Blocking the way upstream
The correct terms to fill in the blanks are lateral ventricles and venous sinus blood. Cerebrospinal fluid (CSF) is formed by lateral ventricles and reabsorbed through arachnoid granulations into the venous sinus blood. The CSF is a fluid that is clear and colorless found in the spinal cord and in the brain, generally the central nervous system. The CSF functions as a buffer or a shock absorber for the brain. It provides basic mechanical protection for the brain. Also, it helps in the circulation of nutrients and the chemicals that are filtered and aids in the elimination of waste products.
Mainly by nitrogen-fixing bacteria in the soil and oceans
