How the Brain Dumps Its Trash (2016) [video]

Other organs and tissues are "cleaned" using the lymphatic system that almost works as a sewage system for the body. The lymphatic system does not extend into the brain. The so-called "blood-brain barrier" limits fluid channel exchanges between the brain and the rest of the body to protect the brain.

The extracellular fluid in the brain – the wetness between the neurons – is part of a system that essentially flushes the brain and removes waste. This has been named the glymphatic system. It was previously thought that waste products were metabolized and broken down by the neurons themselves and the results of that breakdown carried away in capillaries and ultimately removed by the kidneys.

http://www.sleepdex.org/reboot.htm