Why Is Cerebrospinal Fluid in The Ponytail

The subarachnoid space is a space in the spine,
In the spinal cord between the arachnoid and the pia, the waist is the most extensive, containing cerebrospinal fluid, and ventricle communication. In adults, the spinal cord is terminated to the lower margin of the first lumbar spine. Lumbar puncture is generally performed between the 3rd ~ 4th or 2nd ~ 3rd lumbar vertebrae. Here, the subarachnoid space is the cauda equina nerve, because it is very thin like the cauda equina and is floating in the cerebrospinal fluid. It's a safe place to go through. The subarachnoid spinal nerve and the cauda equina nerve both run up and down, parallel to the spine.