Third Ventricle

The third ventricle is a narrow cavity located between the two hemispheres of the diencephalon of the forebrain. The third ventricle is part of a network of linked cavities (cerebral ventricles) in the brain that extend to form the central canal of the spinal cord. The cerebral ventricles consist of the lateral ventricles, third ventricle, and fourth ventricle.

The ventricles contain cerebrospinal fluid, which is produced by specialized epithelium located within the ventricles called the choroid plexus. The third ventricle is connected to the fourth ventricle via the cerebral aqueduct, which extends through the midbrain.

Third Ventricle Function

The third ventricle is involved in several functions of the body including:

• Protection of the Brain From Trauma
• Pathway for the Circulation of Cerebrospinal Fluid
• Transportation of Nutrients to and Waste from the Central Nervous System

Third Ventricle Location

Directionally, the third ventricle is situated in the middle of the cerebral hemispheres, between the right and left lateral ventricles. The third ventricle is inferior to the fornix and corpus callosum.

Third Ventricle Structure

The third ventricle is surrounded by a number of structures of the diencephalon. The diencephalon is a division of the forebrain that relays sensory information between brain regions and controls many autonomic functions. It links endocrine system, nervous system, and limbic system structures. The third ventricle can be described as having six components: a roof, a floor, and four walls. The roof of the third ventricle is formed by a part of the choroid plexus known as the tela chorioidea. The tela chorioidea is a dense network of capillaries that is surrounded by ependymal cells. These cells produce cerebrospinal fluid. The floor of the third ventricle is formed by a number of structures including the hypothalamus, subthalamus, mammilary bodies, infundibulum (pituitary stalk), and the tectum of the midbrain. The lateral walls of the third ventricle are formed by the walls of the left and right thalamus. The anterior wall is formed by the anterior commissure (white matter nerve fibers), lamina terminalis, and optic chiasma. The posterior wall is formed by the pineal gland and habenular commissures. Attached to the external walls of the third ventricle are interthalamic adhesions (bands of gray matter) that cross the third ventricle cavity and connect the two thalami.

The third ventricle is connected to the lateral ventricles by channels called interventricular foramina or foramina of Monro. These channels allow cerebrospinal fluid to flow from the lateral ventricles to the third ventricle. The cerebral aqueduct connects the third ventricle to the fourth ventricle. The third ventricle also has small indentations known as recesses. Recesses of the third ventricle include the preoptic recess (near the optic chiasma), infundibular recess (funnel shaped recess that extends downward into the pituitary stalk), mammillary recess (formed by protrusions of the mammilary bodies into the third ventricle), and pineal recess (extends into the pineal gland).

Third Ventricle Abnormalities

Third ventricle issues and abnormalities can occur in a variety of conditions like stroke, meningitis and hydrocephalus. A relatively common cause of an abnormality of the third ventricle occurs with congenital hydrocephalus (abnormal contour with a dilated third ventricle).

Ventricular System of the Brain

The ventricular system consists of two lateral ventricles, the third ventricle, and the fourth ventricle.

More Information

For additional information on the third ventricle, see:

• The Third Ventricle

Anatomy of the Brain

The brain is the body's control center. It receives, interprets, and directs sensory information in the body. Find out more about the brain's anatomy.

Divisions of the Brain

• Forebrain - encompasses the cerebral cortex and brain lobes.
• Midbrain - connects the forebrain to the hindbrain.
• Hindbrain - regulates autonomic functions and coordinates movement.

Sources

• Glastonbury, Christine M., et al. “Masses and Malformations of the Third Ventricle: Normal Anatomic Relationships and Differential Diagnoses.” RadioGraphics, pubs.rsna.org/doi/full/10.1148/rg.317115083.