NEUROGLIA – 1
The neuroglia consists of a large population of neuroglial cells or simply glial cells. They are non-neural cells that perform important functions in the the support, protection, nutrition, trophism of the central nervous system.
Neuroglial cells do not own the properties of neurons: they do not transmit nerve impulses along their processes.
They exist in the central nervous system. Equivalent cells that some authors include as neuroglial cells and others consider in a separate category exist in the peripheral nervous system.
This and the next pages will deal with the neuroglial cell types of the central nervous system:
Astrocytes, cells with many cytoplasmic processes support and help the nourishment of neurons and enfold blood vessels providing part of the blood-brain barrier that regulates the traffic of substances that may enter the brain tissue.
There are two types of astrocytes, the protoplasmic and the fibrous astrocytes.
The protoplasmic astrocytes reside mainly in the gray matter of the central nervous system. Fibrous astrocytes, found mainly in the white matter, have less and longer processes.
Oligodendrocytes are found in the gray matter of the central nervous system and in a greater amount in its white matter where more neuronal processes are present.
The microglia is formed by the microglial cells. They have phagocytic properties and participate in the immunological protection of the nervous tissue.
It is not easy to recognize and differentiate the diverse neuroglial cells in regular paraffin sections stained with routine stains. For this reason many procedures have been developed in the past to demonstrate these cells using metal impregnation techniques, based on the precipitation of metal atoms on them. It is not easy to control the results of metal impregnation techniques and sometimes a larger amount of metal atoms precipitates over the cells. Also, they not allow the observation of details of the nucleus and cytoplasm.
Nowadays, immunocytochemical methods are intensively used to recognize the various neuroglial cells in sections.