does not contain blood vessels and is a thin transparent film 0.01–0.03 mm thick. This shell has numerous slot-like openings. In the area of the foramen magnum it passes into the arachnoid membrane of the brain, and below, at the level of the 11th sacral vertebra, it merges with the soft membrane of the spinal cord.
- 3. The dura mater of the spinal cord is itself outer shell(Fig. 2.9).
It is a long connective tissue tube separated from the periosteum of the vertebrae by the epidural (peridural) space. In the area of the foramen magnum it continues into the dura mater of the brain. Below, the hard shell ends in a cone that extends to the level of the II sacral vertebra. Below this level, it merges with the other membranes of the spinal cord into the common membrane of the filum terminale. The thickness of the dura mater of the spinal cord ranges from 0.5 to 1.0 mm.
Branches in the form of sleeves for the spinal nerves are separated from the lateral surface of the dura mater. These meningeal sheaths continue into the intervertebral foramina, cover the sensory ganglion of the spinal nerve and then continue into the perineural sheath of the spinal nerve.
Rice. 2.9.
1 – vertebral periosteum; 2 – dura mater of the spinal cord; 3 – arachnoid membrane of the spinal cord; 4 – subarachnoid ligaments; 5 – epidural space; 6 – subdural space; 7 – subarachnoid space; 8 – dentate ligament; 9 – sensitive node of the spinal nerve; 10 – posterior root of the spinal nerve; 11 – anterior root of the spinal nerve; 12 – soft membrane of the spinal cord
Between the inner surface of the spinal canal and the hard shell there is a space called the epidural. The contents of this space are adipose tissue and internal vertebral venous plexuses. Between the dura and arachnoid membranes there is a slit-like subdural space containing a small amount of cerebrospinal fluid. Between the cobweb and soft shells there is a subarachnoid space, which also contains cerebrospinal fluid.
