Ependymal cells are neuroglial cells found within the central nervous system. They function as a specialized lining, contributing to the internal environment of the brain and spinal cord. They help maintain stable conditions for neurological function. These cells originate from neuroepithelial cells during early development.
Primary Locations in the Central Nervous System
Ependymal cells line the fluid-filled ventricles of the brain and the central canal of the spinal cord. This continuous lining forms a specialized epithelial layer called the ependyma. This ependymal lining separates neural tissue from the cerebrospinal fluid (CSF).
In these regions, ependymal cells exhibit a cuboidal or columnar morphology. They are often ciliated, with hair-like projections that help circulate cerebrospinal fluid. Their placement allows direct interaction with the CSF, which bathes the brain and spinal cord, providing nutrients and removing waste. This creates a regulated interface between nervous tissue and the circulating fluid.
Specialized Ependymal Cell Types and Their Distinct Locations
Beyond the general ventricular lining, some ependymal cells have specialized forms and functions. Tanycytes are a distinct type, primarily located in the floor of the third ventricle near the median eminence. These cells are characterized by elongated processes that extend deep into the brain parenchyma, connecting with blood capillaries and neurons.
Another specialized group is found within the choroid plexus, a capillary network in each brain ventricle. The ependymal cells in the choroid plexus are highly modified, forming a tight barrier that regulates the passage of substances from the blood into the cerebrospinal fluid. Their structure here relates to their role in fluid dynamics.
How Location Dictates Function
The location of ependymal cells, lining the ventricles and central canal, is key to their diverse functions. Their position allows them to form the blood-cerebrospinal fluid (CSF) barrier, regulating the exchange of substances between the blood and the CSF. This barrier protects the brain from harmful substances while allowing necessary nutrients to pass through.
Their placement is linked to cerebrospinal fluid production. Ependymal cells in the choroid plexus, through selective uptake from the blood, are primarily responsible for generating CSF. This fluid cushions the brain and spinal cord, distributes nutrients, and removes metabolic waste products. Ciliary action of many ependymal cells also aids in circulating this fluid throughout the central nervous system.