Microglia act as the immune cells of the Central nervous system. Microglia are close cousins of other phagocytic cells including macrophage and dendritic cells. Microglia are derived from myeloid progenitor cells (the same as macrophages and dendritic cells) which come from the bone marrow. During embryonic development however, they migrate to the CNS to differentiate into microglia. Microglia are thought to be highly mobile cells that play numerous important roles in protecting the nervous system. They are also thought to play a role in neurodegenerative disorders such as Alzheimers disease, dementia, and multiple schlerosis.