Degenerative Disc Disease
The spine is made up of several bones known as vertebrae. The spine helps provide flexible structure to the neck
and back. It also serves to protect the spinal cord, which carries sensory and motor signals between the brain and
the rest of the body.
The 7 vertebrae in the neck are known collectively as the cervical spine. The 12 vertebrae in the thorax are known
as the thoracic spine. The 5 vertebrae in the low back are known as the lumbar spine. The sacrum is formed by 5
fused vertebrae below the lumbar spine. And the coccyx, or tailbone, is formed by 4 fused vertebrae below the
sacrum.
Each vertebra consists of a vertebral body, a vertebral arch, and several processes that provide points of
attachment for ligaments or articulate with other vertebrae.
The spinal cord passes through the vertebral foramen, meaning the space created by the vertebral arch. The arch
consists of the pedicle, which attaches the main body of the vertebra to the transverse processes, and the lamina,
which attaches the transverse processes to the spinous process.
Jutting out above and below the transverse processes are the articular processes. Each articular process has a facet
that articulates with the facets of the vertebrae above and below it.
Between the vertebral bodies are shock absorbers known as intervertebral discs. The discs are more flexible than
the bony vertebrae, and allow for a small amount of movement between each vertebra. The cumulative movement
between several vertebrae allows for a great deal of flexibility in the neck and back.
Each disc is composed of a gel-like core, the nucleus pulposus, surrounded by a ring of fibrocartilage, the anulus
fibrosus. The semifluid nature of the nucleus pulposus allows for compression and stretching which absorbs shock
between the vertebrae and allows for flexibility.
Ligaments (strong, fibrous bands of soft tissue) hold the different parts of the vertebrae together, contributing to
the stability of the spine. The anterior and posterior longitudinal ligaments run along the anterior and posterior
aspects of the vertebral bodies. The laminae are connected by the ligamenta flava. The facet joints are surrounded
by small, ligamentous capsules. Each transverse process is connected by an intertransverse ligament. Each
spinous process is connected by a thin interspinous ligament and a stronger supraspinous ligament.
The notches above and below the pedicles form spaces for the spinal nerves to leave the spinal cord and branch out
to the body. These spaces are known as the intervertebral foramen.