QS Study

The cerebrospinal fluid (CSF) is found in the arachnoid spaces of the brain and cord. It is a clear, colorless modified tissue fluid, formed by ultrafiltration of plasma in the CNS.  It acts as a cushion or buffer for the brain, providing basic mechanical and immunological protection to the brain inside the skull. The CSF is contained within a system of fluid-filled cavities called ventricles.

Circulation

  • CSF is secreted by choroid plexus in each lateral ventricle.
  • Flows through interventricular foramina into the third ventricle.
  • Choroid plexus in the third ventricle adds more CSF.
  • CSF flows down cerebral aqueduct to the fourth ventricle.
  • Choroid plexus in the fourth ventricle adds more CSF.
  • CSF flows out two lateral apertures and one median aperture.
  • CSF fills subarachnoid space and bathes external surfaces of the brain & spinal cord.
  • At arachnoid villi, CSF is absorbed into venous blood of dural venous sinuses.
  • From lateral ventricles, CSF reaches 3rd ventricle through foramina of Monroe.
  • From 3rd ventricle to 4th ventricle, it reaches through cerebral aqueduct or aqueduct of Sylvius.
  • From 4th ventricle, it reaches spinal canal through a foramen of Magendie and into subarachnoid spaces throughout CNS through foramina of Luschka.

Cerebrospinal Fluid (CSF) circulation 1

Fig: Cerebrospinal Fluid (CSF) circulation

Absorption –

  1. Chiefly through the arachnoid villi & granulations and is thus drained into the cranial venous sinuses.
  2. Partly by the perineural lymphatics around the 1st, 2nd, 7th & 8th cranial nerves.
  3. Also by veins related to spinal nerves.
  4. In the cranial subarachnoid space, CSF flows towards arachnoid villi in the wall of venous sinuses from which it is absorbed.

Functions

  • Acts as cushions and protects the central nervous system from trauma.
  • Provides mechanical buoyancy and support for the brain.
  • Serves as a reservoir and assists in the regulation of the contents of the skull.
  • Nourishes the CNS.
  • Removes metabolites from the CNS.
  • Serves as a pathway for pineal secretions to reach to the pituitary gland.
  • Acts as an effective interstitial fluid so that exchange of substances can take place between blood and brain tissues.
  • Interstitium of the brain (microenvironment in the brain) is maintained so that excitability of neuronal tissue is achieved and properly maintained.
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