The Ependymal cells , Also known as ependymocytes, are a type of epithelial cells. They form part of the set of neurogliagular cells of the nervous tissue and cover the cerebral ventricles and the central conduit of the spinal cord.
They are characterized by a cylindrical or cuboid shape and contain in their cytoplasm a large number of mitochondria and intermediate filament beams.
Three major types of ependymal cells have now been described: ependymocytes, tanicites, and choroidal epithelial cells.
As regards their functionality, these types of cells seem to play an especially important role in the generation of cerebrospinal fluid And other substances.
This article reviews the main characteristics of ependymal cells. The different types are explained and the functions performed are discussed.
Characteristics of Ependymal cells
Ependymal cells are a type of cells that are part of the neuroglia of nerve tissue. Thus, they are encompassed within the set of neuroglial cells.
These cells stand out by forming the lining of the ventricles of the Encephalon And the ependymal conduit of the spinal cord . They have a columnar morphology and form a single layer of cubic and cylindrical cells.
Inside they have microvilli and cilia. Such cilia are usually mobile, a fact that contributes to the flow of cerebrospinal fluid. Specifically, the cilia allow the liquid on the surface of the cell to orient towards the ventricle.
The base of the ependymal cells lies on the internal glial limiting membrane. As regards its cytoplasm, this is composed of mitochondria and intermediate filament beams.
Finally, it should be noted that at the level of the cerebral ventricles, the ependymal cells undergo modifications. These changes give rise to the formation of Choroid plexus , Vascular structures of the brain that are responsible for forming the cerebrospinal fluid.
Formation of ependymal cells
Ependymal cells form at the root of the embryonic neruoepithelium of the nervous system Developing.
During the embryonic phase, the extensions arising from the cell body reach the surface of the encephalon. However, in adulthood, such prolongations are characterized by being reduced and presenting only near terminations.
Through their development, the ependymal cells generate, inside, a cytoplasm very rich in mitochondria and intermediate filamentous beams.
Also, in their development process these cells acquire a hairy shape in certain regions. These characteristics facilitate movement of the cerebrospinal fluid .
In brain structures where neural tissue is thin, ependymal cells form an internal limiting membrane that lines the ventricle and an outer limiting membrane just below the piamadre.
Finally, at the level of the cerebral ventricles, this type of cells are characterized by changes and originate the choroid plexus.
Types of ependymal cells
Three major types of ependymal cells have now been described. This classification is done mainly through the encephalic location of each one of them.
In this sense, ependymal cells can be divided into: ependymocytes, tanicites and choroidal epithelial cells.
Ependymocytes
Ependymocytes are the most prevalent type of ependymal cells. The ventricles of the Encephalon And the central canal of the spinal cord.
These types of cells are characterized by being in direct contact with the cerebrospinal fluid. The adjacent surfaces of the ependymocytes have joints.
However, the cerebrospinal fluid communicates completely free with the intercellular spaces of the central nervous system.
Tanicitos
Tanicites are the type of ependymal cells that line the floor of the third ventricle. Specifically, these cells are just above the mean eminence of the Hypothalamus .
They are characterized by having long basal extensions traversing the cells of the middle eminence. Likewise, they place their terminal basal cells just above the blood capillaries.
The role of tanicites is not well documented today, although it has been given an important role in the transport of substances between the third ventricle and the middle hypothalamic eminence.
Choroidal epithelial cells
Finally, choroidal epithelial cells are the ependymal cells that are located in the cerebral ventricles. These cells are characterized by being modified and forming the choroid plexus.
Both its base and its lateral regions form a series of folds. Epithelial cells are characterized by being held together through the close junctions surrounding them on their luminous surface.
The tight junctions between these cells are of vital importance in preventing the leakage of cerebrospinal fluid into the underlying tissues and in limiting the entry of other substances into the cerebrospinal fluid conduit.
Functions
The functions of ependymal cells are mainly based on the formation and distribution of cerebrospinal fluid.
Cerebrospinal fluid (CSF) is a colorless substance that bathes both the brain and spinal cord. Circulates through the subarachnoid space and the cerebral ventricles and is a basic substance to protect the brain .
More specifically, CSF acts as a buffer to protect the central nervous system from trauma, provides nutritional elements to the brain and removes metabolites
As far as ependymal cells are concerned, their main functions are:
- They contain in their interior the CSF that is produced in the choroid plexus, reason why they are a vital cells in guaranteeing the protection of the central nervous system.
- The choroidal epithelial cells are responsible for producing the cerebrospinal fluid directly. This fluid is secreted in the choroid plexus so without the operation of this type of ependymal cells the brain would lack CSF.
- Certain studies postulate that the ependymal cells also perform absorption functions since the free surfaces of the ependymocytes present microvilli.
- The tanicites are responsible for transporting chemicals from the cerebrospinal fluid to the pituitary portal system.
- It is now postulated that ependymal cells could play a role in controlling the hormonal production of the anterior lobe of the hypophysis .
References
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