Which structure contributes to the blood-brain barrier via the glial limiting membrane?

Which structure contributes to the blood-brain barrier via the glial limiting membrane?

• A. Astrocytic end-feet form the glial limiting membrane.
• B. Ependymal cells lining ventricles.
• C. Pia mater.
• D. Choroid plexus.

Answer: (A)

The blood-brain barrier is strengthened not only by tight junctions between endothelial cells but also by a glial layer called the glial limiting membrane, formed by astrocyte end-feet that envelop brain capillaries. These end-feet wrap around the vessels and, through signaling to the endothelial cells, help maintain and regulate the barrier’s selective permeability. Among the options, the astrocytic end-feet are the ones that form this glial limiting membrane. Ependymal cells line the ventricles and are not part of the glial limiting membrane, the pia mater is a meningeal layer, and the choroid plexus epithelium forms the blood-CSF barrier but is distinct from the glial limiting membrane.

The blood-brain barrier is strengthened not only by tight junctions between endothelial cells but also by a glial layer called the glial limiting membrane, formed by astrocyte end-feet that envelop brain capillaries. These end-feet wrap around the vessels and, through signaling to the endothelial cells, help maintain and regulate the barrier’s selective permeability. Among the options, the astrocytic end-feet are the ones that form this glial limiting membrane. Ependymal cells line the ventricles and are not part of the glial limiting membrane, the pia mater is a meningeal layer, and the choroid plexus epithelium forms the blood-CSF barrier but is distinct from the glial limiting membrane.