A water-clear fluid formed inside the ventricular system of the brain primarily by the choroidal braids and partly by the cell layer that otherwise limits the cavities of the ventricular system, i.e. from the ependym. The fluid flows through the ventricular system and out to the subarachnoid space through holes in 4.de posterior wall of the cerebral ventricle. The ventricular system holds approx. 30 ml of liquid and the subarachnoid space about 100 ml.
During a day, just over 500 ml of cerebrospinal fluid is formed, which corresponds to a production of approx. 0.35 ml/min. In order for the pressure conditions inside and outside the brain to remain constant, an equal amount of cerebrospinal fluid - e.g. 0.35 ml - must be equal. - which are formed during 1 min while returning to the bloodstream.
Likvor leaves the subarachnoid space and crosses the bloodstream with the help of the arachnoid midges that flow into the upper midstical blood channel.
Likvor has several tasks:
1) works as an excellent packaging material (compare with the fetal packaging in amniotic fluid). Since the brain has almost the same specific gravity as the cerebrospinal fluid, the brain where it more or less floats "weightless", suspended in cerebrospinal fluids, will have lost as much weight as the weight of the displaced cerebrospinal fluid volume (Archimedes' principle!). This fluid suspension means that the brain is very little affected by the inertial forces that would otherwise make themselves felt and tear and repel the brain.
2) acts to some extent as a substitute for lymph.
3) transports various substances, for example, from the 3rd ventricle to recipients in the 4th ventricle.