Answer
Cerebrospinal fluid is a clear liquid that fills the cavities of the brain and spinal cord. It also surrounds and covers both of these major structures of the central nervous system. It is produced mainly by the choroid plexi of the lateral, third, and fourth ventricles. However, some ependymal cells outside the choroid plexi also form som cerebrospinal fluid. The path of the flow of CSF is from lateral ventricles to third ventricle through the Aqueduct of Sylvius to the fourth ventricle. From the fourth ventricle some of the CSF goes to the central canal of the spinal cord ; the rest , most of it, leaves the ventricular system for the subarachnoid space and flows over the cerebral hemispheres.
CSF is drained into the venous system through arachnoid granulation in the dorsal sagittal sinus. which is located in the folds of the falx of the dura mater covering the cerebral hemispheres. Some of the CSF also flows past the the end of the spinal cord into a dilation of the subarachnoid space.
The CSF is reabsorbed and returned to the venous drainage system either directly by villi of blood vessels of arachnoid granulations or by way of lymphatic system. It is important
Work Step by Step
The cerebrospinal fluid is a light colored fluid filtrate of blood plasma. It is formed by bunches or small networks of capillaries located in the cavities of the brain called ventricles. These are the lateral ventricles, the third ventricle, and the fourth ventricle. The cerebrospinal fluid also flows into the central canal of the spinal cord; it also and bathes the outer surfaces of the brain and spinal cord.
Some important functions of CSF are support of the brain; lubrication of the brain; cushioning or absorbing shocks, transport of nutrients, gases, metabolites and waste; maintenance of a constant chemical environment for the brain.
A simplified description of the circulation of CSF is as follows:
CSF produced in lateral ventricles of the cerebral hemispheres. It the passes through the interventricular foramen ( Foramen of Monro, one on each side ) into the third ventricle. From the third ventricle CSF travels through the Aqueduct of Sylvius to get to fourth ventricle. From the fourth ventricle some CSF flows through the Foramen of Magendie to the subarachnoid space. The rest of the CSF is divided; some flows to the central canal of the spinal cord; this residue also reaches the subarachnoid space, but indirectly, through the two foramina of Luschka. In the subarachnoid space CSF is absorbed by villi of cells of the arachnoid granulations that intrude into venous sinuses.
The brain produces between 450 and 500 ml of CSF per day, but the volume in the brain at any one time is less than 160 mls. This means that the circulation of the CSF must be constant and unimpeded or brain functions may be impaired.
