Neuroglia cells makes up most of the nervous system tissues and they outnumber neurons five to ten times. Neuroglia plays a major role in proper functioning of the nervous system. There are four main types in central nervous system and two main types in the peripheral nervous system. They differ from neurons because they do not produce propagating action potentials.
Neuroglia cells found in central nervous system function as filling in between the neurons and scavenger cells. They also maintain necessary environment for the neurons to act.
What are the types found in Central nervous system?
Astrocytes
They are multipolar cells, meaning that they have several projections coming out from its cell body. They offer structural support to the neurons. Gaps created by the nervous tissue damage are filled by the scar tissues consisting astrocytes.
Astrocyte projections cover blood vessels and form the blood brain barrier. Blood brain barrier prevents harmful chemicals from entering into the brain. Astrocytes are also involved in the phagocytosis of dead tissues and pathogens.
There are two types of astrocytes in the central nervous system. They are fibrous astrocytes and protoplasmic astrocytes. Fibrous astrocytes have long thin projections and they are mainly found in the white matter of the brain. Protoplasmic astrocytes have thick and short projections and are found in the grey matter.
Oligodendrocytes
Compared with the astrocytes, oligodendrocytes have a smaller cell body with fewer cell projections. They form myelin sheaths in the central nervous system. Oligodendrocytes are also involved in phagocytosis.
Microglia
As the name suggests, they are the smallest neuroglia cells. They are commonly found in the grey matter. They have many projections, when inactive. They migrate in to the injured nervous tissues and clean up the dead tissues. So they are called the scavenger cells.
Ependyma cells
They cover the lining of the central nervous system cavities. That is ventricular system of the brain, and the central canal of the spinal cord. Unique feature of these cells are the presence of cilia. They beat rhythmically and allow cerebrospinal fluid to flow. Main types are ependymocytes, tancytes and the choroidal epithelial cells. Ependymocytes line the ventricals and the spinal cord central canal. Tancytes cover the floor of the third ventricle over the hypothalamic median eminence. Choroidal cells cover the choroid plexus which is responsible for the production of cerebrospinal fluid.
What are the types found in peripheral nervous system?
Schwann cells form the myelin sheaths of the peripheral nerve axons. They also involved in the formation of neurilemma.
Satellite cells are flattened cells found in autonomic ganglia. They have a supporting role.
