The ventricular system of the brain

The ventricular system forms the cavities of the central nervous system and is filled with cerebrospinal fluid. It arises from the original cavity of the neural tube, which transforms into the canalis centralis medullae spinalis in the spinal cord and expands into the cerebral ventricles (ventriculi cerebri) at the base of the brain. We refer to these according to the order in the CNS in the caudocranial direction as ventriculus quartus, ventriculus tertius and ventriculus lateralis dexter et sinister.

Ventriculus quartus (Fourth ventricle)
It is an unpaired cavity, the bottom of which is formed by the dorsal surface of the brainstem, the so-called fossa rhomboidea, the ceiling is formed by the cerebellum and other components, and laterally the ventricle extends as recessus lateralis ventriculi quarti. On the bottom IV. ventricles, into the fossa rhomboidea, the nuclei of the cranial nerves are projected. The areas of the motor and sensory nuclei are separated by the sulcus limitans. Two rows of somatomotor nuclei lie medially. A row of nuclei closer to the median sulcus is formed by the ncl. III., IV., VI., XII. and laterally from them are stored ncl. V., VII. and ''ncl. ambiguus'', to which are attached visceromotor nuclei sending fibers to smooth muscle and glands. This is ''ncl. oculomotorius accesorius, ncl. salivatorius superior et inferior and ncl. dorsalis n. vagi. Lateral to the sulcus limitans lies the single viscerosensitive nucleus of the ncl. solitarius, completely laterally are the somatosensitive nuclei - ncl. spinalis et pontinus n. V.  and sensory nuclei ncll. vestibulares et cochleares''. The nuclei of the reticular formation are also arranged in the fossa rhomboidea in three longitudinal bands.

Ventriculus tertius (Third ventricle)
It is an unpaired cavity in the diencephalon, closed from the side by the thalamus and the right and left halves of the hypothalamus, which form its floor. The junction of the right and left thalamus, adhaesio interthalamica, passes through the middle of the ventricle.

Ventriculi laterales (lateral cerebral ventricles)
They are paired horseshoe-shaped cavities located in the right and left cerebral hemispheres. We can also label them as '''I. and II. cerebral ventricle.''' We distinguish 4 sections in each. The cornu frontale arches into the frontal lobe, continues as the pars centralis, which runs above III. cerebral ventricle. Next is the cornu occipitale extending into the occipital lobe, and the last section is the cornu temporale, which is located in the temporal lobe and on whose basal wall lies the hippocampus.

Liquor cerebrospinalis (cerebrospinal fluid)
Cerebrospinal fluid is formed in all four cerebral ventricles in the choroid plexus. These grape-like formations arise from the vascular plexus. The cerebrospinal fluid flows from the lateral ventricles through the foramen interventriculare '''into III. ventricle and from there through the aquaeductus mesencephali, the so-called Sylvian canal, to IV. ventricle'''. From the IV. ventricle is distributed through the apertura mediana, the so-called foramen Magendi, et aperturae laterales ventriculi quarti (foramina Luschkae) into the subarachnoid space (spatium subarachnoideum) of the brain and spinal cord and into the canalis centralis medullae spinalis. From the spatium subarachnoideum, the fluid is then absorbed into the veins on the surface of the CNS and through them it reaches the plexus venosi vertebrales interni in the spinal canal, the sinus durae matris in the skull - mostly the sinus sagittalis superior. Arachnoid protrusions - granulationes arachnoideae - participate in the absorption of cerebrospinal fluid. Decreased resorption of cerebrospinal fluid leads to increased intracranial pressure and hydrocephalus. The total amount of liquor is 150 ml. However, approximately 500 ml of it is formed daily in the choroid plexus. Its main functions include buoyancy and protection of the brain – it balances pressure changes caused by arterial pulsation. It contains proteins, glucose, lymphocytes and other substances and therefore also has a nutritional and immunological function.

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