Which statement best describes the blood-CSF barrier and the role of ventricular lining cells in CNS homeostasis?

Which statement best describes the blood-CSF barrier and the role of ventricular lining cells in CNS homeostasis?

• A. Ependymal cells line the ventricles and regulate CSF turnover.
• B. The barrier is formed by the blood-brain barrier endothelial tight junctions.
• C. Astrocyte endfeet form the barrier at the ventricles.
• D. The barrier is formed by choroid plexus epithelium; ependymal cells line ventricles and regulate CSF composition.

Answer: (D)

The main idea is that the barrier between blood and CSF is created by the choroid plexus epithelium, which forms tight junctions between its cells. This blood-CSF barrier controls what passes from the blood into CSF and helps set the composition of CSF, which is essential for CNS homeostasis. The ventricles themselves are lined by ependymal cells; these cells line the ventricular surface and help move CSF (via cilia) and fine-tune its composition, but they do not form the primary barrier between blood and CSF. Astrocyte endfeet contribute to the blood-brain barrier at brain capillaries, not to the CSF barrier at the ventricles. So the best description is that the barrier is formed by the choroid plexus epithelium, while ventricular lining cells (ependymal cells) line the ventricles and regulate CSF composition.

The main idea is that the barrier between blood and CSF is created by the choroid plexus epithelium, which forms tight junctions between its cells. This blood-CSF barrier controls what passes from the blood into CSF and helps set the composition of CSF, which is essential for CNS homeostasis. The ventricles themselves are lined by ependymal cells; these cells line the ventricular surface and help move CSF (via cilia) and fine-tune its composition, but they do not form the primary barrier between blood and CSF. Astrocyte endfeet contribute to the blood-brain barrier at brain capillaries, not to the CSF barrier at the ventricles. So the best description is that the barrier is formed by the choroid plexus epithelium, while ventricular lining cells (ependymal cells) line the ventricles and regulate CSF composition.