part of central nervous system portion of tissue neuropil glial sheath fly_anatomy.ontology VFB:FBbt_00007117 FBbt:00007117 Glial layer that largely surrounds a region of synaptic neuropil in the central nervous system (Younossi-Hartenstein et al., 2003). It is mainly formed by synaptic neuropil ensheathing glia, but these cells also frequently branch into neuropil domains and the layer also contains nuclei of reticular glia (Kremer et al., 2017). glial boundary glial septum