👉 The "fellow fluid" often refers to the cerebrospinal fluid (CSF), a clear, colorless liquid that surrounds the brain and spinal cord in the central nervous system. Produced by the choroid plexus within the ventricles of the brain, CSF serves multiple critical functions including cushioning and protecting the delicate neural tissues from mechanical shocks, regulating intracranial pressure, and facilitating the removal of waste products through a process called glymphatic clearance. Unlike blood, CSF is not directly reabsorbed into the bloodstream but instead flows through the ventricular system and into the subarachnoid space surrounding the brain and spinal cord, where it helps maintain a stable environment for optimal neural function.
