Head and neck anatomy may be important in the development of the BBB. Astrocytes may also be responsible for transporting ions (electrolytes) from the brain to the blood. Blood from the brain and neck flows from: (1) within the cranium via the internal jugular veins, a continuation of the sigmoid sinuses. The right and left external jugular veins drain from the parotid glands, facial muscles, scalp into the subclavian veins. The right and left vertebral veins drain the vertebrae and muscles into the right subclavian vein and into the superior vena cava, into the right atrium of the heart. The lymphatic system drains the
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,