Anatomy of the Spine

The spinal column provides the main support for the body and is comprised of thirty-three individual vertebrae that are divided into the five sections of the spine: cervical, thoracic, lumbar, sacral, and coccygeal. The cervical region is made up of seven vertebrae that support the skull and move the spine. All seven vertebrae are numbered from C1 to C7. The C1 vertebra is closest to the skull and is known as the atlas. The vertebra below it is the C2 and is known as the axis. The cervical region connects to the thoracic region. The thoracic region is located in the chest area of the body and is comprised of twelve vertebrae that attach the ribcage to the thoracic region. The twelve vertebrae are numbered from T1 to T12 and are numbered in descending order with T1 at the top. The lumbar region is located in the lower back and is comprised of five vertebrae labeled from L1 through L5. The lumbar region carries the most weight and is the area most prone to injury. The sacral region is comprised of five vertebrae that are fused and numbered S1 through S5. The five fused vertebrae form the sacrum. The sacrum is located near the bottom of the spine and is the attachment point for the pelvis. The coccygeal region is located at the very bottom of the spine and is comprised of four small vertebrae that may be fused or separate. Combined they form the coccyx, which serves as an attachment point for muscles, tendons and ligaments. There is limited movement between the coccyx and the sacrum.


The vertebrae of the spine’s five regions serve to protect the spinal cord and to provide support for the weight of the body. Each vertebra is composed of a set of structures that are vital to the overall function of the spine. The vertebral body is the largest section of a vertebra. It is cylindrical in form and is the primary load-bearing section of the vertebra. The vertebral canal lies behind the vertebral body and is the space through which the spinal cord travels. The spinal cord is a bundle of nerves that is enclosed in the spine and connects nearly every part of the body with the brain. It ends near the L1 and L2 vertebrae, where it divides into nerve roots called the cauda equine. Nerve roots function in transmitting signals between the spinal cord and other parts of the body. Pedicles extend on the left and right sides of the vertebral canal and connects the lamina to the vertebral body. The lamina is part of the roof of the vertebral canal. It aids in covering and protecting the spinal cord and nerves. On the back of the lamina is a bony protrusion called the spinous process. It functions in providing a point of attachment for the muscles and ligaments that move and stabilize the vertebrae. Transverse processes are bony structures that protrude on the left and right sides of each vertebra. Transverse processes function in attaching the muscles and ligaments that move and stabilize the vertebrae. Each vertebra has two sets of articular facets that form the joints where each vertebra connect. One pair of facets faces upward and the other pair faces downward. The facets are cartilaginous and allow movement. Intervertebral discs lie between the vertebral bodies and forms a tough fibrocartilaginous joint that is flexible enough to allow movement of the vertebrae. The tough outer wall of the intervertebral disc is called the annulus fibrosus and the soft interior is called the nucleus pulposus.