Normal Anatomy of the Spine
The spine, also called the back bone, is designed to give us stability, smooth movement, as well as providing a corridor of protection for the delicate spinal cord. It is made up of bony segments called vertebrae and fibrous tissue called intervertebral discs. The vertebrae and discs form a column from your head to the pelvis, giving symmetry and support to the body.
The spine can be divided into 4 parts. The uppermost is the cervical region, consisting of 7 small vertebrae that form the neck. As we move down the body, the next 12 vertebrae make up the thoracic region or mid back, from which the ribs are hinged. The 5 lumbar vertebrae are the largest of the mobile vertebrae and support 2/3 of the body's weight. The lowest region of the spine is the sacrum and coccyx. The sacrum is a triangular plate made up of five fused vertebral segments, while the four fused vertebrae of the coccyx form the terminus of the spine.
A single vertebra is made up of two parts, the front portion is called the body, cylindrical in shape, and it is strong and stable. The back portion of the vertebra is referred to as the vertebral or neural arch and is made up of many parts. The strong 2 pedicles join the vertebral arch to the front body.
The lamina forms the arch itself while the transverse process spread out from the side of the pedicles like wings to help anchor the vertebral arch to surrounding muscle. The spinous process forms a steeple at the apex of the lamina and is the part of our spine that is felt directly under the skin.
- Lamina: The lamina of the vertebra can be described as a pair of flat arched bones that form a component of the vertebral arch.
- Spinal canal: This canal is formed by the placement of single vertebral foramina one on top of the other to form a canal. The purpose of the canal is to create a bony casing from the head to the lower back through which the spinal cord passes.
- Pars interarticularis: Known as the pars, it is the part of the vertebral arch where the pedicle, transverse process, and articular process transect.
- Intervertebral Disc: The intervertebral disc sits between the weightbearing vertebral bodies, servicing the spine as "shock absorbers". The disc has fibrous outer rings called the annulus fibrosus with a watery, jelly-filled nucleus called the nucleus Pulposus.
The spinal cord is the means by which the nervous system communicates the electrical signals between the brain and the body. It begins at the brain stem and is held within the spinal canal until it reaches the beginning of the lumbar vertebra. At L1 the spinal cord resolves down to a grouping of nerves that supply the lower body.
Facet joints are the paired articular processes of the vertebral arch.
These synovial joints give the spine its flexibility by sliding on the articular processes of the vertebra below.