The spinal canal is referred to as the vertebral canal. The spinal cord and the cauda equina run through it.
What is spinal canal?
The vertebral canal (canalis vertebralis) is a canal formed by superimposed vertebral holes in the spine. Its course extends from the first cervical vertebra through the cervical spine (C-spine), thoracic spine (thoracic spine), and lumbar spine (lumbar spine) to the sacrum. The spinal cord and the cauda equina pass through the vertebral canal. The spinal canal is also known as the spinal cord canal or spinal canal. Injuries to the spinal canal can have serious consequences. Thus, in the worst case, paraplegia is imminent.
Anatomy and structure
The spinal canal begins at the foramen occipitale magnum (large hole). From there, it runs through the cervical spine, thoracic spine, and lumbar spine toward the sacrum (Os sacrum). On the ventral side, the vertebral bodies (corpora vertebrae) as well as the intervertebral discs delimit the spinal canal. On the side and back, this is the case through the vertebral arches (arcus vertebrae). In the space between two neighboring vertebrae, there is an intervertebral foramen on both sides, which serves as an opening for the paired spiral nerves. The vertebral canal is equipped with two robust elongated ligaments. They are named ligamentum flavum and ligamentum longitudinale posterius (posterior longitudinal ligament). While the ligamentun longitudinale posterius is located at the front of the spinal canal, the ligamentum flavum is located at its rear. The spinal cord, which is located within the spinal canal, is surrounded by the spinal meninges, which are special layers of tissue. The outermost layer is the periosteum, which is fused with the vertebrae. It is also called the stratum periostale or outer leaf. Under the outer leaf lies the stratum meningeale (outer spinal cord skin of the dura mater spinalis). It includes the so-called spider web skin (arachnoid spinalis). This is followed by the pia mater spinalis (soft spinal cord skin). In the spinal canal, there are also several clefts between the spinal meninges. These include the epidural space (spatium epidurale), which is located between the periosteum and the stratum meningeale. The epidural venous plexus and fatty tissue are located there. Another cleft space is the subdural space (spatium subdurale), which is located between the arachnoid spinalis and the dura mater spinalis. The last cleft space is the subarachnoid space (spatium subarachnoidale) between pia mater spinalis and arachnoid spinalis. This space contains cerebrospinal fluid (CSF). In the area of the spinal canal, there are also the blood vessels that serve to supply the spinal cord. The spinal cord branches (rami spinales) of the arteriae lumbales, the arteria vertrebralis and the arteriae intercostales posteriores participate in this. A dense vascular network is formed epidurally by the veins. This includes the vertrebral internal ventral plexus, which is located on the anterior side. This area of the spinal canal is considered particularly vulnerable to injury when surgery is performed near it.
Function and Tasks
The spinal canal houses the spinal cord, which together with the brain forms the central nervous system. The spinal cord is important for communication between the brain and the internal organs, skin and muscles. At its most extensive, the spinal cord reaches about the width of a finger. In adult humans, the spinal cord finds its end at the first lumbar vertebra. Before birth, however, it extends toward the sacrum. In babies, it extends to the lower lumbar vertebrae because the growth of the spine proceeds more rapidly than the development of the spinal cord. This phenomenon allows the spiral nerves exiting the spinal canal to travel a longer passage in the lower section of the spinal canal before leaving it. From the end of the spinal cord at the 1st lumbar vertebra, there are then only the spiral nerves in the spinal canal, from which the so-called horse tail (cauda equina) is formed.
Diseases
The spinal canal can be affected by injury or disease. One of the most common impairments is spinal stenosis, in which there is a narrowing of the spinal canal. Elderly people are particularly affected.While the lumbar and cervical spine suffer most frequently from spinal stenosis, the thoracic spine is rarely affected. Causes of spinal stenosis include natural aging processes, lack of exercise, bone loss (osteoporosis) or predisposition. Sometimes several factors apply at the same time. In most cases, wear and tear of the spine is responsible for spinal stenosis. The intervertebral discs, which are located between the vertebral bodies, increasingly lose fluid and height over the years. The space between the vertebrae decreases and the lack of cushioning results in their greater stress. The loss of height causes the ligaments to lose extensibility. In some cases, the narrowing is already congenital. Spinal stenosis does not always cause symptoms. Usually, the symptoms develop over time. Those affected usually suffer from muscle tension in the lower back, back pain that radiates into the leg, and restricted mobility in the lumbar spine. If the spinal stenosis progresses further, there is a risk of sensory disturbances such as cold, tingling, burning and numbness in the legs, problems with urination or defecation, incontinence and sexual dysfunction. The most serious injuries to the spinal canal include herniated discs and vertebral fractures. If the spinal cord is injured in the process, there is a risk of paraplegia. If the blood vessels tear, hemorrhage between the meninges is possible, causing pressure on the spinal cord.
