What is the ventricular system? 

Pic: http://www.buzzle.com/images/diagrams/labeled-brain-diagrams/brain-ventricles.jpg

Pic: http://www.buzzle.com/images/diagrams/labeled-brain-diagrams/brain-ventricles.jpg

The ventricular system within the brain is located centrally and is composed of several parts, including the two lateral ventricles (otherwise known as the first and second ventricles), the third ventricle, the fourth ventricle, the central canal, the interventricular foramen and the cerebral aqueduct. In preserved specimens of brain, these spaces are hollow cavities.

What is the purpose of the ventricular system? 

The ventricular system is responsible for carrying around cerebrospinal fluid or CSF around the brain. The CSF is responsible for lubricating the brain and spinal cord within the skull and vertebrae, respectively.

How is CSF circulated?

The CSF is created within the choroid plexus, which is found in all components of the ventricular system except for the cerebral aqueduct. It then follows the following sequence of circulation:

Pic: http://hydrocephalus.in/yahoo_site_admin/assets/images/HC4.355124932_std.jpg

  1. Through the lateral ventricles
  2. Enters third ventricle via foramina of Monro
  3. Enters fourth ventricle from third ventricle via cerebral aqueduct
  4. From fourth ventricle, it enters the central canal of the spinal cord or the subarachnoid space in the meninges.
  5. The CSF flows around the spinal cord and then back into the brain

Afterwards, the CSF is then resorbed back into the venous circulation (in the bloodstream) via the arachnoid villi.

The functions of CSF are discussed further in Meninges + CSF= Brain Protection.