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Central Nervous System

5 out of 10

The arachnoid villi responsible for CSF absorption protrude mainly in the: (LQ)

A Superior sagittal sinus

B Inferior sagittal sinus

C Straight sinus

D Transverse sinus

Ans. C Straight sinus
  1. The arachnoid granulations are small fleshy looking elevations, collected in clusters, which are present in the vicinity of the superior sagittal, transverse, and some other sinuses Q.
  2. Arachnoid granulations are macroscopic enlargements of minute projections of the arachnoid matter, termed arachnoid villi, which are normally present in great number in young subjects.
  3. The cerebrospinal fluid is a clear, slightly alkaline fluid, with a specific gravity of about 1007 Q.
  4. It is secreted into the ventricles of the brain by the choroid plexus and into the subarachnoid space by the plexuses sited in the lateral recesses of the 4th ventricle.
  5. From the ventricles it passes through the median aperture and the foramina of the lateral recesses of the 4th ventricle and so gains the subarachnoid space in the cerebello medullary cistern and the pontine cistern.
  6. Within the cranium the CSF flows upwards through the gap in the tentorium and then forwards and laterally over the inferior surface of cerebrum.
  7. Finally it ascends over the lateral aspect of each hemisphere to reach the arachnoid villi associated with the superior sagittal sinus, and so is able to pass back again into the bloodstream.