👉 The fifth fluid, often referred to as the "cerebrospinal fluid" (CSF), is a clear, colorless liquid that circulates within the central nervous system (CNS) of vertebrates. Unlike blood, which is pumped by the heart, cerebrospinal fluid is produced by the choroid plexus in the brain's ventricles and flows through the ventricular system, subarachnoid space surrounding the brain and spinal cord. This fluid serves multiple critical functions: it cushions the brain and spinal cord from mechanical injury, provides nutrients to neural tissues, and removes waste products. Additionally, cerebrospinal fluid plays a role in maintaining the chemical balance of the CNS by regulating ion concentrations and pH levels.
