A) Where does the blood brain barrier (BBB) exist? (state whereit anatomically is) B) How are the capillaries at the BBB differentfrom capillaries at the blood-CSF barrier, include where thisblood-CSF barrier exists)Â Â C) Why do they have thisdifference? D) Where does CSF flow as it circulates and what is itsfunction? What anatomy is involved with the return of CSF toblood?