Spine Anatomy

The spinal column is a flexible group of bones. The human spine is an amazing thing. It supports all bones in the skeleton while providing protection for our spinal cord, blood vessels, and spinal nerves. In order to better communicate and understand the language that your doctor may use, it is important to have a basic understanding.

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Spinal Column

The spinal column is a flexible group of bones connected by small joints that allow for a large range of motion. Each part of the spinal column is connected by muscles and ligaments that keep the spine stable. A healthy spinal column is straight when viewed from the front, and curved when viewed from the side. The spinal column is made of of many individual bones, called "vertebrae." Spinal nerves exit the spinal column at every level, and provide electrical signals for the body to move and provide sensation.

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Vertebrae

The spinal column is made of many spinal bones (vertebrae) stacked on top of each other. Each of these bones is joined with ligaments and muscles. They are named based on their location in the spine.

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The bones of the neck are known as the cervical spine, and are made up of seven bones, named C1 through C7. The spinal roots at these levels go to the arms. The cervical spine is extremely flexible, but each level contributes to only a small amount of motion.

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The next twelve vertebrae make up the thoracic spine, are connected to ribs, and are labeled T1 through T12. All thoracic vertebrae are connected to ribs, and do not move very much. Because of the ribs, this area of the spine is the most stable and least susceptible to injury. There are fewer problems with the thoracic spine that require an operation.

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The five vertebrae in the lower back make up the lumbar spine, labeled L1 though L5. Spinal roots that exit the spine at these levels provide strength and sensation for the legs. There is a great deal of motion in the lumbar spine, and it supports the greatest amount of weight in the body. The lumbar spine is the most common place for "wear and tear" that may require an operation.

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At the bottom of the spinal column is the sacrum. The sacrum is a large bone made of up vertebrae that are joined together. The spinal roots here control bowl and bladder function. The sacrum connects to the pelvis by the "sacroiliac joints" on either side.

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Intervertebral Disc

The front part of vertebrae are connected to each other by intervertebral discs. These discs serve as a flexible cushion and allow for a large range of motion in the spine. The outer portion of these discs is a firm ring of tissue, called the annulus fibrosus (disc wall). Within the center of these discs is a jelly-like substance called the nucleus pulposus.

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A young, healthy disc has an intact disc wall and is filled with jelly-like substance inside with a large amount of water to allow for movement. As we age, these discs dry out and lose some of the water in the center. These discs will become "degenerative", less flexible, lose height, and may cause bone spurs which press on spinal nerves.

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Scoliosis and Kyphosis

When viewed from the front, a healthy spine is a straight line. "Scoliosis" is a curvature in the spine when viewed from the front. Many people will have some natural curve in the back and not even know it. This condition only rarely becomes painful or a problem, and does not usually require treatment. Although it may be bothersome to someone, surgery should not be offered for "cosmetic" reasons. In severe cases, the spine may twist or collapse from advanced degeneration. This may cause painful spinal joints or cause spinal nerves to become damaged. In some cases, an operation may be offered to correct the curvature and relieve pressure on joints and nerves.

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A healthy spine will appear in an S-shape when viewed from the side. Forward curvature of the spinal column is called "kyphosis," and backward curvature is called "lordosis." There is a normal amount of curvature or kyphosis in the thoracic spine, while the cervical and lumbar spines have lordosis. As we age, the kyphosis in the thoracic spine may increase, or the lordosis decreases in the neck or back. If this happens, posture may be affected and the body leans forward. This is a normal process of aging, however in severe cases an operation may be recommended to correct posture.

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Muscles

Muscles provide support for the spine and allow for motion. Abdominal muscles allow for flexion of the spine, extensor muscles in the back allow for extension, and oblique muscles allow for side-bending and twisting. Maintaining healthy and strong muscles is an important part of a healthy back. There are many small muscles in the back which coordinate complex movement. Muscle strains of the back are unfortunately very common. Physical therapy and sometimes medications may sometimes help pain of muscle strains. There is no surgery to help with muscle strains in the back.

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Joints

The vertebrae are connected in the front of the body by vertebral discs, and in the back by a "facet joint" on both sides. Just like in other joints in the body, these joints are susceptible to arthritis, or "wear and tear." As they become arthritic, they may become painful and even unstable. Unstable joints in the spine may require an operation to stabilize the vertebral bones.

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Spondylosis and Spondylolisthesis

"Spondylosis" refers to a condition where a vertebra has separated, usually from a fracture. This condition is relatively common and often occurs in people who do activities that require extreme extension of the back, such as gymnastics.

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"Spondylolisthesis" refers to a condition where one vertebra moves forward on the one below. This is also referred to as a "slip," or "degenerative spondylolisthesis" when it occurs from wear and tear. When this occurs and nonsurgical methods fail to provide relief, an operation may be recommended to move the vertebra back into place. For more information, see Spondylosis and Spondylolisthesis.