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
Anterior spinal veins the intramedullary and extramedullary systems which are sets of highly reliable veins. This is because they are vastly redundant in what they do and so only fail under exceedingly unfavorable conditions. Their dependability can be compromised, however, by the bridge that connects them. This fragile link across the dura mater of the spine is known as the radiculomedullary veins. Although these veins connect the trustworthy intramedullary and extramedullary veins, they have no support network to protect them and are seen in much fewer numbers by comparison. This may lead to complications such as thrombosis. For example patients that have spinal