To help further understand and describe the anatomy, spine specialists often refer to specific body planes. The Pelvis and the SkullĪlthough not typically viewed as part of the spine, the pelvis and the skull are anatomic structures that closely inter-relate with the spine, and have a significant impact on the patient’s balance. Immediately below the sacrum are five additional bones, fused together to form the Coccyx (tailbone). The last lumbar vertebra (L5) articulates (moves) with the sacrum. The sacrum fits between the two hipbones connecting the spine to the pelvis. Five bones (abbreviated S1 through S5) fused into a triangular shape, form the sacrum. The lumbar facet joints allow for significant flexion and extension movement but limit rotation. The lumbar spine has more range of motion than the thoracic spine, but less than the cervical spine. Each structural element of a lumbar vertebra is bigger, wider and broader than similar components in the cervical and thoracic regions. The size and shape of each lumbar vertebra is designed to carry most of the body’s weight. The Lumbar Spine has 5 vertebrae abbreviated L1 through L5 (largest). In addition, the rib cage and ligament systems limit the thoracic spine’s range of motion and protect many vital organs. These structures make the thoracic spine more stable than the cervical or lumbar regions. In addition to longer spinous processes, rib attachments add to the thoracic spine’s strength. The thoracic vertebrae are larger than the cervical bones and have longer spinous processes. T1 is the smallest and T12 is the largest thoracic vertebra. These are abbreviated T1 through T12 (top to bottom). Thoracic Spineīeneath the last cervical vertebra are the 12 vertebrae of the Thoracic Spine. The other cervical vertebrae (C3 through C7) are shaped like boxes with small spinous processes (finger-like projections) that extend from the back of the vertebrae. Together, the Atlas and Axis enable the head to rotate and turn. It is circular in shape with a blunt peg-like structure (called the Odontoid Process or “dens”) that projects upward into the ring of the Atlas. The Atlas is ring-shaped and it supports the skull. The first cervical vertebra (C1) is called the Atlas. These vertebrae protect the brain stem and the spinal cord, support the skull, and allow for a wide range of head movement. This region consists of seven vertebrae, which are abbreviated C1 through C7 (top to bottom). The neck region of the spine is known as the Cervical Spine. Each region has specific characteristics and functions. Typically, the spine is divided into four main regions: cervical, thoracic, lumbar and sacral. Provide structural support and balance to maintain an upright posture.Protect the spinal cord, nerve roots and several of the body’s internal organs.The three main functions of the spine are to: This is followed by detailed information on specific anatomic elements such as vertebral structures, intervertebral discs, the spinal cord and nerve roots, joints, muscles and ligaments. It begins by providing a “big picture” of the functions of the spine, its regions, and major curves. This article provides a straightforward overview of the spine’s remarkable and complex anatomy. A basic understanding of the spine’s anatomy and its functions is extremely important for patients with spinal disorders.