What Protects the Spinal Cord?

The spinal cord is a cylindrical collection of nerve fibres and other tissue that connects all parts of the body to the brain. This intricate and amazing communication system extends from the base of the brain stem down to the lumbar region and is responsible for transmitting messages to and from the brain.

When we touch something, the sensation is carried through our spinal cord and registers in our brain. When we walk, messages are first sent from the brain to the legs to move via the same system of nerves. While the spinal cord is a vital part of the body, it is also extremely delicate. Even minor damage to this area can cause a life-changing spinal cord injury.

Fortunately, surrounding the spinal cord are various protective layers. The first, and most easily recognisable, are the vertebrae – hard, bony structures that form a kind of linked chain down the middle of the back with the spinal cord contained at its centre.

Next, there are a series of membranes called the meninges which cover both the brain and the spinal cord. As added protection, there is also a clear liquid between the membranes which is called the cerebrospinal fluid (CSF), which performs the dual role of protecting and nourishing.

What Bones Protect the Spinal Cord?

The vertebral column is made up of separate vertebrae that are interconnected and, in the most part, moveable. This allows us to perform tasks such as bending and turning while the spinal cord remains protected. There are 33 individual bones in the spine and their function is supported by strong muscles and ligaments.

The spinal cord is split into several distinct sections:

• The seven cervical vertebrae support the head and have the greatest range of motion, allowing us to turn or nod yes and no. Common traumas to this area include whiplash injuries where the head is snapped back and forth at high speed causing damage to the bone and connecting tissue.
• The 12 thoracic vertebrae protect the heart and lungs along with the connecting rib cage. The range of movement in this area is limited compared to the cervical vertebrae.
• The five lumbar vertebrae bear most of the weight of the body and are larger in size. They are designed to absorb the stress of lifting and carrying heavy things. This is a common place for injuries to occur, especially with today’s more sedentary lifestyles.
• Finally, there are the nine bones of the sacrum and coccyx which attach the spinal cord to the pelvic region.

Between each vertebrae, there are discs or cushions that prevent the individual bones rubbing together.

Meninges

The meninges have a couple of different functions. The first is to protect the spinal cord and the second is to provide important nutrients.

There are three distinct membranes: the dura mater, the arachnoid mater and the pia mater.

The outer layer or dura mater is a thick membrane that is responsible for keeping in the cerebrospinal fluid and protecting various blood vessels. The arachnoid mater is a much thinner layer and gets its name because it resembles a spider’s web. Inside this is the pia mater which protects but also holds more blood vessels that nourish the spinal cord.

Cerebrospinal Fluid

In total, our bodies have about 150 millilitres of cerebrospinal fluid which is constantly being replaced. That may not sound a lot (about half a cup in total) but it performs vital functions in the body.

Not only does it protect the brain and spinal cord, it also supplies nutrients to the nervous system and helps get rid of waste products. The fluid occupies the space between the arachnoid mater and the pia mater and is similar to normal blood plasma except that it almost entirely protein free.

The cerebrospinal fluid is constantly being absorbed so we need to create a lot of it to replace the fluid which has been used up – in a normal, healthy human being you can expect 25 ml to be produced every hour and distributed around the brain and spinal cord.

Medically speaking, cerebrospinal fluid is also important because it can be used to indicate a variety of different neurological diseases including multiple sclerosis. The fluid is normally collected by a process called lumbar puncture which involves inserting a need into the spinal area.

Summary

The spinal cord is a delicate network of nerves controlling functioning and sensation in the body. There are several layers that help to protect the spinal cord, including vertebrae, surrounding muscles and ligaments, meninges surrounding the spinal cord as well as cerebrospinal fluid.