The cerebrospinal fluid
High-Yield Explanation
The cerebrospinal fluid is a modified tissue fluid. It is contained in the ventricular system of the brain and in the subarachnoid space around the brain and spinal cord. The bulk of cerebrospinal fluid is formed by the choroid plexuses of the lateral ventricles and lesser amounts by the choroid plexuses of third and fouh ventricles Ref BDC volume3,6th edition pg 331