Cerebral Ventricles

The cerebral ventricles are the four fluid-filled cavities located in the human brain. Since these four cavities are interconnected, they are often called the ventricular system, which is the continuation and extension of the spinal cord central canal. There are the fourth, third, and lateral ventricles, with the latter one being a paired cavity, left and right lateral ventricle. In each one of these ventricles, there is a folded, highly-vascular membrane called the choroid plexus, which produces the cerebrospinal fluid (CSF) that flows through these cavities and the central canal. The choroid plexuses attach to the wall of the ventricles by a thin stalk, which is known as 'tela choroidea'.

The fourth ventricle lies posteriorly to the brainstem, at the base of the brain, at a point where the central canal suddenly widens to form an irregular shape cavity. It has a tent-like roof and a rhomboid fossa or floor. The apex projects into the cerebellum, and two lateral recesses. The caudal part of the fourth ventricle is formed by the tela choroidea. This cavity reaches its greatest width at the pontomedullary transition, expanding laterally behind the cerebellar peduncles. The diamond-shaped rhomboid fossa at the dorsal aspect of the brainstem forms the 'floor' of the fourth ventricle.

The third ventricle is a vertically-oriented, quadrilateral cavity, lying in the midplane of the brain between the two thalami. It extends from the lamina terminalis to the rostral opening of the mesencephalic aqueduct. This ventricle communicates at its rostrodorsal corner with each of the two lateral ventricles through the left and right interventricular foramen of Monro. Its narrow roof is formed by the tela choroidea. It is connected to the fourth ventricle through the Sylvian aqueduct, which is canal containing CSF. The loose masses of connective tissue between the cerebral hemispheres form a horizontal plate that constitutes the roof of the third ventricle. The choroid plexus is attached to the inside of the roof.

The two lateral ventricles represent the first and second ventricles. However, these terms are not used. They are large cavities that extend antero-posteriorly, slightly curving or arching downwards in conformity with the general shape of each of the cerebral hemisphere. Stretching sagittally, they have an anterior and a posterior horn, with an inferior temporal horn, which extends downwards into the temporal lobe of the cerebrum. The anterior horn is the larges one, lying in the frontal lobe, while the posterior horn nestles in the occipital lobe. Both lateral ventricles communicate with the third ventricle through the interventricular foramen of Monro. Medially, in the inferior horn, there is an elongated anatomical elevation; it is the hippocampus.

Above, lateral, frontal, and superior view of all fou cerebral ventricles.