Superior sagittal sinus Choroid plexus Arachnoid villus Subarachnoid space Cerebrum covered -Arachnoid with pia mater Meningeal dura mater Periosteal dura mater Corpus callosum Tentorium Third ventricle cerebelli Pituitary gland Cerebellum Cerebral aqueduct Choroid plexus Fourth ventricle Central canal of spinal cord (b)