FB2026_03 , released September 17, 2026
CV Term Report
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General Information
Term perineurium ID (Ontology) FBbt:00007090 (Fly Anatomy)
Definition The outer two layers of glial cells that cover the central nervous system and the nerves. The outer layer is the perineurial glial sheath (sometimes referred to as the perineurial sheath outer layer); the inner layer is the subperineurial glial sheath (sometimes referred to as the perineurial sheath inner layer).[ FlyBase:FBrf0057603 FlyBase:FBrf0191040 FlyBase:FBrf0226917 FlyBase:FBrf0239343 ]
CommentSome authors use this term only to refer to the double layer of cells covering the CNS (e.g. Hartenstein and Jan, 1992), while other authors use it more broadly to include the covering of nerves (e.g. Banerjee et al., 2006). This ontology uses the term in its broad sense. 'Blood-brain barrier' may refer to this (e.g. Limmer et al., 2014) or the subperineurial glial sheath alone (e.g. Morante et al., 2013).
Links to External Ontologies
VFB:FBbt_00007090
Annotations
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Direct annotations: records annotated with this exact term (child terms are NOT included)
Data ClassFieldDirect annotations
Alleles (FBal)PHENOTYPE_MANIFEST_IN
Insertions (FBti)PHENOTYPE_MANIFEST_IN
Constructs (FBtp)PHENOTYPE_MANIFEST_IN
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 Full annotation statements 
Relevant FlyBase reports
 Alleles Genes Insertions Constructs
 perineurium (all annotations which use CV term, excluding "NOT" statements)
     perineurium | adult stage
      --
     perineurium | embryonic stage
      --
     perineurium | larval stage
      --
     perineurium | P-stage
      --       --
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organ system
 |__nervous system__________
multicellular structure     |
 |__multi-tissue structure__|
                            perineurium  839 rec.
                             |__perineurial glial sheath 143 rec.
                             |   |__perineurial glial cell(+) 142 rec.
                             |__subperineurial glial sheath 247 rec.
                             |   |__subperineurial glial cell(+) 241 rec.
                             |__surface glial cell 806 rec.
                                 |__adult surface glial cell(+) 164 rec.
                                 |__CNS surface glial cell(+) 597 rec.
                                 |__larval lateral VNC surface glial cell 50 rec.
                                 |__larval surface glial cell(+) 239 rec.
                                 |__perineurial glial cell(+) 142 rec.
                                 |__subperineurial glial cell(+) 241 rec.
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Is a multi-tissue structure
Part of nervous system
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VFB:FBbt_00007090