Which glial component supports the blood-brain barrier by contacting CNS capillaries?

Which glial component supports the blood-brain barrier by contacting CNS capillaries?

• A. Microglia
• B. Oligodendrocytes
• C. Ependymal cells
• D. Astrocyte endfeet

Answer: (D)

Astrocyte endfeet are specialized processes of astrocytes that wrap around CNS capillaries, forming a key part of the glial-vascular unit that supports the blood-brain barrier. They help maintain the barrier by signaling to endothelial cells to preserve tight junction integrity and by regulating water and ion balance through channels like aquaporin-4. This direct contact and regulatory role with the capillaries is what makes the endfeet essential for the BBB. Other glial types have different jobs: microglia are immune cells surveying the brain, oligodendrocytes myelinate axons, and ependymal cells line the ventricles and assist cerebrospinal fluid movement.

Astrocyte endfeet are specialized processes of astrocytes that wrap around CNS capillaries, forming a key part of the glial-vascular unit that supports the blood-brain barrier. They help maintain the barrier by signaling to endothelial cells to preserve tight junction integrity and by regulating water and ion balance through channels like aquaporin-4. This direct contact and regulatory role with the capillaries is what makes the endfeet essential for the BBB. Other glial types have different jobs: microglia are immune cells surveying the brain, oligodendrocytes myelinate axons, and ependymal cells line the ventricles and assist cerebrospinal fluid movement.