Third ventricle
Encyclopedia
The third ventricle is one of four connected fluid-filled cavities comprising the ventricular system
Ventricular system
The ventricular system is a set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal of the spinal cord.-Components:The system comprises four ventricles:* right and left lateral ventricles* third ventricle...

 within the human brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

. It is a median cleft between the two thalami
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...

, and is filled with cerebrospinal fluid
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...

 (CSF).

It is in the midline, between the left and right lateral ventricles. Running through the third ventricle is the Interthalamic adhesion
Interthalamic adhesion
The medial surface of the thalamus constitutes the upper part of the lateral wall of the third ventricle, and is connected to the corresponding surface of the opposite thalamus by a flattened gray band, the Interthalamic adhesion .In non-human mammals it is a large structure...

, fibers which connect the two thalami.

Communication

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

It communicates with the fourth ventricle
Fourth ventricle
The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle...

 posteriorly by the cerebral aqueduct
Cerebral aqueduct
The mesencephalic duct, also known as the aqueductus mesencephali, aqueduct of Sylvius or the cerebral aqueduct, contains cerebrospinal fluid , is within the mesencephalon and connects the third ventricle in the diencephalon to the fourth ventricle in the mesencephalon, which is between the pons...

 (of Sylvius).

Development

The third ventricle, similarly to other parts of the ventricular system of the brain, develop from the central canal of the neural tube. Specifically, the third ventricle originates from the portion of the tube that is present in the developing prosencephalon, and subsequently in the developing encephalopathy.

Boundaries

It is bounded by the thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...

 and hypothalamus
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...

 on both the left and right sides. The lamina terminalis
Lamina terminalis
The median portion of the wall of the fore-brain vesicle consists of a thin lamina, the lamina terminalis, which stretches from the interventricular foramen to the recess at the base of the optic stalk and contains the organum vasculosum of the lamina terminalis, which regulates the osmolarity of...

 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
    Infundibular recess
    The floor of the third ventricle is prolonged downward as a funnel-shaped recess, the infundibular recess, into the infundibulum, and to the apex of the latter the hypophysis or pititary is attached....

     (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
Interthalamic adhesion
The medial surface of the thalamus constitutes the upper part of the lateral wall of the third ventricle, and is connected to the corresponding surface of the opposite thalamus by a flattened gray band, the Interthalamic adhesion .In non-human mammals it is a large structure...

(not seen in all people).
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