Final answer:
After circulation through the brain, blood is collected in the venous sinuses like the superior sagittal sinus and ultimately the jugular veins, from where it is directed back to the heart.
Step-by-step explanation:
After blood circulates through the brain, it collects in the venous sinuses before returning to the heart. The network of venous drainage includes the superior sagittal sinus, straight sinus, transverse sinuses, sigmoid sinuses, and ultimately the jugular veins.
As blood circulates through the brain, it carries oxygen and nutrients to its tissues and collects metabolic wastes. These are then deposited into the cerebrospinal fluid (CSF), which is filtered through the choroid plexuses located in the ventricles of the brain. The CSF circulates, collects waste, and then the waste-laden fluid is reabsorbed into the venous system through the arachnoid granulations. This venous blood drains from the dural sinuses into the jugular veins and travels back toward the heart, where it will be reoxygenated.
The blood that nourishes the brain and spinal cord is behind the glial-cell-enforced blood-brain barrier, which limits the exchange of material from blood vessels with the interstitial fluid of the nervous tissue. Thus, metabolic wastes are collected in cerebrospinal fluid (CSF) that circulates through the CNS. CSF is produced by filtering blood at the choroid plexuses in the brain's ventricles and then circulates into the subarachnoid space. From there, CSF is reabsorbed into the blood through arachnoid granulations, removing waste from the CNS.