Answer:
A. form myelin in CNS - oligodendrocytes
B. separate CNS fluid compartments - ependymal cells
C. help form the blood-brain barrier - astrocytes
D. modified immune cells - microglia
E. form myelin in PNS - Schwann cells
Explanation:
All of these cells form the glia in the nervous system.
Oligodendrocytes are located in the Central Nervous System and have the function to create the myelin sheath, important for the transmission of the nervous impulse through the axon. One oligodendrocyte can create the myelin sheath of 50 axons at a time.
Ependymal cells are the ones that form the inner lining of the ventricular system. These neuroepithelial cells are involved in the production of cerebrospinal fluid (CSF), a liquid important for the protection and homeostasis of the CNS.
Astrocytes are cells shaped like stars that are located in the CNS with the function to give support to the endothelial cells that form the blood-brain barrier, which separates the blood from the nervous system. Astrocytes have other important functions like metabolic support, glucose sensing, regulation of ion concentration in the extracellular space, and modulation of the synaptic transmission, among others.
Microglia are the resident macrophages of the brain and spinal cord, thus becoming the main form of immune defense in the CNS. As other macrophages, they are capable of phagocytosis (eating pathogens and apoptotic cells) and antigen presentation, important for cellular-mediated immunity.
Schwann cells are analog to the oligodendrocytes: their function is to create myelin sheath, only they do it in the Peripheral Nervous System. Unlike oligodendrocytes, Schwann cells can only create the myelin sheath of an axon at a time.
