The CSF is formed in the lateral ventricles, circulates through the interventricular foramens into the third ventricle, and then via the cerebral aqueduct into the fourth ventricle. Here the fluid scapes via the lateral apertures of the fourth ventricle and the medial foramen of the fourth ventricle into the subaracnoid spaces, where it difuses over the brain and spinal cord. It has been calculated that 430 to 450 ml of CSF are produced every day, so the fluid must be changes every 6 to 7 hours (Neter, 31).Respiratory and circulatory changes are belivied to change the pressure within the closed system and promote the mixing and diffusion of fluid.

Circulation

CSF Circulation (in light-green, CSF) lateral ventricles--> foramen of Monro third ventricle --> aqueduct of Sylvius --> fourth ventricle --> foramina of Magendie and Luschka --> subarachnoid space over brain and spinal cord --> reabsorption into venous sinus blood via arachnoid granulations. See an animation of CSF circulation (3.8 Mb, MOV movie) Obs: A Quicktime or other plugin capable to play MOV video clips is needed. See instructions to install one. Click on the first animation frame to start. Picture: Crump Institute for Biological Imaging. Reproduced with permission

The fluid flows through the interventricular foramen (of Monro) into the third ventricle, is augmented by fluid formed by the choroid plexus of this ventricle, and passes through the cerebral aqueduct (of Sylvius) to the fourth ventricle, which also possesses a choroid plexus. The CSF from all theses sources , as well as any formed in the central canal of the spinal cord, escapes from the fourth ventricle into the subarachnoid space through the median aperture (of Magendie) and lateral aperture (of Luschka).

The CSF then circulates through the freely communicating subaracchnoid cisterns at the base of the brain. From the cisterns, most of the CSF is directed upward over the cerebral hemispheres and smaller amounts pass downward around the spinal cord.

Blood Brain Barrier

Neurons of the brain and spinal cord are protected from many chemical damage and biological substances by "blood brain barrier", interposed between the blood and the CSF by the endothelial cells of the capillaries and the choroid plexus. This is clinically important because some drugs cannot penetrate the barrier. This protective device has many elements, ranging from junctions between endothelial cells in the capillaries of the brain, restricting permeability of larger molecules to neuroglia. Large blood vessels penetrating the brain tissue are lined with an inner layer of endothelium reinforced by fibromuscular tissue.

See

Visible Human: Frozen Anatomical Sections and MRI Sections of Ventricular System

Author: Silvia Helena Cardoso, PhD. Psychobiologist, master and doctor in Sciences by the University of São Paulo and post doctoral fellowship by the University of California, Los Angeles. Invited Professor and Associate Researcher of the Center for Biomedical Inofrmatics, State University of Campinas (Unicamp), Brazil.

Reviewed and commented by the neuroanatomist Dr. Norberto Cysne Coimbra , MD, PhD. Neuoanatomist, Neuroscientist, Molecular Biologist. Laboratory of Neuroanatomy and Neuropsichobiology, Department of Morphology, Faculty of Medicine, Ribeirão-Preto USP (São Paulo), Brazil.

Translation: Silvia Helena Cardoso