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.

Communication

It communicates with the lateral ventricles anteriorly by the interventricular foramina (of Monro).

It communicates with the fourth ventricle posteriorly by the cerebral aqueduct (of Sylvius).

Development

Developmentally the third ventricle represents the cavity of the diencephalon.

Boundaries

It is bounded by the thalamus and hypothalamus on both the left and right sides. The lamina terminalis forms the anterior wall of the third ventricle.

Protrusions

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).

See also

• Suprapineal recess

Additional images

<gallery> Image:Gray717.png|Coronal section of brain immediately in front of pons. Image:Gray718.png|Coronal section of brain through intermediate mass of third ventricle. Image:Gray723.png|Coronal section of lateral and third ventricles. Image:Gray735.png|Drawing of a cast of the ventricular cavities, viewed from above. Image:Gray744.png|Coronal section of brain through anterior commissure. Image:Gray768.png|Diagram showing the positions of the three principal subarachnoid cisternæ. Image:Gray1181.png|Median sagittal through the hypophysis of an adult monkey. Semidiagrammatic. </gallery>

External links

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