Protoplasmic astrocytes
|
Uniformly distributed within the grey matter [3] |
Bushy appearance, with numerous short, branched, thick processes [50]. The cell body is ovoid or fusiform (see Figure 5) |
• Form the blood–brain barrier |
Their processes exhibit endfeet enveloping the synapses and the blood vessels [51]. The processes express |
• Regulate the blood flow |
• Neuronal metabolism |
• Receptors for neurotransmitters, cytokines, growth factors |
• Implicated in the synapse function |
• Transporters |
• Fluid, ion, pH and transmitter homeostasis [45] |
• Ion channels [7]. In rodents, there is minimal overlapping between the processes of the neighbouring astrocytes [43, 44, 52–54]. In humans, the superposition of the domains occupied by the astrocytes processes is augmented [3] |
Fibrous astrocytes
|
Within the white matter, oriented longitudinally, along the nervous fibers bundles [1] |
Star-shaped cells. Posses long, thin and straight processes [45] (see Figure 6) |
|
Their endfeet processes envelop the nodes of Ranvier and the blood vessels [45] |
Interlaminar astrocytes
|
In the molecular 1st layer of the cerebral cortex, next to the pial surface |
Spherical cell bodies and processes |
Unknown Support the calcium wave propagation in humans [3] |
Are found only in humans and primates. Their processes are included in the pial glial membrane, creating a thick network of GFAP fibers [46–49] |
Varicose projection astrocytes
|
In the 5th and the 6th layers of the cerebral cortex |
Exhibit 1 to 5 long processes (up to 1 mm in length), characterized by evenly (10 μm) spaced varicosities [3, 46] |
Unknown |
Were identified only in humans and chimpanzees. They are GFAP+ cells [3, 46] |
Bergmann glia (epithelial glial cells)
|
In the Purkinje-cell and the granular layers of the cerebellar cortex |
Posses long processes extending towards the molecular layer of the cerebellar cortex, in a fan-like arrangement, exhibiting pial vascular endfeet [23] |
Implicated in synapse function: capable to interfere with synaptic transmission by communicating with neurons via the extracellular space, by modulating ion concentrations or transmitter levels in the synaptic cleft [23] |
Display receptors with distinct biophysical and pharmacological features allowing them to sense the activity of synapses [23] |
Fananas cells
|
In the molecular layer of the cerebellar cortex |
Posses several short side processes with a characteristic feather-like arrangement [23] |
|
|
Müller cells
|
In the 6th layer of the visual retina |
|
Supportive cells: they form the inner and the outer limiting membranes |
The limiting membranes consist of junctional complexes between the cellular processes of the Müller cells |
The outer membrane separates the external segment of the photoreceptor cells from the cell bodies and the outer membrane separates the retina from the vitrous body [23] |
They have an intense metabolic activity and contain microfilaments and glycogen within their cytoplasm [23] |
Pituicytes
|
In the neurohypophysis |
Irregular in shape with many cytoplasmic processes extending in the proximity of the capillaries and surrounding the Herring bodies [24] |
|
Their cytoplasm contains lipid droplets and pigment granules. |
They are immunoreactive for GFAP, vimentin and S100 protein [24] |
Inerstitial epiphysial cells
|
In the epiphysis |
Exhibit cytoplasmic processes |
|
Contain numerous filaments within their processes [23] |