Ventricles are cerebrospinal fluid (CSF) filled cavities inside of the brain.They are connected to each other by foramina and structures like the aqueduct. The ventricle system comprises 4 ventricles and develops from the central canal of the neural tube.This cavity system contains CSF and is also called the inner subarachnoid space. The outer subarachnoid space is located between arachnoidea and pia mater. Both spaces communicate with each other via the fourth ventricle.The brain has one lateral ventricle in each hemisphere, a third ventricle in the diencephalon and a fourth ventricle in the rhombencephalon. The choroid plexus inside of the ventricles secretes the CSF.
