Shells of the spinal cord

The spinal cord is surrounded by three membranes of mesenchymal origin. External - a hard shell of the spinal cord. Behind it lies the middle - arachnoid shell, which is separated from the previous subdural space. The inner soft membrane of the spinal cord is directly attached to the spinal cord. The inner membrane is separated from the arachnoidal space by the subarachnoid space. In neurology, these two last, in contrast to the dura mater, are called soft membranes.

The solid membrane of the spinal cord (dura mater spinalis) is an elongated sac with fairly strong and thick walls (compared to other membranes) located in the spinal canal and containing the spinal cord with the anterior and posterior roots of the spinal nerves and the rest of the membranes. The outer surface of the dura mater is separated from the periosteum, lining the vertebral canal from the inside, with the epiduralpal space (cavitas epiduralis). The latter is filled with fatty tissue and contains an internal vertebral venous plexus. Above, in the region of the large occipital orifice, the solid membrane of the spinal cord firmly fuses with the edges of the large occipital foramen and continues into the hard shell of the brain. In the vertebral canal, the hard shell is strengthened with the help of processes that continue into the perineural shells of the spinal nerves, which coalesce with the periosteum in each intervertebral foramen. In addition, the hard shell of the spinal cord is strengthened by numerous fibrous bundles that are guided from the membrane to the posterior longitudinal ligament of the spinal column

The inner surface of the hard shell of the spinal cord is separated from the arachnid by a narrow slit subdural space. Which is permeated with a large number of thin bundles of connective tissue fibers. In the upper parts of the vertebral canal, the subdural space of the spinal cord is freely communicating with a similar space in the cranial cavity. At the bottom, its space ends blindly at level 11 of the sacral vertebra. Below the bundles of fibers belonging to the hard shell of the spinal cord, continue into the terminal (outer) filament.

The spinal cord of the spinal cord (arachnoidea mater spinalis) is a thin plate located inside the solid shell. The spider vein fuses with the latter near the intervertebral foramen.

The soft (vascular) membrane of the spinal cord (pia mater spinalis) is tightly attached 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 cheeks the succinic space (cavitas subarachnoidalis) filled with cerebrospinal fluid (liquor cerebrospinalis), the total amount of which is about 120-140 ml. In the lower parts of the subarachnoid space contains spine nerves surrounded by cerebral fluid. In this place (below the II lumbar vertebra) it is most convenient to pierce the spinal fluid by piercing the needle (without risk of damaging the spinal cord).

In the upper parts, the subarachnoid space of the spinal cord extends into the subarachnoid space of the brain. The subarachnoid space contains numerous connective tissue bundles and plates that connect the arachnoid membrane to the soft and 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 lamina (ligamentum denticulatum) departs to the arachnoid membrane. The ligament has a continuous origin from the soft membrane, and in the lateral direction it divides into teeth (in the amount of 20-30), which grow together not only with the arachnoid, but also with the hard shell of the spinal cord. The upper claw of the ligament is at the level of the large occipital orifice, 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 aid of a frontal-toothed ligament. On the back surface of the spinal cord along the posterior median sulcus from the soft membrane to the arachnoid there is a sagittally located septum. In addition to the dentate ligament and posterior septum, in the subarachnoid space there are unstable thin bundles of connective tissue fibers (septa, filaments) connecting the soft and spider webs of the spinal cord.

In the lumbar and sacral parts of the spinal canal, where there is a bundle of roots of the spinal nerves (ponytail, cauda equina), the dentate ligament and the posterior subaerine septum are absent. The fat cell and venous plexuses of the epidural space, the spinal cord, spinal fluid and ligamentous apparatus do not constrain the spinal cord during spine movements. They also protect the spinal cord from tremors and shocks that occur when the body moves.

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