Your spine is divided into regions: there’s your neck (cervical spine), mid-back (thoracic spine), and low back (lumbar spine). At the bottom of your spine, you also have the sacrum and the coccyx, which is commonly called your tailbone. Your iliums or hips then attach to the sacrum.The vertebrae in your neck are labeled C1-C7, meaning that you have seven vertebrae in that region. Most adults have 12 vertebrae in the thoracic spine (T1-T12), which goes from your shoulders to your waist. Then there are five vertebrae in your low back (L1-L5), and below that, your sacrum is made up of five vertebrae between the hipbones. By the time you’re an adult, these five bones have fused into one bone. The coccyx is made of small fused bones at the very tail of your spine (hence the tailbone). Your spine also has facet joints, which are on the posterior side (back) of your vertebrae. These joints (like all joints in your body) help facilitate movement and are very important to your flexibility. They are surrounded by a ligamentous capsule that can become inflamed and become a cause of low back pain know as facet syndrome. Patients who wear high heels or place their back into extension will aggravate this condition.
Another vertebral bone structure that’s labeled in the image is the pedicle. These are on either side of your vertebrae, and they are part of the “walls” for your spinal canal.
In between your vertebrae, you have intervertebral discs (also labeled on the image). These act like pads or shock absorbers for your spine as it moves. Each disc is made up of a tire-like outer band called the annulus fibrosus and a gel-like inner substance called the nucleus pulpous.
Together, the vertebrae and the discs provide a protective tunnel (the spinal canal) to house the spinal cord and spinal nerves. The spinal cord gives off branches or pairs of nerves at each level of the back. These nerves exit neural foramens and extend into various parts of the body, where they help you feel and move.
Your back also has muscles, ligaments, tendons, and blood vessels. Muscles are strands of tissues that act as the source of power for movement. Ligaments are the strong, flexible bands of fibrous tissue that link the bones together, and tendons connect muscles to bones and discs. Blood vessels provide nourishment. These parts all work together to help you move.
Back pain may be a result of injury to any or all of these body parts. Injury to the muscles, ligaments, tendons can result in sprains or strains. Injury to bones, nerves, or blood vessels may be more serious. Also, the outer layers of the intervertebral discs can get tears or cracks, allowing the annulus fibrosus or nucleus pulposus to bulge out. Any of these injuries can cause inflammation and pain.
Image source: Public domain, via Wikimedia Commons