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Satellite glial cell
Satellite glial cells are glial cells that cover the surface of nerve cell bodies in sensory, sympathetic and parasympathetic ganglia. Both satellite glial cells (SGCs) and Schwann cells – the cells that ensheathe some nerve fibers – are derived from the neural crest of the embryo during development. SGCs have been found to play a variety of roles, including control over the microenvironment of sympathetic ganglia.〔 They are thought to have a similar role to astrocytes in the central nervous system (CNS).〔 They supply nutrients to the surrounding neurons and also have some structural function. Satellite cells also act as protective, cushioning cells. Additionally, they express a variety of receptors that allow for a range of interactions with neuroactive chemicals. Many of these receptors and other ion channels have recently been implicated in health issues including chronic pain and herpes simplex. There is much more to be learned about these cells, and research surrounding additional properties and roles of the SGCs is ongoing.
==Anatomy==
Satellite glial cells are the principal glial cells found in the peripheral nervous system, specifically in sensory,〔 sympathetic, and parasympathetic ganglia.〔 They compose the thin cellular sheaths that surround the individual neurons in these ganglia.
In an SGC, the cell body is denoted by the region containing the single, relatively large nucleus. Each side of the cell body extends outward, forming perineuronal processes. The region containing the nucleus has the largest volume of cytoplasm, making this region of the SGC sheath thicker.〔 The sheath can be even thicker if multiple SGCs are layered on top of one another, each measuring .
Despite their flattened shape, satellite glial cells contain all common organelles necessary to make cellular products and to maintain the homeostatic environment of the cell. The plasma membrane of SGCs is thin and not very dense, and it is associated with adhesion molecules, receptors for neurotransmitters and other molecules,〔 and ion channels, specifically potassium ion channels. Within individual SGCs, there is both rough endoplasmic reticulum and smooth endoplasmic reticulum, but the latter is much less abundant.〔 Most often the Golgi apparatus and the centrioles in an SGC are found in a region very close to the cell’s nucleus. On the other hand, mitochondria are found throughout the cytoplasm〔 along with the organelles involved in autophagy and other forms of catabolic degradation, such as lysosomes, lipofuscin granules, and peroxisomes. Both microtubules and intermediate filaments can be seen throughout the cytoplasm, and most often they lie parallel to the SGC sheath. These filaments are found in greater concentrations at the axon hillock and at the beginning portion of an axon in an SGC of the sympathetic ganglia.〔 In some SGCs of the sensory ganglia researchers have seen a single cilium that extends outward from the cell surface near the nucleus and into the extracellular space of a deep indentation in the plasma membrane. The cilium, however, only has the nine pairs of peripheral microtubules while it lacks the axial pair of microtubules, making its structure very similar to the cilia of neurons, Schwann cells, and astrocytes of the CNS.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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