Which components form the Blood-Brain Barrier?

Which components form the Blood-Brain Barrier?

• A. Tight endothelial junctions and astrocytic end-feet
• B. Tight junctions between neurons
• C. Ependymal cells lining ventricles
• D. Dural folds around brain

Answer: (A)

Capillary tight junctions between brain endothelial cells, together with astrocytic end-feet wrapping around those vessels, establish the Blood-Brain Barrier. The endothelial tight junctions create a seal that restricts paracellular diffusion, while the astrocyte end-feet provide signals that maintain and regulate the barrier’s properties. This combination selectively permits essential nutrients to pass while keeping out most circulating substances. Other structures listed don’t form the BBB: neuronal tight junctions aren’t the barrier at brain vessels, ependymal cells line the ventricles and are more related to CSF dynamics, and dural folds are protective coverings of the brain rather than components of the capillary barrier.

Capillary tight junctions between brain endothelial cells, together with astrocytic end-feet wrapping around those vessels, establish the Blood-Brain Barrier. The endothelial tight junctions create a seal that restricts paracellular diffusion, while the astrocyte end-feet provide signals that maintain and regulate the barrier’s properties. This combination selectively permits essential nutrients to pass while keeping out most circulating substances. Other structures listed don’t form the BBB: neuronal tight junctions aren’t the barrier at brain vessels, ependymal cells line the ventricles and are more related to CSF dynamics, and dural folds are protective coverings of the brain rather than components of the capillary barrier.