About The Spine

The cervical spine consists mainly of the vertebrae or bone of the spine with a disc in between each bone. There are seven cervical vertebrae (referred to as C1-7). The main part of the vertebra is called the body and is located at the front. The disc is located between the vertebral bodies. Each disc is referred to by the bones between which it sits. For example, the C5/6 disc is located between the C5 and C6 vertebral bodies.

Behind the vertebral bodies there is a ring of bone that contains the spinal cord. The back of this ring is made of the lamina and spinous processes to which the muscles are attached. The spinal cord is surrounded by spinal fluid and is enclosed in a sac called the dura. At each level a nerve root emerges from the spinal cord exits the spine through a hole between each bone called the intervertebral foramen. That nerve root will supply feeling (sensation) to an area of the arm and will also supply muscles that perform different movements.

The disc is made of two main elements. The first is the annulus fibrosis. This is a strong outer layer made of criss-crossing fibres. The inside of the disc, or nucleus pulposus, is the soft gel-like centre which normally provides the cushioning function of the disc.

The lumbar spine is made up of five vertebrae (L1–L5), with a disc sitting between each one. The main part of the vertebra, known as the body, is positioned at the front, while the discs act as cushions between these vertebral bodies. Each disc is named after the vertebrae it lies between; for example, the L4/5 disc sits between the L4 and L5 vertebrae.

Behind the vertebral bodies is a bony ring that houses the lower end of the spinal cord, which ends around the L1/2 level, and the nerve roots that continue downward. The back of this ring is formed by the lamina and spinous processes, which also serve as attachment points for muscles supporting and moving the spine. Below the end of the spinal cord, the nerve roots extend in a bundle called the cauda equina, meaning ‘horse’s tail’. These nerve roots are surrounded by spinal fluid within a protective sac called the dura and exit the spine through openings known as intervertebral foramina. Each nerve root provides sensation and muscle control to specific parts of the body.

The discs themselves consist of two main components. The annulus fibrosus forms a tough outer layer of criss-crossing fibres, while the nucleus pulposus is a soft, gel-like centre that provides cushioning and flexibility to the spine during movement.