Understanding Your Spine
January 28, 2011
By: Stephanie Burke
Spinal anatomy is a remarkable combination of strong bones, flexible ligaments and tendons, large muscles and extremely sensitive nerves and nerve roots. Without question, the anatomy of the spine is a marvel of nature.
Importantly, the spine provides our bodies with:
- Structure to allow us to stand upright and move with precision
- Protection for the spinal cord and nerve roots to safely relay messages to and from the brain and the rest of the body
- Shock absorption capability as we move about
- Flexibility at the joints to allow us to bend, twist, move our heads and adjust to a wide variety of positions.
- Strength provided by the bones, discs, joints and supportive muscles and connective tissue.
For more information, see the following article on:
Most of us take this juxtaposition of strength, structure and flexibility for granted - until something goes wrong. Once we have neck pain or back pain, we're driven by a need to know exactly what is wrong and what it will take to relieve the pain and prevent a recurrence.
Starting at the Top of the Spine
The cervical spine (neck) supports the weight of your head and protects the nerves that come from your brain to the rest of the body. This section of the spine has seven vertebral bodies (bones) that get smaller as they get closer to the base of the skull.
- The top two segments are unique: The top cervical segment (C1) is a ring that is attached to and rotates around the second vertebral body (C2), which acts as a post. Most of the rotation in the neck is located in these top two segments.
- The next five vertebral segments (C3 - C7) are like the rest of the spine, with three joints at each segment, including one disc in the front and paired facet joints in the back.
Most episodes of acute neck pain are due to a muscle, ligament or tendon strain. This type of injury is usually caused by a sudden force (e.g. whiplash from a car accident), or from straining the neck (e.g. carrying something heavy, cradling the phone on your shoulder for too long).
For patients with neck pain that lasts longer than two weeks to three months, or with predominantly arm pain, numbness or tingling, there is often a specific anatomic abnormality causing the symptoms (such as a herniated disc, spinal stenosis, etc.). Treatment options will differ depending on the diagnosis. For more information, see the following article:
The Upper Back Is Not Usually a Source of Pain
The 12 vertebral bodies in the upper back that are attached to the rib cage make up the thoracic spine (middle or upper back). The firm attachment of the rib cage at each level of the thoracic spine provides for a great deal of stability and structural support, and very little motion.
Because there is limited motion in the upper back, it is rare for a thoracic disc to herniate or degenerate. However, irritation of the large back and shoulder muscles or joint dysfunction in this area can be very painful. For more information, see the following article:
The Lower Back Is Most Prone to Injury
The lower back is the most frequently injured area of the spine because it has the least structural support and endures the most strain. Fifty percent of flexion (bending forward) occurs at the hips and fifty percent occurs in the lower back. The motion is divided between the five motion segments in the lumbar spine, although a disproportionate amount of the motion is in the lower segments (lumbar segment 4-5 and lumbar segment 3-4). Consequently, these two segments are the most likely to be injured.
Most episodes of lower back pain are caused by muscle strain. Even though this doesn't sound like a serious injury, the pain can be severe. Strong abdominal muscles and back muscles are important to provide support for this area of the spine and avoid injury.
For more information, see the following article on:
The Bottom of the Spine Can Cause Pain Too
Below the lumbar spine is a bone called the sacrum, which makes up the back part of the pelvis. Five bones fused together comprise a single bone called the sacrum. This bone is shaped like a spade that fits between the two halves of the pelvis, connecting the spine to the lower half of the body.
The iliac bones are part of the pelvis and the sacrum is connected to this part of the pelvis by the sacroiliac joints. Pain here is often called sacroiliac joint dysfunction, and is more common in women than men.
The coccyx is at the very bottom of the spine (also called the "tailbone"). It consists of 3-5 fused bones at the base of the back that don't move. Pain here is called coccydynia and is more common in women than men. For more information, see the following article: