CHAPTER 1
ANATOMY OF THE SPINE
The spine consists of bones (vertebrae) that encircle and protect the spinal
cord. These vertebrae are responsible for allowing the spine to move while
protecting the spinal cord. To allow for movement and stability, the vertebrae
interlock with one another by means of a joint on either side. The vertebrae
are also separated from one another by intervertebral discs.
These intervertebral discs are made of a type of cartilage. The disc is made
up of a soft, gel-like centre, called the nucleus pulposus, and this gel is kept
in position by a tough outer fibrous layer called the annulus fibrosus. The ver-
tebrae of the spine are further kept in position by an array of ligaments.
Muscles also attach to the vertebrae. Nerves leave the spinal canal, formed by
the vertebrae, through small openings called the neural foramina.
There are 7 neck (cervical) vertebrae, 12 chest (thoracic) vertebrae, 5 lower
back (lumbar) vertebrae and 5 sitting bone (sacral) vertebrae. The sacral ver-
tebrae are fused into a single mass called the sacrum or sitting-bone.
It is unusual for the thoracic spine to undergo wear and tear changes as it is
stabilised by the rib cage that is attached to it. The cervical spine and the lum-
bar spine, on the other hand, are subject to a lot of movement and this is
where most of the wear and tear takes place. The lower part of the neck where
it attaches to the rigid thoracic spine, is under a lot of biomechanical stress.
The same is true for the lumbar spine. The bottom end of the lumbar spine is
attached to the sitting-bone and the pelvis, which is rigid. The same types of
mechanical stresses are found here as well as where it attaches at the top to
the thoracic spine.
5