Ventricles The brain has a series of ventricles that hold CSF (Cerebrospinal Fluid).  There are four main ventricles: the lateral ventricles (one on each side- these are the ones you typically notice in imaging), the third ventricle, and the fourth ventricle.  They are connected by the foramen of Monro (lateral -> third), cerebral aqueduct (aka Sylvius, third -> fourth), and the foramen of Magendie and Luschka (fourth -> subarachnoid space/cisterna magna).  CSF is created in the lateral ventricles by the choroid plexus and circulates through the ventricles until it is absorbed by the arachnoid layer (the middle meninges of the brain that is very well vascularized).  CSF seems to act as a fluid cushion for the brain, but it also transports some substances into/out of the brain and maintains homeostasis of pressure around the brain and of certain molecules absorbed by the brain.  In certain disorders (Alzheimer’s, for instance), we notice that the ventricles seem to be getting larger- this is due to brain tissue around them dying.  In these cases, the ventricles are “growing” to fill up the extra space in the head left by neurodegeneration (neurons dying). [Image Source]

Ventricles

The brain has a series of ventricles that hold CSF (Cerebrospinal Fluid).  There are four main ventricles: the lateral ventricles (one on each side- these are the ones you typically notice in imaging), the third ventricle, and the fourth ventricle.  They are connected by the foramen of Monro (lateral -> third), cerebral aqueduct (aka Sylvius, third -> fourth), and the foramen of Magendie and Luschka (fourth -> subarachnoid space/cisterna magna).  CSF is created in the lateral ventricles by the choroid plexus and circulates through the ventricles until it is absorbed by the arachnoid layer (the middle meninges of the brain that is very well vascularized).  CSF seems to act as a fluid cushion for the brain, but it also transports some substances into/out of the brain and maintains homeostasis of pressure around the brain and of certain molecules absorbed by the brain.  In certain disorders (Alzheimer’s, for instance), we notice that the ventricles seem to be getting larger- this is due to brain tissue around them dying.  In these cases, the ventricles are “growing” to fill up the extra space in the head left by neurodegeneration (neurons dying).

[Image Source]