4. Describe the ventricular system of the brain. 
  • The ventricular system consists of lateral, third and fourth ventricles and the cerebral aqueduct. 
  • The lateral ventricle is located within the cerebral hemisphere and is approximately C-shaped. It communicates, via the interventircular foramen (foramen of Monro) with the third ventricle 
  • The third ventricle is a midline, slit-like cavity. Its lateral wall consist of the thalamus and hypothalamus. Caudally, the third ventricle becomes continuous with the cerebral aqueduct (aqueduct of Sylvius). 
  • The aqueduct of Sylvius extends throughout the midbrain, linking the third and fourth and ventricles. 
  • The fourth ventricle is located between the brain stem (pons and medulla) and the cerebellum. A median aperture (foramen of Magendie) and two lateral apertures (foramina of Luschka) communicate with the subarachnoid space surrounding the brain. 
  • Each ventricle contains choroid plexus, which secretes CSF. CSF flows in the direction: lateral ventricle ->third ventricle -> cerebral aqueduct-> fourth ventricle-> subarachnoid space 
  • The combined ventricular system and subarachnoid space contains about 150 ml of CSF, this volume being produced several times each day. 
  • CSF is reabsorbed into the venous system through arachnoid villim which project into the superior sagittal dural sinus. 
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