Spinal cord. The structure and function of the membranes of the spinal cord The outer membrane of the spinal cord is called

Spinal cord dressed in three connective tissue membranes, meninges, originating from the mesoderm. These shells are as follows, if you go from the surface inward: hard shell, dura mater; arachnoid shell, arachnoidea, and soft shell, pia mater.

Cranially, all three shells continue into the same shells of the brain.

1. Dura mater of the spinal cord, dura mater spinalis, envelops the spinal cord in the form of a bag on the outside. It does not adhere closely to the walls of the spinal canal, which are covered with periosteum. The latter is also called the outer sheet of the hard shell.

Between the periosteum and the hard shell is the epidural space, cavitas epiduralis. It contains fatty tissue and venous plexuses - plexus venosi vertebrales interni, into which venous blood flows from the spinal cord and vertebrae. Cranially, the hard shell fuses with the edges of the foramen magnum of the occipital bone, and caudally ends at the level of II-III sacral vertebrae, tapering in the form of a thread, filum durae matris spinalis, which is attached to the coccyx.

arteries. The hard shell receives from the spinal branches of the segmental arteries, its veins flow into the plexus venosus vertebralis interims, and its nerves come from the rami meningei of the spinal nerves. The inner surface of the hard shell is covered with a layer of endothelium, as a result of which it has a smooth, shiny appearance.

2. arachnoid mater of the spinal cord, arachnoidea spinalis, in the form of a thin transparent avascular leaf, adjoins from the inside to the hard shell, separated from the latter by a slit-like subdural space pierced by thin crossbars, spatium subdurale.

Between the arachnoid and the pia mater directly covering the spinal cord is the subarachnoid space, cavitas subarachnoidalis, in which the brain and nerve roots lie freely, surrounded by a large amount of cerebrospinal fluid, liquor cerebrospinalis. This space is especially wide in the lower part of the arachnoid sac, where it surrounds the cauda equina of the spinal cord (sisterna terminalis). The fluid that fills 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 cervical region behind, along the midline, a septum, septum cervicdle intermedium, is formed. In addition, on the sides of the spinal cord in the frontal plane is the dentate ligament, lig. denticulatum, consisting of 19-23 teeth passing 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 subarachnoid space is divided into anterior and posterior sections.

3. Pia mater of the spinal cord, pia mater spinalis, covered from the surface with endothelium, directly envelops the spinal cord and contains vessels between its two sheets, together with which it enters its furrows and the medulla, forming perivascular lymphatic spaces around the vessels.

Vessels of the spinal cord. Ah. spinales anterior et posterior, descending along the spinal cord, are interconnected by numerous branches, forming a vascular network (the so-called vasocorona) on the surface of the brain. Branches depart from this network, penetrating together with the processes of the soft shell into the substance of the brain.

Veins are similar in general to arteries and ultimately empty into the plexus venosi vertebrales interni.

To lymphatic vessels of the spinal cord can be attributed to the perivascular spaces around the vessels, communicating with the subarachnoid space.

Sheaths of the spinal cord. Dura mater, arachnoid mater, pia mater of the spinal cord. The spinal cord is dressed in three connective tissue membranes, meninges, originating from the mesoderm. These shells are as follows, if you go from the surface inward: hard shell, duramater; arachnoid, arachnoidea, and soft shell, piamater. Cranially, all three shells continue into the same shells of the brain.

1. The hard shell of the spinal cord, duramaterspinalis, wraps the outside of the spinal cord in the form of a bag. It does not adhere closely to the walls of the spinal canal, which are covered with periosteum. The latter is also called the outer sheet of the hard shell. Between the periosteum and the hard shell is the epidural space, cavitasepiduralis. It contains fatty tissue and venous plexuses - plexus venosivertebrales interni, into which venous blood flows from the spinal cord and vertebrae. Cranially, the hard shell grows together with the edges of the large foramen of the occipital bone, and caudally ends at the level of 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, adheres to the hard shell from the inside, separating from the latter by a slit-like subdural space pierced by thin crossbars, spatium subdurale. Between the arachnoid and the pia mater directly covering the spinal cord is the 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 (sisternaterminalis). 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 and the pia mater covering the spinal cord in the cervical region behind, along the midline, a septum, septumcervicdleintermedium, is formed. In addition, on the sides of the spinal cord in the frontal plane is the dentate ligament, lig. denticulatum, consisting of 19 - 23 teeth passing 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 subarachnoid space is divided into anterior and posterior sections.

