Question

During a spinal tap to obtain CSF, list the spaces and/or meninges that the needle would have to penetrate to reach the CSF.

Also

List the flow of CSF in the brain and spinal cord.

Be sure to include where CSF is made and where it finally ends up after cycling through the brain. Also, discuss the glial cells involved in the BBB of the brain.

Answer 1

During a spinal tap to collect CSF, a spinal needle is inserted in between the lumbar region L3/L4, L4/L5 OR L5,S1. The needle enters the lumbar cistern/subarachnoid cistern region. The subarachnoid cistern are the spaces that separates the arachnoid matter and the pia matter. These ciosterns are filled with CSF. The needle is further pushed till it enters the dura matter and also the thinner arachnoid membrane. Finally, the needle is withdrawn from the subarachnoid space.

CSF is formed within the ventricles by tufts of specialized tissues called the choroid plexus. Ventricles are cavities present in the brain. The CSF circulation begins in the lateral ventricles, from there it enters into the third ventricle via two pathways. The 3rd and the 4th ventricles are connected via the aqueduct of Sylvius. Through this aqueduct of sylvius, CSF enters the 4th ventricle.From there, CSF enters into the subarachnoid space from the small openings called foramina present in the 4th ventricle. The subarachnoid space surrounds the brain and the spinal cord. CSF enters the bloodstream from the vessels covering the surface of the brain. It is also absorbed in the lymphatic system when it exits the brain and the spinal cord. Once it enters the blood stream, it is filtered through the kidneys in the same way as other fluids.

The Blood Brain Barrier restricts the flow of immune cells and other soluble substances from the systemic circulation into the CNS. The glial cells involved in the functioning of BBB are astrocytes and mircoglia. These cells work with pericytes and endothelial cells to maintain the induction of BBB.