Ventricles of the brain (2024)

Choroid plexus

Each ventricle is home to a choroid plexus. The vascular part of the pia mater, which is called the tela choroidea, folds into the cavity of the ventricle and is further covered by ependymal. It contains choroid epithelium, which is simply cuboidal or low columnar epithelium. The extensive folding of themembrane gives the structure an expansive surface area. The capillaries of the plexus are fenestrated with specific permeability.

The choroid plexuses in each ventricle are responsible for the synthesis of cerebrospinal fluid (CSF). The fluid consists of water and other plasma components, amino acids, and glucose that nourish brain tissue. In addition to providing nutrients for the brain to complete its metabolic activity, CSF travels through the ventricles and eventually surrounds the entire brain in the subarachnoid space (between the arachnoid mater and the pia mater). It therefore acts as a shock absorbent in instances of mild or severe head injury. The choroid plexus of the lateral ventricles produces the most CSF, followed by that of the third ventricle then that of the fourth ventricle.

Lateral ventricles

Third ventricle

The third ventricle is located in the diencephalic part of the brain. It is a narrow slit that is bordered laterally by the medial nuclei of each thalamus, the hypothalamus and interrupted anteriorly by the interthalamic adhesion. The roof of the cavity is formed anteriorly by the fornix and posteriorly by the splenium of the corpus callosum.

Anteriorly, the space is limited by the lamina terminalis and the anterior commissure. Inferiorly, it continues into the infundibular and supraoptic recesses of the hypothalamus and the tuber cinereum. Posterosuperiorly the cavity extends into the pineal recess with the Habenular commissure making an impression in the region.

Its lateral wall, on either side, is indented by the hypothalamic sulcus running from the foramen of Monro to the opening of the cerebral aqueduct of Sylvius. It should also be noted that the foramen of Monro provides a passage way for the choroid plexus of the lateral ventricles to enter the third ventricle. The plexus then resides in a groove inferior to the fornix and splenium of the corpus callosum. Posteroinferiorly, the posterior commissure makes a slight extension above the opening of the aqueduct of Sylvius.

Fourth ventricle

The fourth ventricleis the most inferior of the four ventricles. It is situated in the brainstem where the ventricular surface of the rhombencephalon constitutes its floor (rhomboid fossa): inferior to the midbrain, posterior to the pons, anterior to the cerebellum and superior to the medulla oblongata.

The nuclei of several cranial nerves make important impressions on the floor of the fourth ventricle. Protuberances of equal size, known as the medial eminence, are observed on either side of the floor extending craniocaudally. The left and right medial eminences are separated by a dorsal median sulcus. At the inferior part of the medial eminence, the fibers of each facial nerve produce a larger bulge known as the facial colliculus.

Lateral to the medial eminence and facial colliculus (on either side) is the sulcus limitans; it continues caudally to the termination of the region. The locus coeruleus (pigmented area that responds to stress) is anterolateral to the medial eminence. Further inferior to the medial eminence are the hypoglossal trigone, the vagal trigone and theobex (in that craniocaudal order). A bundle of fibers, called the striae medullares, cross the floor horizontally at its midpoint towards the foramen of Luschka.

The roof of the fourth ventricle is formed by the superior and inferior medullary vela of the cerebellum. Laterally, the inferior cerebellar peduncles limit the space. On either side are apertures (foramina of Luschka) that open into the quadrigeminal cisterns. Similarly, in the inferior roof of the fourth ventricle is another aperture known as the foramen of Magendie that opens into the cerebellomedullary cistern.

Cisterns

The subarachnoid space is described as a cistern at points where spaces exist between it and the underlying pia mater. At different points around the brain, the cisterns are described with respect to adjacent anatomical landmarks. Notable cisterns include the:

• suprasellar or chiasmatic cistern
• interpeduncular cistern
• prepontine cistern
• cistern of the corpus callosum

Test your knowledge on the ventricles of the brain with this quiz.

Flow of cerebrospinal fluid (CSF)

Once CSF is produced in the lateral ventricle, it fills the cavity then leaves to enter the third ventricle by way of the interventricular foramen of Monro. In addition to the CSF from the lateral ventricle, the CSF produced in the third ventricle then exits the space through the cerebral aqueduct of Sylvius to enter the fourth ventricle.

Very little CSF is produced in the fourth ventricle; however, it – along with that coming from the above ventricles – exits the fourth ventricle to either enter the central canal of the spinal cord or by the foramina of Luschka and foramen of Magendie to enter the cisterns. CSF surrounds the brain, and then leaves by way of arachnoid granulations to enter the superior sagittal sinus and subsequently join the systemic circulation.