Microglia are important neuronal cells of the central immune system. As their name suggests, microglia are the smallest type of neuroglia, but they have proved to be the fastest and possibly the most intelligent. Microglia migrate independently around the brain to maintain neural circuits and activity. In this way, the brain is protected from microbes, cleaned of cancerous/defective cells, and maintained in optimal condition.
Microglia are first created from the early mesodermal tissue of the fetus and migrate to the brain where they proliferate. As the brain develops, microglia replenish themselves independently, but the presence of abnormalities causes microglia to make more new cells.
In its resting state, microglia are seen as cells with long branches and tendrils. If they detect microbes or injury to nerves, they transform into an ameboid form, retracting their tendrils and increasing the size of their cell body to be able to engulf microbes and debris. Observation of this process, called “microglial activation,” proves that microglia are certainly the most active cells of the brain.
Microglia are closely related to macrophages, as evidenced by their similar roles in maintenance and protection through gobbling up pathogens and debris.
Normally, microglia are distributed evenly throughout the brain, each with its own “territory” (15-30 µm) to strictly patrol. They are responsible for protection and maintenance of synapses and will move out of their territory in order to cluster around sites of trauma or infection.
Because of their active role in the brain, scientists are studying the functions of microglia- in relation to the abnormalities that occur in neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease.