Quick Facts
Microglial cells are the small, nonneural, interstitial cells of mesodermal origin that form part of the supporting structure of the central nervous system. They are of various forms and may have slender branched processes. They are migratory and act as phagocytes to waste products of nerve tissue (Dorland, 2011).
Related parts of the anatomy
Structure and/or Key Features
Microglial cells originate from granulocyte (or monocyte) progenitor cells, and so they are members of the mononuclear phagocytic system. Microglia are the smallest cell and the least numerous of neuroglia in the central nervous system.
Microglia have cell processes or projections which have an appearance of a thorny bush. The nuclei of microglia are small, dense, and elongated which distinguishes them from other glial cells which exhibit spherical nuclei. The cytoplasm of microglia appears pale and contains granules, scattered cisternae of endoplasmic reticulum, and Golgi complexes.
Function
Microglia in a healthy brain and spinal cord are inactive and are called resting microglial cells. These resting cells function as surveying microglia. The processes of microglia are fast-moving and rapidly scan their territory with their cell body remaining fixed in position (Standring, 2016).
Microglia become activated, or primed, by traumatic injury and ischemic injury. When the brain or the spinal cord becomes injured, microglia become immune effector cells. They migrate to the site of injury, proliferate, and become antigen presenting cells that present invading organisms to T lymphocytes for elimination from the body (Splittgerber, 2018).
Microglia become phagocytic cells in many diseases and are involved in synaptic stripping, a process by which microglia remove damaged cells and dysfunctional synapses (Mancall and Brock, 2011). When microglia function as phagocytic cells their cytoplasm becomes filled with lipids and cell remnants (Splittgerber, 2018).
Clinical Correlates
When the myelin sheath degenerates in neurodegenerative diseases such as multiple sclerosis, microglia remove the degenerated myelin sheath.
References
Dorland, W. (2011) Dorland's Illustrated Medical Dictionary. 32nd edn. Philadelphia, USA: Elsevier Saunders.
Mancall, E. L. and Brock, D. G. (2011) Gray's Clinical Neuroanatomy: The Anatomic Basis for Clinical Neuroscience. Elsevier Health Sciences.
Splittgerber, R. (2018) Snell's Clinical Neuroanatomy. Wolters Kluwer Health.
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41 edn.: Elsevier Limited.
