In Depth: Meninges and Nerves
The spinal cord is a long tube of nervous tissue that connects to the brain. Together, these make up the central nervous system, the main communication tool within the body.
As the spinal cord descends down the back, its nerves branch many times, and these branches extend all over the body — to the tip of each finger and toe. As these nerves receive information, such as pressure, heat, and much more, they send messages into the spinal cord and up to the appropriate part of the brain. These signals travel up the ascending tract, one of two spinal cord pathways.
The brain sends messages back through the descending tract. The responses tell muscles what they should do, whether it’s pulling the hand away from a hot surface or preparing for sexual intercourse.
Because the spinal cord is so important, it needs protection. Its first layer of protection is a series of membranes called meninges. These three membranes cover the brain and spinal cord to protect them. Within the spaces between the meninges is a fluid known as cerebrospinal fluid. It is more commonly known as spinal fluid. This fluid helps protect the brain and spinal cord from shocks and other types of damage by maintaining uniform pressure. It also acts as a transport system for nutrients to keep the spinal cord healthy.
The three meningeal membranes are:
- Dura mater, the outermost layer
- Arachnoid, the middle layer
- Pia mater, the innermost layer closest to the spinal cord
The spinal cord’s greatest protection is the spinal column, a set of 24 bony segments known as vertebrae that envelop the cord and its membranes.
Although protected, the spinal cord can be damaged in traumatic injuries. If the injury is severe enough, it can hamper or even halt communication between the brain and body, causing paralysis.
The spinal cord is also subject to disease and disorder. For example, spina bifida, is a congenital condition in which the spinal column and/or cord doesn’t properly develop. The spinal cord can also be damaged by tumors, whether cancerous or benign. These tumors can put pressure on the cord, which impairs function.