Which structure forms the blood-CSF barrier and provides signaling molecules during CNS development?

Which structure forms the blood-CSF barrier and provides signaling molecules during CNS development?

• A. Cerebral cortex
• B. Choroid plexus
• C. Cortex-specific glia
• D. Meninges

Answer: (B)

The choroid plexus does this. It lines the brain’s ventricles with a specialized epithelium that forms tight junctions between cells, creating the barrier between blood and cerebrospinal fluid and regulating what substances reach the CSF. Beyond forming the barrier, the choroid plexus actively secretes CSF and releases signaling molecules and growth factors into the CSF, providing essential cues for neural progenitor proliferation, differentiation, and neuronal migration during CNS development. The other options don’t fit this role: the cerebral cortex is the tissue where neurons reside, not the barrier-forming structure; the meninges are protective coverings rather than the source of the blood-CSF barrier; cortex-specific glia aren’t the structure responsible for establishing this barrier or delivering developmental signals in this context.

The choroid plexus does this. It lines the brain’s ventricles with a specialized epithelium that forms tight junctions between cells, creating the barrier between blood and cerebrospinal fluid and regulating what substances reach the CSF. Beyond forming the barrier, the choroid plexus actively secretes CSF and releases signaling molecules and growth factors into the CSF, providing essential cues for neural progenitor proliferation, differentiation, and neuronal migration during CNS development.

The other options don’t fit this role: the cerebral cortex is the tissue where neurons reside, not the barrier-forming structure; the meninges are protective coverings rather than the source of the blood-CSF barrier; cortex-specific glia aren’t the structure responsible for establishing this barrier or delivering developmental signals in this context.