Anatomy
The spine of most people is composed of 24 freely moving vertebrae, which in turn are flexibly connected to each other by a total of 23 intervertebral discs. The deeper lying vertebrae of the coccyx and sacrum have grown together as bones. From person to person, however, deviations can occur.
Although the vertebrae of the different spinal column sections differ in their external shape and size, the general structure of a vertebra remains similar. Thus, each vertebra is composed of a round vertebral body and a vertebral arch attached to the back. All vertebral arches taken together form the spinal canal, in which the spinal cord runs.
The cerebrospinal fluid, the cerebrospinal fluid, flows around this channel. In addition, it is surrounded by the connective tissue of the spinal cord, which merges into the meninges and is also called meninges. Viewed from the side, there is always a small, round space between two adjacent vertebral arches, the intervertebral foramen (foramen inervertebrale).
The spinal nerves that originated from the spinal cord on the respective level emerge through this hole. These holes exist not only between the freely moving vertebrae, but also in the lower rigid sections of the spinal column. In total, there are usually 31 of these intervertebral holes and thus also 31 spinal nerves.
Here, too, there can be variations from person to person. The points from which the spinal nerves originate are called nerve roots. In each segment of the spinal column, there are two of these on both the right and left side of the spinal cord.
After a short period of time, these merge to form one spinal nerve on each side, which soon emerges through the intervertebral hole. Interestingly, however, the adult spine is longer than the spinal cord. In adults, the spinal cord only extends to about the second lumbar vertebra.
The reason for this is that the spinal column grows more strongly than the spinal cord, which still fills the entire spinal canal until the 3rd embryonic month. As a result, the spinal nerves have to travel an increasingly longer distance downwards until they can exit through the intervertebral hole. In their entirety, these spinal nerves, which run freely through the spinal canal, form the so-called ponytail (cauda equina).
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