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Central Nervous System

2 out of 10

With CSF all are true except? (AIIMS NOV 2012)

A Persistent leakage causes headache

B Neutrophils are normally not presents

C p H is less than that of blood

D Secreted by the arachnoid villi

Ans. D Secreted by the arachnoid villi

Cerebrospinal Fluid

  1. Formation & Absorption: CSF fills the ventricles and subarachnoid space. In humans, the volume of CSF is about 150ml and the rate of CSF production is about 550mL/d.
  2. Thus the CSF turns over about 3.7times a day In experiments on animals, it has been estimated that 50-70% of the CSF is formed in the choroids plexuses and the remainder is formed around blood vessels and along ventricular walls.
  3. Presumably, the situation in humans is similar.
  4. The CSF in the ventricles flows through the foramens of Magendie and Luuschka to the subarachnoid space and is absorbed through the arachnoid villi into veins, primarily the cerebral venous sinuses.
  5. The villi consist of projection of the fused arachanoid membrane and endothelium of the sinuses into the venous sinuses.
  6. These are similar, smaller villi projecting into veins around spinal nerve routes.
  7. In a poorly understood way, these projections acts as valves which permits bulk flow (direct flow) of CSF into venous blood.
  8. Bulk flow through these villi is about 500ml/d, with the addition small amounts of CSF being absorbed by diffusion into cerebral blood vessels.
  9. Concentration of Substances in human CSF and plasma.

Substance CSF Plasma

p H 7.33 7.40