2. An intervertebral disk (between two adjacent vertebrae) in which the nucleus pulposus has protruded through the surrounding fibrocartilage, occurring most frequently in the lower lumbar region, and less commonly in the cervical region.
Mild to severe symptoms may result from pressure on spinal nerves; also known as, "a ruptured intervertebral disk", or "a slipped disk" (the action of the nuclear tissue when it is forced from the center of the disc).
The center of the disc, which is called the nucleus, is soft, springy, and receives the shock of standing, walking, running, etc.
The outer ring of the disc, which is called the annulus (Latin for "ring"), provides structure and strength to the disc. The annulus consists of a complex series of interwoven layers of fibrous tissue that hold the nucleus in place.
When the disc has herniated, or ruptured, it may create pressure against one or more of the spinal nerves which can cause pain, weakness, or numbness in the neck and arm. Other names for herniated discs are "prolapsed discs" and "ruptured discs".