The Spinal cord is a delicate structure within the Spinal canal. The Spinal cord runs from the base of the brain to the Thoracolumbar junction, where it ends in a bunch of nerve roots called the Cauda equina (Horse's tail). The connection between the brain and the spinal cord is at the base of the brainstem in the region of the Craniocervical junction. The spinal cord is normally surrounded by Cerebrospinal fluid (CSF) and is covered by a very thin protective membrane called the Pia mater. There is another membane called the Dura mater which contains the Cerebrospinal fluid (CSF). Within the Cerebrospinal fluid (CSF) is the middle membrane that is thin and resembles a spider's web, called the Arachnoid membrane. The spinal cord itself has a tiny, centrally-located canal that runs the length of the spinal cord, that normally contains a droplet of Cerebrospinal fluid (CSF). It is also called the central canal, though these structures are unrelated.