Spinal regions.The spine comprises three main regions: cervical, thoracic, and lumbar. Starting at the top of the neck, there are seven cervical vertebrae called C1-C7, 12 thoracic vertebrae called T1-T12, and five lumbar vertebrae called L1-L5. Below the lumbar region, there are five fused vertebrae that make up the sacrum and three to five fused vertebrae known as the coccyx or tailbone.

Vertebrae. Each individual vertebra is made up of a rounded vertebral body toward the front and a bony element called the spinous process at the back. The body and the spinous process are connected by more bony parts known as pedicles and laminae. Together, these bones form the vertebral foramen (opening). Along the length of the spine, the vertebral foramina form the spinal canal.

Discs. The vertebral body is located in front of the spinal canal. A soft disc sits between each vertebral body, helping the spine bear weight, absorb shock, and maintain flexibility. The disc has two main parts, a tough ring called the annulus fibrosis and a water-filled center called the nucleus pulposus.

Spinal cord and nerves. The spinal cord travels from the brain and through the spinal canal of the spine’s cervical and thoracic regions. Below each vertebra, nerve roots extending from the spinal cord exit the spine and enter muscles. The spinal cord ends at the lumbar region of the spine (L1-L2). At that point, the spinal cord divides into a bundle of nerves called the cauda equina (Latin for “horse’s tail”).

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