|Brain: Third ventricle|
|Scheme showing relations of the ventricles to the surface of the brain.|
|Latin||ventriculus tertius cerebri|
The third ventricle (ventriculus tertius) is one of four connected fluid-filled cavities comprising the ventricular system within the human brain. It is a median cleft between the two thalami, and is filled with cerebrospinal fluid (CSF).
It is in the midline, between the left and right lateral ventricles.
Developmentally the third ventricle represents the cavity of the diencephalon.
There are two protrusions on the front of the third ventricle:
- the supra-optic recess (above the optic chiasma)
- the infundibular recess (above the pituitary stalk).
In casts of the ventricular system, a small 'hole' may be seen in the body of the third ventricle. This is formed where the two thalami are joined together at the interthalamic adhesion (not seen in all people).