Human brain in the midline on top of the brain. Blood from here joins with blood from the straight sinus at the confluence of sinuses. Blood from here drains into the left and right transverse sinuses. These then drain into the sigmoid sinuses, which receive blood from the cavernous sinus and superior and inferior petrosal sinuses. The sigmoid drains into the large internal jugular veins. The larger arteries throughout the brain supply blood to smaller capillaries. These smallest of blood vessels in the brain, are lined with cells joined by tight junctions and so fluids do not seep in or leak out
Drug delivery to the brain that they must pass through the cell membranes of the endothelial cells. Because of this, the only molecules that are easily able to transverse the blood–brain barrier are ones that are very lipid-soluble. These are not the only molecules that can transverse the blood–brain barrier; glucose, oxygen and carbon dioxide are not lipid-soluble but are actively transported across the barrier, to support normal cellular function of the brain. The fact that molecules have to fully transverse the endothelial cells makes them a perfect barricade to unspecified particles from entering the brain, working to protect the brain at all costs. Also,