3. The soft shell of the spinal cord, piamaterspinalis, covered from the surface with endothelium, directly envelops the spinal cord and contains vessels between its two sheets, together with which it enters its furrows 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 the lower surface - the base of the brain - is thickened and uneven. In the region of the base, 12 pairs of cranial (or cranial) nerves depart from the brain. In the brain, the hemispheres of the cerebrum (the newest part in evolutionary development) and the trunk with the cerebellum are distinguished. The mass of the brain of an adult is on average 1375 g for men, 1245 g for women. The mass 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 intensively, but only by the age of 20 reaches its final size.

Scheme brain development

A. Neural tube in longitudinal section, three cerebral vesicles are visible (1; 2 and 3); 4 - part of the neural tube from which the spinal cord develops.
B. Brain of the fetus from the side (3rd month) - five brain bubbles; 1 - terminal brain (first bubble); 2 - diencephalon (second bladder); 3 - midbrain (third bubble); 4 - hindbrain (fourth bubble); 5 - medulla oblongata (fifth brain bladder).

The brain and spinal cord develop on the dorsal (dorsal) side of the embryo from the outer germ layer (ectoderm). In this place, the neural tube is formed with an expansion in the head section of the embryo. Initially, this expansion is represented by three brain bubbles: anterior, middle and posterior (diamond-shaped). In the future, the anterior and rhomboid bubbles divide and five brain bubbles are formed: final, intermediate, middle, posterior and oblong (additional).

In the process of development, the walls of the cerebral vesicles grow unevenly: either thickening or remaining thin in some areas and pushing into the cavity of the bladder, participating in the formation of the vascular plexuses of the ventricles.

The remains of the cavities of the cerebral vesicles and the neural tube are the cerebral ventricles and the central canal of the spinal cord. From each cerebral vesicle, certain parts of the brain develop. In this regard, five main sections are distinguished from the five cerebral vesicles in the brain: medulla oblongata, hindbrain, midbrain, diencephalon, and terminal brain.

The spinal cord is surrounded by three membranes of mesenchymal origin. Outer - hard shell of the spinal cord. Behind it lies the middle - arachnoid membrane, which is separated from the previous one by the subdural space. Directly adjacent to the spinal cord is the inner pia mater 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, in contrast to the dura mater, the pia mater.

The hard shell of the spinal cord (dura mater spinalis) is an oblong bag with rather strong and thick (compared to other shells) walls, located in the spinal canal and containing the spinal cord with the anterior and posterior roots of the spinal nerves and other shells. The outer surface of the dura mater is separated from the periosteum, which lines the inside of the spinal canal, by the supra-shell 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 fuses firmly 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 by processes that continue into the perineural sheaths of the spinal nerves, which fuse with the periosteum in each intervertebral foramen. In addition, the dura mater of the spinal cord is strengthened by numerous fibrous bundles that go from the shell to the posterior longitudinal ligament of the 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 sections of the spinal canal, the subdural space of the spinal cord communicates freely with the analogous 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 hard shell of the spinal cord continue into the terminal (outer) thread.

arachnoid mater of the spinal cord (arachnoidea mater spinalis) is a thin plate located medially from the hard shell. The arachnoid fuses with the latter near the intervertebral foramina.

The soft (vascular) membrane of the spinal cord (pia mater spinalis) is tightly adjacent to the spinal cord, fuses with it. The connective tissue fibers branching off from this membrane accompany the blood vessels and together with them penetrate into the substance of the spinal cord. The arachnoid space (cavitas subarachnoidalis), filled with cerebrospinal fluid (liquor cerebrospinalis), the total amount of which is about 120-140 ml, separates the arachnoid from the soft shell. In the lower sections, the subarachnoid space contains the roots of the spinal nerves surrounded by cerebral fluid. In this place (below the II lumbar vertebra), it is most convenient to obtain cerebrospinal fluid for examination by puncturing with a needle (without the risk of damaging the spinal cord).

