Your Back

The back is the ultimate piece of engineering. It is composed of bone, joints, discs, ligaments, muscles and nerves which all work together to support the body and enable movement they also support and protect the spinal cord.

 

Spine

 

The spine has a column of building blocks called vertebra. There are seven vertebrae that make up the cervical spine, twelve in the thoracic region and five in the lumbar region. The remainder form the sacrum and coccyx. The vertebra form a bony tunnel called the spinal canal in which the spinal cord runs. The cord is a collection of nerves which link the brain and the body. It runs from the brain to the first or second lumbar vertebrae. Below this the nerves are in strands called cauda equina. The cord is protected by three membranes called meninges. The outer membrane is called the dura, the space between the spinal canal and the dural sac is called the epidural space.

 

Discs

 

The vertebras are linked by an intervertebral disc at the front and by two facet joints at the back.

The intervertebral discs formed of a tough outer part called the annulus, and a softer inner part called the nucleus pulposus. The nucleus pulposus is a gelatinous substance which helps articulate the vertebra and cushion the spine.

The disc can efficiently absorb compressive and jarring forces but is more susceptible to twisting forces which can result in the outer layers weakening and occasionally tearing or stretching.

Credit:PASIEKA / SCIENCE PHOTO LIBRARY - Lumbar vertebrae, side (lateral) view. This computer artwork shows the 5 lumbar vertebrae (pink) in the lower part of the spine. The sacrum at the base of the spine is just visible. The back of the spine is on the left, where the bony projections or processes can be seen; these are where the muscles and ligaments of the back attach to the spine. Intervertebral discs (brown) form joints between the vertebrae, allowing for slight movement and cushioning against impact. They consist of an outer layer of fibrous and cartilaginous tissue and a jelly-like centre.
As we get older the consistency of the nucleus changes. It can deteriorate and dehydrate -this is part of normal wear and tear and is also known as disc degeneration.
The wear to the spinal discs in the vast majority of the population does not reach a level that produces pain and disability that requires treatment.

The vertebras are linked by an intervertebral disc at the front and by two facet joints at the back.

The intervertebral discs formed of a tough outer part called the annulus, and a softer inner part called the nucleus pulposus. The nucleus pulposus is a gelatinous substance which helps articulate the vertebra and cushion the spine.

The disc can efficiently absorb compressive and jarring forces but is more susceptible to twisting forces which can result in the outer layers weakening and occasionally tearing or stretching.

As we get older the consistency of the nucleus changes. It can deteriorate and dehydrate -this is part of normal wear and tear and is also known as disc degeneration.
The wear to the spinal discs in the vast majority of the population does not reach a level that produces pain and disability that requires treatment.

 

Facet Joints

 

The facet joint is the joint between the vertebrae towards the back of the spine. The surfaces of the facet joints are cartilage lined and they are lubricated with synovial fluid.
Like other joints in the body they can wear (degenerate). Degeneration of both the discs and facet joints are part of the normal ageing process. These changes are often widespread and cannot be reversed. Any wear on a joint can produce arthritis.


Wear or degeneration may be the source of back or neck pain, but in many cases as the changes occur very slowly the process does not result in significant ongoing pain.

 

Spinal Nerves

 

The spinal nerve roots exit the spinal canal through foramina (holes) between the vertebra and facet joints. They are often compressed or irritated by surrounding tissues which can result in the patient experiencing leg pain, back pain or arm pain. This is known as sciatica when it affects the legs and radiculopathy in the arms.

Slipped disc. Artwork of a slipped (herniated) intervertebral disc seen from above. The front of the body is at left. The spine consists of blocks of bone (brown) called vertebrae. Adjacent vertebrae are cushioned by flexible pads of cartilage called intervertebral discs (blue). The spinal cord (yellow and black) runs down the centre of the vertebrae. The disc seen here has ruptured and its internal jelly-like fluid (green) has leaked and is putting pressure on a spinal nerve (yellow). This can cause severe pain and paralysis. Most slipped discs heal with rest and anti-inflammatory drugs, although some may require surgery.
Credit:
BO VEISLAND / SCIENCE PHOTO LIBRARY

Ligaments

 

The ligaments help to hold the vertebra together. The main ligaments run the whole length of the spinal column anteriorly and posteriorly.

Without regular movement or through normal ageing ligaments can become stiff which can reduce their function resulting in reduced spinal movement and pain.

 

Muscles

 

The spine is supported by many groups of muscles. There are smaller deeper muscles close to the vertebrae which help to control spinal posture and there are larger more superficial muscles surrounding the trunk which enable the major movements of the back. The vast majority of short lived episodes of acute back pain are due to muscle pain.

Illustration of the anatomy of the neck, shoulders and back, showing important muscles (brown), bones (white), nerves (yellow) and blood vessels (red/blue). The nerve network seen at upper right is the right brachial plexus, where nerves run from the cervical (neck) part of the spine into the arm, shoulder and chest. The backbone (centre) runs down from the skull (top centre) to the pelvis, where it ends in four fused vertebrae called the coccyx (lower centre). The large red blood vessel seen in the left hand side of the neck is one of the carotid arteries. The large red blood vessel entering the left arm is one of the subclavian arteries.
Credit:
JOHN DAUGHERTY / SCIENCE PHOTO LIBRARY