<prompt> True about oligodendrocytes is?Forms Myelin sheathForms blood brain barrierSecretes CSFAll of the above  <response>: ANSWER: A Forms Myelin sheathREF: Grays anatomy 39th ed page 51, Basic histology, Carlos Jose, 11thedition, Chapter 9. Nerve Tissue the Nervous SystemThe myelin sheath is produced by oligodendrocytes in the central nervous system and by Schwann cells in the peripheral nervous systemOligodendrocytes myelinate CNS axons and are most commonly seen as intrafascicular cells in myelinated tracts.Oligodendrocytes may enclose up to 50 axons in separate myelin sheaths: the largest calibre axons are usually ensheathed on a 1:1 basis. 