The central canal, or canalis centralis, is a tubular structure that runs through the spinal cord and extends into the medulla oblongata. Errors in embryonic development can result in neural tube defects; one example is anencephaly. In addition, tumors can form from the ependyma of the central canal.
What is the central canal?
The central canal (canalis centralis) is an anatomical structure that is part of the spinal cord and extends into the medulla oblongata. There, the central canal is clearly visible as a protruding tube. It belongs to the internal cerebrospinal fluid space, to which the cerebral ventricles also belong. The central canal is located in the gray matter of the spinal cord. It owes its name to its grayish coloration, which distinguishes the gray matter from the white matter. The latter contains mainly isolated nerve fibers, whereas the gray matter consists mainly of nerve cell bodies. These tissue designations apply to both the spinal cord and the brain. Together, these two anatomical structures form the central nervous system; in this context, the medulla oblongata, which contains the uppermost part of the central canal, belongs to the brain and represents the transition from the spinal cord to the brain stem.
Anatomy and structure
The interior of the central canal is filled with a fluid known as cerebrospinal fluid. The substance is also found in the inner and outer cerebrospinal fluid spaces of the brain and is composed primarily of water. Cells and proteins are few and far between in CSF. Proteins found in CSF include albumin (human albumin) and beta-trace protein. Most of the cells in CSF are white blood cells or leukocytes, which are part of the human immune system and are also found in the blood. Glial cells are responsible for the production of cerebrospinal fluid, and these cells form tangles to form the choroid plexus. At the head, there is a connection between the central canal and the cerebral ventricles, which are part of the internal cerebrospinal fluid spaces. In some individuals, the central canal merges into the ventriculus terminalis at the lower end, but this thickening of the canal has no functional significance and usually regresses during embryonic development. The ventriculus terminalis represents merely an evolutionary remnant (rudiment).
Function and Tasks
A single-layered layer of ependyma, composed of glial cells, extends over the walls of the central canal inside. Biology counts them as a subtype of neuroglial cells. On the outside of the central canal is the substantia gelatinosa centralis, which contains numerous glial cells. On the outside of their membrane, ependymal cells bear two functionally significant structures: the microvilli and the kinocilia. The microvilli are protrusions from the cell and reach a length of 1-4 µm and a width of 0.08 µm on average. They serve to increase the surface area of the ependymal cells. The kinocilia are also protrusions from the cell, but they are somewhat larger and can reach 10 µm in length and 0.25 µm in width. With the help of the kinocilia, the glial cells can move the cerebrospinal fluid and thus actively contribute to its transport. Glycoproteins, which are important for the function of long-term memory, are also found in the ependyma. The central canal arises from the hollow interior (lumen) of the neural tube, which forms during embryonic development of a human within the first four weeks. Subsequently, the two openings of the neural tube close at the upper and lower ends, and disruptions can lead to the development of neural tube defects.
Diseases
Neural tube defects are pathologic conditions that form during embryonic development when the neural tube does not close properly. A severe form of neural tube defect is anencephaly; even in infants born alive, survival is usually only a few hours, even if intensive medical care is provided. The reason for this is the missing parts of the brain that do not develop in anencephaly. Anencephaly is therefore an indication for termination of pregnancy, but the mother of the child may also choose to carry the child to term. Often, psychological care for the mother is useful in order to emotionally process the trial.Physically, anencephaly of the unborn child usually poses no danger to the pregnant woman. In addition, tumors known as ependymomas can develop from the ependyma. The neoplasms result from uncontrolled cell growth in the tissue layer and often appear as elongated structures resembling the shape of a pencil. The ependymoma is surrounded by a capsule. The treatment options available depend on the individual case; in principle, surgical procedures and radiation therapy are the main options for combating the tumor. Inflammation of the ependyma is also possible. Such ependymitis may occur as a result of an infectious disease; possible causes include syphilis, a sexually transmitted disease with possible neurological disorders, and toxoplasmosis. The latter is an infectious disease resulting from parasitic infestation with Toxoplasma gondii. The disease mainly affects cats, but can also be transmitted from them to humans. In a healthy person, the majority of affected individuals do not manifest any visible or noticeable symptoms. However, particularly if immunodeficiency is present at the same time, other inflammations may occur, for example, in the meninges or lungs.
