The human spine extends from the skull to the pelvis and is made up of individual bones called vertebrae. These are stacked on top of one another and are grouped into four regions:

• Cervical (neck) - seven vertebrae
• Thoracic (chest area) - 12 vertebrae
• Lumbar (lower back) - five vertebrae
• Sacrum (pelvis area) - five fused vertebrae

The base of the spine, the coccyx (tailbone) includes partially fused vertebrae. The vertebrae are separated from one another by soft pads, called intervertebral discs, which allow the spine to bend and flex, as well as act as shock absorbers.

Throughout the length of the spine, there is a central tube, which is surrounded by bone and discs, called the spinal canal. Inside the canal is the spinal cord, which begins at the base of the brain and ends in the lumbar spine area in a bundle of nerves known as the cauda equina (it is said to resemble a horse's tail). A pair of spinal nerves branch out, right and left, at each vertebral level.

The spinal column is responsible for three main functions:

1. To protect the spinal cord that runs through the centre
2. To keep the body in an upright position
3. To help the body move

It runs from the base of the skull to the pelvis, and is made up of 33 bones called vertebrae. Each vertebra, apart from the top two, differs in shape and size but has the same anatomy. They are held together by muscles and ligaments, which provide the back with its flexibility, and are separated by cartilage disks to absorb shock. There are two joints attached to the back of each bone that increases the spine’s flexibility. At each level of the spine, a pair of nerves exit the spinal cord to send messages from the brain to and from various parts of the body.

From the front, the spinal column would appear as a straight line. While looking from the side, a fully-developed spine has an ‘S’ shape, with the neck and lower back curving slightly inwards and the upper back curving out. This is known as a non-degenerate spine, meaning it has not suffered from degeneration or deterioration.

The spinal cord is a very important part of the body, acting as the foundation for the central nervous system by linking the brain to the rest of the body. Damage to the cord can have a devastating impact on a person’s ability to function properly.

Millions of nerve fibres make up the cord, which is white in colour and approximately the same diameter as a human finger. The cord is protected from damage by the vertebrae by cerebrospinal fluid (CSF).

It begins immediately below the brainstem and travels down to the first lumbar vertebrae (L1) for approximately 43cm. On its way down the back, 31 pairs of nerves, known as nerve roots, exit the spinal cord through holes in the vertebrae, branching out to various parts of the body. Where these nerves have control in the body depends on where they branch out of the spinal cord.

These nerves, the nerve cell clusters (ganglia) and the limb and organ connections form the peripheral nervous system (PNS), which is responsible for relaying electronic signals to and from the brain. Nerves that carry information from the brain to the body are called motor neurones, while nerves that transport information to the brain are called sensory neurones.

The spinal cord ends at the conus medullaris before joining a mass of nerves at the base of the spine called the cauda equina.