What is the Spine?
The spine is, in reality, the “backbone” of our bodies. It is an important and complex structure that provides the body with support, function, and protection. Without it, it would be impossible to sit, stand, walk, run, or of course, be alive.
The spine also allows for a wide range of the body’s movement. It allows:
- Flexion – bending forward
- Extension – bending backward
- Lateral Flexion – left to right bending (and vice versa)
- and Rotation – moving the hips in a circular motion
In addition to structural support and mobility, the spine is also a point of attachment for many structures, including ligaments, muscles, and tendons. The bones of the spine, or vertebral bodies, also protect the spinal cord. The spinal cord passes through the vertebral bodies at each level. In addition to being protected by bone, the spinal cord is further protected by muscles, ligaments and tendons.
The Vertebral Bodies of the Spine
The spine is comprised of three regions: cervical, thoracic (sometimes called dorsal), and lumbar region. Each of these regions contains a group of bones collectively known as vertebrae or vertebral bodies. These are each separated by intervertebral discs. There are normally a total of 24 vertebrae in the spine divided as follows:
- Cervical spine – 7 cervical vertebra
- Thoracic thoracic – 12 thoracic vertebra
- Lumbar spine – 5 lumbar vertebra
Each vertebral body is identified by a letter/number combination. For example, in the low back or lumbar spine, the 5 lumbar vertebral bones are referred to as L1 through L5. The letter “L” is used to designate that the vertebral bone is in the lumbar region of the spine, while the number 5 identifies which bone, ie. the 5th bone or the lowest lumbar bone in the spine.
A vertebral bone is composed of different parts, each with its own corresponding function. The body of each vertebra is the area that bears an individual’s weight, while the lamina provides a covering for the spinal canal. The pedicle is the backward extension coming from the sides of the vertebral body.
A vertebra also has a spinous process. This is the part of the spine that can be felt on a person’s back. There is also a pair of transverse processes that are positioned at 90 degrees facing the spinous process which functions as an attachment for the muscles of the back.
Another area of a vertebra is the transverse foramen. This is a gap or hole that functions as a conduit for vertebral blood vessels and nerves to pass through. The larger hole in the middle is called the vertebral foramen, which is where the spinal cord passes through.
Intervertebral Discs of the Spine
Intervertebral discs are positioned in between vertebral bones. These discs serve to cushion and separate vertebrae from each other. Together, vertebral bones and intervertebral discs create the stacked shape of the spine. In total, there are twenty-three intervertebral discs in the spine, divided as follows:
- Cervical spine – 6 intervertebral discs
- Thoracic spine – 12 intervertebral discs
- Lumbar spine – 5 intervertebral discs
Each intervertebral disc is identified by location relative to the vertebral bones between which it is positioned. For example, an intervertebral disc in the low back identified as the L4-L5 disc refers to the intervertebral disc positioned between the L4 and L5 vertebral bones.
Common Injuries To the Spine
The spine can be injured in many different ways. There can be damage to ligaments, muscles, tendons, vertebral bodies, intervertebral discs, as well as facet joints. Here are some common injuries that can happen as a result of an accident:
Sprains and strains occur when spinal ligaments experience over-stretching and twisting. This can result in the tearing of soft tissue in the spine. Symptoms usually include intense pain within the first few hours or days of the incident, stiffness, and localized tenderness;
A herniated disc occurs when the outer structure of the disc, called the annulus fibrosis, tears. When this happens, the inner contents of the disc, known as the nucleus pulposus, can ooze out causing pressure on adjacent nerve roots. This can result in a painful condition called radiculopathy that is associated with tingling, radiculopathy, burning, and numbness down the affected extremity;
A bulging disc occurs when a disc sags and loses its shape. This condition is degenerative in nature but can be trauma related. However, it is not uncommon for trauma to cause a painless disc bulge to become painful.
Vertebral fractures can occur when there is a forceful impact on the spine. These types of fractures can involve the spinous process, vertebral body, or other portions of the vertebrae. Usually diagnosed by X-ray or CT Scan, vertebral fractures require immediate management to prevent and/or minimize injury to the spinal cord and nerves.