Intervertebral disc

Intervertebral discs lie between adjacent vertebrae in the spine. Each disc forms a cartilaginous joint, and allows movement of the vertebrae.

Related Topics:
Vertebrae - Spine - Joint

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Discs consist of an outer annulus fibrosus, which surrounds the inner nucleus pulposus.

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The nucleus pulposus is viscous fluid (like jelly), and acts like air in a pneumatic tyre. It can also shift slightly within the disc, depending on how the back is angled.

Related Topics:
Jelly - Tyre

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The annulus fibrosus consists of several layers of fibrocartilage, with the fibres of each layer running perpendicular its neighbours. (So it forms a criss-cross pattern). This is designed to be very strong.

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As people age, the annulus fibrosus gets weaker, and the pulposus can herniate through it. This is called a slipped disc, and the nuclear pulposus may press against nerve roots, causing radicular pain.

Related Topics:
Hernia - Slipped disc - Radicular pain

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There is one disc between each pair of vertebrae, increasing in size as they descend, with the largest located at the base of the spine. There is a disc located below each vertebra except for the first vertebra, the Atlas. The discs separate the vertebrae and are attached to the body section of each vertebrae. The Atlas has no body, as it forms a ring around the roughly cone shaped extension of the Axis (second cervical vertebra) to form a pivoting joint on which the skull can turn. Thus there are twenty-four individual vertebra and only twenty-three discs.

Related Topics:
Spine - Atlas - Axis

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Discs are identified by specifying the particular vertebrae they separate. For example, the disc between the fifth and sixth cervical vertabrae is designated "C5-6".

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A common problem often associated with a fall, car accident, or improper bending/lifting can result in the tearing, herniation (swelling), displacement (slippage), or shattering of these discs. Sometimes an afflicted person will feel pain only at the spot of the injury, however others experience other symptoms. All along the spine, near the posterior side of each disc, the major spinal nerves extend out to different organs, tissues, extremities etc. It is very common in such injuries for the herniated disc to press against these nerves (pinched nerve) causing radiating pain, numbness, tingling, diminished strength and/or range of motion. Any of these symptoms can be present alone or in various combinations. Often the afflicted individual will feel a sharp pain or numbness in their leg up to two feet from the spinal cord, yet the cause is a pinched nerve in the lumbar region. The same is possible in the arms, hands, feet shoulders, neck and face. Discs can cause more severe issues when they pinch off nerves leading to organs. A common symptom of a lumbar disc injury is diminished capacity of the bladder or bowel.

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