Your back is an amazing structure that combines strength with flexibility.
This strength and flexibility is very important since your spinal column provides vital postural support to all other body parts while at the same time it allows you to move in many different directions. Below you can find more information on the various structures in your back and what their function is.
- More about the various structures in your back (the anatomy)
- More about how the structures in your back work (the physiology)
Anatomy (the structures)
The spinal column is made up of 33 bones called vertebrae with discs that act as shock absorbers in between. These bones are given a letter and a number depending on where they are located in the spinal column:
- C (cervical) followed by a number from 1 to 7, refers to the vertebrae in the neck.
- T (thoracic) followed by 1 to 12, refers to the thoracic spine (where the 12 ribs are attached). Sometimes the vertebrae in the thoracic spine are referred to as dorsal with the letter D.
- L (lumbar) followed by 1 to 5, refers to the lumbar (or lowest) section of the spine.
- S (sacral) followed by 1 to 5, refers to the lowest vertebrae, although these vertebrae are fused together, forming the sacrum.
- Coccyx (or tail bone), formed out of 4 fused vertebrae at the very bottom of your spinal column.
Your spinal column consists of 33 vertebrae
The shape of the vertebrae in your neck is different from the vertebrae in your lower spine. For example, the vertebrae at the bottom are much bigger and heavier since these support almost your whole upper body while the ones in the neck only support your head. Secondly the shape of the vertebrae determine in what directions you can move; you can move your neck much more freely than your lower spine.
The vertebrae have a small gap (called the ‘foramen’) through which the spinal nerves run. The spinal nerves (which are part of the central nervous system) run all the way from the base of your brain to the bottom of the spinal column. The nerves exit the spinal column at the level where they need to be, for example the nerves that go to your arms, exit the spinal column in the neck area (cervical), and the nerves going to your legs exit much lower and run along the whole length of the spinal column.
The discs (the structures between the vertebrae) are made up of a soft jelly like substance (the nucleus), which is held inside a tough, elastic and fibrous outer casing (the annulus). The official name of the discs is intervertebral discs.
The spinal column (consisting of the vertebrae and discs) is supported by numerous muscles, tendons and ligaments. These provide strength and stability to the ‘chain’ of vertebrae and discs. The muscles are connected to your bones with tendons; when a muscle contracts the forces are passed on to the skeletal system via the tendons. This ensures that a muscle contraction results in a movement of a certain body part. The ligaments provide stability to joints, but are also somewhat flexible so they can stretch or contract when the joint moves.
You will notice that your spine is not straight, but is actually an 'S' shape. Not all backs are the same 'S' shape but they are usually curved with a hollow in the base of your neck and another in the lower part of your back.
Physiology (how it all works)
From the above you can see that your back consists of many different structures; vertebrae, discs, nerves, muscles, tendons, ligaments. But this does not fully explain how they all work. Similarly, you may know all the parts of the engine in your car, but in order to really understand the engine, you will also have to know how they work. In other words you need to know about the structures (the anatomy) and the working mechanisms. The latter is called physiology.
One of the key elements of how the structures in your body function is blood flow. Your blood provides the various parts in your body with oxygen and nutrients (‘energy’). Furthermore, your blood also provides a ‘waste-removal’ service by taking away the waste that is being produced when body structures use the available oxygen and energy (for example carbondioxide, CO2). One of the factors that may restrict the blood flow is smoking. This is especially important in the discs that have a very minimum blood flow (due to the high pressure in the discs it is difficult for the blood to enter the discs). Research has now shown that smoking can indeed be one of the factors that contributes to back pain.
Nerves pass on messages from your body to your brain and back
A second element of how your spinal structures work is how the various functions are being co-ordinated. This is done via messages that travel through your nerves. One type of nerves passes messages from your brain to the rest of your body and a second type ensures that information from the various body parts is fed back to your brain. This messaging service is however slightly more complicated because before a message from let’s say your lower spine reaches your brain, there can be many factors that can either suppress or re-enforce the original message.
This is of particular interest for a pain message because it provides the option to alter a pain message and by doing so turn down the volume of the pain signal. Unfortunately your body is also able to ‘increase’ the volume of the pain signal and this is targeted in many treatments for chronic pain. Researchers still find new factors that can alter pain messages.