Cerebrospinal fluid

 This fluid, a variant of tissue fluid, fills the brain ventricles, reservoirs, and subarachnoid space located under the arachnoid mater (Lat. pia arachnoidea). Ependymal cells of the ventricular vascular plexuses produce it. Most of it from the arachnoid granulations (nipple-shaped protrusions on the surface of the arachnoid mater) immediately enters the blood, while the remaining part goes into the lymph. Cerebrospinal fluid freely circulates in the lateral, fourth, and third ventricles, interventricular foramen, and cerebral aqueduct. CSF changes 5-7 times a day.

In adults, cerebrospinal fluid is clear, colorless, and contains proteins and lymphocytes. Its volume measures about 100-150 ml. The density of cerebrospinal fluid is 1007-1009 kg/m³, and its pH is around 7.4. The pressure ranges from 11-18 mm Hg when sitting and 7-15 mm Hg when lying down (11 mm Hg ≈ 133 Pa). Its chemical composition is similar to that of blood serum. CSF supports the brain’s structure, maintains pressure, and protects against minor mechanical impacts. It nourishes brain tissues and maintains constant osmotic pressure. Additionally, it contains antibodies with bactericidal properties to protect the brain from infections.Impaired CSF circulation can cause hydrocephalus.

Doctors sample cerebrospinal fluid from the lumbar cistern, which communicates with the subarachnoid space, for examination. They perform this procedure when they suspect brain injuries or infections (e.g., meningitis).