Microglia: the dormant phagocytes of the CNS.
Microglia exist in several forms: they are normally present in an inactive form, but can be stimulated or primed to become active.
Active microglia are phagocytic and remove cell debris such as dead or damaged, degenerating neurones, bacteria and viruses.
The factors that trigger activation of Microglia include:
Ependymal cells line the cavities of the CNS and make up the walls of the ventricles.
Ependymal cells have cilia that beat and help circulate the CSF and make up the Blood-CSF barrier.
Tanycytes are specialised ependymal cells found in the floor of the third ventricle; these cells have processes that extend deep into the hypothalamus and it is thought that they may convey signals from the CSF to the nuclei of the rostral ventral hypothalamus.
Tanycytes possibly have a role in the release of gonadotrophic hormone releasing hormone.