The “Spine” or your Vertebral Column is formed by 26 bones and is generally thought to be divided into 3 different segments. The names we are most familiar with are the following: the CERVICAL Spine, the THORACIC Spine, and the LUMBAR Spine. Let’s count the number in each segment.
The CERVICAL Spine consists of 7 bones; they are numbered C1 through C7 respectively.
The THORACIC Spine consists of 12 bones; they are numbered T1 through T12.
The LUMBAR Spine consists of 5 bones; they are numbered L1 through L5.
Now if you add those numbers you come to 24. Where are the other 2 of the 26 bones? The other 2 bones are the SACRUM and COCCYX. Both of these bones consist of a number of fused vertebrae.
The first 24 vertebral bones are separated by Intervertebral Discs, commonly called “Discs”.
The INVERTEBRAL DISCS are cushions between each of the 24 bones in the Spine. They make up about 25% of the length of the Spine. These discs consist of 2 parts the inner “nucleus pulposus” and outer “annulus fibrosus”. The inside is a gel like fluid surrounded by the outside a fiberous band which keeps the disc intact. As you become older the inside gel looses water and may cause a decrease in height. If you injure your back you may either cause a “rupture” or “herniation” of one or more of these discs. This will cause you PAIN. A herniated disc may also be called a “slipped disc”. These are other topics we can discuss later.
The average length of the adult Spine is about 28 inches. The bones become larger as you go from top to bottom, the CERVICAL Spine has the smallest bones and they become larger through the THORACIC Spine and LUMBAR Spine due to the larger amount of weight they have to support. Your LUMBAR Spine discs are the 5 largest.
If you view your SPINE from the side you can see 4 curvatures the resemble an “S” shape. The CERVICAL and LUMBAR Spine have a “concave” or “outward” curve posteriorly, whereas the THORACIC and SACRAL Spine have a “convex” or “inward” curve posteriorly. These curves allow the Spine to be able to bend or flex.
You may have heard the term “Kyphosis” which is too much of a curve in the THORACIC Spine. This has also been called “hunchback” in the past. You may see this in the elderly and could be caused by “osteoporosis”.
“Lordosis” is too much of a curve in the LUMBAR Spine, this has been called “swayback”. A temporary cause of lordosis can be caused in women during pregnancy or men with a potbelly. Both of these conditions will throw off your center of gravity and add undue stress on your Spine.
You may ask what supports the “SPINE”?
Your SPINE is supported by numerous ligaments and muscles. There are 2 main ligaments supporting your SPINE. The ANTERIOR and POSTERIOR Longitudinal Ligaments which run down the front and rear of the Spine. The ANTERIOR LONGITUDINAL LIGAMENT connects to the vertebrae and discs which prevents the spine from bending too far backwards or “hyperextension”. The POSTERIOR LONGITUDINAL LIGAMENT is attached to only your discs and prevents you from bending too far forward or “hyperflexion”.
Finally, if you have pain in your back it may be caused by an injury to any part of your SPINE. The SPINE is much more complicated then the brief description above and pain in the spine may be caused by many other reasons than injury.If your pain lasts more then a few days or is more chronic I recommend you see your doctor for proper medical care and diagnosis.
