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]]

* The CNS is surrounded by several layers of tissue.

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. Cushions the cord as it flexes. Can be used for nerve blocks (epidural). In cranium, dura fused with periosteum, one single layer in effect.

*# Bone layer with periosteum

*#* E.g. the skull and the vertebrae.

*# Epidural Space

*#* Lies between periosteum and dura in vertebral canal. Contains loose connective tissue, veins and lymphatics. Cushions the cord as it flexes. Can be used for nerve blocks (epidural). In cranium, dura fused with periosteum, one single layer in effect.

*# Dura mater

*# Dura mater

*#* dense connective tissue

*#* dense connective tissue