Cerebrospinal fluid or CSF

Cerebrospinal fluid or CSF

Cerebrospinal fluid or CSF is formed by the choroid plexus of the lateral, third and fourth ventricles of the brain.

CSF is periodically absorbed by the arachnoid villi of the subarachnoid space. This structure is quite large in man and horse, but generally small or microscopic in other domestic animals.

The piamater covering the surface of the brain and spinal cord also contributes small quantities of CSF. This fluid circulates throughout the sub arachnoid space between the piamater and arachnoid membrane, ventricles of the brain and central canal of spinal cord.

CSF contains a very small quantity of protein. The concentration of sodium and chloride are higher and potassium, urea and glucose are lower in CSF than plasma. The pH is same as blood. It does not contain cellular elements except very few lymphocytes.

CSF secretion is an active process and is not affected by the blood pressure or CSF pressure. The choroid plexus provides some selectivity of permeability for certain substances of the blood and the CSF is not identical with the blood plasma. It contains lower concentration of proteins, K⁺ and glucose than plasma, but has higher concentration of Na⁺ ions. Thus the choroid plexus functions as blood-cerebrospinal fluid barrier which protects the CNS from the influence of a variety of substances.

CSF is absorbed by the arachnoid villi of the arachnoid membrane, which project through the venous sinuses of the duramater.

The CSF serves partly as a nutritive medium for the brain and spinal cord as well as cushioning these structures against shock. It also aids in the transport of some peptide hormones and other substances of the brain into the circulation.