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==CSF Circulation==

==CSF Circulation==

Once produced, CSF is then circulated from the choroid plexus through the interventricular foramina into the 3rd ventricle, and then through the cerebral aqueduct (aqueduct of Sylvius) into the 4th ventricle before flowing through the cerebromedullary cistern down the spinal cord and over the cerebral hemispheres. Most CSF escapes from the ventricular system at the hindbrain foramen of Luschka. CSF then flows down the length of the spinal cord in the subarachnoid space. Large amounts are drained into venous sinuses through arachnoid granulations in the dorsal sagittal sinus. Arachnoid granulations contain many villi that are able to act as a one way valve helping to regulate pressure within the CSF.

Once produced, CSF is then circulated, due to hydrostatic pressure, from the choroid plexus of the lateral ventricles, through the interventricular foramina into the 3rd ventricle. The lateral ventricles are paired and are located in the cerebral hemispheres. The 3rd ventricle is located in the diencephalon and surrounds the thalamus. CSF then flows through the cerebral aqueduct (aqueduct of Sylvius or mesencephalic aqueduct) into the 4th ventricle. The 4th ventricle is located in the hindbrain. From the 4th ventricle the CSF may flow down the central canal of the spinal cord, or circulate in the subarachnoid space. The central canal of the spinal cord is in direct communication with the 4th ventricle. Most CSF escapes from the ventricular system at the hindbrain Foramen of Luschka (lateral apertures) into the subarachnoid space. Once in the subarachnoid space, the CSF may enter the cerebromedullary cistern (a dilation of the subarachnoid space between the cerebellum and the medulla) and then circulate over the cerebral hemispheres. CSF also flows down the length of the spinal cord in the subarachnoid space. Another dilation of the subarachnoid space occurs caudally due to the dura and arachnoid meninges continuing on past the end of the spinal cord. This gives rise to the Lumbar cistern, and can be used to take a CSF sample in large species. In some species there is an exit which allows CSF to flow from the caudal end of the central canal into the lumbar cistern.

Large amounts of CSF are drained into venous sinuses through arachnoid granulations in the dorsal sagittal sinus. The dorsal sagittal sinus is located between the folds of dura, known as the falx cerebri, covering each of the cerebral hemispheres. Arachnoid granulations contain many villi that are able to act as a one way valve helping to regulate pressure within the CSF, and these arachnoid villi push through the dura and into the venous sinuses.

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Any disruption to this flow can result in increased pressure building up within parts of the CSF system which can cause compression of neural structures surrounding the area of increased pressure. Clinical examples of this are [[Hydrocephalus|hydrocephalus]] and syringohydromyelia.

Because CSF is continuously produced, any disruption to this flow can result in increased pressure building up within parts of the CSF system which can cause compression of neural structures surrounding the area of increased pressure. Clinical examples of this are [[Hydrocephalus|hydrocephalus]] and syringohydromyelia.