The brain contains pockets or spaces called ventricles with a spongy layer of cells and blood vessels called the choroid plexus. This is
in the middle of the
fetal brain. The choroid plexus has the important function of producing a fluid called cerebrospinal fluid. The fluid produced by the cells of the choroid plexus fills the ventricles and then flows around the brain and the spinal cord to provide a cushion of fluid around these structures.