Microglia are macrophages in the brain. Macrophages are the immune cells in the blood and other parts of the body. Microglia can be activated upon neuronal damages or infections, to destroy foreign stuff or pathogens, as well as necrotic tissues. They can send signals and request help from other parts of the immune system.
Polydendrocytes are the precursor cells in the central nervous system (CNS). They are involved in regeneration upon injuries and damages. They can be changed to astrocytes, oligodendrocytes, and even neurons.
Ependymal cells are the cells around the ventricles, the fluid spaces in the brain. They can cluster with blood vessels to form choroid plexuses that generate cerebrospinal fluid. Ependymal cells can also generate new neurons to replace old dysfunctional neurons.
The embryonic neural tube has three swellings as brain vesicles. These brain vesicles become the forebrain, midbrain, and hindbrain vesicles. A vesicle is around a chamber filled with fluid. The forebrain vesicle becomes a midline part including the diencephalon and hypothalamus. The lateral part becomes the cerebral vesicle that becomes the cerebral cortex and deep cerebral structures. The midbrain vesicle develops into the first part of the brainstem and four swellings. The hindbrain vesicle develops into the last part of the brainstem and the cerebellum.
The brain structures of other animals are similar to those of humans, except the part of the cerebral cortex. For example, the basic structures of the rat brain and the human brain are similar as in the typical mammalian brain. Because of such similarity, animal models including mouse and rat models are often used for studying disorders such as Parkinson’s disease. However, the human brain has a significantly more developed cerebral cortex with characteristics that other animals don’t have.