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
Jean Riolan the Younger through the blood vessels to the body's extremities and returned to the heart only two or three times a day. He also postulated that blood often ebbed and flowed in the veins and that it was taken in as nourishment by different parts of the body. Riolan also did not believe that the heart propelled the blood, instead he proposed that the blood kept the heart in motion, analogous to a stream moving the wheel of a water mill. Riolan had other disagreements with Harvey, such as the role of the liver as a blood-manufacturing organ. Riolan was an opponent