Glossary term:

Choroid plexus

This structure (more accurately a series of structures) lies within all four ventricles of the brain. Viewed through a ventriculoscope, it has the appearance of pink seaweed. Blood flows through the choroid plexus and clear, water-like fluid, i.e. cerebrospinal fluid, is produced, passing into the ventricles. Not all of the cerebrospinal fluid forms from the choroid plexuses but a substantial proportion does, probably at least half of the daily production of about half a litre, or one pint.