In the upper sections, 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 that connect the arachnoid membrane with the soft and spinal cord. From the lateral surfaces of the spinal cord (from the soft membrane covering it), between the anterior and posterior roots, to the right and left to the arachnoid, a thin strong plate extends - the dentate ligament (ligamentum denticulatum). The ligament has a continuous beginning from the soft shell, and in the lateral direction it is divided into teeth (20-30 in number), which fuse not only with the arachnoid, but also with the hard shell of the spinal cord. The upper tooth of the ligament is at the level of the foramen magnum, the lower tooth is between the roots of the 12th thoracic and 1st lumbar spinal nerves. Thus, the spinal cord is, as it were, suspended in the subarachnoid space with the help of a 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 non-permanent thin bundles of connective tissue fibers (septa, filaments) connecting the soft and arachnoid membranes of the spinal cord.

In the lumbar and sacral sections of the spinal canal, where the bundle of spinal nerve roots (cauda equina, cauda equina) is located, the dentate ligament and the posterior subarachnoid septum are absent. The fat cell and venous plexuses of the epidural space, the membranes of the spinal cord, the cerebrospinal fluid and the ligamentous apparatus do not constrain the spinal cord during spinal movements. They also protect the spinal cord from shocks and shocks that occur during the movements of the human body.

Enters the central nervous system. In the human body, it is responsible for motor reflexes and the transmission of nerve impulses between organs and the brain. The membranes of the spinal cord cover it, providing protection. What features and differences do they have?

Structure

The arches of the vertebrae form a cavity called the spinal canal, in which the spinal cord is located along with the vessels and nerve roots. Its upper part is connected to the medulla oblongata (head section), and the lower part is connected to the periosteum of the second coccygeal vertebra.

The spinal cord looks like a thin white cord, the length of which in a person reaches 40-45 centimeters, and the thickness increases from bottom to top. Its surface is slightly concave. It consists of thirty-one segments, from which pairs of nerve roots emerge.

The spinal cord is covered with membranes on the outside. Inside it contains gray and their ratio varies in different parts. The gray matter has the shape of a butterfly, it contains the bodies of nerve cells, their processes contain white matter, which is located at the edges.

The canal is located in the center of the gray matter. It fills (liquor), which constantly circulates in the brain and spinal cord. In an adult, its volume is up to 270 milliliters. Liquor is produced in the ventricles of the brain and is updated 4 times a day.

Meninges of the spinal cord

Three shells: hard, arachnoid and soft - cover both the brain and spinal cord. They perform two main functions. Protective prevents the negative impact of mechanical effects on the brain. associated with the regulation of cerebral blood flow, due to which metabolism in tissues is carried out.

The membranes of the spinal cord are made up of connective tissue cells. Outside there is a hard shell, under it is arachnoid and soft. They don't fit tightly together. Between them there is a subdural and subarachnoid space. They are attached to the spine by plates and ligaments that prevent the brain from stretching out.

Shells are formed at the beginning of the second month of embryo development. Connective tissue is formed on the neural tube and spreads along it. Later, tissue cells separate to form the outer and inner membranes. After some time, the inner shell is divided into soft and arachnoid.

hard shell

The outer hard shell consists of upper and lower layers. It has a rough surface on which many vessels are located. Unlike a similar membrane in the brain, it does not adhere tightly to the walls of the spinal canal and is separated from them by the venous plexus, fatty tissue.

The dura mater of the spinal cord is a dense shiny fibrous tissue. It envelops the brain in the form of an elongated cylindrical bag. Coverings make up the bottom layer of the shell.

It envelops the nodes and nerves, forming cavities that expand, approaching the intervertebral foramens. Near the head, the shell is connected to the occipital bone. From top to bottom, it narrows and is a thin thread that joins the coccyx.

Blood passes to the sheath through arteries connected to the abdominal and thoracic aorta. Venous blood enters the venous plexus. The shell is fixed in the spinal canal with the help of processes in as well as fibrous bundles.

