Changes

[[Image:meninges.jpg|thumb|right|200px|'''Diagram of the meninges''', 1.Skin 2.Periosteum 3.Bone 4.Dura mater 5.Arachnoid 6.Pia mater. SEER Cancer Institute, WikiMedia Commons]]

[[Image:meninges.jpg|thumb|right|200px|'''Diagram of the meninges''', 1.Skin 2.Periosteum 3.Bone 4.Dura mater 5.Arachnoid 6.Pia mater. SEER Cancer Institute, WikiMedia Commons]]

===Outer Layers===

==Outer Layers==

The central nervous system (CNS) is surrounded by several layers of tissue, with several outer layers not directly related to the CNS and three membranes that directly envelope the CNS. The outer layers are the skin and then a bone layer with associated periosteum. This layer includes the skull and the vertebrae. Below the periosteum is the '''Epidural Space''' which lies between periosteum and dura in the vertebral canal. The epidural space contains loose connective tissue, veins and lymphatics. It cushions the cord as it flexes. The epidural space is regularly used for nerve blocks. In cranium, the dura layer is fused with the periosteum and therefore is in effect single layer without an epidural space.

The central nervous system (CNS) is surrounded by several layers of tissue, with several outer layers not directly related to the CNS and three membranes that directly envelope the CNS. The outer layers are the skin and then a bone layer with associated periosteum. This layer includes the skull and the vertebrae. Below the periosteum is the '''Epidural Space''' which lies between periosteum and dura in the vertebral canal. The epidural space contains loose connective tissue, veins and lymphatics. It cushions the cord as it flexes. The epidural space is regularly used for nerve blocks. In cranium, the dura layer is fused with the periosteum and therefore is in effect single layer without an epidural space.