Astrocytes are the most abundant cells in the brain, accounting for approximately 50% of all cells. They are star-shaped glial cells that play important roles in many brain functions, including supporting neuronal function, regulating synaptic transmission, and forming the blood-brain barrier. Astrocytes are also involved in neuroinflammation and neurogenesis.
Astrocytes were first described in 1869 by Rudolf Virchow, who observed them under a microscope as small, round cell bodies with numerous processes (or “arms”) extending from them. The name astrocyte comes from the Greek word for “star” (astron), because of their star-like shape. There are three main types of astrocytes: protoplasmic, fibrous, and gemistocytic. Protoplasmic astrocytes are the most common type and are found mainly in the grey matter of the brain. Fibrous astrocytes are located mainly in white matter regions such as the corpus callosum and cerebellum. Gemistocytic astrocytes are less common and tend to be larger than other types of astrocyte; they are found mainly in areas of high activity such as the hippocampus