Arachnoid

A slit-like space with a large number of connecting bundles separates the hard and arachnoid membranes of the spinal cord. The latter has the appearance of a thin sheet, it is transparent and contains fibroblasts (connective tissue fibers that synthesize the extracellular matrix).

The arachnoid membrane of the spinal cord is shrouded in neuroglia - cells that ensure the transmission of nerve impulses. It does not contain blood vessels. Processes, filiform trabeculae, depart from the arachnoid membrane, weaving into the next soft shell.

Under the shell is the subarachnoid space. Inside it contains liquor. It is expanded in the lower part of the spinal cord, in the region of the sacrum and coccyx. In the neck area there is a partition between the soft and arachnoid membranes. The septum and dentate ligaments between the nerve roots fix the brain in one position, preventing it from shifting.

soft shell

The inner shell is soft. It envelops the spinal cord. Compared to a similar structure in the brain, it is considered to be stronger and thicker. The pia mater of the spinal cord consists of loose tissue, which is covered by endothelial cells.

It has two thin layers, between which are numerous blood vessels. On the upper layer, represented by a thin plate or leaf, there are jagged ligaments that fix the shell. Adjacent to the inside is a membrane that connects directly to the spinal cord. The membrane forms a sheath for the artery and, together with it, penetrates the brain and its gray matter.

The soft shell is present only in mammals. Other terrestrial vertebrates (tetrapods) have only two - solid and internal. In the course of evolutionary development, the inner shell in mammals was divided into arachnoid and soft.

Conclusion

The spinal cord is part of the central nervous system of all vertebrates, including humans. It performs reflex and conductive functions. The first is responsible for the reflexes of the limbs - their flexion and extension, jerking, etc. The second function is the conduction of nerve impulses between the organs and the brain.

Hard, arachnoid and soft shells envelop the spinal cord from the outside. They perform protective and trophic (nutritional) functions. The membranes are formed by connective tissue cells. They are separated by spaces that are filled with cerebrospinal fluid - a fluid that circulates in the spinal cord and brain. Between themselves, the shells are connected by thin fibers and processes.

The 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 the metabolism and production of hormones and mediators necessary for normal human life.

What membranes cover the human spinal cord

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

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

Functions and structural features of the spinal membranes

The main task of shells is:

• Functions of the hard shell - are a natural shock absorber that reduces the mechanical impact on the brain during movement or injury. Takes a direct part in the blood supply.
• The function of the arachnoid membrane - the layer plays an important role in the formation of hormones and the metabolic processes of the body. Functions are related to the structure of the shell. So between the soft and arachnoid layer, a subarachnoid space is formed - a cavity in which the cerebrospinal fluid is located.
  The significance of this is difficult to overestimate. The liquid not only creates the 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 the creation of nervous tissue. The middle shell of the spinal cord is a reticular connective tissue, which has a small thickness and maximum strength.
  The appearance of the layer resembles the endothelium or mesothelium. The difference between the shell is the absence of nerves (some professors of medicine question this statement).
• soft shell function. The anatomy of the spinal canal shows the close relationship of all layers surrounding the brain. The soft and hard shell supplies blood and essential nutrients to the human brain. Contribute to the normalization of metabolism and maintenance of the body's performance.

The anatomy of the shells shows a strong relationship between the work of the whole organism and the structure of the spine. Any violations: changes in the volume of cerebrospinal fluid, inflammation of the layers lead to serious malfunctions in the internal organs.

What diseases are the membranes susceptible to?

The most common diseases are:

The morphophysiological characteristics characteristic of the inflammation of the membranes in their clinical picture resemble the signs characteristic of any infectious diseases and the development of oncological pathologies. To determine the exact diagnosis, it is necessary to conduct a differential diagnosis, including MRI.

How to treat inflammation of the membranes

What is dangerous disease of the spinal membranes

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

For example, the outermost shell that covers 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 a patient's disability.

The outer shell 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 the normal development of a person and the functioning of internal organs.

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

Measures to prevent inflammation of the membranes

It is possible to reduce the percentage of diseases due to the attentive attitude to 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.