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
Vorticose veins vortex veins drain into the superior orbital veins and thence to the cavernous sinus. Some vortex veins drain into the inferior orbital vein which drains into the pterygoid plexus. There is usually collateral circulation between the superior and inferior orbital veins. Vorticose veins The vorticose veins, referred to clinically as the vortex veins, drain the ocular choroid. The number of vortex veins is known to vary from 4 to 8 with about 65% of the normal population having 4 or 5. In most cases, there is at least one vortex vein in each quadrant. Typically, the entrances to the vortex