Human Anatomy, Part 2 - K. A. Dyubenko, A. K. Kolomiysev, Yu. B. Chaykovsky 2008

Specialized Section
Nervous System, systema nervosum — Specialized Section
Meninges of the Brain — Cerebrospinal Fluid

CEREBROSPINAL FLUID, liquor cerebrospinalis, is a biological fluid of the body that circulates within the cerebral ventricles, cerebrospinal pathways, and the subarachnoid space of the Brain AND SPINAL cord.

In the Central Nervous system, cerebrospinal fluid performs protective and trophic Functions:

- protects the brain and Spinal Cord from mechanical impacts (jolts and concussions);

- helps maintain constant intracranial pressure;

- maintains constant osmotic pressure in brain Tissues;

- participates in brain METABOLISM;

- serves a transport function in the exchange of substances between tissues and Blood;

- takes part in developing compensatory and protective mechanisms during pathological conditions in the central nervous system, accumulating Antibodies, bactericidal agents, and other substances;

- ensures the maintenance of Water-electrolyte Homeostasis.

Under normal conditions, cerebrospinal fluid is clear, colorless, and chemically resembles blood serum. It contains small amounts of glucose, calcium, sodium, and magnesium salts, chlorides, lactic acid, Amino Acids, urea, and Cholesterol. The total volume of cerebrospinal fluid in an adult is 90-200 ml. According to current data, 50-100 ml of cerebrospinal fluid is produced daily, which maintains its total volume within the ventricular system and subarachnoid space.

Cerebrospinal fluid is produced by the choroid plexuses of the Lateral ventricles of the brain via secretion by glandular Cells, as well as through blood dialysis across the walls of Blood Vessels and the ependymal lining of the brain ventricles, which function as dialyzing membranes. Cerebrospinal fluid is located primarily in the lateral, third, and fourth ventricles of the brain, the cerebral aqueduct, the cerebral cisterns, and the subarachnoid space.

Cerebrospinal fluid circulates continuously. From the lateral ventricles, the fluid passes through the interventricular foramen, foramen interventriculare (Monro's foramen), into the Third ventricle, and then through the narrow cerebral aqueduct into the Fourth ventricle (Fig. 171). From the fourth ventricle, through the lateral apertures, apertura lateralis ventriculi quarti (foramen of Luschka), and the median aperture, apertura mediana ventriculi quarti (foramen of Magendie), the cerebrospinal fluid flows into the cerebral cisterns and the subarachnoid space of the brain. A small portion of the cerebrospinal fluid flows caudally into the subarachnoid space of the spinal cord. Reabsorption of cerebrospinal fluid into the bloodstream occurs through arachnoid granulations (projections of the arachnoid mater) that protrude into the superior sagittal sinus, sinus sagittalis superior, which is part of the venous System of the brain.

An excessive amount of cerebrospinal fluid leads to a condition known as Hydrocephalus. This can be caused by hyperproduction of cerebrospinal fluid, or more commonly by inflammatory states (accompanied by blockage of the foramina of Luschka or obliteration of the third ventricle), which obstruct the normal flow of cerebrospinal fluid. Another cause can be atresia or obstruction of the cerebral aqueduct.