MEATHERS OF THE SPINAL CORD
Spinal cord dressed in three connective tissue membranes, meninges, originating from the mesoderm around the brain tube. These shells are as follows, if you go from the surface inward: hard shell, dura mater, or pachymeninx; arachnoid, arachnoidea, and choroid, pia mater. The last two shells, in contrast to the first, are also called the soft shell, leptomeninx. 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 their own periosteum (endorachis). The latter is also called the outer sheet of the hard shell. Between the endorachis and the hard shell is the epidural space, cavum epidurale. It contains fatty tissue and venous plexuses - plexus venosi vertebrates 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.
The dura receives its arteries from the spinal branches of the segmental arteries, its veins flow into the plexus venosus vertebralis internus, and its nerves originate 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 membrane of the spinal cord, arachnoidea spinalis, in the form of a thin transparent avascular sheet adjoins the hard shell from the inside, separating from the latter by a slit-like subdural space pierced by thin crossbars, cdvum subdural. Between the arachnoid and the choroid directly covering the spinal cord is the subarachnoid space, cavum subarachnoideale, in which the brain and nerve roots lie freely, surrounded by a large amount of cerebrospinal fluid, liquor cerebrospinal. This space is especially wide in the lower part of the arachnoid sac, where it surrounds the Cauda equina 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 and the choroid covering the spinal cord in the cervical region behind along the midline, a septum, septum cervicale 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, denticulata, the subarachnoid space is divided into anterior and posterior sections.
3. Choroid of the spinal cord, pia mater spinalis, covered from the surface with endothelium, directly envelops the spinal cord and contains vessels between its 2 sheets, together with which it enters its furrows and the medulla, forming perivascular lymphatic spaces around the vessels.
Vessels of the spinal cord. aa. spinales anterior et posteriores, 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 choroid into the substance of the brain (Fig. 271).
Veins are similar in general to arteries and ultimately empty into the plexus venosi vertebrales interni. The lymphatic vessels of the spinal cord include perivascular spaces around the vessels that communicate with the subarachnoid space.
The spinal cord is covered by three membranes of connective tissue ( meninges). If we consider these shells from the outer layers to the inner ones, then we will talk about a hard shell ( dura mater), arachnoid ( arachnoidea) and soft shell ( pia mater). Let's consider them in more detail.
Dura mater of the spinal cord
Dura mater spinalis, or dura mater, is like a sac that contains the spinal cord. It does not come into close contact with the walls of the spinal canal, covered with periosteum. Another name for the periosteum of the spinal canal is the outer sheet of the hard shell.
Between the hard shell and the periosteum is the epidural space, or cavitas epiduralis. This is a storage of fatty tissue and venous plexuses, venous blood from the vertebrae and spinal cord enters here. From the side of the skull, the hard shell is fused with a large opening of the occipital bone, and it ends in the region of the II or III sacral vertebra, and at the end it narrows almost to the size of a thread that is attached to the coccyx.
The inner surface of the hard shell is covered with a layer endothelium so it looks smooth and shiny on that side.
Arachnoid
Next comes the arachnoid membrane of the spinal cord, or arachnoidea spinalis. It looks like a thin and transparent sheet without vessels, which comes into contact with the hard shell from the inside, but at the same time is separated from it with the help of a slit-like subdural space penetrated by thin crossbars ( Spatium subdurale).
The spinal cord is covered by a pia mater, but between it and the arachnoid there is a subarachnoid space ( cavitas subarachnoidalis). In it, the nerve roots and the brain are in a free position, they are irrigated with cerebrospinal fluid ( liquor cerebrospinalis). The widest part of this space occupies the lower part of the arachnoid sac, here it is surrounded by a ponytail ( cauda equina). The subarachnoid space fills with fluid, which continuously communicates with the fluid from the subarachnoid space of both the brain and the cerebral ventricles.
You can also find a partition ( septum cervicale intermedium), which runs along the midline between the soft and arachnoid membranes and covers the cervical region from behind. The frontal plane (sides of the spinal cord) is occupied by dentate ligaments ( lig. denticulatum). The ligament consists of two dozen teeth (from 19 to 23), which occupy the gaps between the posterior and anterior roots. The dentate ligaments help hold the brain in place and prevent it from stretching out in length. These two ligaments divide the subarachnoid space into two sections: front and rear.
Pia mater of the spinal cord
The last, pia mater of the spinal cord ( pia mater spinalis) is the surface that covers the endothelium. It is directly adjacent to the spinal cord.
The soft shell between the two sheets contains vessels, along with them, enters the grooves of the spinal cord and medulla, which forms near the vessels the so-called perivascular lymphatic spaces.
Other structures
Vessels of the spinal cord Ah. spinales anterior and posterior) descend along the spinal cord. They are interconnected by numerous branches that form the vasculature (or vasocorona) in the upper part of the brain. Branches depart from it to the sides, which penetrate, like the processes of the soft shell, into the medulla. The veins have a similar function to the arteries and eventually flow into the internal vertebral plexuses.
To spinal lymphatic system include the spaces surrounding the vessels (the so-called perivascular spaces), which communicate with the subarachnoid space.
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 intershell 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 elastic enough, directly adjacent to the surface of the spinal cord. At the top, it passes into the soft shell 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.
From the lateral surface of the soft shell, closer to the anterior roots of the spinal nerves, the dentate ligaments depart. They are located in the frontal plane and have the form of triangular teeth. The tops of the teeth of these ligaments are covered by the processes of the arachnoid membrane and end on the inner surface of the hard shell in the middle between two adjacent spinal nerves. The duplication of the soft membrane plunges into the anterior median fissure during the development of the spinal cord and in an adult takes the form of a septum.
- 2. The arachnoid of the spinal cord is located outside the pia mater. It does not contain blood vessels and is a thin transparent film 0.01–0.03 mm thick. This shell has numerous slit-like holes. In the region of the foramen magnum, it passes into the arachnoid membrane of the brain, and below, at the level of the 11th sacral vertebrae, it merges with the pia mater of the spinal cord.
- 3. The hard shell of the spinal cord is its outermost shell (Fig. 2.9).
It is a long connective tissue tube separated from the periosteum of the vertebrae by the epidural (epidural) space. In the region of the foramen magnum, it continues into the dura mater. Below, the hard shell ends with a cone that goes to the level of the II sacral vertebra. Below this level, it merges with other sheaths of the spinal cord into a common sheath of the terminal filament. The thickness of the hard shell of the spinal cord is from 0.5 to 1.0 mm.
From the lateral surface of the hard shell, processes are separated in the form of sleeves for the spinal nerves. These sheath 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 - periosteum of the vertebra; 2 - hard shell 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 shell of the spinal cord
Between the inner surface of the spinal canal and the hard shell is a space called the epidural. The contents of this space are adipose tissue and internal vertebral venous plexuses. Between the hard and arachnoid membranes there is a slit-like subdural space containing a small amount of cerebrospinal fluid. Between the arachnoid and soft shells is the subarachnoid space, which also contains cerebrospinal fluid.
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 fairly 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. From the soft shell, the arachnoid is separated by the utia space (cavitas subarachnoidalis), filled with cerebrospinal fluid (liquor cerebrospinalis), the total amount of 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 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, spinal cord membranes, 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 the movements of the human body.
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 fuses with the edges of the foramen magnum of the occipital bone, and caudally ends at the level of II-III sacral vertebrae, narrowing 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 bubbles, 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 cerebral hemispheres (the newest part in evolutionary development) and the brainstem with the cerebellum are distinguished. The mass of the brain of an adult is on average 1375 g in men, 1245 g in 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.
Loading...