In Depth: Spine and Nerves
The vertebral column’s most important physiologic function is protecting the spinal cord, which is the main avenue for communication between the brain and the rest of the body. The spinal cord is nestled in a cavity called the vertebral foramen inside of the vertebrae.
Many nerves of the peripheral nervous system, which transport signals to and from specific parts of the body, meet the spinal cord at the vertebral column.
Other roles for the vertebrae include helping support the body’s weight and providing an anchor for the ribs.
The typical adult has 33 total vertebrae, although it can range from 32 to 34 due to individual variance. Between most are ‘discs’ of cartilage that help cushion these bones and give them flexibility.
The vertebrae are divided into five sections:
- Cervical: The seven cervical vertebrae are those that are closest to the skull. The first is known as the atlas because the skull rests on it. The name comes from the myth of the Greek titan who bore the world on his shoulders. The second also has a special name: the axis. It has a special shape that allows the head to turn from side to side.
- Thoracic: The 12 thoracic vertebrae are where the ribs attach to the spine.
- Lumbar: The five lumbar vertebrae are among the largest and do much of the work of supporting the body’s weight.
- Sacral: This section has only one bone: the sacrum. Although considered one bone, it is actually comprised of five vertebrae fused together. The sacrum is part of the pelvis.
- Coccygeal: This section is similar to the sacral. It contains a single bone, the coccyx (tailbone), which is made up of three to five fused vertebrae.
Most vertebrae are identified by a letter-number combination based on where they are in the spine. The atlas is also known as C1 because it is the first cervical vertebra; T11 is the 11th thoracic vertebra. There are seven cervical vertebrae at the top, followed by 11 thoracic vertebrae, five lumbar vertebrae at the lower back, and five fused vertebrae at the bottom to create the sacrum. The coccyx, or tailbone, is the lowest bone of the spinal column.
Many of the peripheral nerves are named after the part of the spine where they join the spinal cord. There are cervical, thoracic, and lumbar nerves.