In the spine, the<unk>  is the<unk>  outside the tough membrane called the dura mater (sometimes called the "dura"), and within the spinal canal, which is formed by the surrounding vertebrae. Adherent to the inside of the dura is a much thinner and more fragile membrane, the arachnoid mater. Enclosed within the arachnoid is the subarachnoid<unk> , which contains the cerebrospinal fluid, and the spinal cord.
Epidural space
Subdural space
Subarachnoid space
Arachnoid mater
Danger space
Cerebral crus
Intervertebral foramina
Cerebral aqueduct