Extracellular interstitial fluid
Extracellular interstitial fluid is a thin layer of fluid that surrounds the body's cells.
Although there is no lymphatic system in the central nervous system (CNS), there seems to be a mechanism to remove macromolecules from the brain. Cerebrospinal fluid (CSF) and interstitial fluid (ISF) are thought to be parts of this pathway, but the details are not known.
Since substance exchange occurs between the CNS extracellular interstitial fluid (ISF) and CSF, it is assumed that CSF serves as a sink for the removal of various metabolites out of the CNS by its unidirectional pulsatile flow and absorption 1) 2) 3)
1)
Davson H, Welch K, Segal MB. The physiology and pathophysiology of the cerebrospinal fluid. 1st edition. Edinburgh: Churchill Livingstone; 1987.
2)
Fishman AR. Cerebrospinal fluid in disease of the nervous system. Philadelphia: W B Saunders Co; 1991.
3)
Irani DN. Cerebrospinal fluid in clinical practice. Philadelphia: Saunders Elsevier; 2009.